Principles of Inheritance & Variation Test

Result

Principles of Inheritance & Variation Test - 5

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Weekly Quiz Competition

Question 1
4 / -1

What is true about the crossing over between linked genes?

A
No crossing over at all

B
High percentage of crossing over

C
Hardly any crossing over

D
None of these

Solution

Linked genes are those genes which do not show independent assortment but remain together because they are present on the same chromosome. In linkage there is a tendency to maintain the parental gene combination except for occasional crossovers.
Question 2
4 / -1

Chromosome maps/genetic maps were first prepared by

A
Sutton and Boveri (1902)

B
Bateson and Punnett (1906)

C
Morgan (1910)

D
Sturtevant (1911)

Solution

Linkage or genetic or chromosome map is a linear graphical representation of the sequence and relative distances of the various genes present in a chromosome. The first chromosome maps were prepared by Sturtevant in 1911 for two chromosomes and in 1913 for all the four chromosomes of Drosophila.
Question 3
4 / -1

Depending upon the distance between any two genes which is inversely proportional to the strength of linkage, cross overs will vary from

A
50−100%

B
0−50%

C
75−100%

D
100−150%

Solution

The physical distance between two genes determines both the strength of the linkage and the frequency of the crossing over between two genes The strength of the linkage increases with the closeness of the two genes. On the other hand the frequency of crossing over increases with the increase in the physical distance between the two genes.
Question 4
4 / -1

The distance between the genes is measured by

A
angstrom

B
map unit

C
Dobson unit

D
millimetre

Solution

The distance between genes is measured by map unit. 1 crossing over between two linked genes is known as 1 map unit or centi Morgan (cM). 100% crossing over is termed as Morgan (M) and 10% crossing over as deci Morgan (dm).
Question 5
4 / -1

Which of the following is suitable for experiment on linkage?

A
aaBB x aaBB

B
AABB x aabb

C
AaBb x AaBb

D
AAbb x AaBB
Solution
Linked and unlinked genes can be easily known from breeding experiments. Unlinked genes show independent assortment in a dihybrid ratio of 9:3:3:1 and the dihybrid or double test cross-ratio of 1:1:1:1 with two parental and two recombinant types. The linked genes do not show independent assortment but remain together and are inherited en block producing only parental type of progeny. They give a dihybrid ratio of 3:1 and a test cross-ratio of 1:1.
Linkage can be shown by a cross between homozygous dominant AABB and homozygous recessive aabb.