Chapter 6

Front 1

somatic cell

Back 1

cell that makes up all of the body tissues and organs, except gametes.

Front 2

gamete

Back 2

sex cell; and egg or sperm cell.

Front 3

homologous chromosome

Back 3

chromosomes that have the same length, appearance, and copies of genes, although the alleles may differ.

Front 4

autosome

Back 4

chromosome that contains genes for characteristics not directly related to the sex of the organisms.

Front 5

sex chromosome

Back 5

chromosome that directly controls the development of sexual characteristics.

Front 6

sexual reproduction

Back 6

process by which two gametes fuse and offspring that are genetic mixture of both parents are produced.

Front 7

fertilization

Back 7

fusion of an egg and sperm cell.

Front 8

diploid

Back 8

cell that has two copies of each chromosome, one from an egg and one from a sperm.

Front 9

haploid

Back 9

cell that has only one copy of each chromosome.

Front 10

meiosis

Back 10

form of nuclear division that divides a diploid cell into haploid cells; important in forming gametes for sexual reproduction.

Front 11

gametogenesis

Back 11

process by which gametes are produced through the combination of meiosis and other maturational changes.

Front 12

sperm

Back 12

male gamete.

Front 13

egg

Back 13

female gamete.

Front 14

polar body

Back 14

haploid cell produced during meiosis in the female of many species; these cells have little more than DNA and eventually disintegrate.

Front 15

trait

Back 15

characteristic that is inherited.

Front 16

genetics

Back 16

study of the heredity patterns and variation of organisms.

Front 17

purebred

Back 17

type of organism whose ancestors are genetically uniform.

Front 18

cross

Back 18

mating of two organisms.

Front 19

law of segregation

Back 19

Mendel’s first law, stating (1) organisms inherit two copies of genes, one from each parent, and (2) because the genes separate during gamete formation.

Front 20

gene

Back 20

specific region of DNA that codes for a particular protein.

Front 21

allele

Back 21

any of the alternative forms of a gene that occurs at a specific place on a chromosome.

Front 22

homozygous

Back 22

characteristic of having two of the same alleles at the same locus of sister chromatid.

Front 23

heterozygous

Back 23

characteristic of having two different alleles that appear at the same locus of sister chromatid.

Front 24

genome

Back 24

all of an organism’s genetic material.

Front 25

genotype

Back 25

collection of all of an organism’s genetic information that codes for traits.

Front 26

phenotype

Back 26

collection of all of an organism’s physical characteristics.

Front 27

dominant

Back 27

allele that is expressed when two different alleles are present in an organism’s genotype.

Front 28

recessive

Back 28

allele that is not expressed unless tow copies are present in an organism’s genotype.

Front 29

Punnett square

Back 29

model for predicting all possible genotypes resulting from a cross, or mating.

Front 30

monohybrid cross

Back 30

cross, or mating, between organisms that involves only one pair of contrasting traits.

Front 31

testcross

Back 31

cross between an organism with an unknown genotype and an organism with a recessive phenotype.

Front 32

dihybrid cross

Back 32

cross or mating between organisms involving two pairs of contrasting traits.

Front 33

law of independent assortment

Back 33

Mendel’s second law, stating that allele pairs separate from on another during gamete formation.

Front 34

probability

Back 34

likelihood that a particular event will happen.

Front 35

crossing over

Back 35

exchange of chromosome segments between homologous chromosomes during meiosis I.

Front 36

genetic linkage

Back 36

tendency for genes located close together on the same chromosome to be inherited together.