7.
Which best describes the Chromosomal Theory of Inheritance?
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The theory was proposed by Charles Darwin. It describes the units of inheritance between parents and offspring as well as the processes by which those units control offspring development.
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The theory was proposed by Boveri-Sutton. It describes linkage, recombination, and crossing over and states that Mendelian genes have specific loci on chromosomes, which undergo segregation and independent assortment.
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The theory was proposed by Charles Darwin. It states the Mendelian genes have two alternate forms and undergo independent assortment. It helped increase understanding of linkage and recombination.
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The theory was proposed by Boveri-Sutton. It describes the units of inheritance between parents and offspring as well as the processes by which those units control development in offspring.
8.
In a test cross for two characteristics (dihybrid cross), can the predicted frequency of recombinant offspring be 60%? Justify your claim with relevant reasoning.
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No. The predicted frequency of recombinant offspring ranges from 0% (for linked traits) to 50% (for unlinked traits) because of both parental and nonparental cases.
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Yes. The predicted frequency of recombinant offspring can be 60% if genes are located very far from each other.
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Yes. The predicted frequency can be 60% if crossing over occurs during every meiotic event.
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No. The predicted frequency can never be 60% due to the presence of mutations such as deletions.
9.
Choose the statement that best describes how nondisjunction (see Figure 13.6) can result in an aneuploid zygote.
- Nondisjunction only occurs when homologous chromosomes do not separate during meiosis I, resulting in the formation of gametes containing n+1 and n-1 chromosomes.
- Nondisjunction only occurs when sister chromatids do not separate in meiosis II, resulting in the formation of gametes containing n+1 and n-1 chromosomes.
- Nondisjunction is the failure of homologous chromosomes to separate during meiosis I or the failure of sister chromatids to separate during meiosis II, leading to the formation of n+1/n-1/n chromosomes.
- Nondisjunction occurs when the sister chromatids fail to separate during mitosis II, resulting in the formation of gametes containing n+1 and n-1/n chromosomes.
10.
Compare the statements below, which describe chromosomal aberrations. Select the one that correctly identifies the various chromosomal aberrations that can occur and explains their respective genetic consequences.
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nondisjunction - aneuploid gametes; duplication - physical and mental abnormalities; deletion - lethal to a diploid organism; inversion - chromosomal breaks in gene; translocations - effects depend on how positions of genes are altered
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nondisjunction - physical and mental abnormalities; inversion - genetic imbalance; duplication - aneuploid gametes; translocations - chromosomal breaks in the gene; deletion - effects depend on how positions of genes are altered
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deletion -aneuploid gametes; translocations - physical and mental abnormalities; duplication - effects depend on positions of genes; nondisjunction - causes genetic imbalance lethal to a diploid organism; aneuploidy - leads to various syndromes
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nondisjunction - chromosomal breaks in gene; duplication - physical and mental abnormalities; deletion - genetic imbalance lethal to a diploid organism; inversion - aneuploid gametes; translocations - effects depend on positions of genes