Biology Test Review: Meiosis and Genetics

somatic cell

any cell of a living organism other than the reproductive cells.

homologous chromosomes

Chromosomes that have the same sequence of genes, that have the same structure, and that pair during meiosis.

locus

Location of a gene on a chromosome

sex chromosomes

Chromosomes that determine the sex of an individual

autosomes

Any chromosome that is not a sex chromosome

diploid

containing two complete sets of chromosomes, one from each parent.

gametes

reproductive cells

haploid

An organism or cell having only one complete set of chromosomes.

fertilization

Process in sexual reproduction in which male and female reproductive cells join to form a new cell

zygote

fertilized egg

meiosis

Cell division that produces reproductive cells in sexually reproducing organisms

crossing over

Process in which homologous chromosomes exchange portions of their chromatids during meiosis.

chiasma

site of crossing over

recombinant chromosomes

Chromosomes that carry genes from each parent.

nondisjunction

Error in meiosis in which homologous chromosomes fail to separate.

karyotype

A display of the chromosome pairs of a cell arranged by size and shape.

trisomy 21

condition in which an individual has three number 21 chromosomes, resulting in Down syndrome

Down syndrome

a condition of intellectual disability and associated physical disorders caused by an extra copy of chromosome 21.

deletion

A change to a chromosome in which a fragment of the chromosome is removed.

inversion

chromosomal fragment breaks off and attaches at the other end

duplication

change to a chromosome in which part of the chromosome is repeated

translocation

Change to a chromosome in which a fragment of one chromosome attaches to a nonhomologous chromosome.

heredity

Passing of traits from parents to offspring

traits

Characteristics that are inherited

genetics

The scientific study of heredity

true-breeding

term used to describe organisms that produce offspring identical to themselves if allowed to self-pollinate

hybrids

Offspring of crosses between parents with different traits

cross

mating of two organisms

P generation

Parental generation, the first two individuals that mate in a genetic cross

F1 Generation

the first generation of offspring obtained from an experimental cross of two organisms

F2 generation

offspring of the F1 generation

alleles

different versions of a gene

homozygous

An organism that has two identical alleles for a trait

heterozygous

An organism that has two different alleles for a trait

dominant allele

An allele whose trait always shows up in the organism when the allele is present.

recessive allele

An allele that is masked when a dominant allele is present

law of segregation

Mendel's law that states that the pairs of homologous chromosomes separate in meiosis so that only one chromosome from each pair is present in each gamete

Punnett square

A chart that shows all the possible combinations of alleles that can result from a genetic cross

phenotype

An organism's physical appearance, or visible traits.

genotype

genetic makeup of an organism

monohybrid cross

A cross between individuals that involves one pair of contrasting traits

dihybrid cross

A cross between individuals that have different alleles for the same gene

law of independent assortment

the law that states that genes separate independently of one another in meiosis

testcross

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

rule of multiplication

A rule stating that the probability of a compound event is the product of the separate probabilities of the independent events.

rule of addition

A rule stating that the probability that an event can occur in two or more alternative ways is the sum of the separate probabilities of the different ways.