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8 Jan 2018

GENETICS PROBLEMS

PLEASE help me with these questions! I've provided the answers I just need to see the WORK, detailed work so I can understand. Thank you sooo much.

29. In a dihybrid cross AAbb × aaBB, what proportion of homozygotes is expected among the F2 offspring?

Answer: 1/2

30. In a dihybrid cross AABB × aabb, what proportion of heterozygotes for both gene pairs is expected among the F2 offspring?

Answer 1/2


31. In the dihybrid cross AaBb × aabb, what proportion of homozygotes is expected among the F1 offspring?

Answer: 1/2

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Related questions

Problem A. You cross two homozygous parents: RRYY (round yellow) and rryy (wrinkled green) to produce an F1 generation. Round seeds are dominant, yellow seeds are dominant. You cross two F1s to produce the F2 generation. In the F2 generation, you find an individual with round yellow seeds. You do a testcross to find out the genotype of this “mystery” dominant/dominant phenotype. In the offspring of the cross, you find 1?2 have round yellow seeds and 1?2 have wrinkled yellow seeds.
1. Based on these data what was the genotype of the mystery F2?

Problem B. You carry out a dihybrid cross between a red-flowered rose with long pollen grains (A1A1 LL) and a white-flowered rose with round pollen (A2A2 l l). The flower color gene (A) shows incomplete dominance, and long pollen is completely dominant to round pollen. The genes for these traits are on different chromosomes so assort independently
2. What would be the phenotypes of the F1 generation?
3. What fraction of the F2 generation is expected to have red flowers and long pollen? (As always when traits are independent, what rule can you apply to save time?)

Problem D. In the example of epistasis presented in class, the agouti allele in mice (A) codes for striped hairs and is dominant to the allele for all black hairs (a). A loss-of-function allele for the pigment gene (b) produces no pigment and is recessive to the normal, dominant allele (B). The recessive allele at b masks the effect of the A gene. A dihybrid cross of AABB and aabb is carried out.
5. Name all of the genotypes in the F2 generation that can produce an albino (no pigment) phenotype.

Problem E. A cross is made between homozygous fruit flies that differ for eye color (the st gene) and
body color (the e gene). The F1 double heterozygote is shown below using chromosome notation.
st+ e
--------------------------------------
st e+
st = the recessive allele for scarlet eyes; st+ = the dominant wildtype allele for red eyes e = the recessive allele for ebony body; e+ is the dominant wildtype allele for gray body

6. Are the chromosomes shown in the genotype above in cis or trans configuration?
7. Based on this notation, what were the genotypes and phenotypes of the two parents of the F1? (Think carefully here...)
8. With what phenotype would you cross this F1 to measure recombination frequency?

GENETICS PROBLEMS

PLEASE help me with these questions! I've provided the answers I just need to see the WORK, detailed work so I can understand. Thank you sooo much.

21. In some genetically engineered corn plants the dominant gene (BT) produces a protein that is lethal to certain flying insect pests that eat the corn plants. It was also found that the pollen could cause death in some flying insects. If the corn plant is heterozygous for BT, what proportion of the pollen would carry the dominant gene?

Answer: 1/2

25. Sickle cell anemia is a recessive trait in humans. In a cross between a father who has sickle cell anemia and a mother who is heterozygous for the gene, what is the probability that their first three children will have the normal phenotype?

Answer: 1/8

26. The dominant trait, Huntington disease causes severe neural/brain damage at approximately age 40. A female whose mother has Huntington disease marries a male whose parents are normal. It is not known if the female has the disease. What is the probability that their firstborn will inherit the gene that causes Huntington disease?

Answer: 25%

Alleles at the IGF-1 locus in dogs, encoding insulin-like growth factor, largely determine whether a domestic dog will be large or small. Dogs with an ancestral dominant allele are large, whereas dogs homozygous for the mutant recessive allele are small. Chondrodysplasia, a short-legged phenotype (as in dachshunds and basset hounds), is caused by a dominant gain-of-function allele of the FGF4 gene. The MSTN gene encodes myostatin, a negative regulator of muscle development. Dogs with a dominant ancestral allele of the MSTN gene have normal muscle development, while dogs homozygous for recessive mutants in the MSTN gene are "double muscled" and have trouble running quickly. However, dogs heterozygous for the mutant allele run faster than either of the homozygotes. You breed a pure-breeding small basset hound of normal musculature with a pure-breeding "bully" whippet, a double-muscled large dog with normal legs.

A)what is the genotype of the F1 puppies? Let I and i designate IFG-1 alleles, F and f - FGF4 alleles, and M and m - MTSN alleles

Answer: Ii Ff Mm

B) What is the phenotype of the F1 puppies?

ANSWER: The puppies are large, have short legs, and run fast.

C) If the F1 of this cross is interbred, what proportion of the F2 are expected to be fast runners ?

answer: 1/2

D) If the F1 of this cross is interbred, what proportion of the F2 are expected to be normal-speed runners?

Part D is the section I am having trouble with. The answer is not 1/2. Please help thank you!

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