Chapter 8

Front 1

chromatin

Back 1

The combination of DNA and proteins that constitute chromosomes; often used to refer to the diffuse, very extended form taken by the chromosomes when a eukaryotic cell is not dividing.

Front 2

histone

Back 2

A small basic protein molecule associated with DNA and important in DNA packing in the eukaryotic chromosome.

Front 3

nucleosome

Back 3

The bead-like unit of DNA packing in a eukaryotic cell; consists of DNA wound around a protein core made up of eight histone molecules.

Front 4

sister chromatid

Back 4

One of the two identical parts of a duplicated chromosome in a eukaryotic cell.

Front 5

centromere

Back 5

The region of a chromosome where two sister chromatids are joined and where spindle microtubules attach during mitosis and meiosis. The centromere divides at the onset of anaphase during mitosis and anaphase II of meiosis.

Front 6

cell cycle

Back 6

An orderly sequence of events (including interphase and the mitotic phase) that extends from the time a eukaryotic cell divides to form two daughter cells to the time those daughter cells divide again.

Front 7

interphase

Back 7

The period in the eukaryotic cell cycle when the cell is not actually dividing. See also mitosis.

Front 8

mitotic phase

Back 8

The part of the cell cycle when mitosis divides the nucleus and distributes its chromosomes to the daughter nuclei and cytokinesis divides the cytoplasm, producing two daughter cells.

Front 9

mitosis

Back 9

The division of a single nucleus into two genetically identical daughter nuclei. Mitosis and cytokinesis make up the mitotic (M) phase of the cell cycle.

Front 10

cytokinesis

Back 10

The division of the cytoplasm to form two separate daughter cells. Cytokinesis usually occurs during telophase of mitosis, and the two processes (metosis and cytokinesis) make up the mitotic (M) phase of the cell cycle.

Front 11

somatic cell

Back 11

Any cell in a multicellular organism except a sperm or egg cell or a cell that develops into a sperm or egg.

Front 12

karyotype

Back 12

A display of micrographs of the metaphase chromosomes of a cell, arranged by size and centromere position.

Front 13

homologous chromosomes

Back 13

The two chromosomes that make up a matched pair in a diploid cell. Homologous chromosomes are of the same length, centromere position, and staining pattern and possess genes for the same characteristics at corresponding loci. One homologous chromosome is inherited from the organism’s father, the other from the mother.

Front 14

sex chromosome

Back 14

A chromosome that determines whether an individual is male or female.

Front 15

autosome

Back 15

A chromosome not directly involved in determining the sex of an organism; in mammals, for example, any chromosome other than X or Y.

Front 16

How meiosis halves chromosome number.

Back 16

Each of the chromosomes is duplicated during the preceding interphase. The first division, meiosis I, segregates the two chromosomes of the homologous pair, packaging them in separate (haploid) daughter cells. But each chromosome is still doubled. Meiosis II separates the sister chromatids. Each of the four daughter cells is haploid and contains only one single chromosome from the homologous pair.

Front 17

___________ is to somatic cells as haploid is to ___________.

Back 17

Diploid; gametes

Front 18

If a single diploid cell with 18 chromosomes undergoes meiosis and produces sperm, the result will be ___________ sperm, each with ___________ chromosomes. (Provide two numbers.)

Back 18

four; nine

Front 19

Comparing mitosis and meiosis

Back 19

The events unique to meiosis occur during meiosis I: In prophase I, duplicated homologous chromosomes pair to form tetrads, and crossing over occurs between homologous (nonsister) chromatids. In metaphase I, tetrads (rather than individual chromosomes) are aligned at the center of the cell. During anaphase I, sister chromatids of each chromosome stay together and go to the same pole of the cell as homologous chromosomes separate. At the end of meiosis I, there are two haploid cells, but each chromosome still has two sister chromatids. Meiosis II is virtually identical to mitosis and separates sister chromatids. But unlike mitosis, meiosis II yields daughter cells with a haploid set of chromosomes.

Front 20

Number of chromosomal duplications in
1. Mitosis
2. meiosis

Back 20

1
1

Front 21

Number of cell divisions in
1. mitosis
2. meiosis

Back 21

1
2

Front 22

Number of daughter cells produced in
1. mitosis
2. meiosis

Back 22

2
4

Front 23

Number of chromosomes in daughter cells
1. Mitosis
2. meiosis

Back 23

2n
n

Front 24

How chromosomes line up during metaphase in
1. mitosis
2. meiosis

Back 24

individually
by homologous pair

Front 25

Genetic relationship of daughter cells to parent cells
1. mitosis
2. meiosis

Back 25

identical

unique

Front 26

functions performed in the human body
1. mitosis
2. meiosis

Back 26

repair, growth, development

gamete formation

Front 27

crossing over

Back 27

The exchange of segments between chromatids of homologous chromosomes during synapsis in prophase I of meiosis; also, the exchange of segments between DNA molecules in prokaryotes.

Front 28

chiasma

Back 28

The microscopically visible site where crossing over has occurred between chromatids of homologous chromosomes during prophase I of meiosis.

Front 29

How does the karyotype of a human female differ from that of a male

Back 29

A female has two X chromosomes; a male has an X and a Y.

Front 30

Explain how nondisjunction in meiosis could result in a diploid gamete

Back 30

A diploid gamete would result if there were nondisjunction of all the chromosomes during meiosis I or II.

Front 31

What is the chromosomal basis of Down syndrome?

Back 31

Three copies of chromosome 21 (trisomy 21)

Front 32

5 phases of mitosis

Back 32

Interphase
Prophase
Metaphase
Anaphase
Telophase

Front 33

Interphase

Back 33

During interphase, cellular organelles double in number, the DNA replicates, and protein synthesis occurs. The chromosomes are not visible and the DNA appears as uncoiled chromatin.

Front 34

3 stages of interphase

Back 34

G1 phase
S phase (synthesis)
G2 phase

Front 35

G1 phase

Back 35

The period prior to the synthesis of DNA. In this phase, the cell increases in mass in preparation for cell division. Note that the G in G1 represents gap and the 1 represents first, so the G1 phase is the first gap phase.

Front 36

S phase

Back 36

The period during which DNA is synthesized. In most cells, there is a narrow window of time during which DNA is synthesized. Note that the S represents synthesis.

Front 37

G2 phase

Back 37

The period after DNA synthesis has occurred but prior to the start of prophase. The cell synthesizes proteins and continues to increase in size. Note that the G in G2 represents gap and the 2 represents second, so the G2 phase is the second gap phase.

Front 38

Prophase

Back 38

-Nuclear membrane disintegrates
-Strands of chromosomes condense and become visible
-Nucleolus disappears
-Longest phase of mitosis

Front 39

Metaphase

Back 39

-Chromosomes line up single file on the metaphase plate
-Centrioles are at opposite ends of the cell
-Spindle fibers run from centrioles to kinetochores

Front 40

Anaphase

Back 40

-Sister chromatids separate as spindel fibers pull them apart
-Shortest phase of mitosis

Front 41

Telophase

Back 41

-Chromosomes cluster at opposite ends of cell
-Nuclear membrane reforms
-Supercoiled chromosomes unravel and become invisible again
-Spindle fibers may still be visible

Front 42

Mitosis

Back 42

-Is the division of the chromosomes
-Is preceeded by interphase

Front 43

Cytokinesis

Back 43

-typically occurs during telophase
-Is the division of the cytoplasm
-is different in plant and animal cells

Front 44

Meiosis

Back 44

Meiosis is a two-part cell division process in organisms that sexually reproduce. Meiosis produces gametes with one half the number of chromosomes as the parent cell.