Lecture 13 Study Questions

You have isolated DNA from three different cell types of an organism, determined the relative DNA content for each type, and plotted the results on the graph shown below. Which sample might represent a newly formed zygote?

1

You have isolated DNA from three different cell types of an organism, determined the relative DNA content for each type, and plotted the results on the graph shown below. Which sample of DNA might be from a nerve cell arrested in G0 of the cell cycle?

1

Synaptonemal complexes form or are still present during which of the following stages of meiosis:

1 only

Which of the following best describes the frequency of crossing over in mammals?

1-2 per chromosome pair

How many different combinations of maternal and paternal chromosomes can be packaged in gametes made by an organism with a diploid number of 8 (2n = 8)?

16

Pairs of homolgous chromosomes are aligned at the equator of the spindle; alignment determines independent assortment during which of the following stages of meiosis:

2

You have isolated DNA from three different cell types of an organism, determined the relative DNA content for each type, and plotted the results on the graph shown below. Which sample might represent an animal cell in the G2 phase of the cell cycle?

2

If the DNA content of a diploid cell in the G1 phase of the cell cycle is x, then the DNA content of the same cell at metaphase of meiosis I would be

2x

Which of the following steps takes place in both mitosis and meiosis?

3

A triploid cell contains three sets of chromosomes. If a cell of a usually diploid species with 42 chromosomes per cell is triploid, this cell would be expected to have which of the following?

63 chromosomes in 21 sets of 3

For a species with a haploid number of 23 chromosomes, how many different combinations of maternal and paternal chromosomes are possible for the gametes?

8 million

Which of these statements is FALSE?

At sexual maturity, ovaries and testes produce diploid gametes by meiosis.

If a horticulturist breeding gardenias succeeds in having a single plant with a particularly desirable set of traits, which of the following would be her most probable and efficient route to establishing a line of such plants?

Clone the plant asexually to produce an identical one.

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

Each cell has eight homologous pairs.

A certain (hypothetical) organism is diploid, has either blue or orange wings as the consequence of one of its genes on chromosome 12, and has either long or short antennae as the result of a second gene on chromosome 19, as shown in the figure below. A female with a paternal set of one orange allele of the wing color gene and one long allele of the antennae length gene and a maternal set comprised of one blue allele of the wing color gene and one short allele of the antennae length gene is expected to produce which of the following types of eggs after meiosis?

Each egg has a one-fourth chance of having either blue long, blue short, orange long, or orange short combinations.

The somatic cells of a privet shrub each contain 46 chromosomes. To be as different as they are from human cells, which have the same number of chromosomes, which of the following must be true?

Genes of privet chromosomes are significantly different than those in humans.

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

Homologous chromosomes are separated.

A given organism has 46 chromosomes in its somatic cells. We can therefore conclude which of the following?

Its gametes must have 23 chromosomes.

In human somatic cells, 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, and traits coded for by their genes.

How is natural selection related to sexual reproduction as opposed to asexual reproduction?

Sexual reproduction results in many new gene combinations, some of which will lead to differential reproduction.

When homologous chromosomes crossover, what occurs?

Specific proteins break the two strands and re-join them with their homologs.

Independent assortment of chromosomes occurs.

The statement is true for meiosis I only.

A cell divides to produce two daughter cells that are genetically different.

The statement is true for meiosis I.

Chromatids are separated from each other.

The statement is true for mitosis and meiosis II.

Whether during mitosis or meiosis, sister chromatids are held together by proteins referred to as cohesins. Such molecules must have which of the following properties?

They must be removed, at least along the chromosome arms, before anaphase can occur.

Which of the following might result in a human zygote with 45 chromosomes?

an error in either egg or sperm meiotic anaphase

If an organism is diploid and a certain gene found in the organism has 18 known alleles (variants), then any given organism of that species can/must have which of the following?

at most, 2 alleles for that gene

Experiments with cohesins have found that

cohesins are protected from cleavage at the centromere during meiosis I.

A species of primate has 48 chromosomes. In a particular female, cell division goes awry and she produces one of her eggs with an extra chromosome (25). The most probable source of this error would be a mistake in which of the following?

either anaphase I or II

The human genome is minimally contained in which of the following?

every human cell

After telophase I of meiosis, the chromosomal makeup of each daughter cell is

haploid, and the chromosomes are each composed of two chromatids.

When does the synaptonemal complex disappear?

late prophase of meiosis I

Homologous chromosomes move toward opposite poles of a dividing cell during

meiosis 1

A certain (hypothetical) organism is diploid, has either blue or orange wings as the consequence of one of its genes on chromosome 12, and has either long or short antennae as the result of a second gene on chromosome 19, as shown in the figure below. A particular female's number 12 chromosomes both have the blue allele of the wing color gene and number 19 chromosomes both have the long allele of the antennae length gene. As cells in her ovaries undergo meiosis, her resulting eggs (ova) may have which of the following?

one chromosome 12 with one blue allele of the wing color gene and one chromosome 19 with one long allele of the antennae length gene

When we see chiasmata under a microscope, that lets us know which of the following has occurred?

prophase I

Meiosis II is similar to mitosis in that

sister chromatids separate during anaphase.

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

synapsis of chromosomes

Which of the following defines a genome?

the complete set of an organism's genes

Independent assortment of chromosomes is a result of

the random and independent way in which each pair of homologous chromosomes lines up at the metaphase plate during meiosis I.

If the DNA content of a diploid cell in the G1 phase of the cell cycle is x, then the DNA content of a single cell at metaphase of meiosis II would be

x