Principles of Inheritance & Variation Test

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Principles of Inheritance & Variation Test - 2

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Question 1
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Statement I: The bridge between one generation and the next is sperm and ovum.
Statement II: Both sperm and ovum contribute equally to heredity.
Statement III: Somatic diploid cells possess two chromosomes as well as two mendelian factors of each type.

A
Only statements II and III are correct.

B
Only statements I and II are correct.

C
All three statements are correct.

D
All three statements are incorrect.
Solution
Bridge between one generation and the next is through sperm and ovum.

The sperm provides only the nuclear part to the zygote. As such hereditary characters must be carried by nuclear materials.

There is fusion of the sperm and egg nuclei during fertilization.

Both the sperm and egg contribute equally in the heredity of the offspring.

Hence , the correct answer is option B.

NCERT Reference: Topic- basic understanding of inheritance.of chapter "Principles of Inheritance and Variation " of NCERT.
Question 2
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Sex determination in human beings is _________.

A
XY type

B
XZ type

C
XXY type

D
YY type
Solution
In humans, the males are heterogametic as they have XY sex chromosomes , so they make 50% sperms with X chromosome and 50% sperms with Y chromosome. Females are homogametic. All gametes made by them have X chromosomes. So, humans show XX-XY type of sex determination.

Hence, the correct option is A.
NCERT Reference: Topic SEX DETERMINATION of chapter "Principles of Inheritance and Variation " OF NCERT.
Question 3
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In the case of Co-dominance when red and white flowers is crossed, the F1 generation resembles:

A
Both the parents

B
Recessive parent

C
Dominant parent

D
None of the parents
Solution
In Co-dominance, both alleles for a specific trait are expressed equally in the heterozygous offspring.

This means that the F1 generation will display traits from both the dominant and recessive parents, rather than resembling only one of the parents.

Hence the correct Answer is "A "
NCERT Reference: Topic- Co- dominanace of chapter "Principles of Inheritance and Variation " of NCERT.
Question 4
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In human beings, if ovum fertilizes with a sperm carrying X-chromosome, the zygote develops into _________.

A
Male

B
Female

C
Sterile

D
Any of the above
Solution
Females have the genetic composition XX , while males have the genetic makeup XY.

The female ovum has an X chromosome, whereas male sperm might have either an X or a Y chromosome.

When X chromosome-carrying sperm fertilises an egg with an X chromosome, the zygote grows into a female .

Hence, the correct option is B.

NCERT Reference: Topic- SEX DETERMINATION ”of chapter "Principles of Inheritance and Variation " Of NCERT.
Question 5
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Henking X-body present in 50% of sperms are now known as:

A
Lamp brush chromosomes

B
Autosomes

C
Y-chromosome

D
X-chromosome
Solution
Henking traces a specific structure in 50% of sperms. He gave the name x-body to this structure but he was not able to explain the significance of this structure.

Further, investigation revealed that the x-body was a chromosome, calledX-chromosome .

Hence, the correct option is D.

NCERT Reference: Topic- SEX DETERMINATION ”of chapter "Principles of Inheritance and Variation " of NCERT.
Question 6
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How can a female be haemophilic?

A
Mother is haemophilic and father is normal

B
Both mother and father are carriers

C
Both mother and father are haemophilic

D
Mother is a carrier and father is haemophilic
Solution
A female can only be haemophilic if Both mother and father are haemophilic

But the possibility of a female becoming haemophilic is extremely rare because being haemophilic for the parents at the later stage of life is unviable.

Hence, the correct option is C.

NCERT Reference: Topic “Haemophilia ”of chapter "Principles of Inheritance and Variation " of NCERT.
Question 7
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A colour blind girl is rare because she will be born only when

A
Her mother and maternal grand father were colour blind

B
Her father and maternal grand father were colour blind

C
Her mother is colour blind and father has normal vision

D
Parents have normal vision but grand parents were colour blind.
Solution
The father of a colour blind female must be colour blind.

The mother has to be at least a carrier. This is possible if the maternal grandfather was colour blind [remember criss-cross].

Hence, the correct option is B.

NCERT Reference: Topic- Colour Blindness of chapter "Principles of Inheritance and Variation " of NCERT.
Question 8
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Which of the following is a recessive trait for a character chosen by Mendel in garden pea?

A
Violet flower colour

B
Yellow pod colour

C
Axial flower position

D
Tall stem height
Solution
Yellow pod colour of the pea plant is a recessive trait.

Mendel studied seven contrasting traits in pea (Pisum sativum), which are as follows:

Hence, the correct option is B.

NCERT Reference: Topic- MENDEL ’S LAWS OF INHERITANCE ”of chapter "Principles of Inheritance and Variation " of NCERT.
Question 9
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Identify the incorrect statement:

A
Tall plants produce gametes by meiosis and dwarf plants by mitosis.

B
Only one allele is transmitted to a gamete.

C
The segregation of alleles is a random process.

D
Gametes will always be pure for the trait.
Solution
Bothtall and dwarf plants produce gametes by mitosis .

Plants use meiosis only to produce spores that develop into multicellular haploid gametophytes which produce gametes by mitosis.

Therefore, gamete formation in both tall and dwarf plants is by mitosis.

Hence, the correct option is A.
Note: This question is based on basic understanding of inheritance of genes.
Question 10
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The ultimate source of allelic variation is:

A
Recombination

B
Natural selection

C
Mutation

D
Drift
Solution
Gene is a segment of DNA and new alleles arise by mutation - a sudden inheritable change in DNA. Mutations can alter single nucleotides or entire chromosomes.

The ultimate source of genetic variation is random mutation i.e. changes in nucleotide sequences of DNA. They may involve only a single base pair or many as in chromosomal mutations.

Change in the allele frequency and introduction of new alleles are the basis of genetic variation occurring in any population.

Fig : Showing Mutation

Hence, the correct option is C.
NCERT Reference: Topic- MUTATION ”of chapter "Principles of Inheritance and Variation " of NCERT.