In the cells of all human females, one X chromosome is inact…

In the cells of all human females, one X chromosome is inactivated. The opsin1 gene is on the X chromosome and it is transcribed in the retinal cells of the eye. Loss-of-function mutations in this gene cause the recessive trait of color blindness. Most women who have one mutant allele of the opsin1 gene and one normal allele of the opsin1 gene (heterozygotes) can still see color. What is the most likely explanation for this finding?

As shown at left in the diagram below, a plasmid vector has…

As shown at left in the diagram below, a plasmid vector has three Eco RI sites. The vector also has one Bam HI site located within the polylinker (Multiple Cloning Site). The numbers in kb (1 kb = 1000 bp) are the numbers of base pairs between two adjacent EcoRI sites. After digesting this vector to completion with either Eco RI or Bam HI in separate reactions, you electrophorese each reaction in separate lanes on an agarose gel. On the right is the result of gel electrophoresis produced by exposing the ethidium bromide–stained gel to UV light. What are the sizes of DNA fragments in the four bands from top to bottom?

Cystic fibrosis in humans is caused by mutations in a single…

Cystic fibrosis in humans is caused by mutations in a single gene and is inherited as an autosomal recessive trait. A couple where neither has cystic fibrosis has two children. The first child has cystic fibrosis, and the second child is unaffected. What is the probability that the second child is a carrier (heterozygous) for the mutation that causes the disease?