Exam 3: Mendelian Genetics

Which types of phenotypic ratios are likely to occur in testcrosses when dealing with two gene pairs for which all the genotypic combinations are of equal viability?

The autosomal (not X-linked) gene for brachydactyly, short fingers, is dominant to normal finger length. Assume that a female with brachydactyly in the heterozygous condition is married to a man with normal fingers. What is the probability that a) their first child will have brachydactyly? b) their first two children will have brachydactyly? c) their first child will be a brachydactylous girl?

What are two typical testcross ratios?

Among dogs, short hair is dominant to long hair and dark coat color is dominant to white (albino) coat color. Assume that these two coat traits are caused by independently segregating gene pairs. For each of the crosses given below, write the most probable genotype (or genotypes if more than one answer is possible) for the parents. It is important that you select a realistic symbol set and define each symbol below.

Parental Phenotypes	Phenotypes of Offspring
	Short	Long	Short	Long
	Dark	Dark	Albino	Albino
(a) dark, short × dark, long	26	24	0	0
(b) albino, short × albino, short	0	0	102	33
(c) dark, short × albino, short	16	0	16	0
(d) dark, short × dark, short	175	67	61	21

Assume that for cross (d), you were interested in determining whether fur color follows a 3:1 ratio. Set up (but do not complete the calculations) a Chi-square test for these data [fur color in cross (d)].

Mendel's postulate of independent assortment is supported by a 1:1:1:1 testcross ratio.

According to Charles Darwin and Alfred Wallace, variations followed a more continuous pattern. According to Mendel's model, variation due to dominance-recessive relationships followed a more ___________ form.

Which types of phenotypic ratios are likely to occur in crosses when dealing with three gene pairs for which all the genotypic combinations are of equal viability?

Polydactyly is expressed when an individual has extra fingers and/or toes. Assume that a man with six fingers on each hand and six toes on each foot marries a woman with a normal number of digits. Having extra digits is caused by a dominant allele. The couple has a son with normal hands and feet, but the couple's second child has extra digits. What is the probability that their next child will have polydactyly?

Which phenotypic ratio is likely to occur in crosses of two completely dominant, independently segregating gene pairs when both parents are fully heterozygous?

Under what conditions does one expect a 1:1:1:1 ratio?

According to Mendel's model, because of the ________ of chromosomes during meiosis, all possible combinations of gametes will be formed in equal frequency.

Which types of phenotypic ratios are likely to occur in crosses when dealing with two gene pairs for which all the genotypic combinations are of equal viability?

Which of the following groups of scientists were influential around the year 1900 in setting the stage for our present understanding of transmission genetics?

To test Mendel's Law of Segregation, the experimenter needs a minimum of two contrasting forms of a gene.

In studies of human genetics, usually a single individual brings the condition to the attention of a scientist or physician. When pedigrees are developed to illustrate transmission of the trait, what term does one use to refer to this individual?

Assuming a typical monohybrid cross in which one allele is completely dominant to the other, what ratio is expected if the F₁s are crossed?

Name the single individual whose work in the mid-1800s contributed to our understanding of the particulate nature of inheritance as well as the basic genetic transmission patterns. With what organism did this person work?

What conditions are likely to apply if the progeny from the cross AaBb × AaBb appear in the 9:3:3:1 ratio?

What is the probability of flipping a penny and a nickel and obtaining one head and one tail?

Assuming no crossing over between the gene in question and the centromere, when do alleles segregate during meiosis?