Principles of Inheritance and Variation Test

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Principles of Inheritance and Variation Test - 25

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Weekly Quiz Competition

Question 1

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Match the terms in Column I with their description in Column II and choose the correct option:

Column I	Column II
(a) Dominance	(i) Many genes govern a single character
(b) Codominance	(ii) In a heterozygous organism only one allele expresses itself
(c) Pleiotropy	(iii) In a heterozygous organism both alleles expresses themselves fully
(d) Polygenic inheritance	(iv) A single gene influences many characters

(ii), (i), (iv), (iii)

(ii), (iii), (iv), (i)

(iv), (i), (ii), (iii)

(iv), (iii), (i), (ii)

Solution

Dominance refers to the ability of one allele to mask the expression of another allele of same gene present together in a heterozygous individual.

When both recessive and dominant traits are expressed in a heterozygous genotype, it is codominance. This means that none of the factors is recessive but both can express themselves irrespective of their presence in homozygous or heterozygous condition.

Pleiotropy is the condition where a gene has its own independent effect but also modifies the expression of a completely different gene quantitatively.

A polygenic trait is the one that is governed by more than one gene were dominant allele of each gene express only a part of trait and the full trait is expressed only in the presence of dominant alleles of all multiple genes.

The correct answer is B.

Question 2
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Among the following characters, which one was not considered by Mendel in his experiments on pea?

A
Pod - Inflated or Constricted

B
Stem - Tall or Dwarf

C
Trichomes - Glandular or non-glandular

D
Seed - Green or Yellow

Solution

The 7 characters studied by Mendel using the pea plant were stem height, flower color, flower position, pod shape, pod color, seed shape and seed color. Thus the correct answer is option C.
Question 3
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In the given human pedigree, the filled symbols represent an affected individual. Identify the type of given pedigree.

A
X-linked dominant

B
Autosomal dominant

C
X-linked recessive

D
Autosomal recessive

Solution

From the given pedigree chart, following information can be interpreted:
1. The trait is occurring in both male and female individuals with an equal frequency.
2. Affected offspring are borne to healthy or unaffected parents.
3. The trait is skipping generations i.e. it is not occurring in every generation.
From this information, it is clear that this pedigree chart shows an Autosomal recessive disease.
So, the correct answer is D.
Question 4
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A pleiotropic gene

A
Controls multiple traits in an individual

B
Is expressed only in primitive plants

C
Is a gene evolved during Pliocene

D
Controls a trait only in combination with another gene
Solution
Correct Option: A
Explanation:
- Pleiotropism is the phenomenon of multiple effects of a gene in which a single pair of genes influences more than one character at the same time.
- A classic example of pleiotropy is the human disease PKU (phenylketonuria). This disease can cause mental retardation and reduced hair and skin pigmentation, and can be caused by any of a large number of mutations in a single gene that codes for an enzyme (phenylalanine hydroxylase) that converts the amino acid phenylalanine to tyrosine, another amino acid.
- Hence, a pleiotropic gene controls multiple traits in an individual.
- So, the correct answer is option A.
Question 5
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The idea of mutations are brought forth by

A
Gregor Mendel, who worked on Pisum sativum

B
Hardy Weinberg, who worked on allele frequencies in a population

C
Charles Darwin, who observed a wide variety or organisms during sea voyage

D
Hugo do Vries, who worked on evening primrose

Solution

Hugo de Vries based on his work on evening primrose brought forth the idea of mutations- large arising suddenly in a population. He believed that it is mutation which causes evolution and not the minor variations (heritable) that Darwin talked about. Mutations are random and directionless while Darwinian variations are small and directional.
Question 6
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In a testcross involving $$F_1$$ dihybrid flies, more parental type offsprings were produced than the recombinant type offsprings. This indicates that

A
The two genes are located on two different chromosomes.

B
Chromosomes failed to separate during meiosis.

C
The two genes are linked and present on the same chromosome.

D
Both of the characters are controlled by more than one gene.

Solution

The linkage is the tendency of closely placed genes on a chromosome to stay together during inheritance (no crossover and independent assortment). Completely linked genes do not show crossover and independent assortment; thereby produce only parental combinations. Linked genes are the genes which are closely located on the same chromosome. This makes option C correct for the given case. Option A is incorrect as genes present on different chromosomes exhibit crossing over to make more recombinant offspring; not linkage. Option B is incorrect as a failure of chromosomes to separate during meiosis results in chromosomal abnormalities. Option D is incorrect as the production of recombinant and parental offspring is determined by presence or absence of crossing over; not by type of inheritance.
Question 7
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A tall true breeding garden pea plant is crossed with a dwarf true breeding garden pea plant. When the $${ F }_{ 1 }$$ plants were selfed the resulting genotypes were in the ratio of

A
1:2:1 :: Tall homozygous : Tall heterozygous : Dwarf

B
1:2:1 :: Tall heterozygous : Tall homozygous : Dwarf

C
3:1 :: Tall : Dwarf

D
3:1 :: Dwarf : Tall

Solution

A cross between pure breeding tall (TT) and dwarf (tt) plants produce all tall (Tt) plants in $$F_1$$ progeny. These heterozygous tall plants produce 50% gametes with "T" allele and 50% with "t" allele. Random fusion of these gametes from two heterozygous tall plants gives tall and dwarf plants in 3:1 ratio. out of 3/4 tall plants; 1/4 are homozygous tall (TT) and 2/4 are heterozygous tall (Tt). This makes the genotypic ratio for $$F_2$$ generation as 1 homozygous tall (TT): 2 heterozygous tall (Tt): 1 homozygous dwarf (tt). This makes option B incorrect and option A correct. Option D is incorrect as 3/4 plants are tall while 1/4 are the dwarf in $$F_2$$ generation. Option C is incorrect as the question is asking the genotypic ratio. The correct answer is A.
Question 8
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Study the pedigree chart of a certain family given above and select the correct conclusion which can be drawn for the character.

A
The male parent is homozygous dominant.

B
The female parent is heterozygous.

C
The parents could not have had a normal daughter for this character.

D
The trait under study could not be colour-blindness.
Solution
- To have both sons and daughters showing the trait, both parents should have at least one copy of the allele. In given pedigree, female parent is shown normal which makes her heterozygous carrier.
- The trait is recessive as it is not expressed in a heterozygous female parent. The male parent is homozygous recessive as the trait is recessive.
- Daughters get one X chromosome from the father and other from the mother; daughters receiving normal X chromosome from carrier female parent and affected X chromosome from an affected male parent will be normal.
- The trait is X-linked recessive and could be colorblindness which is also X-linked recessive trait.
  
  Thus, the correct answer is option B.
Question 9
1 / -0

A woman has an X linked condition on one of her X chromosomes. This chromosome can be inherited by

A
Only grandchildren

B
Only daughter

C
Both sons and daughters

D
Only sons

Solution

The mother is carrying X-linked condition on one X chromosome means the genotype is X X’. The gametes will be X and X’. The condition can be carried/transmitted by the son as well as the daughters since, the X’ gamete can be involved in the development of a boy X’Y (X’ from mother and Y from father) or a girl X’X (X’ from mother and X from father).
Thus, the correct answer is option C.
Question 10
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Select the correct statements:

A
Spliceosomes take part in the transcription.

B
Franklin Stahl coined the term "linkage".

C
Transduction was discovered by S. Altman.

D
Punnett square was developed by British scientist.
Solution
Correct Answer: (D) Punnett square was developed by British scientist.
Explanation:
Spliceosomes are the large protein complex that is commonly found in the nucleus of the eukaryotic cells.
The primary function of the spliceosomes is to remove the non-coding sequences (Introns) in the newly formed pre-mRNA.
And this process is known as splicing and occurs after the transcription process.
Thomas Hunt Morgan coined the term linkage and did the experiment with fruit fly to gather information about the linkage phenomenon.
Joshua Lederberg and Norton Zinder discovered the transduction process by which a virus transfers its genetic material to the host.
R C Punnett was a British scientist who is known for his development of Punnett Square, which is widely used in the field of genetics.
Hence, option (D) is the correct answer.

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Principles of Inheritance and Variation Test - 25

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Principles of Inheritance and Variation Test - 25

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SHARING IS CARING

Question 1

(ii), (i), (iv), (iii)

(ii), (iii), (iv), (i)

(iv), (i), (ii), (iii)

(iv), (iii), (i), (ii)

Solution

Question 2

Pod - Inflated or Constricted

Stem - Tall or Dwarf

Trichomes - Glandular or non-glandular

Seed - Green or Yellow

Solution

Question 3

X-linked dominant

Autosomal dominant

X-linked recessive

Autosomal recessive

Solution

Question 4

Controls multiple traits in an individual

Is expressed only in primitive plants

Is a gene evolved during Pliocene

Controls a trait only in combination with another gene

Solution

Question 5

Gregor Mendel, who worked on Pisum sativum

Hardy Weinberg, who worked on allele frequencies in a population

Charles Darwin, who observed a wide variety or organisms during sea voyage

Hugo do Vries, who worked on evening primrose

Solution

Question 6

The two genes are located on two different chromosomes.

Chromosomes failed to separate during meiosis.

The two genes are linked and present on the same chromosome.

Both of the characters are controlled by more than one gene.

Solution

Question 7

1:2:1 :: Tall homozygous : Tall heterozygous : Dwarf

1:2:1 :: Tall heterozygous : Tall homozygous : Dwarf

3:1 :: Tall : Dwarf

3:1 :: Dwarf : Tall

Solution

Question 8

The male parent is homozygous dominant.

The female parent is heterozygous.

The parents could not have had a normal daughter for this character.

The trait under study could not be colour-blindness.

Solution

Question 9

Only grandchildren

Only daughter

Both sons and daughters

Only sons

Solution

Question 10

Spliceosomes take part in the transcription.

Franklin Stahl coined the term "linkage".

Transduction was discovered by S. Altman.

Punnett square was developed by British scientist.

Solution

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