Principles of Inheritance and Variation Test

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Principles of Inheritance and Variation Test - 26

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Question 1
1 / -0

Experimental verification of the chromosomal theory of inheritance was done by

A
Sutton

B
Boveri

C
Morgan

D
Mendel

Solution

Experimental Verification of the Chromosomal Theory of Inheritance was done by Thomas Hunt Morgan and his colleagues. He observed that the two genes under consideration in his experiments did not segregate independently as in the case of characters studied by Mendel. Morgan carried out various dihybrid crosses in Drosophila, with the genes that were sex-linked, i.e., the genes are present on the X-chromosome.
So, the correct answer is 'Thomas Hunt Morgan'.
Question 2
1 / -0

Variations caused by mutation, as proposed by Hugo de Vries are:

A
Random and directional

B
Random and directionless

C
Small and directional

D
Small and directionless

Solution

According to Hugo de Vries, mutations are random and directionless.
De Vries believed mutations caused speciation and hence called saltation (single step large mutation).
So, the correct answer is 'Random and directionless'
Question 3
1 / -0

The percentage of heterozygous individuals obtained in F$$_{2}$$ generation from selfing the plants with genotype Rr would be

A
24

B
50

C
75

D
100

Solution

The percentage of heterozygous individuals obtained in F$$_2$$ generation from selfing the plants with genotype Rr would be 50. This is because in F$$_2$$ generation the ratio between heterozygous and homozygous is 1:1. It means that it yields two homozygous individuals and 2 heterozygous individuals. Hence the final answer is 50%.
So, the correct answer is option B.
Question 4
1 / -0

Discontinuous variations are

A
Mutations

B
Acquired characters

C
Essential features

D
Nonessential features

Solution

Mutation is a sudden heritable change in the genetic material. It causes discontinuous variations.
Question 5
1 / -0

Assertion: Plasmids are single stranded extra chromosomal DNA.

Reason: Plasmids are found in Eukaryotic cells.

A
If both the assertion and the reason are true and the reason is a correct explanation of the assertion

B
If both the assertion and reason are true but the reason is not a correct explanation of the assertion

C
If the assertion is true but the reason is false

D
If both the assertion and reason are false

E
If the assertion is false but reason is true

Solution

Plasmids are extrachromosomal double stranded small circular DNA usually found in bacterial cell in addition to main genetic material. Therefore, both assertion and reason is false.
So, the correct answer is 'If both the assertion and reason are false'
Question 6
1 / -0

Grain colour in wheat is determined by three pairs of polygenes. Following cross AABBCC (dark colour) $$\times$$ aabbcc (light colour), in F$$_2$$ generation what proportion of the progeny is likely to resemble either parent?

A
Half

B
Less than 5 per cent

C
One third

D
None of the above

Solution

A trait governed by more than one gene where dominant allele of each gene express only a part of trait and the full trait is expressed only in presence of dominant alleles of all multiple genes, is called as polygenic inheritance. A cross between AABBCC and aabbcc produces AaBbCc F$$_1$$ hybrid. The hybrid produce 2$$^3$$=8 gametes and selfing of gametes from two hybrids produce total 64 genotypes with 1/64 AABBCC and 1/64 aabbcc (the parental types). Thus, total number of parental types in F$$_2$$ generation= 2/64= 3.12, i.e., less than 5%. This is because polygenic trait expresses the full trait (parental phenotype) in pure breeding genotypes only.

Question 7

1 / -0

Grain colour in wheat is determined by three pairs of polygenes. Following the cross AABBCC (dark colour) x aabbcc (light colour), how many plants will be produced with the genotype AABBCC?

None

Five

One

Ten

Solution

The above cross is a trihybrid cross as it involves three pairs of genes showing grain colour in a Wheat plant. By self crossing the given F$$_{1}$$ generation that is AABBCC (dark colour) X aabbcc (light colour), we will get F$$_{2}$$ generation, using punnett square. The results obtained will be :-

female male gamets	ABC	ABc	AbC	Abc	aBC	aBc	abC	abc
ABC	AABBCC	AABBcc	AABbCc	AABbCC	AaBBCC	AaBBCc	AaBbCC	AaBbCc
ABc	AABBCc	AABBcc	AABbCc	AABbcc	AaBBCc	AaBBcc	AaBbCc	AaBbcc
AbC	AABbCC	AABbCc	AAbbCC	AAbbCc	AaBbCC	AaBbCc	aAbbCC	AabbCc
Abc	AABbCc	AABbcc	AAbbCc	AAbbcc	AaBbCc	AaBbcc	AabbCc	Aabbcc
aBC	AaBBCC	AaBBCc	AaBbCC	AaBbCc	aaBBCC	aaBBCc	aaBbCC	aaBbCc
aBc	AaBBCc	AaBBcc	AaBbCc	AaBbcc	aaBBCc	aaBBcc	aaBbCc	aaBbcc
abC	AaBbCC	AaBbCc	AabbCC	AabbCc	aaBbCc	aabbCC	aabbCC	aabbCc
abc	AaBbCc	AaBbcc	AabbCc	Aabbcc	aaBbcc	aaBbCc	aabbCc	aabbcc

Here in the punnett square table it is seen that only one plant with the genotype AABBCC is produced.

The Phenotypic ratio obtained is - 27 : 9 : 9 : 9 : 3 : 3 : 1.

Question 8
1 / -0

Given above is a pedigree chart of a family with five children. It shows the inheritance of attached earlobes as opposed to the free ones. The squares represent the male individuals and circles the female individuals. Which one of the following conclusions drawn is correct?

A
The parents are homozygous recessive.

B
The trait is Y linked.

C
The parents are homozygous dominant.

D
The parents are heterozygous.
Solution
- In the given pedigree chart, parents from the 1st generation are normal, yet they transfer disease to their children in the second generation. This would be possible only if both parents are carriers (heterozygous) for recessive inheritance.
So the correct answer is option D.
Question 9
1 / -0

Given above is a pedigree chart showing the inheritance of a certain sex-linked trait in humans. Which is the trait traced in the above pedigree chart?

A
Dominant X-linked

B
Recessive X-linked

C
Dominant Y-linked

D
Recessive Y-linked
Solution
- The pedigree is showing that in generation 1, the male is affected and the female is unaffected.
- In generation 2, the females are affected and the males are unaffected. This means the female in generation 1 was a carrier for a particular trait.
- In generation 3, both males and females are affected.
From this information, it can be predicted that the trait is Dominant X-linked because it is appearing in both males and females and occurring in every generation.
So, the correct answer is 'Dominant X-linked'.
Question 10
1 / -0

Assertion: Phenylketonuria is a recessive hereditary disease caused by body's failure to oxidise an amino acid phenylalanine to tryrosine, because of a defective enzyme.

Reason: It results the presence of phenylalanine acid in urine.

A
If both the assertion and the reason are true and the reason is a correct explanation of the assertion

B
If both the assertion and reason are true but the reason is not a correct explanation of the assertion

C
If the assertion is true but the reason is false

D
If both the assertion and reason are false

E
If the assertion is false but reason is true

Solution

Phenylketonuria is due to deficency of liver enzyme Phenyanaline hydroxylase which converts phenylanine into tryosine. It occurs in person who are homozygous recessive. It results with a high level of phenylalanine in blood, tissue fluids and urine. Therefore both assertion and reason is true.
So, the correct answer is 'If both the assertion and reason are true but the reason is not a correct explanation of the assertion'

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Principles of Inheritance and Variation Test - 26

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Principles of Inheritance and Variation Test - 26

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SHARING IS CARING

Question 1

Sutton

Boveri

Morgan

Mendel

Solution

Question 2

Random and directional

Random and directionless

Small and directional

Small and directionless

Solution

Question 3

24

50

75

100

Solution

Question 4

Mutations

Acquired characters

Essential features

Nonessential features

Solution

Question 5

If both the assertion and the reason are true and the reason is a correct explanation of the assertion

If both the assertion and reason are true but the reason is not a correct explanation of the assertion

If the assertion is true but the reason is false

If both the assertion and reason are false

If the assertion is false but reason is true

Solution

Question 6

Half

Less than 5 per cent

One third

None of the above

Solution

Question 7

None

Five

One

Ten

Solution

Question 8

The parents are homozygous recessive.

The trait is Y linked.

The parents are homozygous dominant.

The parents are heterozygous.

Solution

Question 9

Dominant X-linked

Recessive X-linked

Dominant Y-linked

Recessive Y-linked

Solution

Question 10

If both the assertion and the reason are true and the reason is a correct explanation of the assertion

If both the assertion and reason are true but the reason is not a correct explanation of the assertion

If the assertion is true but the reason is false

If both the assertion and reason are false

If the assertion is false but reason is true

Solution

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