1. A heterozygous mouse AAy does not produce enough pigment and it is yellow. Homozygous individuals die during development, but AAy heterozygous do not. Why? You may use any graphic aid to explain this, if necessary. This means that you may use a Punnett square or a forking segregation diagram, or computations with fractions.2. Explain why there is a non-Mendelian 2:1 yellow/agouti phenotypic ratio in this cross. 3. What is the Raly gene? What does it encode? How does it relate to the lethality of Ay? The Yellow Agouti Conundrum: Mendelian Genetics Meets Molecular GeneticsYellow mouseAgouti mouse(AA; also represented as A'/A")(AA"; also represented as A/A)Agouti is the common name for some animals of the genus Dasiprocta. The term "agouti" is also used todescribe the fur color of other mammals, such as the mouse (Mus musculus)* if they show a banded furcolor reminiscent of Dosiprocta. Very importantly, the agouti gene (a) may be associated with obesity.Overexpression of the murine agouti gene in cultured human adipocytes prevents degradation of fats.After mating two mice, i.e., a yellow doe (9 ) with a yellow buck ( ), their litter will be comprised of 2/3yellow pups, 1/3 agouti (see genotypes above; A' indicates the wild type allele). Since by now you are morefamiliar with transmission genetics, you notice that this phenotypic proportion is not right (i.e., it is not % to%). You will find in the formal scientific literature that A' (yellow) is a recessive lethal allele: a homozygousA'A" does not develop after fertilization or perishes early in pre-natal development. Phenotypes areanalyzed only in living offspring, hence recessive lethal alleles are considered when considering genotypesand discrepancies between the genotypic proportions vs. phenotypic proportions.This seemingly incongruous relation between lethality and fur color has been explained at the level ofmolecular genetics. See articles (posted on Canvas): Michaud et al. (1993) Genes Dev 7:1203-1213 and Duhlet al. (1994) Development 120:1695-1708. Here's an intriguing thing: The embryonic lethality ofhomozygous lethal yellow mice (A'/A") is associated with the disruption of an RNA-binding protein. You mayobtain more information in Silvers WK (1979) The Coat Colors of Mice, Springer Verlag, Chapter 2 (posted onCanvas). Remember to cite bibliographic or Internet sources if you happen to use additional references.You may not need this information, but it is here to give you an idea of the complexity of the alleles A/a, andits relationship with obesity. According to Hollander WF and Gowen JW (1956) J Hered 47:221-224, other furcolor alleles at the agouti locus and their phenotypes in the mouse (Mus musculus) are:a "black," non-agouti, yellow hair in the ears and around the perineuma* extreme non-agoutia' "black-and-tan" (belly yellowish, rest of the body black)A wild type (uniformly agouti)A" "white-bellied," or yellow-bellied agoutiA "yellow," lethal if homozygous; the heterozygote is obese

Within organisms, many various forms of mutations occur, and depending on the type of mutation, it…

1. A heterozygous mouse AAy does not produce enough pigment and it is yellow. Homozygous individuals die during development, but AAy heterozygous do not. Why? You may use any graphic aid to explain this, if necessary. This means that you may use a Punnett square or a forking segregation diagram, or computations with fractions. 2. Explain why there is a non-Mendelian 2:1 yellow/agouti phenotypic ratio in this cross. 3. What is the Raly gene? What does it encode? How does it relate to the lethality of Ay?

1. A heterozygous mouse AAy does not produce enough pigment and it is yellow. Homozygous individuals die during development, but AAy heterozygous do not. Why? You may use any graphic aid to explain this, if necessary. This means that you may use a Punnett square or a forking segregation diagram, or computations with fractions. 2. Explain why there is a non-Mendelian 2:1 yellow/agouti phenotypic ratio in this cross. 3. What is the Raly gene? What does it encode? How does it relate to the lethality of Ay?

Human Heredity: Principles and Issues (MindTap Course List)

11th Edition

ISBN:9781305251052

Author:Michael Cummings

Publisher:Michael Cummings

Chapter6: Cytogenetics: Karyotypes And Chromosome Aberrations

Section: Chapter Questions

Problem 1CS: Genetics in Practice case studies are critical-thinking exercises that allow you to apply your new...

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