BIO152H5 Lecture Notes - Lecture 7: Sun Tanning, Plant Genetics, Meiosis

50 views6 pages

erinturtle513

23 May 2017

School

Department

Course

Professor

For unlimited access to Class Notes, a Class+ subscription is required.

Document Summary

Lecture 7: inheritance and genetics part 2. Dominant recessive allele doesn"t disappear but dominant masks the recessive. Incomplete dominance: the heterozygotes have an intermediate phenotype since alleles of a gene are not always clearly dominant or recessive, ex. color in snapdragons and 4 o"clock flowers. F1: appears to support blending hypothesis will be all pink. R allele: has functional enzyme for producing red pigment r allele: has a non-functional enzyme for pigment production, therefore cannot synthesize red pigment. Rr results in a pink color enough enzyme for red but not enough for white. Codominance: produces a heterozygote phenotype that is a combination of the two homozygotes, both alleles are expressed equally unlike incomplete dominance, ex. Roan color in horses there are white hairs and black hairs but to the eye from a far, it looks grey. Frequency of dominant alleles: dominant alleles are not always the more common alleles in a population, polydactyly.

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 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

--------------------------------------

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?

cyansnail823

QUESTION 1

Jim is blood type A, his brother John is type O and his sister Jane is type AB. What are the genotypes of their parents?

Which of the following is true for alleles that show incomplete dominance?

Heterozygotes have a genotype like the dominant allele.

Homozygotes have a genotype like the recessive allele.

Heterozygotes have a phenotype intermediate between the dominant and recessive alleles.

Homozygotes have the same phenotype as the heterozygotes.

QUESTION 3

Which principle of inheritance concluded that when games are formed in meiosis, the two alleles of each gene separate from one another, and each gamete receives only one allele?

independent assortment

Which term best describes a condition in which alleles at one locus can alter the expression of alleles at another locus?

polygenic inheritance

A single unit of genetic information located on a chromosome defines:

The physical expression (appearance or function) of an organism's genes defines:

genotype

a single characteristic

Palomino horses (golden color with a blond mane) are an incompletely dominant trait produced by the combination of the chestnut color allele and the cream color allele. If you wanted to produce as many palominos as possible, which mating strategy below would be the best choice?

Which term best describes the effect of a single gene on multiple aspects of the phenotype?

polygenic inheritance

QUESTION 9

Which term best describes the separate expression of both alleles for a single trait in the same cell?

polygenic inheritance

QUESTION 10

One form of a gene found on a single chromosome defines:

A chocolate lab (whose mother was a yellow lab) is mated with a black lab whose genotype is BbEe. What fraction of the offspring would be expected to be yellow labs?

What type of allele is always expressed regardless of whether the individual is homozygous or heterozygous for it?

Both the dominant and recessive alleles

Given the parents AABBGgHhrr Ã AabbGgHhRr, assume simple dominance and independent assortment. What proportion of the progeny will be expected to have the genotype AaBbggHHrr?

___________________ is defined as having two of the same type of allele for a particular trait.

The physical position of an allele on a single chromosome defines:

Which term best describes two or more genes affecting the phenotype in an additive fashion?

codominance

polygenic inheritance

Q 1 â Manx cats are produced when a dominant allele is inherited for the Manx gene (M). Inheritance of two dominant alleles, however, results in death of the fetus. Coat color in cats is determined by two alleles with incomplete dominance. BB produces black colored cats, Bb produces grey cats, and bb produces white cats. A grey Manx cat is mated with a white Manx. What proportion of the living offspring will be white Manx kittens? (3 points)

Q 2 â In goats, a beard is produced by an autosomal allele that is dominant in males and recessive in females. Weâll use the symbol B^b for the beard allele and B+ for the beardless allele. Another independently assorting autosomal allele that produces a black coat (W) is dominant over the allele for white coat (w). Give the phenotypes and their proportions expected for the following cross: B⁺B⁺Ww male Ã B^bB^bWw female (2 points)

Q 3 â E. W. Lindstrom crossed two corn plants with green seedlings and obtained the following progeny: 3583 green seedlings, 853 virescent-white seedlings, and 260 yellow seedlings.

Give the genotypes for the green, virescent-white, and yellow seedlings

Explain how color is determined in these seedlings (which genotype gives which phenotype). (3 points)

Q 4 â You are studying a gene that controls ossicone (horn) length in giraffes. The wild-type long-ossicone allele (L) is dominant to the mutant short-ossicone (l) allele. However the L allele is only 60% penetrant in both homozygotes and heterozygotes. In a population of 212 giraffes in an African nature preserve, 80 giraffes are either homozygous or heterozygous for the long ossicone allele (L). What proportion of offspring would you expect to exhibit the long ossicone phenotype? (2 points)

harlequinserval672

BIO152H5 Lecture Notes - Lecture 7: Sun Tanning, Plant Genetics, Meiosis

Document Summary

Get access

Related textbook solutions

Molecular Cell Biology

Biology: Science for Life with Physiology

Concepts of Biology

Biology

Essentials of Biology

Related Documents

BIO152H5 Chapter Notes - Chapter 13: Dihybrid Cross, Punnett Square, Nettie Stevens

BIO152H5 Lecture Notes - Lecture 7: Genetic Variation, Monosomy, Pleiotropy

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

Related Questions