Selina Class 10 Biology Solutions

Selina Concise Biology Class 10 ICSE Solutions Genetics Some Basic Fundamentals

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Selina Concise Biology Class 10 ICSE Solutions Genetics- Some Basic Fundamentals

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 10 Biology Chapter 3 Genetics Some Basic Fundamentals. You can download the Selina Concise Biology ICSE Solutions for Class 10 with Free PDF download option. Selina Publishers Concise Biology for Class 10 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

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Selina ICSE Solutions for Class 10 Biology Chapter 3 Genetics – Some Basic Fundamentals

Exercise 1

Solution A.1.
d) Ascaris

Solution A.2.
a) 3 : 1

Solution B.1.
(a) – (iii) Study of laws of inheritance of characters
(b) – (v) Chromosomes other than the pair of sex chromosomes
(c) – (iv) A gene that can express when only in a similar pair
(d) – (ii) The alternative forms of a gene
(e) – (i) Chromosomes similar in size and shape

Solution B.2.
Lion, tiger, domestic cat (Any two)

Solution B.3.
Colour-blindness, Thalassaemia, Sickle cell anaemia and Haemophilia (Any two)

Solution B.4.
Homozygous dominant – RR
Homozygous recessive – rr

Solution C.1.

(a)

Phenotype Genotype
The observable Characteristic which is genetically controlled is called phenotype. The set of genes present in the cells of an organism is called its genotype.

(b)

Character Trait
Any heritable feature is called a character. The alternative form of a character is called trait.

(c)

Monohybrid cross Dihybrid cross
It is a cross between two pure breeding parent organisms with different varieties taking into consideration the alternative trait of only one character. It is a cross between two pure breeding parent organisms with different varieties taking into consideration the alternative trait of two characters.

Solution C.2.
The characteristics of a species such as physical appearance, body functions and behavior are not only the outcome of chromosome number, but these depend on the genotype of every organism. That means the set of genes present in the organisms may very and therefore lion, tiger and domestic cat have the same number of 38 chromosomes, their characteristics (like different appearances) are the result of the genes located on the chromosomes.

Solution C.3.

Character Dominant trait Recessive trait
Flower Colour Purple White
Seed Colour Yellow Green
Seed Shape Round Wrinkled
Pod Shape Inflated Constricted
Flower Position Axial Terminal

(Any 3)

Solution C.4.

  • Colour-blindness is caused due to recessive genes which occur on the X chromosome.
  • Males have only one X chromosome. If there is recessive gene present on X chromosome, then the male will suffer from colour-blindness.
  • Females have two X chromosomes. It is highly impossible that both the X chromosomes carry abnormal gene. Hence, if one gene is abnormal and since it is recessive, its expression will be masked by the normal gene present on the other X chromosome. Females are unlikely to suffer from colour-blindness.

Solution C.5.
Phenotypic Ratio – 3 (Black Fur) :1 (Brown Fur)
Genotypic Ratio – 1(Homozygous Black Fur):2 (Heterozygous Black Fur): 1 (Homozygous Brown Fur)

Solution D.1.

(a)  Heterozygous:  The condition in which a pair of homologous chromosomes carries dissimilar alleles for a particular character.

For example –

  1. A daughter (XXo) from a normal homozygous mother for colour vision (XX) and a colour blind father has one normal and one defective allele (XoY).
  2. Certain tongue rollers are heterozygous with Rr genotype.

(b)  Homozygous:  The condition in which a pair of homologous chromosomes carries similar alleles for a particular character.

For example –

  1. A colorblind daughter (XoXo) will have both the X chromosomes with defective alleles.
  2. A non-roller will have rr (homozygous) genotype.

(c)  Pedigree Chart:  A pedigree chart is a diagram that shows the occurrence and appearance or phenotypes of a particular gene or organism and its ancestors from one generation to the next. In the pedigree chart, males are shown by squares and females by circles.

Solution D.2.
Mendel’s laws of inheritance are:

  1. Law of Dominance: Out of a pair of contrasting characters present together, only one is able to express itself while the other remains suppressed. The one that expresses is the dominant character and the one that is unexpressed is the recessive one.
  2. Law of Segregation : The two members of a pair of factors separate during the formation of gametes. The gametes combine together by random fusion at the time of zygote formation. This law is also known as ‘law of purity of gametes’.
  3. Law of Independent Assortment: When there are two pairs of contrasting characters, the distribution of the members of one pair into the gametes is independent of the distribution of the other pair.

Solution D.3.

    • The sex of the child depends on the father. The egg contains only one X chromosome, but half of the sperms contain X-chromosome whereas the other half contains Y-chromosome. It is simply a matter of chance as to which category of sperm fuses with the ovum and this determines whether the child will be male or female.
    • If the egg fuses with X-bearing sperm, the resulting combination is XX and the resulting child is female.
    • If the egg fuses with Y-bearing sperm, the resulting combination is XY and the resulting child is male.
      Selina Concise Biology Class 10 ICSE Solutions Genetics Some Basic Fundamentals image - 1

Solution E.1.

Selina Concise Biology Class 10 ICSE Solutions Genetics Some Basic Fundamentals image - 2

Solution E.2.
(a) Black
(b) No

Solution E.3.

Selina Concise Biology Class 10 ICSE Solutions Genetics Some Basic Fundamentals image - 3

Solution E.4.
(a) Father
(b) Two sons and three daughters
(c) The child 1 (daughter) is colour blind
(d) X chromosome
(e) Haemophilia

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Selina Concise Biology Class 10 ICSE Solutions Cell Cycle, Cell Division and Structure of Chromosomes

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Selina Concise Biology Class 10 ICSE Solutions Cell Cycle, Cell Division and Structure of Chromosomes

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 10 Biology Chapter 2 Cell Cycle, Cell Division and Structure Of Chromosomes. You can download the Selina Concise Biology ICSE Solutions for Class 10 with Free PDF download option. Selina Publishers Concise Biology for Class 10 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

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Selina ICSE Solutions for Class 10 Biology Chapter 2 Cell Cycle, Cell Division and Structure of Chromosomes

Exercise 1

Solution A.1.
(b) DNA and Histones

Solution A.2.
(c) Coloured bodies

Solution B.1.
(a) – Nucleotides.
(b) – Nucleosome.
(c) – Hydrogen Bond.
(d) – Phosphate, Sugar and Nitrogenous base.

Solution C.1.
Chromatin fibre is unfolded, uncondensed, extended DNA. It is only visible when cell under goes division whereas chromosomes are condensed DNA and they are visible when the cell is divided.

Solution C.2.
Rungs of DNA ladder is made of nitrogenous bases which includes Adenine (A), Guanine (G), Cytosine (C) and Thymine (T).

Solution C.3.
(a) The four nitrogenous bases in the DNA ladder are Guanine, Thymine, Adenine and Cytosine.
(b) Genes are specific sequences of nucleotides on a chromosome.
(c) A nucleotide is composed of a phosphate, sugar (pentose) and a nitrogenous base.
(d) Nucleosomes are groups of histone molecules surrounded by DNA strands.
(e) If there are 46 chromosomes in a cell there will be 46 chromatin fibres inside the nucleus during interphase.

Solution D.1.
Nucleosome is basic structural unit of DNA. Each strand of DNA winds around a core of eight histone molecules. This core can be imagined like a football, around which a long rope is wound with one or two loops. Each such complex structure is called a nucleosome. A single human chromosome may have about a million nucleosomes.

Solution D.2.
Gene is a structural and functional unit of heredity and variations. Genes are specific sequences of nucleotides on a chromosome that encode particular proteins which express in the form of some particular feature of the body. In other words, gene is the DNA segment of the chromosome and it controls the expression of characteristics.

Solution E.1.
(a) 2
(b) 2 on each strand
(c) 1- Phosphate, 2- Sugar, 3- Bases, 4- Hydrogen Bond, 5 – Base
(d)Nucleotide

Solution E.2.
B, C and A.

Exercise 2

Solution A.1.
(c) both ovary and testis

Solution A.2.
(c) Anaphase, telophase

Solution A.3.
(c) DNA

Solution B.1.
Cell A: 2
Cell B: 4

Solution B.2.
(a) – Metaphase.
(b) – Telophase.
(c) – Prophase.
(d) – Anaphase.

Solution B.3.
(a) Somatic (body).
(b) Four.
(c) Reproductive.
(d) 23 and 23.
(e) Haploid.
(f) Centriole.

Solution C.1.

(a) A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences whereas a chromatid is one of the two copies of DNA making up a duplicated chromosome, which are joined at their centromeres, for the process of cell division (mitosis or meiosis).

(b) The centrosome is an area in the cell where microtubules are produced. Within an animal cell centrosome, there is a pair of small organelles called the centrioles. During animal cell division, the centrosome divides and the centrioles replicate (make new copies) whereas each chromosome in its condensed form consists of two chromatids joined at some point along the length. This point of attachment is called centromere.

(c) An aster is a cellular structure shaped like a star, formed around each centrosome during mitosis in an animal cell whereas spindle fibers are aggregates of microtubules that move chromosomes during cell division.

(d) A haploid cell is a cell that contains one complete set of chromosomes. Gametes are haploid cells that are produced by meiosis whereas a diploid cell is a cell that contains two sets of chromosomes. One set of chromosomes is donated from each parent.

Solution C.2.
In this statement, reduction means that the number of chromosomes are reduced to half i.e. out of the 23 pairs of chromosomes in humans, only single set of chromosomes are passed on to the sex cells.

Solution C.3.
Gametes must be produced by meiosis for sexual reproduction because the numbers of chromosomes are reduced to half during meiosis and then the normal diploid numbers of chromosomes are regained during the process of fertilization.

Solution C.4.

(a) F; Surface skin cells are continuously lost and replaced by the underlying cells.

(b) T; All types of human cells, have 46 chromosomes. The only type of cell which does not have 46 chromosomes are the sex cells, which have only half of the number, so they have 23 chromosomes. The egg cell is a sex cell (found in female). So it must have 23 chromosomes.

(c) F; Nuclear membrane disappears in Prophase itself, however it reappears during Telophase.

(d) T; Mitotic cell division can be a mode of asexual reproduction in unicellular organisms like amoeba or yeast cell which divides into two daughter cells.

(e) T; While the maternal and paternal chromosomes are separating, the chromatid material gets exchanged between the two members of a homologous pair resulting in genetic recombination.

Solution D.1.
a.

  1. Centromere
  2. Spindle fibres
  3. Chromatids

b. The stage described in the diagram is the late anaphase of mitosis in an animal cell. The stage can be identified by the presence of separated chromatids which are found at the two poles of the cell. The appearance of the furrow in the cell membrane classifies the stage as the late anaphase.
c. The division is mitotic division and this kind of cell division occurs in all the cells of the body except for the reproductive cells.
d. The stage before anaphase is metaphase.
Selina Concise Biology Class 10 ICSE Solutions Cell Cycle, Cell Division and Structure of Chromosomes image - 1

Solution D.2.

Selina Concise Biology Class 10 ICSE Solutions Cell Cycle, Cell Division and Structure of Chromosomes image - 2

Solution D.3.
The exchange of chromatids between homologous chromosomes is called crossing-over. This is the process by which the two chromosomes of a homologous pair exchange equal segments with each other.
Crossing over occurs in the first division of meiosis. At that stage each chromosome has replicated into two strands called sister chromatids. The two homologous chromosomes of a pair synapse, or come together. While the chromosomes are synapsed, breaks occur at corresponding points in two of the non-sister chromatids, i.e., in one chromatid of each chromosome.
Since the chromosomes are homologous, breaks at corresponding points mean that the segments that are broken off contain corresponding genes, i.e., alleles. The broken sections are then exchanged between the chromosomes to form complete new units, and each new recombined chromosome of the pair can go to a different daughter sex cell. It results in recombination of genes found on the same chromosome, called linked genes that would otherwise always be transmitted together.

Solution D.4.

(a) Late prophase. Because the nuclear membrane and nucleolus have disappeared.
(b) Centrioles.
(c)

  1. Centromere
  2. Chromatids.
  3. Spindle fibre.

(d) Metaphase. The centromeres of chromosomes are drawn to the equator by equal pull of two chromosomal spindle fibres that connects each centromere to the opposite poles, forming a metaphasic plate.

(e)

Mitosis Meiosis
(i) Two daughter cells are produced. (i) Four daughter cells are produced.
(ii) It is equational division i.e. the number of chromosome in the daughter cells or parent cells remains the same. (ii) It is reductional division i.e. the number of chromosomes is reduced to half in the daughter cells.

Solution D.5.
(a) Metaphase.
(b) 4.
(c) A – Animal
B – Animal
C – Plant
(d) (iv)

Solution D.6.
(a) This is an animal cell because:

  1. The outline is circular (in plants it would be angular {rectangular or polygonal}) and cell wall is absent.
  2. Centrosomes on centrioles are present. (These are found only in animal cells)

(b) Mitosis.
(c) B, C, D, A.
(d) Interphase.
(e)
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