Exam 3: Mendelian Genetics

A certain type of congenital deafness in humans is caused by a rare autosomal (not X-linked)dominant gene. (a)In a mating involving a deaf man and a deaf woman (both heterozygous),would you expect all the children to be deaf? Explain your answer. (b)In a mating involving a deaf man and a deaf woman (both heterozygous),could all the children have normal hearing? Explain your answer. (c)Another form of deafness is caused by a rare autosomal recessive gene.In a mating involving a deaf man and a deaf woman,could some of the children have normal hearing? Explain your answer.

A certain type of congenital deafness in humans is caused by a rare autosomal recessive gene.In a mating involving a deaf man and a deaf woman,could some of the children have normal hearing? Explain your answer.

Dentinogenesis imperfecta is a rare,autosomal,dominantly inherited disease of the teeth that occurs in about one in 8000 people (Witkop 1957).The teeth are somewhat brown in color,and the crowns wear down rapidly.Assume that a male with dentinogenesis imperfecta and no family history of the disease marries a woman with normal teeth.What is the probability that (a)their first child will have dentinogenesis imperfecta? (b)their first two children will have dentinogenesis imperfecta? (c)their first child will be a girl with dentinogenesis imperfecta?

Tightly curled or wooly hair is caused by a dominant gene in humans.If a heterozygous curly-haired person marries a person with straight hair,what percentage of their offspring would be expected to have straight hair?

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

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. $\quad$$\quad$$\text { Parental Phenotypes }$ $\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$ $\text { Phenotypes of Offspring }$ Short Dark Long Dark Short Albino Long Albino (a) dark, short X dark, long 26 24 0 0 (b) albino, short X albino, short 0 0 102 33 (c) dark, short X albino, short 16 0 16 0 (d) dark, short X 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)].

Albinism,lack of pigmentation in humans,results from an autosomal recessive gene (a).Two parents with normal pigmentation have an albino child.What is the probability that their next three children will be albino?

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 is used to refer to this individual?

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?

Albinism,lack of pigmentation in humans,results from an autosomal recessive gene (a).Two parents with normal pigmentation have an albino child.What is the probability that their next child will be albino?

Albinism,lack of pigmentation in humans,results from an autosomal recessive gene (a).Two parents with normal pigmentation have an albino child.What is the probability that their next child will be an albino girl?

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

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

A certain type of congenital deafness in humans is caused by a rare autosomal dominant gene.In a mating involving a deaf man and a deaf woman,could all the children have normal hearing? Explain your answer.

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?

How many kinds of gametes will be expected from an individual with the genotype PpCcTTRr?

A 9:3:3:1 phenotypic ratio is expected from a dihybrid testcross.

The nonfunctional form of a gene is called a wild-type allele.

In what ways is sample size related to statistical testing?

Assume that in a series of experiments,plants with round seeds were crossed with plants with wrinkled seeds and the following offspring were obtained: 220 round and 180 wrinkled. (a)What is the most probable genotype of each parent? (b)What genotypic and phenotypic ratios are expected? (c)Based on the information provided in part (b),what are the expected (theoretical)numbers of progeny (400 total)of each phenotypic class?