Sex linkage is the phenotypic expression of an allele that is dependent on the gender of the individual and is directly concerned with the sex chromosomes. The progeny produced are more of parental type and fewer recombinants.

What is the maternal effect? Explain with a suitable example.

A maternal effect is a phenomenon in which the phenotype of an organism is determined not only by the environment it experiences and its genotype but also by the environment and genotype of its mother. It occurs when an organism shows the phenotype expected from the genotype of the mother, irrespective of its own genotype, often due to the mother supplying messenger RNA or proteins to the egg. These maternal effects lead to phenotypes of offspring that increase their fitness. Maternal effect can be best described by studying the coiling in snail. In a cross between a dextral (female) snail and sinistral (male), all the F 1 progeny have dextral coils like their mother and also indicates that dextral character (RR) is dominant over sinistral coiling (rr). However, in the F 1 x F 1 cross (i.e., inbreeding), all the F 2 snails are also dextral. The F 3 progeny from F 2 individuals with the genotype RR and Rr will show dextral coiling, while those from rr of F 2 individuals will exhibit sinistral coiling of their shell, producing a typical 3:1 ratio in the F 3 generation. In a reciprocal cross between dextral (male) and sinistral (female), all the Fx progeny would have sinistral coiling (Rr) instead of dextral coiling. In this case, F 1 x F 1 cross, all the F 2 snails are, again, dextral. These F 3 progenies from F 2 also exhibit the typical monohybrid ratio of 3:1. The 3:1 ratio in the F 3 generation clearly indicates that the coiling of shells is governed by a single nuclear gene. But the segregation of this nuclear gene is apparently delayed by one generation, which is visible in F 3 instead of F 2 as in all other cases of Mendelian inheritance. Such a result has been obtained because the direction of coiling in this snail is primarily determined by some substances already present in the cytoplasm or ooplasm of the egg cell. As a result of this maternal effect, offspring would produce the phenotype (in F 1 ) of the maternal parent since its nuclear gene product is possibly active one generation later and shows delayed segregation in F 3 .

Phenotype is defined as the external appearance of an individual for any trait. It is observable and is determined by different combinations of alleles. For example, in the pea plant, the coloured flower represented by the genotype CC and Cc and the white flower represented by the genotype cc are the two phenotypes.

Heterozygous is a genetic condition in which two different alleles are present at a particular gene locus. In other words, it is a condition in which a person has inherited different forms of a particular gene from each parent. By different forms, we generally mean that there are different portions of the gene where the sequence is different. Examples of heterozygosity: Tt, Rr, etc.

E M B I B E

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR BIOLOGY>Chapter 5 - Principles of Inheritance and Variation>Chattisgarh Board-2018>Q 6

HARD

12th Chhattisgarh Board

IMPORTANT

Earn 100

Explain the sex determination process in humans with the help of ray diagram.

Important Questions on Principles of Inheritance and Variation

HARD

12th Chhattisgarh Board

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR BIOLOGY>Chapter 5 - Principles of Inheritance and Variation>Chattisgarh Board-2018>Q 7

Write the main characteristic features of colour blindness. What will be the hereditary of the offspring when a colourblind man marries with a normal female? Explain it with ray diagram.

EASY

12th Chhattisgarh Board

IMPORTANT

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

What is co-dominance?

MEDIUM

12th Chhattisgarh Board

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR BIOLOGY>Chapter 5 - Principles of Inheritance and Variation>Chattisgarh Board-2019>Q 9

What is sex linkage?

MEDIUM

12th Chhattisgarh Board

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR BIOLOGY>Chapter 5 - Principles of Inheritance and Variation>Chattisgarh Board-2019>Q 10

What is a monohybrid cross? Explain the types of phenotype and genotype found in the F2 generation with the help of a checkerboard.

MEDIUM

12th Chhattisgarh Board

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR BIOLOGY>Chapter 5 - Principles of Inheritance and Variation>Chattisgarh Board-2020>Q 11

Write any two differences between genotype and phenotype.

MEDIUM

12th Chhattisgarh Board

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR BIOLOGY>Chapter 5 - Principles of Inheritance and Variation>Chattisgarh Board-2020>Q 12

What is reciprocal cross?

MEDIUM

12th Chhattisgarh Board

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR BIOLOGY>Chapter 5 - Principles of Inheritance and Variation>Chattisgarh Board-2020>Q 13

What is Down Syndrome? Write its symptoms.

HARD

12th Chhattisgarh Board

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR BIOLOGY>Chapter 5 - Principles of Inheritance and Variation>Chattisgarh Board-2020>Q 14

When a normal female is married to a colour-blind male, then work out the colour blindness in the progeny of these parents with the help of a diagram.

Learn and Prepare for any exam you want !

|

|

|

|

|

|

|

|