Exam 5: Linkage, Recombination, and the Mapping of Genes on Chromosomes

A haploid yeast strain has mating type a and genotype his4 TRP1. A different haploid yeast strain has mating type ? and genotype HIS4 trp1. The two strains mate and produce diploid offspring with genotype his4 TRP1 / HIS4 trp1. The diploid cells undergo meiosis to produce a variety of tetrad types. In the following questions, the genotypes of the spores in a tetrad are shown. For each tetrad, tell what type it is: parental (PD), non-parental (NPD), or tetratype (T). -his4 TRP1; his4 TRP1; HIS4 trp1; HIS4 trp1

A dihybrid testcross is made between genes H and I.Four categories of offspring are produced: H I, H i, h I, and h i.How many degrees of freedom would there be in a chi-square test for goodness of fit of the null hypothesis that the H and I genes are unlinked?

In humans, the genes for red-green color blindness (R = normal, r = color blind) and hemophilia A (H = normal, h = hemophilia) are both X-linked and only 3 map units apart. -Suppose a woman has four sons, and two are color blind but have normal blood clotting and two have hemophilia but normal color vision.What is the probable genotype of the woman?

A haploid yeast strain has mating type a and genotype his4 TRP1. A different haploid yeast strain has mating type ? and genotype HIS4 trp1. The two strains mate and produce diploid offspring with genotype his4 TRP1 / HIS4 trp1. The diploid cells undergo meiosis to produce a variety of tetrad types. In the following questions, the genotypes of the spores in a tetrad are shown. For each tetrad, tell what type it is: parental (PD), non-parental (NPD), or tetratype (T). -his4 TRP1; his4 trp1; HIS4 trp1; HIS4 TRP1

In some fungi, such as the bread mold Neurospora crassa, the arrangement of spores in the ascus directly reflects the order in which they were produced during meiosis.What is the collection of spores produced by meiosis in Neurospora crassa called?

Suppose an individual is heterozygous for alternate alleles of gene A (Aa).Under what conditions would a crossover in a somatic cell of this individual lead to a clone of cells that are homozygous for a? (Pick the most precise answer. )

In Drosophila, the genes y (yellow body)and car (carnation eyes)are located at opposite ends of the X chromosome.In doubly heterozygous females (y⁺ car⁺ / y car), a single chiasma is observed somewhere along the X chromosome in 90% of the examined oocytes.No X chromosomes with multiple chiasmata are observed.What percentage of the male progeny from such a female would be recombinant for y and car?

In peas, tall (T)is dominant to short (t), red flowers (R)is dominant to white flowers (r), and wide leaves (W)is dominant to narrow leaves (w).A tall plant that has red flowers and wide leaves is crossed to a short plant that has white flowers and narrow leaves.The resulting progeny are shown in the table. tall, red, wide 381 tall, white, wide 122 short, red, wide 118 short, white, wide 379 1000 -If two or more of the genes are linked, what map distance separates them?

Mitotic recombination occurs between homologous chromosomes.In which of the following would you not expect to encounter mitotic recombination?

Large sectors suggest a mitotic recombination event late in the growth of a yeast colony.

The measured distance between genes D and E in a two-point testcross is 50 map units.Where are genes D and E in relation to each other? (Select all that apply. )

In peas, tall (T)is dominant to short (t), red flowers (R)is dominant to white flowers (r), and wide leaves (W)is dominant to narrow leaves (w).A tall plant that has red flowers and wide leaves is crossed to a short plant that has white flowers and narrow leaves.The resulting progeny are shown in the table. tall, red, wide 381 tall, white, wide 122 short, red, wide 118 short, white, wide 379 1000 -This cross is not useful to determine if one of the genes is linked to the others.Which gene?

In tetrad analysis, NPD asci can result from (Select all that apply. )

In Drosophila, the autosomal recessive pr and cn mutations cause brown and bright-red eyes, respectively (wild-type flies have brick-red eyes).Flies who are homozygous recessive at both pr and cn have orange eyes.A female who has wild-type eyes is crossed to an orange-eyed male.Their progeny have the following distribution of eye colors: wild-type 8 brown 241 briphit-red 239 orarnge 500 -The mother of these progeny resulted from a cross between two flies from true-breeding lines.What are the genotypes of these two lines?

If the recombination frequency between two genes is close to 50%, what could be true about the location of the two genes? (Select all that apply. )

Two genes are considered linked when there are more F₂ progeny with recombinant genotypes than parental genotypes in the offspring of a dihybrid testcross.

In Drosophila, singed bristles (sn)and carnation eyes (car)are both caused by recessive X-linked alleles.The wild-type alleles (sn⁺ and car⁺)are responsible for straight bristles and red eyes, respectively.A sn car female is mated to a sn⁺ car⁺ male and the F₁ progeny are interbred.The F₂ are distributed as follows: sn\nobreakspacecar 55 sn\nobreakspaceca 45 s 45 s 200 -If you want to analyze this data for evidence of linkage between sn and car, what is the null hypothesis?

When analyzing octads (ordered tetrads), second-division (MII)segregations result from

A haploid yeast strain has mating type a and genotype his4 TRP1. A different haploid yeast strain has mating type ? and genotype HIS4 trp1. The two strains mate and produce diploid offspring with genotype his4 TRP1 / HIS4 trp1. The diploid cells undergo meiosis to produce a variety of tetrad types. In the following questions, the genotypes of the spores in a tetrad are shown. For each tetrad, tell what type it is: parental (PD), non-parental (NPD), or tetratype (T). -HIS4 trp1; HIS4 trp1; his4 TRP1; his4 TRP1

Suppose the L and M genes are on the same chromosome but separated by 100 map units.What fraction of the progeny from the cross L M / l m × l m / l m would be L m / l m?