Exam 3: Independent Assortment of Genes

If an individual has 10 gene pairs,how many different gametes can be formed if 5 of the gene pairs are homozygous and the remaining 5 gene pairs are heterozygous?

In a Drosophila cross,you mate a parental line displaying crossed eyes (recessive trait,autosomal)and corkscrew bristles (recessive trait,autosomal)by a wild-type fly.The sites of the two genes are known to be unlinked.The F₁ flies are wild type. You self the F₁ flies in the hope of regenerating the cross-eyed/corkscrew phenotype. How many individual F₂ flies would you need to analyze to have 95% confidence of finding at least one cross-eyed/corkscrew fly?

A pure line of Guinea pigs with genotype A/A;b/b is crossed to a pure line with genotype a/a;B/B.The F₁ male and female Guinea pigs are crossed to each other to generate the F₂.What proportion of the F₂ individuals are the result of a recombinant egg being fertilized by a recombinant sperm?

Fruit color in a particular plant is controlled by a set of three QTLs (quantitative trait loci,or "polygenes")that work in an equal and additive manner.Each QTL has two alleles (i.e. ,A and a);each allele represented by a capital letter produces one dose of yellow pigment,while alleles represented with lower case letters do not produce any pigment at all. -A trihybrid plant (A/a;B/b;C/c)is selfed.Assuming no effects of the environment,what proportion of the offspring will have the same fruit color phenotype as the dihybrid parent?

Mendel crossed Y/Y;R/R (yellow wrinkled)peas with y/y;r/r (green smooth)peas and selfed the F₁ to obtain an F₂.In the F₂ what proportion of the yellow wrinkled individuals were pure-breeding?

If a plant of genotype A/a;B/b;C/c;D/d is selfed and the genes assort independently,how many different genotypes will be found among the progeny?

In the offspring of a dihybrid self,what percentage of the individuals are themselves dihybrid?

You are studying meiosis in fungi with an organism in which the haploid chromosome number is 5 (n = 5).You combine two haploid cells together (strain 1 by strain 2),and then activate meiosis to regenerate haploid cells.What are the odds that any individual haploid cell will have either the five chromosomes from strain 1 or the five chromosomes from strain 2?

In the cross between a female A/a;B/b;c/c;D/d;e/e and male A/a;b/b;C/c;D/d;e/e,what proportion of the progeny will be phenotypically identical to the female parent? (Assume independent assortment of all genes and complete dominance.)

In a particular dihybrid,the two genes of interest,A and B,are located on different chromosomes.Which of the following diagrams does NOT represent a stage of meiosis in this organism? (Note: For each answer only some chromatids may be represented.)

If stem length in a certain species of crops was solely determined by polygenic inheritance,how many different genes would be required in this system to explain the existence of 15 different stem lengths ranging from 15 to 29 cm?

Vanessa has obtained two true-breeding strains of mice,each homozygous for an independently discovered recessive mutation that prevents the formation of hair on the body.The discoverer of one of the mutant strains calls his mutation naked,and the other researcher calls her strain hairless.To determine whether the two mutations are simply alleles for the same gene,Vanessa crosses naked and hairless mice with each other.All the offspring are phenotypically wild type.After intercrossing these F₁ mice,however,Vanessa observes 115 wild-type mice and 85 mutant mice in the F₂. a)What is the most likely explanation for the segregation of wild-type mice and mutant mice in the F₂? Are the naked and hairless mutations alleles for the same gene? b)Using symbols of your own choosing,indicate the genotypes of the parents,the F₁,and each of the phenotypic classes of the F₂ progeny.Describe any gene interactions in this set of crosses.

Fruit color in a particular plant is controlled by a set of three QTLs (quantitative trait loci,or "polygenes")that work in an equal and additive manner.Each QTL has two alleles (i.e. ,A and a);each allele represented by a capital letter produces one dose of yellow pigment,while alleles represented with lower case letters do not produce any pigment at all. -If a trihybrid plant (A/a;B/b;C/c)is testcrossed,what proportion of the offspring will have a fruit color phenotype that is different from both the trihybrid and the tester parents? (Assume no environmental effects.)

In a perfectly controlled laboratory environment,a pure-breeding fish with a 23-mm tail was crossed to a pure-breeding fish with a 15-mm tail.In the F₁,all individuals had tails of an intermediate length: 19 mm.If tail length is a typical polygenic trait controlled entirely by the equal and additive effect of two unlinked genes,each with two alleles ("+" and "-"),what phenotypic ratios do you expect to find in the F₂?

Two haploid yeast cells,one wild type and one having a mutation blocking the synthesis of adenine,were mated to produce a diploid zygote.Through asexual reproduction (mitosis),this zygote gave rise to hundreds of identical cells,and all were wild type in phenotype.These (diploid)cells were then induced to undergo meiosis,and the progeny (a random sample of haploid meiotic products)consisted of 214 cells able to grow without adenine and 203 unable to grow without adenine. a)Diagram the cross,picturing the chromosomes of the parents,the zygote,metaphase I,and the meiotic products. b)How many genes are involved? c)What are the dominance relationships of the alleles of the gene or genes?

A woman with tritanopia (a rare form of inherited blue-yellow color blindness)marries a man who also has tritanopia.Their first daughter has normal color vision but is diagnosed with PKU. a)Based on this information,what is the most likely mode of inheritance of tritanopia? b)Using symbols of your own invention,write the genotypes of the two parents and of their daughter.(Assume independent assortment.) c)What is the probability that the couple's next child is a son with tritanopia and PKU? (Assume independent assortment.)

In a haploid fungus similar to Neurospora,a red-colored mutant is crossed to an alanine-requiring mutant.Assuming independent assortment,what proportion of the spores produced will be alanine-requiring?

A trihybrid cross is a cross between two individuals who are heterozygous for three genes.Assuming independent assortment and complete dominance,what phenotypic ratios would be observed in F₁?

Mendel crossed Y/Y;R/R (yellow wrinkled)peas with y/y;r/r (green smooth)peas and selfed the F₁ to obtain an F₂.What proportion of the F₂ individuals were pure-breeding?

The pedigree below shows the inheritance patterns of two extremely rare,independent genetic conditions (represented with black and grey symbols,respectively).If individuals A and B have a child,what is the probability that it will have both conditions?