Biology For Class X - Chapter No. 6 - Inheritance - Short Question Answers

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CHAPTER 6: INHERITANCE
B. Short Questions Answers

1. What is gene and how it works?
Ans: GENES:
Genes are the basic structure of Biological information. They are unit of inheritance which is copied and inherited to the next generation.
Gene is the small segment or a localized part of DNA which has a coded information to synthesize a protein which works as enzyme.

LOCATION:
They are found at a specific position on the chromosomes. This position is called Gene Locus (loci).

FUNCTION:
Each gene has a specific function:

• They are a small segment of DNA which has genetic information in the form of code to synthesize a protein.
• The coded information may change due to genetic variation caused by mutation.
• The variation gives rise to alternative forms called alleles or allomorph.
• All the inherited characters are determined by genes which are transmitted from generation to generation.

2. Define following terms:
(a) Homologous Chromosome
(b) Heterologous Chromosome
(c) Dominant allele
(d) Allele
(e) Recessive allele
(f) Homozygous
(g) Heterozygous
(h) Parental generation
(i) Filial one Generation
(j) Second Filial Generation
(k) Phenotype
(l) Genotype
(m) Heredity
(n) Genetics
(o) Inheritance
(p) Variations
Ans: (a) Homologous Chromosome:
Two chromosomes which are similar in their shape, size and position of centromeres and are present in same cell are called homologous pair of Chromosomes.

(b) Heterologous Chromosome:
A heterologous chromosome is a chromosome that contains different set of genes for a given trait.

(c) Dominant allele:
The factor (gene) which express and masks the expression of other factor in heterozygous condition is said to be Dominant factor. Mendel represent it with capital letter like T for tall.

(d) Allele:
The alternative form of gene developed as a result of variation is called allele or allomorph.

(e) Recessive allele:
The factor which is unable to express or masked in heterozygous condition is said to be recessive. It represents by small letter of same alphabet like t for small (dwarf).

(f) Homozygous:
An individual having same factors (allele) of a trait called homozygous. For example, TT (factor for tallness).

(g) Heterozygous:
An individual having different factors of a trait called heterozygous. For example, Tt (factors of tallness and dwarfness both).

(h) Parental generation:
The original true breeding organisms were called parental generation or P1 by Mendel.

(i) Filial one Generation:
The offspring of true breeding organism were called First Filial Generation or F1.

(j) Second Filial Generation:
The offspring of filial one generation produced by crossing self-fertilization were called Second Filial generation or F2.

(k) Phenotype:
It is the physical appearance of the trait on the basis of inherited genes like tall, dwarf, round seed, wrinkled seed etc.

(l) Genotype:
The genetic makeup or genic constitution of a trait like TT, Tt, tt etc.

(m) Heredity:
The characteristics of the offspring’s to resemble their parents is called heredity.

(n) Genetics:
The branch of biology which deals with the study of heredity and Variations is called genetics.

(o) Inheritance:
The process by which characters are transmitted from parents to off springs is called inheritance.

(p) Variations:
The differences in characters such as height, colour etc among individual of same species are called variations.

3. Which of the phenomena of inheritance is there where both factor express in heterozygous condition.
Ans: INCOMPLETE DOMINANCE OR PARTIAL DOMINANCE:
The phenomenon of inheritance where both alleles of a trait express in heterozygous condition and their expression get blended to produce new phenotype is called incomplete dominance or partial Dominance.

4. List out the factors which are involved in theory of natural selection.
Ans: THEORY OF NATURAL SELECTION:
Charles Darwin a naturalist Englishman proposed the Theory of Natural selection as a mechanism for evolution in the year 1859, through his “Origin Of Species”.

FACTORS WHICH ARE INVOLVED IN NATURAL SELECTION:
The main factors involved in his theory are as follows:
1. Over Production:
Living organisms reproduce rapidly so that the number of their offspring could increase rapidly. Overproduction of offspring is the idea that species produce far more offspring than an environment can support.

2. Struggle for Existence:
The concept of the struggle for existence concerns the competition or battle for resources needed to live. Due to the limited available resources of food, shelter, etc. the offspring of species compete not only with each other but also with the members of different species to share these resources. In this struggle a large number of individuals of each species are eliminated. As a result the population remains stable.

3. Heritable Variation:
The ability of species to obtain resources and withstand environmental extremes are referred as minor variations. Those individuals with heritable traits better suited to the environment will survive than less fit individuals who will vanish.

4. Natural selection:
Nature selects the fittest individuals to survive and reproduce. Therefore only the favourable variations are preserved through their inheritance to new young ones.

5. Relate artificial selection with natural selection.

Ans: RELATION OR DIFFERENCE BETWEEN NATURAL AND ARTIFICIAL SELECTION:

NATURAL SELECTION	ARTIFICIAL SELECTION
Natural selection is a process of adaptation by an organism to the changing environment by bringing selective changes to its genotype or genetic composition.	Artificial selection, also called selective breeding, is the process where humans identify desirable traits in animals and plants and use these traits to develop desirable phenotypic traits by breeding.
Natural selection is a natural process.	Artificial selection is an artificial or human-made process.
Natural selection takes place in natural populations within natural conditions.	Artificial selection takes place in domesticated populations put together by humans.
The chances of survival of a fit organism increase as a result of natural selection.	The chance of survival of an organism might be at risk if not performed correctly.
Natural selection is a slow process that completes after many generations.	Artificial selection is a faster process that completes within days or weeks with more apparent effects.
Natural selection is not as controlled as artificial selection as natural processes control it.	Artificial selection can be more controlled as humans control it.
Natural selection might occur on all organisms living on the earth.	Artificial selection can be selective and can be performed on selected groups of animals and plants.
Natural selection is based on the adaptive characteristics of animals.	Artificial selection is based on the desirable characters selected by humans.
Only beneficial or favorable traits are inherited over the successive generations by natural selection.	Artificial selection only allows the selected traits to be passed through successive generations.
Natural selection affects the entire population of a species.	Artificial selection only affects the selected individuals.
Natural selection results in a large amount of biological diversity.	Artificial selection only brings desirable changes and desirable traits and brings a decrease in genetic diversity.
Natural selection facilitates speciation and evolution over many generations.	Artificial selection doesn’t facilitate evolution.
Natural selection exerts on a wide-scale on the natural environment.	Artificial selection exerts only on selected individuals that are economically important.
Hybrid vigor is seen in offspring after natural selection.	Hybrid vigor is lost during artificial selection due to the preservation of desired traits.
Natural selection is a natural process, so no human effort is required.	The artificial selection might be labor-intensive and expensive.
After natural selection, the proportion of heterozygous genotype becomes high.	After artificial selection, the proportion of homozygous genotype becomes high.
Some examples of natural selection include the selection of long-necked giraffes and the changes in the size and shape of beaks of birds according to their feeding habits.	Some examples of artificial selection include dog breeding to produce new breeds of dogs and cross-breeding in cash crops like wheat and rice.

6. How coiling of long DNA is coiled in very small chromosome and nucleus of cell?
Ans: If we gently disrupt a eukaryotic nucleus and examine the DNA with an electron microscope, we find that coiling of long DNA is coiled in very small chromosome and nucleus of cell. It is because the histone is positively charged while DNA is negatively charged. This beads of histone and DNA is called nucleosome. When the string of nucleosomes wraps up into high order coil called super coil. This super coiled chromomers form chromosome.

 
7. Define the species which have similarities in features? 

Ans: Species are closely interrelated in some ways. They have many features in common.

For instance there are fundamental similarities in their chemical structure . Not only in chemistry, there exist similarities in morphology also.
Example: Such as rats with mice, turtle with tortoise, frog with toad etc.

8. Define evolution and organic evolution?
Ans: EVOLUTION:
Evolution is a process where descends become better than ancestors.

ORGANIC EVOLUTION:
Organic evolution explain that present day living things are modified from simple ancestral forms during the course of time through a gradual and continual process of modifications.