MBG 2040 Chapter Notes - Chapter 4: Null Allele, Wild Type, Zygosity

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amethystrat477

25 Nov 2012

School

University of Guelph

Department

Molecular Biology and Genetics

Course

MBG 2040

Professor

Dennis Baker

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Document Summary

Incomplete dominance and co-dominance: when the heterozygote has a different phenotype than the other homozygotes. Semidominant when the heterozygote"s phenotype is midway between the phenotypes of the 2 homozygotes. When a heterozygote shows characteristics found in each of the associated homozygotes. Such as in human blood types, people who are type ab produce antibodies for both the a and b antigens. Codominant because both alleles contribute independently to the phenotype, neither allele is dominant or partially dominant over the other. Multiple alleles: some gene has 3 or 4 or more different alleles. Allelic series: wild-type is completely dominant over all the other alleles, the rest are partially dominant over another, etc. Hypomophic partially functional alleles, they are recessive to alleles that are more functional usually including the wildtype allele. Recessive mutations often involve a loss of gene function, when the gene no longer specifies a polypeptide oe when it specifies a non-functional or underfunctional polypeptide.

Related Questions

GENETICS : You perform a dihybrid cross between two dogs that are each BbFf. Where not specified otherwise, assume black fur B is completely dominant to white fur b and furry F is completely dominant to hairless f

1. What genotypes at one locus will be epistatic to what genotypes at the other locus, if hair color and hair presence were the only measured phenotypes? (you may find it helpful to write out the genotypes and the phenotypes each would produce, and remember that epistasis is involved in this question).

What phenotypic ratios would you expect in the following scenarios (assume, unless otherwise noted, that the epistasis in part 1 still applies)?

2. Black B is completely dominant to albino b, furry F is completely dominant to hairless f

3. Black displays incomplete dominance to albino , and furry is codominant with hairless

4. Animals that are heterozygous at either locus are black and furry, overriding the other locus' geneotype

5. The black allele B displays epistasis when present at even one copy that masks the effects of the hairless f allele

6. It takes two black B alleles to mask the effects of the hairless f allele

7. Both the black alleles B and furry alleles F are lethal in their homozygous dominant states

8. Both the albino alleles b and hairless alleles f are lethal in their homozygous recessive states

9. Female dogs die when they have homozygous recessive or homozygous dominant states for either locus (dogs use XY inheritance for sex like we do). Note sex of doss in your phenotype ratios.

10. The black allele B although completely dominant, is the only 70% penetrant in heterozygotes and is 90% penetrant in homozygotes for the B allele

11. The hairless allele f is dominant in males and recessive in females

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)

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MBG 2040 Chapter Notes - Chapter 4: Null Allele, Wild Type, Zygosity

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