Color-blindness is caused by an X-linked recessive allele. Which of the followin
ID: 82914 • Letter: C
Question
Color-blindness is caused by an X-linked recessive allele. Which of the following statements are true? A = True, B = False A color-blind female must have a colorblind father. A color-blind male must have a colorblind father. A color-blind female must have a colorblind mother. A color-blind male must have a colorblind mother. Given this pedigree and the additional information that I-1, I-2, I-3 and I-4 are all homozygous individuals for the phenotype displayed in this pedigree, could this be: (A = Yes; B = No) Autosomal recessive inheritance? Autosomal dominant inheritance? X-linked recessive? X-linked dominant?Explanation / Answer
44. A colour blind female must have a colour blind father. True
45. A colour blind male must have a colour blind father . False
46. A colour blind female must have a colour blind mother . False
47. A colour blind male must have a colour blind mother . True
Since it is an X linked recessive disorder, this would imply that if out of both the genes, even if one of the alleles carries the gene for colour blindness, then the individual will be colour blind. For males, out of the two alleles X and Y, Y will be inherited from the father. So even if the father has colour blindness associated with the X chromosome, it will not be imparted to the son, but the same will be imparted to the son of the mother is colour blind.
In the case of the female, the father has only one X chromosome, so if that contains the gene of colour blindness, it will definitely be imparted to the female, but since the mother has two X chromosomes, the daughter might inherit one which does not carry the the gene, thus it is not definite that for a colour blind female, the mother will definitely be colour blind.
Considering that all the of the individuals I-1, I-2, I-3, I-4
48. Autosomal recessive inheritance? No
49. Autosomal dominant inheritance? Yes
50. X- linked recessive? No
51. X linked dominant? No