WBBSE Solutions For Class 10 Life Science And Environment Chapter 2 Continuity Of Life Chromosome

Chapter 2 Continuity Of Life Chromosome Summary

• Cell division and reproduction maintain the continuity of life. Ceil contain a nucleus which in turn contain chromosome. The DNA in the chromosome is> the reservoir of genetic information.
• A particular portion or sequence of DNA, that controls one or more characters of an organism is called a gene. It is also known as a basic physical and functional unit of heredity.
• Chromosome is a condensed form of DNA. Hence it is of two types—autosomes and allosomes. Autosomes are mainly responsible for controlling somatic characteristics whereas allosomes are responsible for sexual features. In the human body, 22 pairs of autosomes are there, whereas allosomes are only one pair.
• In males,-allosomes are heterologous in nature and comprise with two different types of chromosome-X and Y. In female, allosomes are homologous in nature and comprise of similar type of chromosome-X and X.
• The physical structure of a chromosome is mainly comprised of chromatids, centromere, secondary constriction and telomere. The chemical components of chromosomes are DNA, histone and non-histone protein.
• DNA or deoxyribonucleic acid is a large molecule mainly composed of two polynucleotide chains, that coil around with each other and form a helical structure. This DNA is chemically composed of N₂ bases, pentose sugar and phosphate. The N₂ bases of DNA are of two types-purines (adenine and guanine) and pyrimidine (cytocine and thymine).
• Other than DNA, RNA also carries genetic information in the case of lower organisms {mainly bacteria and viruses). This RNA or ribonucleic acid is produced or originates from DNA, mainly composed of a single polynucleotide chain and is very unstable in nature.
• Like DNA, it is also comprised with N₂ base, pentose sugar and phosphate. But in RNA pyrimidine base uracil replaces the thymine.
  When the cell is in a quiescence state, the chromosome remains in chromatin form in the cell. On the basis of staining and function, chromatin is of two types-euchromatin and heterochromatin.

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Chapter 2 Continuity Of Life Chromosome Long Answer Type Questions

Question 1. Explain the inter-relationships among Chromosomes, DNA and gene. Distinguish between euchromatin and heterochromatin on the following two aspects: Coiling, Activity.
Or,
Distinguish between euchromatin and heterochromatin.

Answer:

Inter-relationships among Chromosomes, DNA and gene:

There are fine thread-like structures present in the nucleus of cell. These are intermingled twisted ladder-like double-stranded structures. These structures are DNA which are large biomolecules. They occur inside the nucleus in a completely coiled manner.

In an undivided state of cells, the partially uncoiled DNA is called nuclear fibre or chromatin fibre. During cell division, DNA gets coiled. DNA strand surrounds protein molecules firmly and forms a dense coiling.

This coiled structure is called a chromosome. Actually, chromatin fibre and chromosome are respectively the less and much-coiled structures of DNA.

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Difference between euchromatin and heterochromatin

Question 2. Describe the physical structure of the eukaryotic chromosome. Or, Describe the morphological features of the chromosomes of an eukaryotic cell.

Part Question, Explain the importance of the following parts of a eukaryotic chromosome:

1. Centromere,
   
2. Telomere.

Answer:

The physical structure of eukaryotic chromosome:

The morphological features of a chromosome appear ‘most distinctly under a microscope during the metaphase stage of cell division. From this study, we can find 5 parts of a chromosome. These parts are described below.

1. Chromatids:

In a metaphase chromosome, two identical and longitudinal strands are seen. These are chromatids. Two chromatids of the same chromosome are called sister chromatids, which remain attached to a constricted region or centromere.

Each chromatid carries one or few very fine filaments along its length. These are called chromonemata (singular—chromonema). Each chromonema is composed of a longitudinally arranged coiled DNA.

Along each chromonema, everal spherical linearly arranged bead-like structures are seen, which are called chronometers.

2. Primary constriction and centromere:

Each chromosome has a distinct constricted region at which the sister chromatids remain attached to each other. This is known as primary constriction.

At e primary constriction, a round plate-like and dense heterochromatin structure is seen, which is called the centromere. The centromere has a few adhesive points, called kinetochores, which attach to the spindle fibres during metaphase.

The DNA present in the .centromere is genetically inactive in nature.

3. Secondary constriction:

Other than primary constriction, there are one or a few constricted regions in the chromosomes. These are called secondary constrictions. Generally, the nucleolus is seen affixed to the secondary constriction.

During the telophase of cell division, this region helps to reorganise the nucleolus. Therefore, secondary constriction is also known as nucleolar organiser region or NOR.

4. Satellite:

In a few chromosomes, a bulb-shaped terminal portion is seen beyond the secondary constriction. This is called a satellite or SAT body. The chromosomes with SAT body are called SAT chromosomes.

5. Telomere:

The terminal portions of a chromosome are called telomeres. These are genetically inactive regions of a chromosome. During interphase, telomeres help in DNA replication.

It also prevents the joining of a chromosome with another and controls the ageing and death of a cell.

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Question 3. Draw the morphology of an ideal eukaryotic chromosome and label the following parts:

1. Chromatid,
2. Centromere,
3. Nucleolar organizer,
4. Telomere.

Answer:

Question 4. Classify chromosomes based on the position of the centromere. Describe each type.

Answer:

Classification of chromosomes based on the position of the centromere

Based on the position of centromere, chromosomes can be classified into the following types—

1. Metacentric chromosome,
2. Sub-metacentric chromosome,
3. Acrocentric chromosome and
4. Telocentric chromosome.

Description of different types of chromosomes:

Different types of chromosomes have been described below.

1. Metacentric chromosome:

In this type of chromosome, the centromere is located at its middle. The two arms appear almost identical. During anaphasic movement, this type of chromosome appears as the English letter ‘V’.

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2. Sub-metacentric chromosome:

The Centromere of this type of chromosome is located slightly away from the ie centre. The two arms are unequal in length; one arm is slightly longer than the other, tiling anaphasic movement, this type of chromosome appears as the English letter ‘L’.

3. Acrocentric chromosome:

In this type of chromosome, the centromere is located near one end of it. Here, one arm is very long and another one is very short. During anaphasic movement, this type of chromosome appears like the English letter J.

4. Telocentric chromosome:

This type of chromosome has its centromere at one terminal end. During anaphasic movement, this chromosome appears like the English letter ‘I’.

Question 5. Distinguish between

1. Chromosome and chromatid,
2. Centromere and centrosome.

Answer:

Differences between chromosome and chromatid

Differences between centromere and centrosome

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Question 6. Describe the chemical structure of chromosomes.

Answer:

Chemical structure of chromosome:

A eukaryotic chromosome is composed of nucleic acid (DNA and RNA), proteins (basic and acidic) and metallic ions like calcium (Ca²⁺), magnesium (Mg²⁺) etc. Eukaryotic chromosomes contain 90% DNA and histone proteins.

The remaining 10% comprises RNA and acidic (non-histone) proteins.

1. Deoxyribonucleic acid (DNA):

It is a double-stranded helically coiled self-replicating macromolecule, 88 of deoxyribose (pentose) sugars, nitrogenous bases and phosphate molecules. Physically, this molecule appears as a spiral staircase.

The handrail-like portion of this molecule PhyS1Cposed of pentose sugars and phosphates. The steps are made up of pairs of nitrogenous bases, each pair includes one purine and one pyrimidine. Purines are adenine (A) and guanine (G).

Pyrimidines are thymine (T) and cytosine (C) In DNA, adenine joins with thymine and guanine joins with cytosine with two and three weak hydrogen bonds respectively.

2. Ribonucleic acid (RNA):

It is a single-stranded macromolecule, having few loops along the length. RNA is composed of ribose sugars, phosphates and nitrogenous bases. Like DNA, RNA also includes adenine, guanine and cytosine but instead of thymine, it contains uracil (U).

3. Histone and non-histone proteins:

The basic proteins of chromosomes are known as histones. Due to their basic nature, they can easily combine with acidic DNA molecules to provide stability.

Five types of histones are seen in a chromosome. These are H1, H2A, H2B, H3 and H4. Besides these, a few acidic non-histone proteins are also present in chromosomes.

4. Metallic ions:

These include calcium (Ca²⁺) and magnesium (Mg²⁺) ions, which help to maintain the integrity of the chromosome.

Question 7. Distinguish between DNA and RNA

Answer:

Differences between DNA and RNA

Chapter 2 Continuity Of Life Chromosome Short Answer Type Questions

Question 1. State the relation between chromosomes and gene.

Answer:

The relation between chromosomes and gene:

A chromosome is a dense, coiled form of DNA and a gene is a specific sequence of DNA, that can be translated to form a particular protein, which can be expressed in an organism. The number of genes is constant in a particular chromosome.

Not only the number, in a particular chromosome the nature of the gene is also constant. If a particular portion of a chromosome will be deleted mistakenly then the particular gene of that region will also be deleted which leads to mutational abnormality.

Question 2. What is a chromosome?

Answer:

Chromosome:

Chromosome is the self-replicating thread or rod-shaped nucleoprotein structure, present within the nucleus of eukaryotic cells. Chromosome carries genes and thereby controls all features and activities of any organism.

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Question 3. What are autosomes?

Answer:

Autosomes:

Autosomes are the chromosomes, which are present in the nucleus of the cell and regulate all physical features of an organism. Out of 23 pairs of chromosomes in a human somatic cell, 22 pairs are autosomes.

Question 4. Write the name of any two structural parts of the eukaryotic chromosome.

Answer:

Two structural parts of eukaryotic chromo¬some are chromatids and centromere.

Question 5. Mention the types of chromosomes.

Answer:

Functionally, chromosomes can be classified into two types. These are—

1. Autosomes or Somatic chromosomes and
2. Allosomes or sex chromosomes.

Question 6. What are allosomes?

Answer:

Allosomes:

The chromosomes present in the nucleus other than autosomes which mainly carry the sex-determining factors, are called allosomes. Human allosomes are of two types—X and Y chromosomes.

Question 7. What is meant by homologous chromosomes?

Answer:

Homologous chromosomes:

In a diploid (2n) cell, all chromosomes are present in pairs. Both the chromosomes of a pair have identical length, and size and carry the same set .of genes.

Each of these pairs of chromosomes is called a homologous chromosome.

Question 8. What Is Chromatid?

Answer:

Chromatid:

During metaphase, each chromosome splits along the length into two identical thread-like portions, which remain attached to each other at a distinct constriction, called centromere. Each of these two filamentous parts of a chromosome is called a chromatid.

Question 9. What is Chromoneme?

Answer:

Chromoneme:

Chromonema filaments densely coil to form several equidistant bead-like structures serially aligned along its length. These dense granular structures are called chromomeres.

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Question 10. What is meant by chromatin reticulum?

Answer:

Chromatin reticulum:

The delicate network of very fine coiled, thread-like nucleoprotein structures, present in the nucleus of the cell, which shows affinity towards basic dyes, is called chromatin reticulum.

Before cell division, these chromatin reticular coils densely to take the shape of chromosomes.

Question 11. What is meant by primary constriction?

Answer:

Primary constriction:

The lightly stained, constricted part of a chromosome, at which the two chromatids remain attached, is called primary constriction. The region of primary constriction carries the centromere.

It is also the region where the spindle fibres bind during metaphase.

Question 12. What is meant by secondary constriction?

Answer:

Secondary constriction:

Apart from primary constriction, there may be one or few lightly stained constricted points, present on chromosomes. Each of these constrictions is called secondary constriction. The nucleolar organiser region (NOR) is associated with secondary constriction region.

Question 13. What is meant by NOR?

Answer:

NOR:

NOR stands for nucleolar organiser region. It is a chromosomal region around which the nucleolus forms. NOR includes active RNA genes which give rise to secondary constrictions of metaphase chromosomes.

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Question 14. What is meant by constitutive heterochromatin? Where does this occur?

Answer:

Constitutive heterochromatin:

The type of heterochromatin, which always remains within the nuclei of nil types of cells, is called constitutive heterochromatin.

Occurrence of constitutive heterochromatin:

This occurs in the centromere, telomere and nucleolar organiser regions.

Question 15. What is meant by facultative heterochromatin? Where does this occur?

Answer:

Facultative lieterochromatin:

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The type of heterochromatin, which occurs in certain cell types for a brief period of time, is called facultative heterochromatin.

Occurrence of facultative heterochromatin:

This occurs in the nucleus of human female somatic cells as Barr body.

Question 16. What is meant by coiled heterochromatin?

Answer:

Coiled heterochromatin:

In certain cells, during interphase, some heterochromatin fibres occur in coiled form. These are called coiled heterochromatin. These heterochromatin fibers help in gene regulation and are present equally in all cells.

Question 17. What is meant by haploid cells?

Answer:

Haploid cells:

The cells, in which all types of chromosomes occur in an unpaired state, are called haploid cells. The chromosome number of these cells is indicated as (n).

Example: Human spermatozoa and ova are haploid cells.

Question 18. What is meant by diploid cells?

Answer:

Diploid cells:

The cells, in which all types of chromosomes occur in the paired state, are called diploid cells. The chromosome number of these cells is indicated as (2n).

Example: Human somatic or body cells are diploid in nature.

Question 19. what are meant by 44XY and 44XX chromosomes?

Answer:

44XY and 44XX chromosomes:

In human somatic cells, there are 46 chromosomes. Out of these, male body cells have 44 autosomes and XY as two sex chromosomes whereas in females, diere are 44 autosomes and XX as two sex chromosomes.

Therefore, 44XY and 44XX constitute the chromosome number of a human male and female respectively.

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Question 20. Distinguish between primary and secondary constriction.

Answer:

Differences between primary and secondary constriction are—

Question 21. Distinguish between autosome and sex chromosome of humans based on the following features: Nature, Number.
Or,
Distinguish between autosome and allosome.

Answer:

Differences between autosome and allosome are—

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Question 22. What is meant by euchromatin?

Answer:

Euchromatin:

The loosely coiled chromatin fibres, which are lightly stained by basic dyes in a resting nucleus, carry active genetic material and take part in the synthesis of RNA, are called euchromatin. All functional genes of a cell are present in euchromatin.

Question 23. What is heterochromatin?

Answer:

Heterochromatin:

The densely coiled chromatin fibres, which are deeply stained by basic dyes and carry less genetic material are called heterochromatin. These chromatin fibres take part in regulating genes and maintaining chromosomal integrity.

Question 24. What is a gene?

Answer:

Gene:

The specific segment of a DNA molecule that acts as the structural and functional unit of heredity is called a gene. It carries the code for the synthesis of a particular protein within a living cell.

Genes are responsible for determining different characteristics of a living organism.

Question 25. What is locus?

Answer:

Locus:

Every gene is located in a specific position of a particular chromosome. This specific position of the gene on this particular chromosome is known as the locus of that gene.

Question 26. What is a nucleotide?

Answer:

Nucleotide:

The structural unit of a nucleic acid molecule, composed of one nitrogenous base, one pentose sugar and a phosphate group, is known as a nucleotide.

The number of nucleotides present in the nucleic acid conventionally determines the size of the nucleic acid.

Question 27. What is nucleoside?

Answer:

Nucleoside:

The structural subunit of a nucleic acid molecule, composed of one nitrogenous base and a pentose sugar, is known as a nucleoside. Phosphodiester bonds join several nucleosides one after another to form a nucleic acid strand.

Question 28. Distinguish between nucleoside and nucleotide.

Answer:

Differences between nucleoside and nucleotide are—

Question 29. What are histone proteins?

Answer:

Histone proteins:

The basic structural proteins, which bind to DNA to make it stable, are called histone proteins. There are five different histone proteins present in chromosomes. These are HI, H2A, H2B, H3 and 114.

Question 30. What are non-histone proteins?

Answer:

Non-histone proteins:

The acidic proteins associated with DNA molecules are known as non-histone proteins. These proteins help in the regulation of genes.

Question 31. What is meant by deoxyribonucleotide?

Answer:

Deoxyribonucleotide:

The structural unit of a DNA molecule, composed of one nitrogenous base, one deoxyribose sugar and a phosphate, is called deoxyribonucleotide.

Example:

Deoxyadenosine monophosphate, deoxyguanosine monophos¬phate, deoxycytidine monophosphate and deoxythymidine monophosphate.

Question 32. What is meant by ribonucleotide?

Answer:

Ribonucleotide:

The structural unit of an RNA molecule, composed of one nitrogenous base, one ribose sugar and a phosphate group, is called ribonucleotide.

Example: Adenosine monophosphate, guano-sine monophosphate, cytidine monophosphate and uridine monophosphate.

Question 33. What is the full form of DNA? Where does it occur?

Answer:

1. Full form of DNA: Deoxyribonucleic acid.
2. Occurrence of DNA: DNA occurs in chromosomes of the nucleus, mitochondria and plastids in eukaryotic cells. In prokaryotic cells, it occurs as the nucleoid. It also occurs in DNA viruses as genetic material.

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Question 34. Mention the components of DNA.

Answer:

DNA consists, of three components.

These components are—

1. Nitrogenous bases (such as adenine, guanine, thymine and cytosine),
2. Deoxyribose sugar and
3. Phosphate molecule.

Question 35. What is the full form of RNA? Where does it occur?

Answer:

1. Full form of RNA: Ribonucleic acid.
2. Occurrence: RNA occurs in nucleus ribosomes in eukaryotic cells. In prokaryotic cells, it occurs in ribosomes. RNA also occurs as genetic material in RNA viruses.

Question 36. Mention the components of RNA.

Answer:

RNA consists of three components.

These components are

1. Nitrogenous bases [such as adenine (a), guanine (g), cytosine (c) and uracil (u)],
2. Ribose sugar and
3. Phosphate molecule.

Question 37. Mention the types of RNA present in living cells.

Answer:

RNA is of three types.

These are—

1. Messenger RNA or mRNA,
2. Ribosomal RNA or rRNA and
3. Transfer rna or trna.

Question 38. What is a nucleosome? State its significance.

Answer:

Nucleosome:

In eukaryotes,, the basic structural organization of DNA packaging, where the DNA strand wound around the eight histone proteins (octamer) and looks like with a thread wrapped around a spool.

The eight histone proteins that are coiled by DNA are H2A, H2B, H3, and H4.

Significance Of Nucleosome:

Nucleosome is a packaging technique, that allows the DNA to be wrapped into the small area of a cell.

 

Chapter 2 Continuity Of Life Chromosome Very Short Answer Type Questions Multiple Choice Questions And Answers [Mcq]

Question 1. The term ‘chromosome’ was coined by—

1. Robert Hook
2. Darwin
3. Waldeyer-ITartz
4. Lamarck

Answer: 3. Waldeyer-ITartz

Question 2. The nucleolar organiser region refers to—

1. Primary constriction
2. Secondary constriction
3. Nucleolus
4. Nucleoplasm

Answer: 2. Secondary constriction

Question 3. At which region ot a chromosome is the centromere situated?

1. Primary constriction
2. Secondary constriction
3. Telomere
4. Satellite

Answer: 1. Primary constriction

Question 4. The number of types of histone proteins presents in chromosomes are—

1. Two
2. Three
3. Five
4. Six

Answer: 3. Five

Question 5. The chromosome, whose centromere is located at the middle, is known as—

1. Telocentric chromosome
2. Acrocentric chromosome
3. Metacentric chromosome
4. Sub-metacentric chromosome

Answer: 3. Metacentric chromosome

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Question 6. Chromosomes in human somatic cells are—

1. Diploid
2. Haploid
3. Tetraploid
4. Triploid

Answer: 1. Diploid

Question 7. Many mitotic divisions are required to give rise to 128 cells from a single cell.

1. 7 times
2. 14 times
3. 16 times
4. 32 times

Answer: 1. 7 times

Question 8. The nitrogenous base, that is absent in RNA molecules, is called—

1. Adenine
2. Guanine
3. Cytosine
4. Thymine

Answer: 4. Thymine

Question 9. Which of the following is not a structural component of DNA?

1. Deoxyribose sugar
2. Uracil base
3. Thymine base
4. Phosphoric acid

Answer: 2. Uracil base

Question 10. Identify the correct feature of amitosis cell division.

Occurs in germ mother cell of sexually reproducing organism

1. It is called indirect cell division
2. Chromosome and spindle fibre are formed
3. Chromosome and spindle fibre are not formed.

Answer: 2. It is called indirect cell division

Question 11. The number of chromatids present in a chromosome is—

1. 4
2. 2
3. 6
4. 8

Answer: 2. 2

Question 12. The number of chromosomes in a human germ cell is—

1. 46
2. 50
3. 23
4. 10

Answer: 3. 23

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Question 13. The chromosome, which has a centromere located at one end, is called—

1. Metacentric chromosome
2. Sub-metacentric chromosome
3. Acrocentric chromosome
4. Telocentric chromosome

Answer: 4. Telocentric chromosome

Question 14. The number of autosomes in the human somatic cells is—

1. 44
2. 46
3. 23
4. 22

Answer: 1. 44

Question 15. The number of autosomes in human germ cells is—

1. 44
2. 23
3. 22
4. 46

Answer: 3. 22

Question 16. The ratio of autosomes and X chromosomes in the somatic cell of a female is—

1. 44: 1
2. 44: 2
3. 23: 1
4. 44: 0

Answer: 2. 44: 2

Question 17. The ratio of autosomes and Y chromosomes in the somatic cell of a female is—

1. 44: 0
2. 44: 1
3. 44: 2
4. 23: 1

Answer: 1. 44 : 0

Question 18. The ratio of autosomes and X chromosomes in the somatic cell of a male is—

1. 44: 0
2. 44: 1
3. 44: 2
4. 23: 1

Answer: 2. 44: 1

Question 19. The point on primary constriction of a chromosome, that joins with a spindle fibre during cell division, is—

1. Chromomere
2. Centromere
3. Chromatid
4. Centrosome

Answer: 2. Centromere

Question 20. Any constriction on a chromosome, other than that carrying the centromere, is called—

1. Secondary constriction
2. Primary constriction
3. Main constriction
4. Second constriction

Answer: 1. Secondary constriction

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Question 21. The bulbous or swelled portion of a chromosome, beyond the secondary constriction, is called—

1. Stem body
2. Centromere
3. SAT body
4. Centrosome

Answer: 2. Centromere

Question 22. The main structural protein that forms the chromosome in eukaryotic cells is—

1. Albumin
2. Histone
3. Keratin
4. Globulin

Answer: 2. Histone

Question 23. A number of structural units, which combine to construct any ribonucleic and deoxyribonucleic acid molecule, is called—

1. Phosphate
2. Nitrogenous base
3. Pentose sugar
4. Nucleotide

Answer: 4. Nucleotide

Question 24. The term ‘gene’ was coined in 1909 by—

1. Remak
2. Farmer
3. Johannsen
4. Pasteur

Answer: 3. Johannsen

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Question 25. The nitrogenous base absent in DNA is—

1. Cytosine
2. Guanine
3. Adenine
4. Uracil

Answer: 4. Uracil

Question 26. The pair of parallel fibres present along the length of a chromosome is called—

1. Chromatid
2. Chromosphere
3. Chromonema
4. Chromomere

Answer: 1. Chromatid

Question 27. The percentage of DNA present in a chromosome is—

1. 50 %
2. 90%
3. 33.3%
4. 100%

Answer: 3. 33.3%

Question 28. The end portion of a chromosome is called—

1. Chromomere
2. Telomere
3. Centromere
4. Chromatid

Answer: 2. Telomere

Question 29. Each chromatid is composed of two parallel fibres along its length. Each of these fibres is called—

1. Chromatid
2. Chromosphere
3. Chromonema
4. Chromomere

Answer: 3. Chromonema

Question 30. Which of the following is the carrier of genes or genetic material?

1. Mesosome
2. Polysome
3. Chromosome
4. Ribosome

Answer: 3. Chromosome

Question 31. A purine nitrogenous base is—

1. Adenine
2. Cytosine
3. Thymine
4. Uracil

Answer: 1. Adenine

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Question 32. Which of these is not a pyrimidine nitrogenous base?

1. Thymine
2. Cytosine
3. Uracil
4. Guanine

Answer: 4. Guanine

Question 33. A nitrogenous base and a pentose sugar constitute a—

1. RNA
2. Nucleotide
3. Nucleoside
4. DNA

Answer: 3. Nucleoside

 

Chapter 2 Continuity Of Life Chromosome Answer In A Single Word Or Sentence

Question 1. Name the two terminal ends of a chromosome.
Answer: Telomeres

Question 2. Which amino acids are mostly present in histone protein?
Answer: Basic amino acids like lysine, arginine etc. are mostly present in histone protein.

Question 3. How many chromosomes are present in a human somatic cell?
Answer: A human somatic cell contains 46 chromosomes.

Question 4. Give an example of a haploid cell.
Answer: Germ cell or gamete (sperm and ovum)

Question 5. Give an example of a diploid cell.
Answer: Zygote

Question 6. Give an example of a triploid cell.
Answer: The endosperm of angiosperms plant is an example of a triploid cell.

Question 7. How many autosomes are there in a human spermatozoon?
Answer: Autosomes

Question 8. Mention the nitrogenous bases present in DNA.
Answer: The nitrogenous bases present in DNA molecules are adenine (A), guanine (G), cytosine (C) and thymine (T).

Question 9. Mention the nitrogenous bases present in RNA.
Answer: The nitrogenous bases present in RNA molecules are adenine (A), guanine (G), cytosine (C) and uracil (U).

Question 10. Name the nitrogenous base that is present in RNA instead of thymine.
Answer: Uracil

Question 11. Which component is present in nucleotide but absent in nucleoside?
Answer: Phosphate radical ‘is present in nucleotide but absent in nucleoside

Question 12. What is Kinetochore?
Answer:

Kinetochore

A disc-shaped protein structure associated with the centrosome of a chromosome, during cell division, to which microtubules of the spindle are attached.

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Question 13. Which portion of the chromosome is genetically inactive and takes deep stain?
Answer: Heterochromatin region of a chromosome is genetically inactive and takes deep stain.

Question 14. Who coined the term chromosome?
Answer: Von Waldeyer and Hartz

Question 15. What is Karyotype?
Answer:

Karyotype

Karyotype is a picture of all the chromosomes of an organism.

Question 16. Where do you find NOR?
Answer: NOR is present in between the centromere and telomere of the short arm of chromosomes 13, 14, 15, 21, 22.

Question 17. What is the distance between two nucleotides in the DNA?
Answer: 3.4A

Question 18. What is the full form of RNA?
Answer:

Form of RNA

Ribonucleic acid

Question 19. What is the structural unit of chromosomes?
Answer:

The structural unit of chromosomes

Nucleosome

Question 20. What is the function of Euchromatin?
Answer:

Function of Euchromatin

Euchromatin contains more DNA and contains the gene for controlling characters.

Question 21. Which structure bind chromosome with spindle fibre?
Answer: Centromere

Question 22. What are the types of chromatin?
Answer:

Types of chromatin

Chromatin is of two types heterochromatin and euchromatin.

 

Chapter 2 Continuity Of Life Chromosome Fill In The Blanks

Question 1. __________ carries the characteristic features of any organism from one generation to the next.
Answer: DNA

Question 2. DNA is a large __________ molecule.
Answer: Organic

Question 3. A gene is located on a specific __________ of a chromosome.
Answer: Locus

Question 4. The sex-determining chromosome or sex chromosome is also known as __________.
Answer: Allosome

Question 5. The y chromosome carries __________ genes.
Answer: Holandric

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Question 6. Gametes are __________ in nature.
Answer: Haploid

Question 7. The __________ is located at the junction of two chromatids.
Answer: Centromere

Question 8. Somatic cells is __________ in nature.
Answer: Diploid

Question 9. The tiny bead-like structures along the length of a chromonema are called __________.
Answer: Chromomeres

Question 10. NOR is the region of __________ constriction.
Answer: Secondary

Question 11. The terminal portion of the chromosome is called __________.
Answer: Telomere

Question 12. Adenine and guanine is __________ type of N2 base.
Answer: Purine

Question 13. N₂ base + phosphate + Pentose sugar = __________.
Answer: Nucleotide

Question 14. Nucleotide = Nucleoside + __________.
Answer: Phosphate

Question 15. Pentose sugar of RNA is __________.
Answer: Ribose

Question 16. The distance between two strands of DNA is __________.
Answer: 10A

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Question l7. Non-histone proteins contain __________ protein in high amounts.
Answer: Acidic

Question 18. Production of DNA from a DNA is called __________.
Answer: Replication

Question 19. Cytosine, thymine and uracil are __________ types of N₂ base.
Answer: Pyrimidine

Question 20. Chromosome with satellite is called __________.
Answer: Sat chromosome

Question 21. The region of the chromosome containing the gene is called __________.
Answer: Locus

Question 22. A chromosome is the condensed coiled structure of __________.
Answer: DNA

Question 23. Adenine is a __________ type of nitrogenous base.
Answer: Purine

Chapter 2 Continuity Of Life Chromosome State True Or False

Question 1. DNA is a small organic molecule.
Answer: False

Question 2. Within the nucleus, DNA lies in a linear fashion.
Answer: False

Question 3. DNA is a double-stranded molecule.
Answer: True

Question 4. DNA molecules loosely coiled protein molecules.
Answer: False

Question 5. Chromatin reticulum and chromosomes are two different states of coiling of the DNA molecule.
Answer: True

Question 6. The autosome number of a human somatic cell is 44.
Answer: True

Question 7. The number of sex chromosomes in human somatic cells is 2.
Answer: True

Question 8. Human spermatozoa are diploid in nature.
Answer: False

Wbbse Class X Life Science

Question 9. Human ova are haploid in nature.
Answer: True

Question 10. DNA is composed of ribose sugars.
Answer: False

Question 11. RNA is composed of deoxyribose sugars.
Answer: False

Question 12. Germ cells contain a haploid number of chromosomes.
Answer: True

Question 13. In DNA, adenine is linked with guanine by hydrogen bonds.
Answer: False

 

Chapter 2 Continuity Of Life Chromosome Match The Columns

Question 1.

Answer: 1. D, 2. C, 3. B, 4. A, 5. F, 6. E

Question 2.

Answer: 1. D, 2. A, 3. B, 4. C, 5. E, 6. G

 

Chapter 2 Continuity Of Life Chromosome Find The Odd One Out

Question 1. DNA, RNA, Protein, Gene
Answer: Protein

Question 2. Acentric chromosome, -Metacentric chromosome, Telocentric chromosome, Acrocentric chromosome
Answer: Acentric chromosome

Question 3. Arginine, Histidine, Lysine, Tryptophan
Answer: Tryptophan

Question 4. Chromatids, Chromomeres, Centrosome, Centromere
Answer: Centrosome

Question 5. DNA, Histone protein, Non-histone protein, Ribosome
Answer: Ribosome

Question 6. Adenine, Cytosine, Uracil, Guanine
Answer: Uracil

Question 7. Secondary Constriction, Klnetoebore, Mitochondria, Chromatid
Answer: Mitochondria

Question 8. Adenine, Guanine, Thymine, Vitamin
Answer: Vitamin

Question 9. Pentose sugar, Phosphate, N₂ base, Auxin
Answer: Auxin

Question 10. Active gene, HNA production, Heterochromnlin, Lossdensed
Answer: Heterochromnlin

 

Chapter 2 Continuity Of Life Chromosome Fill In The Blanks By Looking At The First Pair

Question 1. Human Autosome: 44:: Human sex chromosome: ______.
Answer: 2

Question 2. Human chromosome in the somatic cell:: 46:: Human chromosome in germ cell: ______.
Answer: 23

Question 3. Heterochromatin : Inactive :: Euchromalin : ______.
Answer: Active

Question 4. XY: Male sex chromosome:: XX: ______.
Answer: Female Sex chromosome

Question 5. Adenine: Purine:: Thymine: ______.
Answer: Pyrimidine

Question 6. Histone: Alkaline:: Non-histone: ______.
Answer: Acidic

Question 7. Nucleosome: Chromosome:: Nucleotide:: ______.
Answer: Nucleic acid

 

Chapter 2 Continuity Of Life Chromosome Among The Four Concepts Given, Three Of Them Belong To One Find That

Question 1. Centromere, Chromosome, Primary Constriction, Secondary Constriction
Answer: Chromosome

Question 2. Chromosome, DNA, Histone protein, Non-histone protein
Answer: Chromosome

Question 3. Pyrimidine, N₂ base, Adenine, Guanine
Answer: N2 base

Question 4. Pyrimidine, Cytoeine, Thymine, Uracil
Answer: Pyrimidine

Question 5. N₂ base, DNA, Phosphate, Deoxyrihose sugar
Answer: DNA

Question 6. Ribose sugar, Phosphate, N₂ base, RNA
Answer: RNA

Question 7. H2A, H2B,H4, Histone
Answer: Histone