BIO152H5 Lecture Notes - Lecture 7: Epistasis, Allele, Zygosity

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brownllama517

4 Nov 2016

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Document Summary

Bio 152, more complex patterns of inheritance, october 4th. Red flower and true breeding white flower, homozygous cross, f1 generation, see a pink flower. If you take the gametes of offspring from parental, your gametes are both the allele for red and white. F2 generation no longer have the idea of blending, red, white, and pink. Big r allele has allele for producing red pigment, heterozygote individual has some production of pigment. Allele has a non-functional enzyme for pigment production therefore cannot synthesize red pigment. Grey horse has black and one white parents, roan colour in horses, black hairs and white hairs. Dominant alleles are not always more common alleles in population. Polydactyly: born with extra fingers or toes. Low frequency (1/500 in na of polydactyly. Recessive allele for 5 digits is more prevalent. Just b/c its dominant doesn"t mean it has a high frequency, expressed very rarely. 3 different alleles, a, b and c carbo.

Related Questions

For each of the genetic results described below, provide the term for the inheritance pattern that is most likely the cause and provide an explanation for your choice. Choose from:

Complete Dominance, Incomplete Dominance, Codominance, Multiple Alleles, Lethal Genes

-Six of the gerbils in a litter have white spotted fur and 3 have solid coloured fur.

-40 plants have red flowers, 41 have white flowers, and 79 have pink flowers. The pink flowers are clearly a lighter version of the red flowers.

-A blended family has 11 children. The children are the products of two previous marriages. There are four different phenotypes in the children for the same characteristic.

-A brown coloured cow has had four calves with a white bull. All of the calves have roan coloured hair. (Roan colour occurs when cattle has both red and white hairs in relatively equal amounts.)

-A grey mare had five foals with a grey stallion. Both horses were heterozygous for grey hair. The foals were all grey except for one that was chestnut in colour.

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 âmysteryâ 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

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st e+