Exam 12: The Chromosomal Basis of Inheritance

Please use the following information to answer the question(s) below. A plantlike organism on the planet Pandora can have three recessive genetic traits: bluish leaves, due to an allele (a) of gene A; a feathered stem, due to an allele (b) of gene B; and hollow roots due to an allele (c) of gene C. The three genes are linked and recombine. A geneticist did a testcross with an organism that had been found to be heterozygous for the three recessive traits and was able to identify progeny of the phenotypic distribution (+ = wild type) shown in Figure 12.3. Figure 12.3 -What is the greatest benefit of having used a testcross for this experiment?

Figure 12.1 shows a map of four genes on a chromosome. Figure 12.1 Between which two genes would you expect the highest frequency of recombination?

Please use the following information to answer the question(s) below. A plantlike organism on the planet Pandora can have three recessive genetic traits: bluish leaves, due to an allele (a) of gene A; a feathered stem, due to an allele (b) of gene B; and hollow roots due to an allele (c) of gene C. The three genes are linked and recombine. A geneticist did a testcross with an organism that had been found to be heterozygous for the three recessive traits and was able to identify progeny of the phenotypic distribution (+ = wild type) shown in Figure 12.3. Figure 12.3 -The greatest distance among the three genes is between a and c. What does this mean?

Please use the following information to answer the question(s) below. A man who is an achondroplastic dwarf with normal vision marries a color-blind woman of normal height. The man's father was 6 feet tall, and both the woman's parents were of average height. Achondroplastic dwarfism is autosomal dominant, and red-green color blindness is X-linked recessive. -They have a daughter who is a dwarf with normal color vision. What is the probability that she is heterozygous for both genes?

If cell X enters meiosis, and nondisjunction of one chromosome occurs in one of its daughter cells during meiosis II, what will be the result at the completion of meiosis?

A couple has a child with Down syndrome. The mother is 39 years old at the time of delivery. Which of the following is the most probable cause of the child's condition?

Normally, only female cats have the tortoiseshell phenotype because

Down syndrome has a frequency in the U.S. population of ~1/830 live births. In which of the following groups would you expect this frequency to be significantly higher?

Map units on a linkage map cannot be relied upon to calculate physical distances on a chromosome for which of the following reasons?

Which of the following statements describes the chromosome theory of inheritance as expressed in the early twentieth century?

A translocation causes which of the following results?

In humans, clear gender differentiation occurs not at fertilization, but after the second month of gestation. What is the first event of this differentiation?

What is the source of the extra chromosome 21 in an individual with Down syndrome?

Please use the following information to answer the question(s) below. A plantlike organism on the planet Pandora can have three recessive genetic traits: bluish leaves, due to an allele (a) of gene A; a feathered stem, due to an allele (b) of gene B; and hollow roots due to an allele (c) of gene C. The three genes are linked and recombine. A geneticist did a testcross with an organism that had been found to be heterozygous for the three recessive traits and was able to identify progeny of the phenotypic distribution (+ = wild type) shown in Figure 12.3. Figure 12.3 -Which of the following are the phenotypes of the parents in this cross?

What does a frequency of recombination of 50% indicate?

What event causes all female mammals to have one active X chromosome per cell instead of two?

What is a syndrome?

What is the reason that closely linked genes are typically inherited together?

An inversion in a human chromosome often results in no demonstrable phenotypic effect in the individual. What else may occur?

Males are more often affected by sex-linked traits than females because