The figure represents a Drosophila linkage map for genes A-E. The numbers between the gene loci are the relative map units between each gene. Based on the linkage map, predict and identify the two genes that are most likely to segregate together.
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A and B
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B and C
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C and D
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D and E
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Not linked: parental genotypes EeWw and eeww; linked: 25% Eeww, 50% eeWw
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Not linked: 25% EeWw, 25% Eeww, 25% eeWw, and 25% eeww; linked: 50% EeWw and 50% eeww
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Linked genotypes (EeWw and eeww) and recombinant genotypes (Eeww and eeWw) in the F2 generation are nearly the same irrespective of their linkage
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Nor linked: 25% EeWw and eeww with 75% Eeww and eeWw; linked: mostly with parental genotypes, Eeww and eeWw
A cross was made with true-breeding AABB flies and true-breeding aabb flies. The resulting generation was then crossed with true-breeding aabb flies. Based on the linkage map, which of the following generation genotype ratios is most likely to be observed?
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Number Observed: AaBb (46), Aabb (4), aaBb (4), Aabb (46)
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Number Observed: AaBb (4), Aabb (46), aaBb (46), Aabb (4)
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Number Observed: AaBb (25), Aabb (25), aaBb (25), Aabb (25)
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Number Observed: AaBb (50), Aabb (0), aaBb (0), Aabb (50)
Which of the following symptoms is most likely associated with the disorder shown in the karyotype?
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lethality
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infertility
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heart and bleeding defects
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short stature and stunted growth
Interpret the karyotype shown to identify the statement that correctly names the disorder caused by this karyotype and describes the potential social, ethical, or medical issues associated with that disorder.
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Down syndrome (47 XY +21) causes intellectual disability, vision problems, congenital heart disease, and susceptibility to cancer. Healthcare providers often do not discuss the positive aspects of raising a child with Down syndrome and often provide out of date information.
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Klinefelter syndrome (47 XY +21) causes intellectual disability, vision problems, congenital heart disease, and susceptibility to cancer. Arguments are often made against abortion of an affected fetus.
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Klinefelter syndrome (47 XXY) causes sterility and reduced testosterone production. Arguments are often made against informing insurance companies about a diagnosis of this disease.
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Down syndrome (47 XXY) causes sterility and lower testosterone production. Arguments are often made against informing insurance companies about a diagnosis of this disease.
Examine the linkage map displayed. Predict which of the following gene orders is the most likely outcome of an inversion mutation in the chromosome shown.
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RSTUV
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RRSTUV
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RSUV
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RTSUV
With the help the diagram given, choose the most appropriate statement describing nondisjunction and its genetic consequences.
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Nondisjunction occurs when a homologous pair is unable to separate during meiosis I, resulting in the formation of gametes containing n+1 and n-1 chromosomes. This is called aneuploidy.
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Nondisjunction occurs due to the inability of sister chromatids to separate during meiosis II, resulting in the formation of gametes containing n+1 and n-1 chromosomes. This results in heart and bleeding defects.
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Nondisjunction is the failure of homologous chromosomes to separate during meiosis I or failure of sister chromatids to separate during meiosis II. This results in aneuploid gametes.
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Nondisjunction occurs when a pair of homologous chromosomes fails to segregate during meiosis II resulting in the formation of gametes containing n+1, n-1, or n numbers of chromosomes. This results in abnormal growth patterns.
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more severe than Down syndrome, due to gene deletions in this syndrome
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more severe than Down syndrome, due to trisomy in Klinefelter syndrome
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less severe than Down syndrome, due to monosomy in Down Syndrome
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less severe than Down syndrome, due to X-inactivation in this disorder