Tparadise Bio 100 Exam 2 Study Guide

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BIO 100 Exam 2 Study Guide

Lesson 7:

1. Describe the basic structure of a chromosome.

• In the nucleus of each cell, the DNA molecule is packaged into thread-like

structures called chromosomes

• Each chromosome has a constriction point called the centromere, which divides

the chromosome into two sections, or “arms.” The short arm of the chromosome

is labeled the “p arm.” The long arm of the chromosome is labeled the “q arm.”

The location of the centromere on each chromosome gives the chromosome its

characteristic shape, and can be used to help describe the location of specific

genes.

2. Explain why it is necessary for mitosis to result in identical daughter cells.

• It can be seen in the stages that mitosis maintains the chromosome number

or complement of a cell. Mitosis therefore maintains the chromosome

complement and ensures that each daughter cell receives all the genetic

information needed to carry out its activities and functions.

3. Describe the cell cycle.

• Mitosis: a type of cell division that results in two daughter cells each

having the same number and kind of chromosomes as the parent nucleus,

typical of ordinary tissue growth.

4. Describe the events that occur in each phase of mitosis.

• Before mitosis starts, all the chromosomes in the nucleus replicate their

DNA to make identical copies. The nucleus now contains two sets of

replicated chromosomes, twice as many as a normal body cell. The stages

outlined in the following example show a cell with a diploid chromosome

number of four (two sets of two chromosomes) undergoing cell division.

• Stage one: The replicated chromosomes 'condense'. Their DNA becomes

tightly coiled up and the replicated chromosomes become visible as

separate units. The chromosomes shorten and thicken and can now be seen

as pairs of chromatids. Replicated chromosomes remain attached to each

other by their central region: the centromere. As long as they remain

attached to each other the two identical copies of the chromosome are

known as sister chromatids.

• Stage two: The nuclear membrane (the boundary of the nucleus) breaks

down.

• Stage three: Rope-like structures called spindle fibres attach themselves

to the centromere region of the sister chromatid pairs. The spindle fibres

line sister chromatid pairs up in the centre of the cell. This location is

known as the equator.

• Stage four: The spindle fibres contract and separate the sister chromatids

from each other. The sister chromatids are pulled to opposite ends of the

cell - the cell poles.

• Stage five: The separated sister chromatids are now known as

chromosomes. Their DNA becomes more loosely coiled (decondensed),

and new nuclear membranes form around them. Two new nuclei are

formed. Each nucleus now contains four chromosomes (two sets of two

chromosomes) exactly the same complement as the original parent cell.

The cytoplasm of the cell then divides in two to produce two daughter

cells. The daughter cells are genetically identical because they each

contain the same diploid chromosome complement as the original parent

cell.

5. Define the term cytokinesis and describe the event in an animal cell and a plant

cell.

• The cytoplasmic division of a cell at the end of mitosis or meiosis,

bringing about the separation into two daughter cells.

• Animal cells divide by a cleavage furrow. Plant cells divide by a cell plate

that eventually becomes the cell wall. Cytoplasm and cell membranes are

necessary for cytokinesis in both plants and animals.

6. Explain what causes a cell to grow uncontrollably.

• Cell growth is carefully regulated because the consequences of

uncontrolled cell growth in a multicellular organism are very severe. -

Cancer is a disorder in which body cells lose the ability to control growth.

Cancer cells do not respond to the signals that regulate the growth of most

cells. As a result, the cells divide uncontrollably -Cancer cells form a mass

of cells called a tumor. Some are serious, while others are benign. -benign-

does not spread to surrounding healthy tissue or to other parts of the body.

-Cancerous tumors-malignant tumors that destroy and invade surrounding

healthy tissue. -As cancer cells spread, they absorb the nutrients needed by

other cells, block nerve connections, and prevent the organs they invade

from functioning properly.

7. Define the following terms: tumor, cancer, benign tumor, malignant tumor, and

metastasis.

• Cancer cells form a mass of cells called a tumor

• Cancer is a disorder in which body cells lose the ability to control growth.

Cancer cells do not respond to the signals that regulate the growth of most

cells. As a result, the cells divide uncontrollably

• Cancer cells form a mass of cells called a tumor. Some are serious, while

others are benign. –Benign, or not harmful because it does not spread to

surrounding healthy tissue or to other parts of the body.

• Cancerous tumors-malignant tumors that destroy and invade surrounding

healthy tissue. -As cancer cells spread, they absorb the nutrients needed by

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BIO 100 Exam 2 Study Guide Lesson 7: 1. Describe the basic structure of a chromosome. • • In the nucleus of each cell, the DNA molecule is packaged into thread-like structures called chromosomes Each chromosome has a constriction point called the centromere, which divides the chromosome into two sections, or “arms.” The short arm of the chromosome is labeled the “p arm.” The long arm of the chromosome is labeled the “q arm.” The location of the centromere on each chromosome gives the chromosome its characteristic shape, and can be used to help describe the location of specific genes. 2. Explain why it is necessary for mitosis to result in identical daughter cells. • It can be seen in the stages that mitosis maintains the chromosome number or complement of a cell. Mitosis therefore maintains the chromosome complement and ensures that each daughter cell receives all the genetic information needed to carry out its activities and functions. 3. Describe the cell cycle. • Mitosis: a type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus, typical of ordinary tissue growth. 4. Describe the events that occur in each phase of mitosis. • Before mitosis starts, all the chromosomes in the nucleus replicate their DNA to make identical copies. The nucleus now contains two sets of replicated chromosomes, twice as many as a normal body cell. The stages outlined in the following example show a ...
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