Launchpad 13

Autosomal trisomies are associated with the X or Y chromosome. True or False

False

Diploid somatic cells of elephants have 56 chromosomes. If nondisjunction of one of an elephant's chromosomes occurs in meiosis I, the resulting sperm are expected to have the chromosome complement: a. 29, 29, 27, 27. b. 56, 56, 57, 55. c. 28, 28, 29, 27. d. 29, 29, 28, 28.

a.

Some common domesticated fruit plants, including seedless watermelon and banana, are triploids. The seeds are small because most are genetically abnormal and do not undergo complete development. Why are most of the seeds genetically abnormal? (Hint: In normal meiosis, the chromosomes form pairs.) a. They have extra and/or missing chromosomes. b. They have broken chromosomes because of crossing over. c. Their DNA replication is disrupted. d. They have excessive numbers of mitochondria.

a.

A recessive trait is expressed when the genotype is: a. heterozygous only. b. homozygous recessive only. c. homozygous dominant only. d. homozygous dominant or heterozygous. e. homozygous recessive or heterozygous.

b.

Mendel's famous experiments were done using which plant? a. Artichokes b. Pea plants c. Tomato plants d. Corn (maize)

b.

You decide to sequence the genome of your resistant S. aureus cells and compare it to the sequence for nonresistant S. aureus cells. What type of genetic difference probably causes this difference in antibiotic resistance in the two cell types? a. It must be a difference in a single base pair of a single gene because the definition of a mutation is a change to a single base pair. b. It may involve a single base pair or many base pairs; genetic changes on both scales are mutations. c. It must involve many base pairs because of the huge selective advantage the mutation confers

b.

If 8 alleles exist in a population, what is the maximum number of copies a normal individual is expected to have? a. 3 b. 5 c. 2 d. 4 e. 8

c.

The failure of a pair of chromosomes to separate during anaphase is referred to as: a. inversion. b. trisomy. c. nondisjunction. d. translocation. e. disjunction.

c.

The principle of independent assortment states that: a. when gametes are formed, the two members of a gene pair will separate equally into gametes. b. one set of alleles of a gene pair always assorts with the alleles of another gene pair. c. alleles of a gene pair assort independently of other gene pairs. d. when gametes are formed, the two members of a gene pair assort together in gametes.

c.

What is the probable origin of Antibiotic X resistance in these cells? a. The cells probably developed resistance to Antibiotic X by undergoing mutation when exposed to the drug, and thus survived the exposure. b. Either of the other answer options could be correct because both happen often in nature, but more information is needed to answer the question. c. A small percentage of the cells had preexisting mutations that confer resistance to Antibiotic X. These cells survived exposure to the drug.

c.

Which of the following statements BEST describes the effect of having the S allele, which codes for sickle-cell anemia? a. Having the allele is always beneficial. b. Having the allele is always harmful. c. The effect depends on whether the allele occurs in its homozygous or heterozygous form, and the environment (i.e., whether malaria is present). d. The effect depends on the environment (i.e., whether malaria is present). e. The effect depends on whether the allele occurs in its homozygous or heterozygous form.

c.

_____ suggests that traits in offspring resemble the average of the parents. a. Eugenic inheritance b. Mendelian inheritance c. Blending inheritance d. Natural selection

c.

Which of the following statements is TRUE about Klinefelter syndrome (47, XXY)? a. None of the other answer options is correct. b. Affected males can reproduce normally. c. The risk increases with the father's age. d. Nondisjunction is the usual cause. e. Most affected fetuses undergo spontaneous abortion.

d.

In a different set of experiments, you identify two kinds of mutations in S. aureus. The first type of mutation makes the bacteria more susceptible to Antibiotic X; the second type of mutation makes it more resistant to Antibiotic X. Which type of mutation is more likely to occur in the population? a. the first type (more susceptible) b. It depends if either type of mutation confers additional survival benefits to S. aureus. c. It depends if the cell population has been exposed to Antibiotic X. d. the second type (more resistant) e. There is no difference in likelihood because the mutation is a random event.

e.