Download Answers to Biological Inquiry Questions – Brooker et al ARIS site

Answers to Biological Inquiry Questions – Brooker et al ARIS site
Chapter 16
Figure 16.7
BIOLOGICAL INQUIRY QUESTION: Let’s suppose we had a plant with purple flowers and unknown
genotype and conducted a testcross to determine its genotype. We obtained 41 plants, 20 of which
had white flowers and 21 with purple flowers. What was the genotype of the original purple-flowered
plant?
ANSWER: It was Pp. To produce white offspring, which are pp, the original plant had to have at least
one copy of the p allele. Since it had purple flowers, it also had to have one copy of the P allele. So,
its genotype must be Pp.
Figure 16.10
BIOLOGICAL INQUIRY QUESTION: When we say that alleles segregate, what does the word
segregate mean? How is this related to meiosis, described in Chapter 15?
ANSWER: The word segregate means that alleles are separated into different places. In this case,
the alleles are segregated into different cells during the process of meiosis. Alleles are located on
chromosomes. A diploid cell has two copies of each allele. During meiosis, a diploid cell divides twice
to produce four haploid cells that each have only one copy of an allele.
Figure 16.12
BIOLOGICAL INQUIRY QUESTION: Let’s suppose a genetic disease is caused by a mutant allele. If
two affected parents produce an unaffected offspring, can the mutant allele be recessive?
ANSWER: No. If two parents are affected with the disease, they must be homozygous for the mutant
allele if it’s recessive. Two homozygous parents would have to produce all affected offspring. If they
don’t, then the inheritance pattern is not recessive.
Figure 16.14
BIOLOGICAL INQUIRY QUESTION: If a person is born with only one X chromosome and no Y
chromosome, would you expect that person to be a male or a female? Explain your answer.
ANSWER: They would be a female. In mammals, the presence of the Y chromosome causes
maleness. Therefore, without a Y chromosome, a person with a single X chromosome would
develop into a female.
Figure 16.18
BIOLOGICAL INQUIRY QUESTION: With regard to baldness, which phenotypes have a single
genotype?
ANSWER: Bald females must be BB, and nonbald males must be bb.