Exam 13: Mendel and the Gene

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?

Assuming independent assortment for all gene pairs,what is the probability that the following parents,AABbCc × AaBbCc,will produce an AaBbCc offspring?

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 they will have a daughter with hemophilia?

Figure 13.2 Analyze the results of crosses and pedigrees to determine whether genes or alleles are autosomal or X-linked, dominant or recessive, linked or on different chromosomes. -In the figure above,flower A was crossed with flower B to produce flower C.The phenotype of flower C is the result of

A man who carries an allele of an X-linked gene will pass it on to

Pseudohypertrophic muscular dystrophy is a human disorder that causes gradual deterioration of the muscles.Only boys are affected,and they are always born to phenotypically normal parents.Due to the severity of the disease,the boys die in their teens.Is this disorder likely to be caused by a dominant or recessive allele? Is its inheritance sex-linked or autosomal?

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 female child will have albinism?

There are 40 different alleles for a gene involved in immune function.What is the maximum number of alleles that a human can have?

Two individuals of genotype AABBCCDD and aabbccdd are mated.The F1 generation is interbred (self-fertilized)to yield 5000 progeny.What proportion of the F2 is expected to be AabbCcDD?

In tigers,a recessive allele causes a white tiger (absence of fur pigmentation).If two phenotypically normal tigers that are heterozygous at this locus are mated,what percentage of their offspring is expected to be white?

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?

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

A black guinea pig crossed with an albino guinea pig produced 12 black offspring.When the albino was crossed with a second black animal,6 blacks and 6 albinos were obtained.What is the best explanation for this genetic situation?

When Mendel crossed yellow-seeded and green-seeded pea plants,all the offspring were yellow seeded.When he took these F₁ yellow-seeded plants and crossed them to green-seeded plants,what genotypic ratio is expected?

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?

Figure 13.3 -The distance between two genes is a determinant of their recombination frequency.Based on the image below,which of the following sets of genes will show the greatest recombination frequency?

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 wings and a hairy body and a fly with vestigial wings and a normal 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?

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?

A heterozygous,but phenotypically wild-type fruit fly (gray body color and normal wings)was mated to a black fly with vestigial wings.The offspring had the following phenotypic distribution: wild type,720;black-vestigial,780;black-normal,280;gray-vestigial,220.What conclusion is likely from these results?

Julie has Harman's ataxia (hh)and also has achrondoplasia (Aa).Josh is a carrier for Harman's ataxia,an autosomal recessive disorder,and has achondroplasia (Aa),which is an autosomal dominant trait.AA human embryos do not survive beyond the first few cell divisions.What is the probability that a child born to them would have only Harman's ataxia? Assume the genes are unlinked.