Chapter 8 Homework

During meiosis I, homologous chromosomes form a tetrad and crossing over occurs. What is the outcome of crossing over?

Crossing over creates new combinations of genes present on a single chromosome.

Asexual and sexual reproduction differ in that sexual reproduction _____.

can produce great variation among the offspring

Cytokinesis

finishes mitosis by dividing the cytoplasm and organelles of the original parent cell into two separate daughter cells

The function of meiosis is to make __________.

four cells with a haploid number of chromosomes

The _____ separate in meiosis I; the _____ separate in meiosis II.

homologous chromosomes ... sister chromatids

During _____, the cell carries out its normal functions and the chromosomes are thinly spread out throughout the nucleus.

interphase

An example of a cell that is 2n is a __________.

somatic cell

The function(s) of meiosis is/are _____.

reproduction (production of gametes)

Which events occur during prophase?

The nuclear envelope breaks down. Chromosomes condense and are attached to spindle fibers.

Which of the following statements correctly describes the timing of DNA synthesis?

DNA is synthesized in the S phase of interphase.

Which of the following occurs during mitosis?

Two daughter nuclei, one at each pole of the cell, are generated.

Meiosis starts with _____ cells and produces _____ gametes.

diploid ... haploid

In bacterial cells, binary fission involves __________.

distribution of a copy of the single parental chromosome to each daughter cell

Looking through a light microscope at a dividing cell, you see two separate groups of chromosomes on opposite ends of the cell. New nuclear envelopes are taking shape around each group. The chromosomes then begin to disappear as they unwind. You are witnessing

telophase

In sexually reproducing multicellular organisms, the main functions of mitosis are

tissue repair/replacement of damaged cells growth and development

Consider the cell cycle shown below. Cells will usually divide if they receive the proper signal at a checkpoint in the __________ phase of the cell cycle.

G1

You suspect that a serious developmental disorder is due to a chromosome abnormality and prepare a karyotype from an affected individual. In analyzing the karyotype, how could you distinguish trisomy from a chromosome structural defect such as a duplication?

In trisomy there would be one extra chromosome; in a duplication, the number of chromosomes would be normal, but one chromosome would have two copies of a portion of the chromosome.

Although in humans there are 22 pairs of autosomal chromosomes, only three different chromosomal trisomies are commonly seen in newborns. Of the remaining 19 autosomes, many trisomies have not been seen in newborns. Why not?

Trisomy for the other autosomal chromosomes is often lethal, and the affected embryos are miscarried.

Which of the following conditions would prevent cell division due to density-dependent factors?

being completely surrounded by other cells

A benign and a malignant tumor differ in that _____.

cells of a benign tumor remain within the tumor, whereas cells of a malignant tumor can spread to other body tissues

Looking through a light microscope at a cell undergoing meiosis, you see that the chromosomes have joined into XX-shaped tetrads. These tetrads are lined up along a plane that runs through the center of the cell. This cell is in _____.

meiosis I

Meiosis is typically accomplished in _____.

three steps. All of the chromosomes are duplicated in a diploid cell, and then there are two cell divisions to produce a total of four haploid gametes.