Mastering Biology Chapter 8

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

somatic cell --Somatic is a word used to refer to the "body." These body cells are diploid and have two homologous copies of each chromosome.

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 arewitnessing _____.

telophase

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.

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 --in mammalian cells, this checkpoint is termed the restriction point

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. --Trisomy means three copies of a chromosome; duplication involves a repeated segment of one chromosome.

__________ is the spread of cancer cells from their site of origin to other sites in the body.

Metastasis

Which events occur during prophase?

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

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

-growth and development -tissue repair/replacement of damaged cells

___________ reproduction is a means of creating new individuals solely by ___________, the form of cell division that creates genetically identical daughter cells.

asexual, mitosis

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 --Prokaryotes reproduce by a type of cell division called binary fission, which involves replicating the single chromosome and distributing the copies equally to two daughter cells.

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 two cell divisions of meiosis, I and II, produce four haploid daughter cells, which are not genetically identical to the diploid parent cell.

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

A ________________ is an abnormally growing mass of cells that is actively spreading through the body.

malignant tumor

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

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. --Crossing over does this by exchange of corresponding parts between homologous chromosomes, creating a patchwork of maternal and paternal chromosome segments along a single chromosome.

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

DNA is synthesized in the S phase of interphase. --Single chromosomes enter the synthesis or S phase of interphase. At the end of this phase, after DNA replication, the chromosomes are double, each consisting of two sister chromatids.

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. --Unfortunately, these trisomies do occur and are commonly observed in spontaneously aborted embryos and fetuses.

Which of the following occurs during mitosis?

Two daughter nuclei, one at each pole of the cell, are generated. -- this is the purpose of mitosis

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

being completely surrounded by other cells --In culture, cells continue to divide until they touch one another, a phenomenon known as density-dependent inhibition.

A __________ is a lump of abnormal cells that, although growing out of control, remains at its original site.

benign tumor

Asexual and sexual reproduction differ in that sexual reproduction _____.

can produce great variation among the offspring --As long as there is some genetic variation in the parents, different offspring will inherit unique combinations of genes from each parent, creating variation among offspring.

An individual with a malignant tumor is said to have _________.

cancer

The most common type of cancer is a _______________; this type always originates in tissues that line organs.

carcinoma

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 there body tissues

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

reproduction (production of gametes)

________ reproduction, in contrast, generates genetically unique offspring. To accomplish this, an organism must produce__________-- sperm and egg -- through the process of ____________. The cells produced this way will be ______________, meaning that they contain a single set of chromosomes. Such cells are produced only in the ____________.

sexual, gametes, meiosis, haploid, gonads