Genetic Analysis: An Integrated Approach (3rd Edition)
3rd Edition
ISBN: 9780134605173
Author: Mark F. Sanders, John L. Bowman
Publisher: PEARSON
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Chapter 18, Problem 7P
Why do loss-of-function mutations in Hox genes usually result in embryo lethality, whereas gain
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Termites have a haplo-diploid sex determination system where females develop from a fertilized egg (they are diploid, having one allele from the
female cueen and one allele from the male), and males develop from unfertilized eggs (they are haploid, having only one allele from the queen).
Assuming that the female parent (queen) is heterozygous for a particular gene, what is the probability that a female offspring will inherit the
recessive allele from her mother? What is the probability that a male offspring will inherit a recessive allele from his mother?
O A. The probability that a daughter will inherit a recessive allele from her mother is 50%; the probability that a son will inherit a recessive allele
from his mather is 50%.
OB. Ihe probobility that a daughter will inherit a recessive allele from her mother is 0%; the probability that a son will inherit a recessive allele
from his mother is 100%.
O C. The probability that a daughter will inherit a recessive allele from her mother is…
One reason that worker bees forgo their own reproduction to help their sister (the queen) reproduce is that female bees are more closely related to their sisters than they are to their own offspring. This quirk of genetics results from the fact that bees have haplodiploid sex determination, in which females are diploid, with a mother and a father, but males are haploid, developing from unfertilized eggs. Because males are haploid, they produce sperm by mitosis. Explainwhy haplodiploid sex determination causes females to be more closely related to their sisters than to their offspring.
In C. elegans there are two sexes: hermaphrodite and male. Sex is determined by the ratio of X chromosomes to haploid sets of autosomes (X/A). An X/A ratio of 1.0 produces a hermaphrodite (XX), and an X/A ratio of 0.5 results in a male (XO). In the 1970s, Jonathan Hodgkin and Sydney Brenner carried out genetic screens to identify mutations in three genes that result in either XX males (tra-1, tra-2) or XO hermaphrodites (her-1). Double-mutant strains were constructed to assess for epistatic interactions between the genes (see table). Propose a genetic model of how the her and tra genes control sex determination.
Chapter 18 Solutions
Genetic Analysis: An Integrated Approach (3rd Edition)
Ch. 18 - 18.1 Explain why many developmental genes encode...Ch. 18 - Bird beaks develop from an embryonic group of...Ch. 18 - 18.3 How is positional information provided along...Ch. 18 - Early development in Drosophila is atypical in...Ch. 18 - 18.5 Consider the evenskipped regulatory sequences...Ch. 18 - What is the difference between a parasegment and...Ch. 18 - Why do loss-of-function mutations in Hox genes...Ch. 18 - 18.8 Compare and contrast the specification of...Ch. 18 - Prob. 9PCh. 18 - Ablation of the anchor cell in wild type C....
Ch. 18 - 18.11 In gain-of-function and. elegans mutants,...Ch. 18 - Prob. 12PCh. 18 - Prob. 13PCh. 18 - 18.14 Given that maternal Bicoid activates the...Ch. 18 - What phenotypes do you expect in flies homozygous...Ch. 18 - The pair rule gene fushitarazu is expressed in...Ch. 18 - 18.17 In contrast to Drosophila, some insects...Ch. 18 - Prob. 18PCh. 18 - 18.19 You are traveling in the Netherlands and...Ch. 18 - 19.20 A powerful approach to identifying genes of...Ch. 18 - The Hoxd 913 genes are thought to specify digit...Ch. 18 - Three-spined stickleback fish live in lakes formed...Ch. 18 - The flowering jungle plant Lacandoniaschismatica,...Ch. 18 - 18.24 Homeotic genes are thought to regulate each...Ch. 18 - Prob. 25PCh. 18 - Basidiomycota is a monophyletic group of fungi...Ch. 18 - Prob. 27PCh. 18 - In C. elegans there are two sexes: hermaphrodite...Ch. 18 - In Drosophila, recessive mutations in the...
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- Certain genes determine sex, fertility, and viability in Drosophila, and mutations in these genes affect the two sexes differently. Classify the descriptions below based on their occurrence in XY or XX flies. Some descriptions may be used in both categories. The expressed form of Dsx activates maleness genes and represses femaleness genes. XY XX Null mutations in the dsx gene result in an intersex phenotype. Loss-of-function mutations in the tra gene have no effect on phenotype. Sxl is expressed in early embryogenesis from the establishment promoter. Flies that produce Fru-M in brain cells from a transgene perform a mating dance and specifically court females. Loss-of-function mutations in the fru gene result in flies who court both males and females. Sxl regulates splicing of its own RNA to produce a functional protein. The expressed form of Dsx activates femaleness genes and represses maleness genes. Loss-of-function mutations in the Sxl gene have no effect on phenotype. Resetarrow_forwardFigure 9.3 Schematic representation of sexual reproduction (hyphal fusion) in Sordaria fimicola. ㅏ (a) Tan X Tan (b) -Haploid- Black X Black (c) Tan X Black (with no crassing-over) Fusion -Diploid- Majosis I 想想 * X* X * Y * X * Meiasis I X X X X X X -Haploid- Mitosis Position in ascus Bad D II CHIXO Nonrecombinant typearrow_forwardIn a haploid yeast strain, eight recessive mutationswere found that resulted in a requirement for theamino acid lysine. All the mutations were found to revert at a frequency of about 1 × 10−6 except mutations5 and 6, which did not revert. Matings were madebetween a and α cells carrying these mutations. Theability of the resultant diploid strains to grow onminimal medium in the absence of lysine is shown inthe following chart (+ means growth and − means nogrowth.)1 2 3 4 5 6 7 81 − + + + + − + −2 + − + + + + + +3 + + − − − − − +4 + + − − − − − +5 + + − − − − − +6 − + − − − − − −7 + + − − − − − +8 − + + + + − + −a. How many complementation groups were revealedby these data? Which point mutations are foundwithin which complementation groups?The same diploid strains are now induced to undergosporulation. The vast majority of resultant spores areauxotrophic; that is, they cannot form colonies whenplated on minimal medium (without lysine). However,particular diploids can produce rare spores…arrow_forward
- What are the sexes and eye colors of flies with the following genotypes: X R X r _____________ X R Y ____________ X r X r ____________ X R X R ____________ X r Y ___________arrow_forwardA heterozygous diploid yeast Aa Bb went through meiosis. What percentage of the haploid spores will have recombinant combinations of alleles? What if genes A and B are unlinked? Explain What is genes A and B are linked? Explainarrow_forwardHow long is Drosophila melanogaster life cycle?arrow_forward
- For a haploid fungus, the starting point in the biosynthesis of the amino acid arginine is Compound X, which is always present in and absorbed from the environment. The arginine biosynthetic pathway is: Enzyme A Enzyme B Enzyme Ç Compound X It is know that genes encoding enzymes A and C are on two different chromosomes. Compound Y Compound Z- Arginine A mutant strain of genotype a (lacking only enzyme A) is crossed to a mutant strain of genotype c (lacking only enzyme C) to generate a diploid strain. Sporulation (i.e. meiosis) is subsequently induced in the resulting diploid strain. What proportion of the spores (haploids formed by sporulation) is expected to grow on medium without arginine but supplemented with Compound Y? O 100% 50% 0% 25%arrow_forwardWhy are chromosomal abberations considered to have less significance than gene mutations for subsequent generations?arrow_forwardWhich of the following is an accurate model and description of anaphase IIII in Cape parrots?arrow_forward
- To understand the genetic basis of locomotion in the diploid nematode Caenorhabditis elegans, recessive mutations were obtained, all making the worm “wiggle” ineffectually instead of moving with its usual smooth gliding motion. These mutations presumably affect the nervous or muscle systems. Twelve homozygous mutants were intercrossed, and the F1 hybrids were examined to see if they wiggled. The results were as follows, where a plus sign means that the F1 hybrid was wild type (gliding) and “w” means that the hybrid wiggled.a. Explain what this experiment was designed to test. b. Use this reasoning to assign genotypes to all 12 mutants. c. Explain why the phenotype of the F1 hybrids between mutants 1 and 2 differed from that of the hybrids between mutants 1 and 5arrow_forwardIn considering the formation of the A–P and D–V axes inDrosophila, we noted that, for mutations such as bcd,homozygous mutant mothers uniformly produce mutant offspring with segmentation defects. This outcomeis always true regardless of whether the offspring themselves are bcd+/bcd or bcd/bcd. Some other maternaleffect lethal mutations are different, in that the mutantphenotype can be “rescued” by introducing a wild-typeallele of the gene from the father. In other words, forsuch rescuable maternal-effect lethals, mut+/mut animals are normal, whereas mut/mut animals have the mutant defect. Explain the difference between rescuableand nonrescuable maternal-effect lethal mutations.arrow_forwardWhy must the life cycle of sexually reproducing species alternate between haploid and diploid stages? A) Mitosis must occur at some point in the life cycle to prevent a doubling of chromosomes in each generation. B) Meiosis must occur at some point in the life cycle to prevent a doubling of chromosomes in each generation. C) Mitosis must occur at some point in the life cycle to prevent a reduction of chromosomes in each generation. D) Meiosis must occur at some point in the life cycle to prevent a reduction of chromosomes in each generation.arrow_forward
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