F 1 progeny of pea plant bearing violet flowers and snapdragon plant bearing red flowers were selfed to produce their respective F 2 progeny. Compare the phenotype, genotype and pattern of inheritance of their respective F 2 progeny.

The snapdragon flower shows incomplete dominance. If a plant with red coloured flowers (RR) is crossed with a plant with white coloured flower (rr), the F 1 progeny shows (Rr) the plant with pink coloured flowers. Hence, in the condition in which the selfing of the plant bearing red flower, they have RR genotype. Phenotype: All plants are bearing red coloured flowers. Phenotypic ratio: 100% Genotype: RR Genotypic ratio: RR (100%) In pea plants, the violet flower is the dominant trait. Hence, the genotype of violet flower may be homozygous (WW) or heterozygous (Ww). The pattern of inheritance is complete dominance. If the plant with violet flower is homozygous, Phenotypic ratio: All are violet (100%) Genotypic ratio: WW(100%) If the plant with violet flower is heterozygous, Phenotypic ratio: 3:1 (3 violet flowers :1 white flower) Genotypic ratio: 1:2:1 (WW:Ww:ww)

F 1 progeny of pea plant bearing violet flowers and snapdragon plant bearing red flowers were selfed to produce their respective F 2 progeny. Compare the phenotype, genotype and pattern of inheritance of their respective F 2 progeny.

The snapdragon flower shows incomplete dominance. If a plant with red coloured flowers (RR) is crossed with a plant with white coloured flower (rr), the F 1 progeny shows (Rr) the plant with pink coloured flowers. Hence, in the condition in which the selfing of the plant bearing red flower, they have RR genotype. Phenotype: All plants are bearing red coloured flowers. Phenotypic ratio: 100% Genotype: RR Genotypic ratio: RR (100%) In pea plants, the violet flower is the dominant trait. Hence, the genotype of violet flower may be homozygous (WW) or heterozygous (Ww). The pattern of inheritance is complete dominance. If the plant with violet flower is homozygous, Phenotypic ratio: All are violet (100%) Genotypic ratio: WW(100%) If the plant with violet flower is heterozygous, Phenotypic ratio: 3:1 (3 violet flowers :1 white flower) Genotypic ratio: 1:2:1 (WW:Ww:ww)

Explain the mechanism of 'sex determination' in birds. How does it differ from that of human beings?

In birds, the male is homogametic (ZZ), forms only Z type of gamete and the female is heterogametic (ZW) produces Z and W type of sex gametes. The W chromosome determines the sex of the progeny. Bird shows the ZZ-ZW system of sex determination, but it is the XY-XX system of sex determination in humans. A human male is heterogametic, i.e., during the process called gametogenesis, half of the sperm produces the X chromosome, and another half will produce the Y chromosome. The males have an XY as sex chromosomes. Females have XX as their sex chromosomes, so they produce only X type of sex egg. The females are homogametic. In birds, females are heterogametic, and in humans, males are heterogametic.

How did Sturtevant explain gene mapping while working with Morgan?

Gene linkage can be shown as the genetic map (linkage map or chromosomal map). Alfred Sturtevant was the first who developed the genetic map. He used the concept of the frequency of recombination to measure the physical distance between two genes and to map their loci on the X-chromosome of Drosophila . The two aspects of genetic mapping are Gene order Gene distance. Crossing over happens as the distance increases between two specific gene loci. Recombinant frequency is calculated as the measure of map distance between the two genes. Map unit or centimorgan (cM) is the unit of measurement of the genetic map. 1 map unit or 1 cM is equal to 1% of recombination. Map distance= N u m b e r o f r e c o m b i n a n t o f f s p r i n g s T o t a l n u m b e r o f o f f s p r i n g s × 100

Name a human genetic disorder due to the following : An additional X-chromosome in a male

The addition or deletion of the extra sex chromosome can cause genetic disorder in the body of an individual. The human male has a 44+XY set of chromosomes in their body. The addition of an extra X chromosome in a male causes Klinefelter syndrome. The primary characteristic feature of this disease is sterility and small testicles. The other symptoms of this disease are weaker muscles, greater height, poor coordination, less body hair, breast growth, and less interest in sex.

Write the scientific name of the organism Thomas Hunt Morgan and his colleagues worked with for their experiments. Explain the correlation between linkage and recombination with respect to genes as studied by them.

T. H. Morgan and his colleagues used the fruit fly, Drosophila melanogaster , for their experiments on linkage. Morgan and his colleagues experimented and allowed cross between the yellow-bodied white-eyed flies with brown-bodied red-eyed flies. They found that the F 2 generation was not according to the 9:2:2:1 ratio. Hence, he suggested the concept of linkage. T. H. Morgan explained that when these genes are present closer on the X-chromosome for the corresponding traits, they are linked to each other, and there is no crossing over taking place. Due to this, the frequency of parental types is much greater than the frequency of recombinant ones as they are inherited together mostly. So, he concluded that the greater the linkage between two genes, the lesser is the recombination.

E M B I B E

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR BIOLOGY>Chapter 5 - Principles of Inheritance and Variation>CBSE-2019>Q 5

EASY

12th CBSE

IMPORTANT

Earn 100

Name a human genetic disorder due to the following :
Deletion of one X-chromosome in a female

Important Questions on Principles of Inheritance and Variation

EASY

12th CBSE

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR BIOLOGY>Chapter 5 - Principles of Inheritance and Variation>CBSE-2019>Q 6

State what does aneuploidy lead to.

EASY

12th CBSE

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR BIOLOGY>Chapter 5 - Principles of Inheritance and Variation>CBSE-2019>Q 7

How does mutation occur?

HARD

12th CBSE

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR BIOLOGY>Chapter 5 - Principles of Inheritance and Variation>CBSE-2019>Q 8

Mendel crossed a homozygous pea plant having yellow and round seeds with another pea plant bearing green and wrinkled seeds. He found that in some of the F₂ population, new combinations of the parental characters were observed. How will you explain the appearance of a new combination of the parental characters in F₂ offspring? Support your answer with the help of a Punnett square.

HARD

12th CBSE

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR BIOLOGY>Chapter 5 - Principles of Inheritance and Variation>CBSE-2020>Q 9

Generally, it is observed that human males suffer from haemophilia more than human females, who rarely suffer from it. Explain giving reasons.

HARD

12th CBSE

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR BIOLOGY>Chapter 5 - Principles of Inheritance and Variation>CBSE-2020>Q 10

F₁ progeny of pea plant bearing violet flowers and snapdragon plant bearing red flowers were selfed to produce their respective F₂ progeny. Compare the phenotype, genotype and pattern of inheritance of their respective F₂ progeny.