front 1 In cats, black fur color is caused by an X-linked allele; the other allele at this locus causes orange color. The heterozygote is tortoiseshell. What kinds of offspring would you expect from the cross of a black female and an orange male? | back 1 tortoiseshell females; black males |
front 2 Calico cats are female because | back 2 a male inherits only one of the two X-linked genes controlling hair color. |
front 3 Women (and all female mammals) have one active X chromosome per cell instead of two. What causes this? | back 3 modification of the XIST gene so that it is active only on one X chromosome, which then becomes inactive |
front 4 Which of the following statements is true of linkage? | back 4 The closer two genes are on a chromosome, the lower the probability that a crossover will occur between them. |
front 5 What does a frequency of recombination of 50% indicate? | back 5 The two genes are likely to be located on different chromosomes. |
front 6 What is the reason that linked genes are inherited together? | back 6 They are located close together on the same chromosome. |
front 7 Recombination between linked genes comes about for what reason? | back 7 Crossovers between these genes result in chromosomal exchange. |
front 8 Why does recombination between linked genes continue to occur? | back 8 New allele combinations are acted upon by natural selection. |
front 9 If nondisjunction occurs in meiosis II during gametogenesis, what will be the result at the completion of meiosis? | back 9 1/4 of the gametes will be n + 1, 1/4 will be n - 1, and 1/2 will be n. |
front 10 Of the following human aneuploidies, which is the one that generally has the most severe impact on the health of the individual? | back 10 47, +21 |
front 11 What is the source of the extra chromosome 21 | back 11 nondisjunction or translocation in either parent |
front 12 At which phase(s) is it preferable to obtain chromosomes to prepare a karyotype | back 12 late prophase or metaphase |
front 13 Which of the following produces a Mendelian pattern of inheritance? | back 13 a trait acted upon by many genes |