Matric Notes Biology Class 10th Ch 15 Inheritance Extra Short and Long Questions

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Q1: Define the following terms. Genetics, Heredity, Variation, Inheritance.

Ans: Genetics:- Genetics is the study of genes and their behaviour.

The branch of biology which deals with the study of heredity and variation is called genetics.

Heredity: The characteristics of parents which are transferred to their offspring, and similar among offspring and parents is called heredity.

Variation: The differences among offspring and their parents is known as variation.

Inheritance: The process by which the characters are transferred from parents to offspring is known as inheritance.

Q2: Describe chromosomes.

Ans: Chromosomes:-

1. A chromosome is a thread like structure in the nucleus of the cell.
2. Chromo means color and Soma means body.
3. Chromosomes was discovered by Waldeyer in 1876.
4. In prokaryotic cells chromosomes consist entirely of DNA and are not enclosed in a nuclear membrane.
5. In eukaryotic cells they are found within the nucleus and are composed of chromatin material which is chemically DNA and proteins.
6. Chromosomes is the name given to that structure as they readily absorb dyes and become colored.
7. In eukaryotic cells number of chromosomes is specific e.g. human has 46 chromosomes in each somatic cell, potato has 48, fruit fly or drosophila has 8 etc.
8. The term chromosomes are usually reserved for the structure when it is condensed and readily visible during cell division. Another times the chromosomes appears as a fibrous structure called chromatin network.

Q3: Describe chromatin material

Ans: Chromatin material:-

1. Chromosomes are composed of chromatin material.
2. Chromatin is the complex combination of protein and nucleic acid (DNA & RNA).
3. The major components of chromatin are
4. DNA
5. Histone protein
6. The unit of chromatin material in nucleosome.

Structure of nucleosome:-

1. Nucleosomes are the unit of chromatin material which is arranged in the form of beads in a linear order.
2. Each nucleosome consists of two main component i.e. a. 200 nucleotides of double DNA b. 8 Histone proteins
3. Histone proteins from core of nucleosome and about 1nm in diameter.
4. The histone proteins which are composed of 8 molecules form an octamere, around which 200 nucleotides of DNA is wrapped to form a super helix.
5. The two turns of DNA are sealed by another type of histone protein (H1).
6. Histones are positively charged due to large number of basic amino acids like organism and line.
7. Due to positive charge, histones are strongly attracted by negative charged phosphate group of DNA.
8. Histones core promote and guide the coiling of DNA.
9. This arrangement shows the knobby appearance of chromatin fiber.

Q4: Define locus.

Ans: Locus:- The location of a gene on chromosome is known as locus.

Loci: Its plural is loci.

Q5: What is gene and alleles?

Ans: Gene:-

• A gene is the fundamental physical and functional unit of heredity.
• A gene is an individual element of a genome.
• Genes are some part of DNA which can determine a character.
• Gene is a group of nucleotides which as code for protein synthesis.

Alleles:-

• The alternate form of genes on homologous chromosomes is called allele.
• Variations between the same genes are also called allele which may also be called as allelic variation.
• Alleles are originated by mutation.
• Mutations are changes in the ends taking place during gene replication.

Q6: Describe the type of genotype?

Ans: There are two types of genotype:

1. Homozygous
2. Heterozygous

Q7: What do you know about homozygous?

Ans: Homozygous The combination of the alleles of gene pair is called genotype. When a gene pair has the same genes, the genotype is called homozygous.

Q8: What do you know about heterozygous?

Ans: Heterozygous The combination of the alleles of gene pair is called genotype. The genotype in which the gene pair has the different alleles, is called heterozygous.

Q9: What do you about dominant allele?

Ans: Dominant allele:- In the heterozygous genotype one allele may mask the working of the other allele, such an allele is called the dominant allele.

Q10: What do you about recessive allele?

Ans: Recessive allele:- The allele which is masked (not expressed) is called a recessive allele.

Q7: Describe the role of genes in protein synthesis.

Ans: Role of genes in protein synthesis: Genes help in the synthesis of protein with the help of RNA and DNA steps. Protein synthesis takes place in the following two major steps which is called the central dogma of life.

i. Transcription
ii. Translation

i. Transcription:

1. Transcription is the process during which DNA prepare messenger (mRNA).
2. The two DNA stands unzip from each other like replication of DNA.
3. A single strand of mRNA is made by pairing of mRNA bones with DNA nucleotide bases in messenger mRNA uracil (I) make pair with adenine “A” of DNA because thiamine “T” is not present.

ii. Translation:

1. Translation is a process during which mRNA make tRNA and sequence of various amino acids (proteins).
2. When the mRNA is manufactured, it leaves the cell nucleus and travels toward ribosome.
3. In the ribosome mRNA code is translated into tRNA code, which in turn transferred into a protein sequence.
4. During this process each set of 3 mRNA bases will pair with complimentary 3 tRNA bases.
5. The mRNA bases triplet is called “codon” and the complimentary tRNA base triplet is called “anticodon”.
6. Each tRNA is specific to amino acid, so by adding of tRNA, amino acid are linked together by peptide bones.
7. Various sequences of amino acids make a protein which is released by tRNA.

Q8: Describe contribution of Gregor Mendel in field of biology.

Ans: Contribution of Gregor Mendel:-

1. Gregor Mendel is regarded as “father of genetics” due to formulation of three laws of inheritance.
2. He was an Austrian monk and performed his experiments on pea plant.
3. He discovered the fundamental mechanism of heredity.
4. Mendel conducted genetic experiments by using simple genetic system.
5. He examined well-defined traits and discovered the following three laws of inheritance. a. Law of Dominance. b. Law of segregation. c. Law of independent assortments. These law (principles) are the corner stone of modern genetics.

Q9: Why Mendel chose pea plant for his experiment?

Reason: Mendel had chosen pea plant for his experiments due to following reasons.

i. Pea plant are easy to grow.
ii. They are fairly resistant to pests.
iii. Pea is a short duration plant and completes its life cycle in 3 months.
iv. Pea plant has a large number of varieties.
v. Pea plant is 100% self-pollinated but cross pollination can also be performed.

Q10: Write the characters (trait) of pea plant which were studied by Mendel.

Ans: seven characters of pea plant studied by Mendel:

Mendel studied the following seven characters for his research work.

Character (traits)	Dominant	Recessive
1. Seed shape	Round	Wrinkled
2. Seed colour	Yellow	Green
3. Flower colour	Violet	White
4. Pod shape	Full	Constricted
5. Pod colour	Green	Yellow
6. Flower position	Axial	Terminal
7. Stem height	Tall	Dwarf
-	-	-
-	-	-

Q11: Describe Mendel law of Dominance. Also draw the checker board.

Ans: Mendel law of dominance: “When two contrasting characters are brought together in cross, only the dominant character will appear in F1 generation”.

Explanation:-

1. When Mendel crossed a pure breed tall plant with a pure breed short plant, all of the offspring in the first generation (the F1 generation) were tall.
2. The same thing happened with the other pairs of contrasting traits studied.
3. Hybrid offspring in the first generation always showed just one of the two forms.
4. Mendel used the word dominant to describe the form that dominated the phenotype, or physical appearance, in F1 generation.
5. The other form he called recessive, because the characteristic receded into the background in the F1 generation.
6. In each F2 generation some of the recessive forms of the traits which had visibly disappeared.
7. Approximately one fourth of the F2 plants exhibited the recessive characteristics, and three fourths continued to exhibit the dominant form of the trait, like their F1 parents.
8. This 3:1 ratio of dominant to recessive remained consist in all of the F2 offspring.

Q12: Describe Mendel law of segregation with the help of checker board.

ANS: Mendel law of segregation: “In individuals the genes (alleles) exist in pairs, but during gametes formation they separate or segregate randomly”.

Explanation:-

1. Mendel discovered the mating a tall pea and a short pea would produce an F1 generation of only tall pea plants.
2. He wondered, were those offspring tall pea plants really identical to their tall parents, or might they still contain some element of their short parents.
3. Mendel let all seven types of hybrid F1 generation plant self-pollinate, producing what he called the F2 (second filial) generation.
4. In each F2 generation some of the recessive form of the traits which had visible traits reappeared.
5. Approximately one fourth of the F2 plants exhibited the recessive characteristic, and three fourths continued to exhibit the dominant form of the trait, like their F1 parents.
6. This 3:1 ratio of dominant to recessive remained consistent in all of the F2 offspring.

Q13: What are the types of variation?

Ans: Types of variation:- Variation is of two types i.e.

i. Continuous variation.
ii. Discontinuous variation.

i. Continuous variation:

1. These type of variations deals with a variety of phenotypes ranging from one extreme to the other, which have a lot of intermediate characters between the two extreme of a character.
2. The genetic reason behind this is the presence of many genes controlling a single character.
3. So, when there are more than one gene controlling the expression of a character then it show the additive affect.
4. All these characters are controlled by many genes and because of this reason expression depends upon the additive effects of these genes.
5. Once of the important aspects of continuous variations is the role of environment in the expression of these variations. IQ needs proper education and training which is provided by the environment and if a child is provided with these basic facilities he/she will be in better position to use his/her IQ.

Examples:

1. Skin color in human is controlled by several genes and more dark genes in an individual will result in the darker skin color. Some is the effect of certain other characters like height, weight and IQ etc.
2. The accumulation of more genes for tallness will result in tall individual and so on.

ii. Discontinuous variation:

1. These type of variations deal with a few clear cut phenotype.
2. These types of characters are controlled by few genes and genes do not show.
3. Additive effect: These variations are not modified by environment changes.
4. In pea plant all the seven characters studied by Mendel were of discontinuous variation.
5. The phenotype expressed were clear cut like for height character, there were either tall plants or short no intermediate.
6. Likewise the flower color was either violet or white.

Example:

1. Human blood group is an example of discontinuous variation. There are only 4 types of blood group which are blood group A, B, AB and O. There is no other possibilities and there are no values in between.
2. Likewise in gender normal possibility is either male or female.

Q14: Describe the DARWIN’s THEORY OF NATURAL SELECTION regarding evolution.

Ans: Darwin’s theory of natural selection:

According to Darwin theory of natural selection evolution occur by the following.

• Over production.
• Competition.
• Survival of the fittest
• Natural selection
• Reproduction
• Speciation.

Over production: It is the general trend in living organisms that they tend to reproduce indefinitely, but resources in environment are not sufficient for such a large population. Among individual of a population there are genetic variation.

Competition: As a resources in the environment are limited, to get sufficient resources to live, organisms compete with one another. The individual who survive are the ones best adapted to exist in their environment due to possession of variations that best suit them to their environment.

Survival of the fittest: The variation of the organisms with in the species increases the likelihood that at least some member of the species will survive under changed environmental condition. So, survival of best fitting the environment will lead to increase the individual of population with well adapted variation.

Natural selection: Those organisms with poor adaptability will be excluded from the environment. So, nature select those organisms who have best adapted with changing environment is called natural selection.

Reproduction: Variation assist or hinder individuals in their struggle for survival. The best adapted individual survive and reproduce, passing on the favorable variations to their offspring.

Speciation: As time and generations continue, adaptation are passed on generation after generation and after many generations through continuous selection: new species may evolve from a common ancestor.

Small differences between parents and offspring can accumulate in successive generation so that descendants become very different from their ancestors.

Q15: Write an example of natural selection.

Ans: Example of natural selection: An example of natural selection is the evolution of pesticides resistance in insect species. Pesticides are poison used to kill pest (harmful insect). When a new type of pesticides is used, a relatively small amount may kill 99% of pests. But later sprayings are less and less effective.

For example: In the early 1950s, a pesticides was introduced to control flour beetles. Only a small concentration of pesticides treatments had variation that enabled them to resist the chemical attack. Their offspring inherited the variation for pesticides resistance. In each generation, the percentage of pesticides-resistant individuals increased in population. Thus, the population underwent an evolution that resultant in adaptation against the pesticides. Today, the flour beetles are not killed even by very high concentrations of the same pesticides.