GENETIC PROBLEMS Question 1 How many different kinds
GENETIC PROBLEMS
Question #1 • How many different kinds of gametes could the following individuals produce? 1. 2. 3. 4. 5. aa. Bb CCDdee AABb. Cc. DD Mm. Nn. Oo. Pp. Qq UUVVWWXXYYZz
Question #1 • Remember the formula 2 n • Where n = # of heterozygous 1. 2. 3. 4. 5. aa. Bb CCDdee AABb. Cc. DD Mm. Nn. Oo. Pp. Qq UUVVWWXXYYZz = = = 2 2 4 32 2
Question #2 • In dogs, wire-haired is due to a dominant gene (W), smooth-haired is due to its recessive allele (w). • WW, Ww • ww = wire haired = smooth haired
Question #2 A • If a homozygous wire-haired dog is mated with a smooth-haired dog, what type of offspring could be produced. W w w W
Question #2 A W fg w Ww Ww F 1 generation all heterozygous
Question #2 B • What type(s) of offspring could be produced in the F 2 generation? • Must breed the F 1 generation to get the F 2. • Results of F 1 Cross: Ww x Ww
Question #2 B W w W WW Ww ww genotype: 1: 2: 1 phenotype: 3: 1 F 2 generation ratio
Question #2 C • Two wire-haired dogs are mated. Among the offspring of their first litter is a smoothhaired pup. • If these, two wire-haired dogs mate again, what are the chances that they will produce another smooth-haired pup? • What are the chances that the pup will wirehaired pup?
Question #2 C W w W WW Ww ww F 2 generation - 1/4 or 25% chance for smooth-haired - 3/4 or 75% chance for wire-haired
Question #2 D • A wire-haired male is mated with a smooth-haired female. The mother of the wire-haired male was smooth-haired. • What are the phenotypes and genotypes of the pups they could produce? • Show the results of crossing: Ww x ww
Question #2 D W w w Ww ww phenotypes: genotypes: 1: 1 ratio
Question #3 • In snapdragons, red flower (R) color is incompletely dominant over white flower (r) color. • The heterozygous (Rr) plants have pink flowers. RR Rr rr - red flowers pink flowers white flowers
Question #3 A • If a red-flowered plant is crossed with a white-flowered plant, what are the genotypes and phenotypes of the plants F 1 generation? • RR x rr
Question #3 A R R r Rr Rr phenotypes: genotypes: F 1 generation 100% pink 100% heterozygous
Question #3 B • What genotypes and phenotypes will be produced in the F 2 generation? • Rr x Rr
Question #3 B R r R RR Rr rr F 2 generation phenotypes: 1: 2: 1 ratio genotypes: 1: 2: 1 ratio
Question #3 C • What kinds of offspring can be produced if a red-flowered plant is crossed with a pink-flowered plant? • RR x Rr
Question #3 C R RR RR r Rr Rr 50%: red flowered 50%: pink flowered
Question #3 D • What kind of offspring is/are produced if a pink-flowered plant is crossed with a white-flowered plant? • Rr x rr
Question #3 D R r r Rr rr 50%: white flowered 50%: pink flowered
Question #4 • In humans, colorblindness (cc) is a recessive sex-linked trait. • Remember: XX - female XY - male
Question #4 A • Two normal people have a colorblind son. • What are the genotypes of the parents? • XCX_? x XCY • What are the genotypes and phenotypes possible among their other children?
Question #4 A XC Y XC X CX C X CY Xc X CX c X c. Y parents 50%: female (one normal, one a carrier) 50%: male (one normal, one colorblind)
Question #4 B • A couple has a colorblind daughter. • What are the possible genotypes and phenotypes of the parents and the daughter?
Question #4 B Xc Y XC X CX c X CY Xc X c. Y parents: Xc. Y and XCXc or Xc. Xc father colorblind mother carrier or colorblind daughter: Xc. Xc - colorblind
Question #5 • In humans, the presence of freckles is due to a dominant gene (F) and the non -freckled condition is due to its recessive allele (f). • Dimpled cheeks (D) are dominant to non -dimpled cheeks (d).
Question #5 A • Two persons with freckles and dimpled cheeks have two children: one has freckles but no dimples and one has dimples but no freckles. • What are the genotypes of the parents? Parents: F__D__ x F__D__ Children: F__dd x ff. D__
Question #5 B • What are the possible phenotypes and genotypes of the children that they could produce? • Cross: Ff. Dd x Ff. Dd • This is a dihybrid cross
Question #5 B • Possible gametes for both: FD Fd f. D fd FD FFDd Ff. DD Ff. Dd Fd FFDd Ffdd f. D Ff. Dd ff. DD ff. Dd fd Ff. Dd Ffdd ff. Dd ffdd FFdd
Question #5 B Phenotype : Freckles/Dimples: Freckles/no dimples: no freckles/Dimples: no freckles/no dimples: 9 3 3 1 Phenotypic ratio will always been 9: 3: 3: 1 for all F 1 dihybrid crosses.
Question #5 B Genotypic ratio: FFDD FFDd FFdd Ff. DD Ff. Dd Ffdd ff. DD ff. Dd ffdd - 1 2 4 2 1
Question #5 C • What are the chances that they would have a child whom lacks both freckles and dimples? • This child will have a genotype of ffdd • Answer: 1/16
Question #5 D • A person with freckles and dimples whose mother lacked both freckles and dimples marries a person with freckles but not dimples whose father did not have freckles or dimples. Ff. Dd x Ffdd • Possible gametes: FD Fd f. D fd x Fd fd • Cross:
Question #5 D • What are the chances that they would have a child whom lacks both freckles and dimples? Fd fd FD Fd FFDd FFdd Ff. Dd Ffdd Answer: 1/8 f. D fd ff. Dd ffdd
Question #6 • Sixteen percent of the human population is known to be able to wiggle their ears. • This trait is determined to be a recessive gene. • These is a population genetics question. • Use the following equation: 1 = p 2 + 2 pq + q 2
Question #6 A • What of the population is homozygous dominant for this trait? • q 2 = 16% or. 16: • then use : q 2 = . 16 q =. 4 1 = p + q 1 = p +. 4 1 -. 4 = p p =. 6 • Now use p 2 for answer: . 62 =. 36 or 36%
Question #6 B • What of the population is heterozygous for this trait? • We know that q =. 4 and p =. 6 • Now use 2 pq for answer: 2(. 6)(. 4) =. 48 or 48%
Question #7 • In dogs, the inheritance of hair color involves a gene B for black hair and gene b for brown hair b. • A dominant C is also involved. It must be present for the color to be synthesized. • If this gene is not present, a blond condition results. BB, Bb bb - black hair brown hair CC, Cc cc - color blond
Question #7 A • A brown haired male, whose father was a blond, is mated with a black haired female, whose mother was brown haired and her father was blond. Male: bb. Cc (gametes: b. C bc) Female: Bb. Cc (gametes: BC Bc b. C bc) • What is the expected ratios of their offspring?
Question #7 A BC Bc b. C bc b. C Bb. Cc bb. CC bb. Cc bc Bbcc bb. Cc bbcc Bb. Cc Offspring ratios: Black: Brown: Blond: 3/8 2/8 or 1/4
Question #8 • Henry Anonymous, a film star, was involved in a paternity case. The woman bringing suit had two children, on whose blood type was A and the other whose blood type was B. • Her blood type was O, the same as Henry’s! • The judge in the case awarded damages to the woman, saying that Henry had to be the father of at least one of the children.
Question #8 A • Obviously, the judge should be sentenced to Biology. For Henry to have been the father of both children, his blood type would have had to be what? IA IB Answer i I Ai I Bi
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