Exam 2: Transmission Genetics

A geneticist is investigating the inheritance of two autosomal recessive genes in mice, one for obesity (LEP) and another for autism (oprm1). The table below provides the number of offspring observed, for each phenotype, when dihybrid mice are testcrossed: Phenotype Observed(O) Expected () - (-)2 (-)2/ wild- type 88 obese 68 autistic 64 obese, autistic 80 (-/= Fill in the table above and determine: a. the chi- square (χ²) value (to the nearest hundredth) for the chance hypothesis that the two genes assort independently b. the degrees of freedom c. whether or not you would reject your chance hypothesis that the two genes assort independently, based on approximate P value, and the justification for why

The law of independent assortment predicts that crossing of dihybrid F1 plants to one another would produce nine genotypes in a _______ ratio among F2 progeny.

What is the probability of rolling one six- sided die and obtaining a 1 or a 2?

The P value is a quantitative expression of the probability that the results of another experiment of the same size and structure will DEVIATE FROM EXPECTED RESULTS AS MUCH AS OR MORE THAN BY CHANCE. The greater the difference between observed and expected results of an experiment,_________ .

In peas, the yellow allele is dominant over the green allele. A plant with yellow peas was crossed to a plant with green peas. The resulting plants were 50% yellow and 50% green. What are the genotypes of the parents in this cross?

The P value is dependent on the number of _______, which is equal to the number of independent variables in an experiment.

What genotypic ratio would you expect to observe among the progeny of a monohybrid cross?

In a test cross, a pure- breeding plant is crossed with a plant suspected to be heterozygous (Aa). What is the genotype of the pure- breeding plant?

A couple has four children. What is the probability that they have four boys?

A ratio of 9:3:3:1 is expected among the F2 progeny of a dihybrid cross as a result of___________of alleles at two loci.

In 1997, a gene called Le was discovered by two research groups led by David Martin and Diane Lester. Allelic variation in the Le gene, which controls elongation of the plant stem between branches, is responsible for which trait in peas?

In peas, axial (A) flower position is dominant to terminal (a), tall (L) is dominant to short (l), and yellow (Y) is dominant to green (y). If a plant that is heterozygous for all three traits is allowed to self- fertilize, how many of the offspring would show the dominant phenotype for all three traits?

A geneticist is investigating the inheritance of two autosomal recessive genes in mice, one for obesity (LEP) and for autism (oprm1). The table below provides the number of offspring observed, for each phenotype, when dihy mice are crossed: Phenotype Observed(O) Expected (E) O- E (-)2 (-)2/ wild- type 154 obese 69 autistic 58 obese, autistic 23 (-/= Fill in the table above and determine: a. the chi- square (χ²) value (to the nearest hundredth) for the chance hypothesis that the two genes assort independently b. the degrees of freedom c. whether or not you would reject your chance hypothesis that the two genes assort independently, based on y approximate P value, and the justification for why

The gene L determines hair length in rabbits. The gene B determines hair color. A rabbit with long, black hair is crossed to a rabbit with short, white hair. All the offspring have long, black hair. What are the genotypes of the parents?

In the accompanying figure, the chance that individual III- 5 is a heterozygous carrier is _________ .

The pedigree suggests which mode of inheritance for an allele on chromosome 15?

In the accompanying figure, the chance that individual IV- 7 is a heterozygous carrier is __________ .

Tim and Mary are planning to start a familiy. While neither of them have cystic fibrosis, a rare autosomal recessi disease, they are concerned that their children could have the disease since Tim's father, John, AND Mary's broth Ralph both have the disease. a. Draw a pedigree of the inheritance of the cystic fibrosis allele in this family. b. On your pedigree, indicate any individuals that must be carriers. c. What is the probability that Tim will be a carrier for the disease allele? d. What is the probability that Mary will be a carrier for the disease allele? e. What is the probability that Tim and Mary will have a child with the disease?

In mice, black coat color is dominant to white coat color. In the pedigree below, mice with a black coat are represented by darkened symbols, and those with white coats are shown as open symbols. What is the genotype of III- 1?

Huntington's disease is an autosomal dominant trait. Given the pedigree below, if individual IV- 2 has three children with a normal man, what is probability that exactly two of the three children would have the disorder?