Principles of Inheritance & Variation Test

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Principles of Inheritance & Variation Test - 1

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Question 1
4 / -1

XO type of sex determination and XY type of sex determination are the examples of

A
male heterogamety

B
female heterogamety

C
male homogamety

D
both (b) and (c)

Solution

In XO type and XY type sex determining mechanisms, males produce two different types of gametes, (a) either with or without X-chromosome (XO type), (b) some gametes with X-chromosome and some with Y-chromosome (XY type). Such type of sex determination mechanism is designated to be the example of male heterogamety. In both, females are homogametic and produce X type of gametes in both the cases and have XX genotype.
Question 2
4 / -1

Which of the following is incorrect regarding ZW-ZZ type of sex determination?

A
It occurs in birds and some reptiles

B
Females are homogametic and males are heterogametic

C
1:1 sex ratio is produced in the offsprings

D
All of these

Solution

In ZW - ZZ type of sex determination, the male has two homomorphic sex chromosomes (ZZ) and is homogametic, and the female has two heteromorphic sex chromosomes (ZW) and is heterogametic. There are, thus, two types of eggs : with Z and with W, and only one type of sperms, i.e., each with Z. Fertilisation of an egg with Z chromosome by a sperm with Z chromosome gives a zygote with ZZ chromosomes (male). Fertilisation of an egg with W chromosome by a sperm with Z chromosome yields a zygote with ZW chromosomes (female). This mechanism operates in some vertebrates (fishes, reptiles and birds).
Question 3
4 / -1

A couple has six daughters. What is the possibility of their having a girl next time?

A
10%

B
50%

C
90%

D
100%

Solution

The possibility of having a girl or boy child is equal i.e., 50% as 50% male gametes are Y type and 50% are X type. Fusion of egg with X type sperm will produce a girl child.
Question 4
4 / -1

Number of autosomes present in liver cells of a human female is

A
22 autosomes

B
22 pairs

C
23 autosomes

D
23 pairs

Solution

In humans, number of autosomes are 2n = 44 or 22 pairs regardless of the sex.
Question 5
4 / -1

In honeybees, females are ___(i)_____ having ___(ii)_____ chromosomes and males are ___(iii)_____ having ___(iv)_____ chromosomes.

A
a

B
b

C
c

D
d

Solution

The sex determination in honeybees is based on the number of sets of chromosomes an individual receives. An offspring formed from the union of a sperm and an egg develops as a female (queen or worker), and an unfertilised egg develops as a male (drone) by means of parthenogenesis. This means that the males have half the number of chromosomes than that of a female. The females are diploid having 32 chromosomes and males are haploid, i.e., having 16 chromosomes. This is called haplodiploid sex-determination system and has special characteristic features such as the males produce sperms by mitosis, they do not have a father and thus cannot have sons, but have a grandfather and can have grandsons.