25) In a will have a woman who is colorblind who has children with a normal-visi

Question

25) In a will have a woman who is colorblind who has children with a normal-vision man A) daughters who are colorblind B) sons who are colorblind C) all children colorblind D) 50% chance of having colorblind daughters E) 50% chance of having colorblind sons 26) A woman, who has normal vision, but whose father was colorblind, has children with a marn who is colorblind. Which of the following is TRUE? A) all of her daughters will be colorblind B) all of her sons will be colorblind C) all children colorblind D) 50% chance of having colorblind daughters and 50% chance of having colorblind sons E) 50% chance of having colorblind sons only 27) When one single gene has multiple phenotypic effects it is called: A) incomplete dominance B) pleiotropy C) codominance D) independent assortment E) crossing over 28) One type of virus that infects bacteria is called a A) phage. B) mage C) rhinovirus D) filovirus. E) coronavirus. 29) The way that genetic material of a bacteriophage enters a bacterium is most like the way that A) a drug is injected with a hypodermic needle. B) a person swallows a pill. C) skin lotion is rubbed onto the hands. D) sugar dissolves in water. E) water soaks into a sponge. 30) The monomers of DNA and RNA are A) amino acids. B) monosaccharides. C) nucleotides. D) fatty acids. E) nucleic acids.

Explanation / Answer

25. (B).

Colourblindness is a sex-linked recessive disorder, the gene for which is present on the X chromosome. A woman is colourblind if she carries the gene for colourblindness in both the X chromosomes. Her genotype will be XcXc ( c for colourblindness), whereas a female carrying one colourblindnes gene in one X chromosome is called a carrier. her genotype will be Xc X.  A son gets the X chromosome from mother and Y from the father. A colourblind woman married to a normal man produces all colour blind sons and carrier daughters.

XcX - carrier daughter XcY - Colourblind son

26. (D).

The woman got the X chromosome, carrying the gene for colourblindness from her father She is normal but carrier (XcX). When she marries a colourblind man (XcY), 50% of sons and daughters will be colourblind.

  

XcXc - Colourblind daughter XXc - Carrier daughter

XcY - Colourblind sons XY - Normal sons.

27. (B).

One gene normally affects only one phenotypic character but, in case of pleiotropy, multiple symptoms appear for certain hereditary diseases. Sickle cell anaemia and phenylketonuria are examples of pleiotropy. the gene for sickle anaemia is lethal(deadly) in homozygous condition (Hbs Hbs ) but has slightly detectable effect in heterozygous condition ( HbA Hbs ).

28.(A).

29.(A). A phage attaches itself on the surface of a bacterial cell. it makes a hole in the bacterial cell and injects its genetic material ( DNA or RNA) into the bacterial cell.

30.(C) DNA and RNA are polymers of nucleiotides.

Xc Xc X XcX XcX Y XcY XcY

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