Inferring incomplete penetrance FIGURE 6-21 In this human pedigree of a dominant allele that is not fully penetrant, person Q does not display the phenotype but passed the dominant allele to at least two progeny. Because the allele is not fully penetrant, the other progeny (for example, R) may or may not have inherited the dominant allele.

Inferring incomplete penetrance FIGURE 6-21 In this human pedigree of a dominant allele that is not fully penetrant, person Q does not display the phenotype but passed the dominant allele to at least two progeny. Because the allele is not fully penetrant, the other progeny (for example, R) may or may not have inherited the dominant allele.

Name: In Figure 6-21, propose a specific genetic explanationfor individual Q
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Description: In Figure 6-21, propose a specific genetic explanationfor individual Q (give a possible genotype, defining thealleles Inferring incompletepenetranceFIGURE 6-21 In this human pedigree ofa dominant allele that is not fully penetrant,person Q does not d

Concepts of Biology

1st Edition

ISBN:9781938168116

Author:Samantha Fowler, Rebecca Roush, James Wise

Publisher:Samantha Fowler, Rebecca Roush, James Wise

Chapter8: Patterns Of Inheritance

Section: Chapter Questions

Problem 11RQ: The ABO blood groups in humans are expressed as the IA,IB and i alleles. The IAallele encodes the A...

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The accompanying pedigree shows a very unusual inheritance pattern that actually did exist. All progeny areshown, but the fathers in each mating have been omittedto draw attention to the remarkable pattern.a. Concisely state exactly what is unusual about thispedigree.b. Can the pattern be explained by Mendelianinheritance?
The accompanying pedigree is for a rare, but relativelymild, hereditary disorder of the skin.a. How is the disorder inherited? State reasons for youranswer.b. Give genotypes for as many individuals in thepedigree as possible. (Invent your own defined allelesymbols.)c. Consider the four unaffected children of parentsIII-4 and III-5. In all four-child progenies from parentsof these genotypes, what proportion is expected tocontain all unaffected children?(picture added)
The accompanying pedigree shows the pattern of transmission of two rare human phenotypes: cataract andpituitary dwarfism. Family members with cataract areshown with a solid left half of the symbol; those withpituitary dwarfism are indicated by a solid right halfa. What is the most likely mode of inheritance of each ofthese phenotypes? Explain.b. List the genotypes of all members in generation III asfar as possible.c. If a hypothetical mating took place between IV-1 andIV-5, what is the probability of the first child’s being adwarf with cataracts? A phenotypically normal child?(Problem 48 is adapted from J. Kuspira and R. Bhambhani, Compendium of Problems in Genetics. Copyright1994 by Wm. C. Brown.)(Picture added)
Albino rabbits (lacking pigment) are homozygous forthe recessive c allele (C allows pigment formation).Rabbits homozygous for the recessive b allele makebrown pigment, while those with at least one copy ofB make black pigment. True-breeding brown rabbitswere crossed to albinos, which were also BB. F1 rabbits, which were all black, were crossed to the doublerecessive (bb cc). The progeny obtained were 34black, 66 brown, and 100 albino.a. What phenotypic proportions would have beenexpected if the b and c loci were unlinked?b. How far apart are the two loci?
. An RFLP analysis of two pure lines A/A • B/B and a/a • b/bshowed that the former was homozygous for a long RFLPallele (l) and the latter for a short allele (s). The two werecrossed to form an F1, which was then backcrossed to thesecond pure line. A thousand progeny were scored asfollows:a. What do these results tell us about linkage?b. Draw a map if appropriate.c. Incorporate the RFLP fragments into your map.
In Drosophila, M. Green found a singed allele (sn) withsome unusual characteristics. Females homozygous forthis X-linked allele have singed bristles, but they havenumerous patches of sn+ (wild-type) bristles on theirheads, thoraxes, and abdomens. When these flies aremated with sn males, some females give only singedprogeny, but others give both singed and wild-type progeny in variable proportions. Explain these results.
Incomplete dominanceIn Mendel's experiments, if the gene for tall (T) plants was incompletely dominant overthe gene for short (t) plants, what would be the result of crossing two Tt plants? Explain result.
Two alleles at one locus produce three distinctphenotypes. Two alleles of two genes lead tofive distinct phenotypes. Two alleles of six geneslead to 13 distinct phenotypes. (These statementsassume that the alleles at any one locus arecodominant or incompletely dominant andthat each gene makes an equal contributionto the phenotype.)a. Derive a formula to express this relationship. (Letn equal the number of genes.)b. Each of the most extreme phenotypes for a traitdetermined by two alleles at one locus are foundin a proportion of 1/4 in the F2 generation. If twoalleles of two genes determine the trait, each extreme phenotype will be present in the F2 as 1/16of the population.In common wheat (Triticum aestivum),kernel color varies from red to white andthe genes controlling the color act additively,that is, alleles for each gene are incompletelydominant and each gene contributes equallyto the color. A true-breeding red variety iscrossed to a true-breeding white variety, and1/256 of the F2…
Female fruit flies homozygous for the X-linked white-eye alleleare crossed to males with red eyes. On very rare occasions, an offspringof such a cross is a male with red eyes. Assuming these rareoffspring are not due to a new mutation in one of the mother’s Xchromosomes that converted the white-eye allele into a red-eyeallele, explain how a red-eyed male arises.
F1 hybrids between two species of cotton, Gossypium barbadenseand Gossypium hirsutum, are very vigorous plants. However, F1crosses produce many seeds that do not germinate and a high percentageof very weak F2 offspring. Suggest two reasons for theseobservations.
. A plant of genotypea bA Bis testcrossed witha ba bIf the two loci are 10 m.u. apart, what proportion of progenywill be AB/ab?
. The production of pigment in the outer layer of seedsof corn requires each of the three independently assorting genes A, C, and R to be represented by at leastone dominant allele, as specified in Problem 64. Thedominant allele Pr of a fourth independently assortinggene is required to convert the biochemical precursorinto a purple pigment, and its recessive allele pr makesthe pigment red. Plants that do not produce pigmenthave yellow seeds. Consider a cross of a strain of genotype A/A ; C/C ; R/R ; pr/pr with a strain of genotypea/a ; c/c ; r/r ; Pr/Pr.a. What are the phenotypes of the parents?b. What will be the phenotype of the F1?c. What phenotypes, and in what proportions, willappear in the progeny of a selfed F1?d. What progeny proportions do you predict from thetestcross of an F1?