AP BIO HEREDITY VOCAB

heredity

the transmission of traits from one generation to the next

genes

segments of DNA that code for basic units of hereditary

mutations

a random error in gene replication that leads to a change

homologous chromosomes

Pair of chromosomes that are the same size, same appearance and same genes.

asexual reproduction

Process by which a single parent reproduces by itself

sexual reproduction

A reproductive process that involves two parents that combine their genetic material to produce a new organism, which differs from both parents

karyotype

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

somatic cells

body cells

gamete cells

sex cells

diploid 2n

two copies of each chromosome

haploid n

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

autosome

Any chromosome that is not a sex chromosome

sex chromosome

Chromosomes that determine the sex of an individual

life cycle

The generation-to-generation sequence of stages in the reproductive history of an organism.

zygote

fertilized egg

genetics

The scientific study of heredity

clones

identical genetic copies

meiosis

Cell division that produces reproductive cells in sexually reproducing organisms

synapsis

Pairing of homologous chromosomes

tetrad

structure containing 4 chromatids that forms during meiosis

chiasmata

X-shaped regions where crossing over occurred.

crossing over

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

independent assortment

One of Mendel's principles that states that genes for different traits can segregate independently during the formation of gametes

steps of meiosis

Prophase 1, Metaphase 1, Anaphase 1, Telophase 1, Prophase 2, Metaphase 2, Anaphase 2, Telophase 2

true breeding

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

p generation

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

f1 generation, first filial generation

offspring of the P generation

f2 generation. 2nd filial generation

offspring of the F1 generation

punnet squares

diagram showing the gene combinations that might result from a genetic cross

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

phenotype

An organism's physical appearance, or visible traits.

the multiplication rule

To determine the probability, we multiply the probability of one event by the probability of another.

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

law of independent assortment

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

the addition rule

Considering mutually exclusive events, the probability of both occurring is the sum of the probabilities of each event.

recessive

An allele that is masked when a dominant allele is present

alleles

Different forms of a gene

heterozygous

An organism that has two different alleles for a trait

genotype

genetic makeup of an organism

dominant

Describes a trait that covers over, or dominates, another form of that trait.

homozygous

An organism that has two identical alleles for a trait

pedigrees

a chart that shows a trait in a family and how it is inherited

incomplete dominance

Situation in which one allele is not completely dominant over another allele

polygenic inheritance

combined effect of two or more genes on a single character

multiple alleles

three or more forms of a gene that code for a single trait

epistasis

A type of gene interaction in which one gene alters the phenotypic effects of another gene that is independently inherited.

x linked

referring to a gene located on the X chromosome

codominance

A condition in which neither of two alleles of a gene is dominant or recessive.

y linked

referring to a gene located on the Y chromosome

hemizygous

A gene present on the X chromosome that is expressed in males in both the recessive and dominant condition

barr body

A dense body formed from a deactivated X chromosome.

recombinants

offspring whose phenotype differs from that of the parents

linkage map

A genetic map based on the frequencies of recombination between markers during crossing over of homologous chromosomes.

chi square

Involves categorical variables. Looks at 2 distributions of categorical data to see if they differ from each other.

phenotypic plasticity

the ability of one genotype to produce more than one phenotype when exposed to different environments

nondisjunction

Error in meiosis in which homologous chromosomes fail to separate.