Genetics Practice Problems s2

Genetics Practice Problems – Q&A

Probability: Q1. A die (singular of dice) has 6 Q2. The Jones family has 8 children, Q3. What types of gametes would be produced by sides. What is the probability that an all of whom are girls. What is the an organism having the genotype AaBB for 2 traits? even number will come up on one chance that the next child will be a (Hint – use arrows to determine all possibilities) throw of a die? boy? Explain. A1: A2: A3:

Traditional Mendelian Dominant/Recessive Inheritance: Q1. Widow’s peak is dominant. Q2. In garden peas, tall vine Q3. Albinism is a recessive Q4. Guinea pigs can have short What are the possible is dominant and short vine is disease causing lack of hair or long hair. A short-haired phenotypes of the offspring of a recessive. If a homozygous pigment. What are the male and a short-haired female man homozygous dominant tall plant is crossed with a chances of an albino man produced mostly short-haired (WW) and a heterozygous homozygous short plant, and a carrier woman having offspring, but a few were long- woman (Ww)? Show Punnett what genotypes are possible an albino child? Show haired. Is short hair dominant or square and answer. in the F1 generation? Show Punnett square and give recessive? Do a Punnett square Punnett square and answer. answer as a percentage. that explains the above. A1. A2. A3. A4.

Mendelian Problems using F1 and F2 generation: Q1. In summer squash, white fruit color is dominant (W) and Q2. In garden peas, inflated pod is dominant and constricted yellow is recessive (w). A squash plant that is homozygous for pod is recessive. A true-breeding inflated pod plant is crossed white (WW) is crossed with a homozygous yellow one (ww). with a true-breeding constricted pod plant. Do a Punnett square and predict the phenotypes of the F1 and Do a Punnett square and predict the phenotypes of the F1 F2 generations. Remember you cross 2 F1’s to get the F2 and F2 generations. Remember you cross 2 F1’s to get the generation. F2 generation. Lastly – if there are a total of 100 offspring in the F2 generation, how many of these will have constricted pods? A1. Punnett Square Phenotype Ratios A2. Punnett Square Phenotype Ratios

F1 F1

F2 F2

How many out of 100 F2 offspring will have constricted pods? ______Incomplete Dominance Codominance Multiple alleles Q1. Snapdragon plants exhibit Q1. Coat color in cattle follows the Q1. Rabbit coat color has multiple incomplete dominance for flower color. codominant pattern of inheritance with alleles with a hierarchy of dominance. What percentage of plants will have red possible phenotypes of red, white, or Grey (C) dominates over chinchilla (cch) flowers if you cross 2 pink-flowered roan (both red and white) hair. What are which dominates over Himalayan (ch) plants? Do the Punnett square and give the genotypes and phenotypes that result which dominates over albino(c). What answer. from crossing a red cow (RR) with a phenotype will result from each of the white bull(rr)? genotypes listed below? A1. A1. A1. Cc = CC = cchc = cc = Cch = ch c =

Blood Types (Codominance and Multiple Alleles) – can use A, B, O instead of I’s Q1. What is the probability that a couple Q2. A type A woman whose father was Q3. A couple has a child with type A whose blood types are AB and O will type B marries a type B man whose blood. If one parent is type O, what are have a type A child? Show Punnett mother was type A. What will be their the possible genotypes of the other square and give answer in percentage. children's possible genotypes and parent? phenotypes? Show Punnett square and Do a Punnett square, filling in everything answers. you know and a question mark for what you don’t know. A1. A2. A3.

X-linked (Sex-Linked) – use N for normal, n for hemophilia or color-blindness or white eyes Q1. If a woman who is a carrier for Q2. If a normal-sighted woman whose Q3. In fruit flies, white eyes is a sex- hemophilia marries a normal male, what father was color-blind marries a color- linked trait. Normal eye color is red. If is the chance they will have a child with blind man, what is the probability that a white-eyed male is crossed with a hemophilia? What is the chance their their son will be color-blind? What is heterozygous female, what proportion of son will have hemophilia? the probability that their daughter will be the offspring will have red eyes? Do the Punnett square – remember your color-blind? Do the Punnett square – remember your X and Y chromosomes!! Don’t put Do the Punnett square – remember your X and Y chromosomes!! Don’t put anything on the Y!! X and Y chromosomes!! Don’t put anything on the Y!! anything on the Y!! A1. A2. A3. Pedigrees: Label each pedigree with the type of inheritance it demonstrates: Choose from Autosomal recessive, Sex-linked (X-linked), or Autosomal dominant

Type: ______Type______Type______

PRACTICE IDENTIFYING TYPES OF INHERITANCE: (Use your guided notes to help) Choose from the following types of inheritance and write in the box which one is described by each situation: 2 linked genes (little or no crossing over) Polygenic (several to many genes) Multiple alleles – hierarchy of dominance Incomplete dominance Dihybrid cross – 2 genes on different chromosomes Type of Inheritance Situation 1) In the F2 generation of a certain plant, ¼ have no thorns, ¼ have long thorns, and ½ have short thorns. 2) In another set of plants, also an F2 generation, you find the following phenotype ratios: 9 red flowers with broad leaves, 3 red flowers with narrow leaves, 3 white flowers with broad leaves, and 1 white flower with narrow leaves. 3) In a certain species of bird, you see some birds with barely any crest on their head, some with very long crests, and many birds with crests of all possible lengths in between. 4) In a certain species of insect, three eye colors are known: red, orange, and yellow. If purebred red-eyed individuals are crossed with purebred orange-eyed, all the offspring are red-eyed. If purebred orange-eyed are crossed with purebred yellow-eyed, all the offspring are orange-eyed. If purebred red-eyed are crossed with purebred yellow-eyed, all the offspring are red-eyed. 5) In another case in which you study 2 traits of a plant at the same time, you find in the F2 generation that ¾ have hairy stems and green seeds while the other ¼ have smooth stems and brown seeds.

Challenge: (How good are your genetic skills?!!) – do on separate paper 1) The polled (hornless) trait in cattle is dominant. The horned trait is recessive. A certain polled bull is mated to 3 cows. Cow A, which is horned, gives birth to a polled calf. Cow B, also horned, produces a horned calf. Cow C, which is polled, produces a horned calf. Name the genotypes of all parents. 2) In poultry, rose comb is a dominat trait (R), single comb is recessive (r). A rose combed male is mated with 2 rose combed females. Female A produces 14 chicks, all rose-combed. Female B produces 9 chicks, 7 rose-combed and 2 single-combed. What are the genotypes of the 3 parent birds? 3) In sheep, white coat is dominant to black. Occasionally, a black sheep appears in a flock. Black wool is worthless. How could a farmer eliminate the genes for black coat from the flock? 4) Suppose you examined the cells of a species of plant and found 12 chromosomes: a long straight pair, a short straight pair, a medium-length straight pair, a long bent pair, a short bent pair, and a medium-length bent pair. You then breed the plants of this species for several generations. At the end of this time, would you expect to find some plants with all the straight chromosomes and none of the bent ones? Or vice versa? Explain. 5) In snapdragons, red flower color (R) is incompletely dominant to white (r), the heterozygotes being pink. And the normal broad leaves (B) are incompletely dominant to narrow leaves, the heterozygotes having leaves of medium breadth. If a red- flowered, broad-leaved plant is crossed with a white-flowered, narrow-leaved one, what will be the phenotypes and their expected ratios in the F2 generation? 6) In mice, black fur color is dominant to brown. A brown mouse is crossed with a heterozygous black mouse. If the mother has a litter of four, what are the chances that all of them will be brown? 7) In dogs, wire hair is a dominant trait, smooth hair is recessive. Two wire-haired dogs produce a male puppy that is wire- haired. To find out most quickly whether he carries the allele for smooth hair, he should be mated to what type of female? How will you know based on the mating?