Understanding Genetics: Karyotypes, Meiosis, and Inheritance

1)Which of the following best describes a karyotype?

·a display of each of the chromosomes of a single cell

2) The human X and Y chromosomes

·include genes that determine an individual's sex.

3) Which of the following is true of a species that has a chromosome number of 2n = 16?

·Each cell has eight homologous pairs.

4) In a human karyotype, chromosomes are arranged in 23 pairs. If we choose one of these pairs, such as pair 14, which of the following do the two chromosomes of the pair have in common?

·Length, centromere position, staining pattern, and traits coded for by their genes.

5) Meiosis II is similar to mitosis in that

·sister chromatids separate during anaphase

6) Which of the following occurs in meiosis but not in mitosis?

·synapsis of chromosomes

7) Which of the following happens at the conclusion of meiosis I?

·Homologous chromosomes are separated.

For the following questions, match the key event of meiosis with the stages listed below.

      I.     Prophase I              V.     Prophase II

      II.    Metaphase I            VI.    Metaphase II

      III.   Anaphase I             VII. Anaphase II

      IV. Telophase I             VIII.       Telophase II

8) Tetrads of chromosomes are aligned at the equator of the spindle; alignment determines independent assortment.

·II

9) Centromeres of sister chromatids disjoin and chromatids separate.

·VII

10) A human cell containing 22 autosomes and a Y chromosome is

·a sperm.

11) What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants?

·Traits are inherited in discrete units, and are not the results of "blending."

12) Through a microscope, you can see a cell plate beginning to develop across the middle of a cell and nuclei re-forming on either side of the cell plate. This cell is most likely:

·a plant cell in the process of cytokinesis.

17) Why did the F1 offspring of Mendel's classic pea cross always look like one of the two parental varieties?

·One phenotype was completely dominant over another.

18) Which of the following describes the ability of a single gene to have multiple phenotypic effects?

·pleiotropy

19) Which of the following is an example of polygenic inheritance?

·skin pigmentation in humans

20) A sexually reproducing animal has two unlinked genes, one for head shape (H) and one for tail length (T). Its genotype is HhTt. Which of the following genotypes is possible in a gamete from this organism?

·HT

21) When Thomas Hunt Morgan crossed his red-eyed F1 generation flies to each other, the F2 generation included both red- and white-eyed flies. Remarkably, all the white-eyed flies were male. What was the explanation for this result?

·The gene involved is on the X chromosome.

22) Red-green color blindness is a sex-linked recessive trait in humans. Two people with normal color vision have a color-blind son. What are the genotypes of the parents?

·XCXc and XCY

23) Calico cats are female because

·a male inherits only one of the two X-linked genes controlling hair color.

24) Which of the following statements is true of linkage?

·The closer two genes are on a chromosome, the lower the probability that a crossover will occur between them.

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

·nondisjunction or translocation in either parent

26) One possible result of chromosomal breakage is for a fragment to join a nonhomologous chromosome. What is this alteration called?

·translocation

The following is a map of four genes on a chromosome.

Figure 15.1

27) Between which two genes would you expect the highest frequency of recombination?

·A and G

28) In his work with pneumonia-causing bacteria and mice, Griffith found that

·some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic.

29) In analyzing the number of different bases in a DNA sample, which result would be consistent with the base-pairing rules?

·A + G = C + T

30) Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?

·8%

31) What is meant by the description "antiparallel" regarding the strands that make up DNA?

·The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand.

32) Which enzyme catalyzes the elongation of a DNA strand in the 5' → 3' direction?

·DNA polymerase III

33) The leading and the lagging strands differ in that

·the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction.

34) A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is

·3' UCA 5'.

35) Transcription in eukaryotes requires which of the following in addition to RNA polymerase?

·several transcription factors (TFs)

36) A transcription unit that is 8,000 nucleotides long may use 1,200 nucleotides to make a protein consisting of approximately 400 amino acids. This is best explained by the fact that

·many noncoding stretches of nucleotides are present in mRNA.

37) In eukaryotic cells, transcription cannot begin until

·several transcription factors have bound to the promoter.

38) Alternative RNA splicing

·can allow the production of proteins of different sizes from a single mRNA.

39) Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the

·bonding of the anticodon to the codon and the attachment of amino acids to tRNAs.

40) Which of the following is not true of RNA processing?

·Exons are cut out before mRNA leaves the nucleus.

41) A frameshift mutation could result from

·either an insertion or a deletion of a base.

42) What is the function of the release factor (RF)?

·It binds to the stop codon in the A site in place of a tRNA.

43) Why might a point mutation in DNA make a difference in the level of protein's activity?

·It might substitute a stop codon for another stop codon

44) Which component is not directly involved in translation?

·DNA

45) Which of the following mutations would be most likely to have a harmful effect on an organism?

a single nucleotide insertion downstream of, and close to, the start of the coding sequence