Au Biology 110 Chapter 12

Front 1

meiosis

Back 1

Nuclear division that leads to a halving of the chromosome number.

Front 2

chromatid

Back 2

One of the daughter strands of a chromosome that has recently been copied (during mitosis or meiosis) and that is still connected to the other daughter strand.

Front 3

centromere

Back 3

The attachment structure joining two sister chromatids during mitosis and meiosis.

Front 4

meiosis I

Back 4

The first of two major cell-division events in meiosis, during which two genetically different haploid daughter cells are produced.

Front 5

meiosis II

Back 5

The second of two major cell-division events in meiosis, during which four genetically different haploid daughter cells are produced.

Front 6

prophase I

Back 6

The first stage of cell division in meiosis I, during which chromosomes begin to move to the middle of the cell.

Front 7

homologous chromosomes (homologs)

Back 7

Chromosomes of the same type, with the same genes in the same locations.

Front 8

diploid

Back 8

Having two sets of chromosomes. Diploid cells have two alleles of each gene--one on each of the homologous pairs of chromosomes.

Front 9

tetrad

Back 9

The structure that results from synapsis, consisting of two homologous chromosomes, each composed of two sister chromatids.

Front 10

synapsis

Back 10

The physical pairing of two homologs during prophase I of meiosis. Crossing over occurs during synapsis.

Front 11

chiasma

Back 11

The X-shaped structure formed during meiosis by crossing over between adjacent chromatids of a pair of homologous chromosomes.

Front 12

metaphase I

Back 12

The second stage of cell division in meiosis I, during which chromosomes line up in the middle of the cell.

Front 13

anaphase I

Back 13

The third stage of cell division in meiosis I, during which chromosomes move to opposite ends of the cell.

Front 14

telophase I

Back 14

The fourth and final stage of cell division in meiosis I, during which chromosomes finish moving and new nuclear envelopes begin to form around each set of daughter chromosomes.

Front 15

haploid

Back 15

Having a single set of chromosomes. Haploid cells have just one allele of each gene; they do not contain homologous chromosomes.

Front 16

mitosis

Back 16

Nuclear division in eukaryotes that produces two daughter nuclei that are genetically identical to the parent.

Front 17

prophase II

Back 17

The first stage of cell division in meiosis II, during which chromosomes begin to move to the middle of the cell.

Front 18

metaphase II

Back 18

The second stage of cell division in meiosis II, during which chromosomes line up in the middle of the cell.

Front 19

diploid

Back 19

Having two sets of chromosomes. Diploid cells have two alleles of each gene--one on each of the homologous pairs of chromosomes.

Front 20

meiosis

Back 20

Nuclear division that leads to a halving of the chromosome number.

Front 21

haploid

Back 21

Having a single set of chromosomes. Haploid cells have just one allele of each gene; they do not contain homologous chromosomes.

Front 22

chromosome

Back 22

A single long molecule of DNA and any associated proteins.

Front 23

nondisjunction

Back 23

An error that can occur during meiosis or mitosis in which both homologous chromosomes of a pair move to the same side of the dividing cell. One daughter cell receives two copies of this chromosome and the other daughter cell receives none.

Front 24

homologous chromosomes (homologs)

Back 24

Chromosomes of the same type, with the same genes in the same locations.

Front 25

gamete

Back 25

A haploid reproductive cell that can fuse with another haploid cell to form a zygote.

Front 26

sister chromatids

Back 26

The paired strands of a recently replicated chromosome that has not yet divided.

Front 27

zygote

Back 27

The diploid cell formed by the union of two haploid gametes. A zygote is capable of undergoing embryological development to form an adult organism.

Front 28

trisomy

Back 28

A condition in which a diploid cell or organism has an extra chromosome of one type, producing a chromosome number of 2n + 1.

Front 29

Down syndrome

Back 29

A chromosomal disorder resulting from trisomy of chromosome 21. The syndrome is characterized by mental retardation, a high risk for heart problems and leukemia, and a degenerative brain disorder similar to Alzheimerπs disease.

Front 30

monosomy

Back 30

A condition in which a diploid cell or organism lacks a chromosome of one type, producing a chromosome number of 2n ≠ 1.

Front 31

Turner syndrome

Back 31

A rare chromosomal disorder in females who have only one X chromosome. The syndrome is characterized by short stature, the lack of sexual development at puberty, and heart abnormalities.

Front 32

triploid

Back 32

Having three sets of chromosomes.

Front 33

aneuploid

Back 33

Having a chromosome number that is not an exact multiple of the normal diploid number, with either more or fewer than the normal number of chromosomes in the cell. Trisomy (having an extra chromosome) and monosomy (missing a chromosome) are examples.

Front 34

polyploid

Back 34

Having more than two sets of chromosomes. Triploidy, in which an organism has three complete sets of chromosomes, is an example.