39. Mendelian traits are described as discrete, or discontinuous because a. Thei

Question

39. Mendelian traits are described as discrete, or discontinuous because a. Their phenotypic expressions overlap b. Their phenotypic expressions do not fall into clearly defined categories c. Their genotypic expression overlap d. Their genotypic expressions do not fall into clearly defined categories e. Their phenotypic expressions do not overlap 40. Two people (both heterozygotes) are able to taste a chemical substance called PTC. The ability to taste PTC is caused by a dominant allele (T). The inability to taste PTC is caused by a recessive allele (t). What proportion of their children would be expected to have the ability to taste PTC? a. 3/4 b. 1/2 C. All d. 1/4 e. 2/3 41. What produces new genetic information within a population? a. natural selection b. recombination c. mutation d. migration e. genetic drift

Explanation / Answer

39. Discrete or discontinuous traits are traits that occur in discrete categories. They are either present or not. Mendelian traits are discrete or discontinuous, as their phenotypes do not overlap. Instead they fall in clearly defined categories. For example, in the ABO system for blood grouping, A, B, AB, and O are distinct phenotypes. There is no intermediate form between A and B. A and B are either present or absent (O). Mendelian traits do not show continuous variation. Hence, option ‘e’ is right choice.

40. Punnett square is as follows:

                                       Heterozygous Male Gametes                         

                                                T                         t

TT

Homozygous

Can taste PTC

Tt

Heterozygous

Can taste PTC

Tt

Heterozygous

Can taste PTC

Tt

Recessive

Cannot taste PTC

                       

Heterozygote             T

Female gametes        t

As heterozygotes can also taste PTC, 3/4th of the children can taste PTC. Hence option ‘a’ is right choice.

41. Migration or gene flow introduces new genetic material in the population. During migration, the populations travel to another population due to scarcity of food or predators. For example, pollen is blown from one place to another or if people migrate to newer places for jobs. These people will inbreed with the native population and hence, their alleles will mix with those of the native people. The genetic material has thus, increased for the newer population. Option ‘d’ is the right choice.

TT

Homozygous

Can taste PTC

Tt

Heterozygous

Can taste PTC

Tt

Heterozygous

Can taste PTC

Tt

Recessive

Cannot taste PTC

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