Exam 13: Mendel and the Gene

A man and woman are both of normal pigmentation and have a one child out of three who is albino (without melanin pigmentation).Albinism is an autosomal (not sex-linked)recessive trait.What are the genotypes of the albino's parents?

Hemophilia is caused by several genetic factors;one,a recessive allele of an X-linked gene,is the subject of this problem.Assume that a man with hemophilia marries a normal woman whose father had hemophilia.What is the probability that their first son will have hemophilia?

Different ratios occur in crosses with single gene pairs or two gene pairs.What types of ratios are likely to occur in crosses dealing with a single gene pair?

A man has extra digits (six fingers on each hand and six toes on each foot).His wife and their daughter have a normal number of digits.Having extra digits is a dominant trait.The couple's second child has extra digits.What is the probability that their next (third)child will have extra digits?

Figure 13.1 -In a Drosophila experiment,a cross was made between homozygous wild-type females and yellow-bodied males.All of the resulting F₁s were phenotypically wild type.However,adult flies of the F₂ generation (resulting from matings of the F₁s)had the characteristics shown in the figure above: (a)Is the mutant allele for yellow body recessive or dominant? (b)Is the yellow locus autosomal (not X-linked)or X-linked?

In Drosophila melanogaster,vestigial wings are caused by a recessive allele of a gene that is linked to a gene with a recessive allele that causes black body color.Morgan crossed black-bodied normal-winged females and gray-bodied vestigial-winged males.The F₁ were all gray bodied,normal winged.After examining the F₂ progeny,Morgan calculated the map distance to be 17 map units.Which of the following is correct about the F₂ progeny?

A man and woman are both of normal pigmentation,but both have one parent who is albino (without melanin pigmentation).Albinism is an autosomal (not sex-linked)recessive trait.What is the probability that their first child will be an albino?

Regarding an allelic pair for flower color in snapdragons,heterozygotes have pink flowers,whereas the two homozygotes have red flowers or white flowers.When plants with red flowers are crossed with plants with white flowers,what proportion of the offspring is expected to have pink flowers?

Mendel crossed yellow-seeded and green-seeded pea plants and then allowed the offspring to self-pollinate to produce an F₂ generation.The results were as follows: 6022 yellow and 2001 green (8023 total).The allele for green seeds has what relationship to the allele for yellow seeds?

In birds,sex is determined by a ZW chromosome scheme that is much like the typical XY scheme seen in humans and many other organisms,except that the system is reversed: Males are ZZ (similar to XX in humans)and females are ZW (similar to XY in humans).A lethal recessive allele that causes death of the embryo occurs on the Z chromosome in pigeons.What would be the sex ratio in the offspring of a cross between a male heterozygous for the lethal allele and a normal female?

Suppose two AaBbCc individuals are mated.Assuming that the genes are not linked,what fraction of the offspring are expected to be homozygous recessive for the three traits?

In Drosophila melanogaster,vestigial (short)wings (vg)are caused by a recessive allele of a gene that independently assorts with a gene pair that influences body hair.Hairy (h)results in a hairy body.A cross is made between a fly with normal (wild)wings and a hairy body and a fly with vestigial wings and a normal (wild)body.The phenotypically normal F₁ flies were crossed among each other,and 1024 F₂ flies were reared.What phenotypes would you expect in the F₂,and in what actual numbers (not ratios)would you expect to find them?