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(c) The two genes are linked and present on the some chromosome

(d) Polygenic inheritance

(c) Pod length

(b) Dominant epistasis

(c) (i), (iii),(iv) are correct

He choose pea plant because, 

1. It is an annual plant and has clear contrasting characters that are controlled by a single gene separately. 

2. Self-fertilization occurred under normal conditions in garden pea plants. Mendel used both self-fertilization and cross fertilization. 

3. The flowers are large hence emasculation and pollination are very easy for hybridization.

(a) 1856 – 1863

Mirabilis Jalapa (4 o’ clock plant). Incomplete dominance ratio is 1 : 2 : 1

(b) Intermediate phenotype

Mendel’s experiments were rediscovered by three biologists, Hugo de Vries of Holland, Car Correns of Germany and Erich von Tschermak of Austria.

Incomplete Dominance: 

1. In incomplete dominance, neither of the allele is not completely dominant to another allele rather combine and produce new trait 

2. New phenotype is formed due to character blending (not alleles) 

3. Example : Pink flowers of Mirabilis Jalapa 

Co-dominance: 

1. In co-dominance, both the alleles in heterozygote are dominant and the traits are equally expressed (joint expression) 

2. No formation of new phenotype rather both dominant traits are expressed, conjointly 

3. Example: Red and white flowers of camellia

The Law of Segregation (Law of Purity of gametes): Alleles do not show any blending. During the formation of gametes, the factors or alleles of a pair separate and segregate from each other such that each gamete receives only one of the two factors. A homozygous parent produces similar gametes and a heterozygous parent produces two kinds of gametes each having one allele with equal proportion. Gametes are never hybrid.

(d) none of the above

Atavism is a modification of a biological structure whereby an ancestral trait reappears after having been lost through evolutionary changes in the previous generations. Evolutionary traits that have disappeared phenotypically do not necessarily disappear from an organism’s DNA. The gene sequence often remains, but is inactive.

Such an unused gene may remain in the genome for many generations. As long as the gene remains intact, a fault in the genetic control suppressing the gene can lead to the reappearance of that character again. Reemergence of sexual reproduction in the flowering plant Hieracium pilosella is the best example for Atavism in plants.

(c) Both genotype & Phenotype ratio

(b) Law of recessiveness

(b) Law of segregation

When two pairs of traits are combined in a hybrid, segregation of one pair of characters is independent to the other pair of characters. Genes that are located in different chromosomes assort independently during meiosis.

(d) Inflated pod

A cross between homozygous parents that differ in three gene pairs (i.e. producing trihybrids) is called trihybrid cross, F Phenotypic ratio -27 : 9 : 9 : 9 : 3 : 3 : 3 : 1

Male sterility found in pearl maize (Sorgum vulgare) is the best example for mitochondrial cytoplasmic inheritance. So it is called cytoplasmic male sterility. In this, male sterility is inherited maternally. The gene for cytoplasmic male sterility is found in the mitochondrial DNA.

Dominant Epistasis – It is a gene interaction in which two alleles of a gene at one locus interfere and suppress or mask the phenotypic expression of a different pair of alleles of another gene at another locus. The gene that suppresses or masks the phenotypic expression of a gene at another locus is known as epistatic.

The gene whose expression is interfered by non-allelic genes and prevents from exhibiting its character is known as hypostatic. When both the genes are present together, the phenotype is determined by the epistatic gene and not by the hypostatic gene.

In the summer squash the fruit colour locus has a dominant allele ‘W’ for white colour and a recessive allele ‘w’ for coloured fruit. ‘W’ allele is dominant that masks the expression of any colour.

Dominant epistasis in summer squash In another locus hypostatic allele ‘G’ is for yellow fruit and its recessive allele ‘g’ for green fruit. In the first locus the white is dominant to colour where as in the second locus yellow is dominant to green. When the white fruit with genotype WWgg is crossed with yellow fruit with genotype wwGG, the F₁ plants have white fruit and are heterozygous (WwGg). When F₁ heterozygous plants are crossed.

they give rise to F₂ with the phenotypic ratio of 12 white : 3 yellow : 1 green.Since W is epistatic to the alleles ‘G’ and ‘g’ , the white which is dominant, masks the effect of yellow or green. Homozygous recessive ww genotypes only can give the coloured fruits (4/16). Double recessive ‘wwgg’ will give green fruit (1/16). The Plants having only ‘G’ in its genotype (wwGg or wwGG) will give the yellow fruit(3/l 6).

The phenomenon in which two alleles are both expressed in the heterozygous individual is known as codominance. The codominance was demonstrated in plants with the help of electrophoresis or chromatography for protein or flavonoid substance. 

Example: Gossypium hirsutum and Gossypium sturtianum, their F₁ hybrid (amphiploid) was tested for seed proteins i by electrophoresis. Both the parents have different banding patterns for their seed proteins. In hybrids, additive banding pattern was noticed. Their hybrid shows the presence of both the types of proteins similar to their parents.

Extra nuclear inheritance is due to genes located on the cytoplasmic organelles such as chloroplast and mitochondrion hence it is called cytoplasmic inheritance.

1. Test cross is crossing an individual of unknown genotype with a homozygous recessive. 

2. Test cross is used to identify whether an individual is homozygous or heterozygous for dominant character.

(d) A is incorrect R is correct

(a) Supplementary genes – 9 : 3 : 4 2 

(b) Complementary genes – 9 : 7

(c) Dominant epistasis -12 : 3 : 1

27 : 9 : 9 : 9 : 3 : 3 : 3 : 1

(a) Phenotypic ratio = 3:1. 

(b) Genotypic ratio =1 : 2 : 1

Law of dominance states that the offsprings of an individual with contrasting (dissimilar) traits will only express the dominant trait in F₁ generation and both the characters are expressed in F₂ generation. This law also explains the proportion of 3 : 1 ratio in F₂ generation.

Mendel was successful because:

1. He applied mathematics and statistical methods to biology and laws of probability to his breeding experiments. 

2. He followed scientific methods and kept accurate and detailed records that include quantitative data of the outcome of his crosses. 

3. His experiments were carefully planned and he used large samples. 

4. The pairs of contrasting characters which were controlled by factor (genes) were present on separate chromosomes. 

5. The parents selected by Mendel were pure breed lines and the purity was tested by self crossing the progeny for many generations.

Mendel’s theory of inheritance, known as the Particulate theory, establishes the existence of minute particles or hereditary units or factors, which are now called as genes.

Three or more alternative forms of a gene that occupy the same locus and control the expression of a single trait. 

E.g : ABO blood group

(c) Hypostatic

Correct Answer is: (b) 12:3:1

(a) Dominance

(c) 50 % recessive 50% dominant

1. They help the individuals to adapt themselves to the changing environment. 

2. Variations allow breeders to improve better yield, quicker growth, increased resistance and lesser input. 

3. They constitute the raw materials for evolution.

(a) Chloroplast inheritance – Gregor Mendel

(c) Law of segregation

 Correct Answer is : (c) 1 : 2 : 1

(c) 9 : 3 : 4

(d) All the above

(a) Tightly linked genes on the same chromosomes show very few combinations

Four gametes – RY, Ry, rY, ry

“Genetics” is the branch of biological science which deals with the mechanism of transmission of characters from parents to off springs. The term Genetics was introduced by W. Bateson in 1906.

Back cross is a cross of F₁ hybrid with any one of the parental genotypes. The back cross is of two types; they are dominant back cross and recessive back cross. It involves the cross between the F₁ off spring with either of the two parents.

“Genetics” is the branch of biological science which deals with the mechanism of transmission of characters from parents to offsprings. The term Genetics was introduced by W. Bateson in 1906.

(a) Classical genetics 

(b) Molecular genetics 

(c) Population genetics 

(d) Quantitative genetics

1. Discontinuous Variation: Within a population there are some characteristics which show a limited form of variation.

Example: Style length in Primula, plant height of garden pea. In discontinuous variation, the characteristics are controlled by one or two major genes which may have two or more allelic forms.

These variations are genetically determined by inheritance factors. Individuals produced by this variation show differences without any intermediate form between them and there is no overlapping between the two phenotypes. The phenotypic expression is unaffected by environmental conditions. This is also called as qualitative inheritance.

2. Continuous Variation: This variation may be due to the combining effects of environmental and genetic factors. In a population most of the characteristics exhibit a complete gradation, from one extreme to the other without any break. Inheritance of phenotype is determined by the combined effects of many genes, (polygenes) and environmental factors. This is also known as quantitative inheritance. 

Example: Human height and skin color.