Short Answer TypeName the type of cross that would help to find the genotype of a pea plant bearing violet flowers.
Both Haemophilia and Thalassemia are blood related disorders in humans. Write their causes and the difference between the two. Name the category of genetic disorder they both come under.
(a) Write the desirable characters a farmer looks for in his sugarcane crop. (b) How did plant breeding techniques help north Indian farmers to develop cane with desired characters ?
Explain the mechanism of ‘sex determination’ in birds. How does it differ from that of human beings?
a) 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.
b) How did Sturtevant explain gene mapping while working with Morgan?
a) Drosophila melanogaster :
Morgan carried out several dihybrid crosses in Drosophila to study gens that were sex-lined.
Morgan and his group knew that the genes were located on the X chromosome and saw quickly that when the two genes in a dihybrid cross were situated on the same chromosome, the proportion of parental gene combinations were much higher than the non-parental type. Morgan attributed this due to the physical association or linkage of the two genes and coined the term linkage to describe this physical association of genes on a chromosome and the term recombination to describe the generation of non-parental gene combination. Morgan and his group also found that even when genes were grouped on the same chromosome, some genes were very tightly linked (showed very low recombination) while others were loosely linked.
b) Morgans student Alfred Sturtevant used the frequency of recombination between gene pairs on the same chromosome as a measure of the distance between genes and ‘mapped’ their position on the chromosome. Today genetic maps are extensively used as a starting point in the sequencing of whole genomes.
Multiple Choice QuestionsAssertion: A middle aged woman is reported to have small breasts and undersized uterus.
Reason: Her genotypic analysis shows XO condition of allosomes.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false
A tall true breeding garden pea plant is crossed with a dwarf true breeding garden pea plant. When the F1 plants were selfed the resulting genotypes were in ratio of
1:2:1 :: Tall heterozygous: Tall homozygous: Dwarf
3:1:: Tall: Dwarf
3:1:: Dwarf: Tall
3:1:: Dwarf: Tall
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