AP Bio Unit 5 HEREDITY

(sister) chromatid

Copies of a duplicated chromosome; when two sister chromatids are joined together it makes up one chromosome

Centromere

Attachment point of two sister chromatids

Interphase

Period of cell cycle when the cell is not physically dividing; consists of following stages:

G1= growth

S= replicates DNA

G2= continued growth; cell prepares for division

G0= cell is at rest (not preparing for division)

Growth factors

Proteins released by certain cells that stimulate other cells to divide; example platelet-derived growth factor (PDGF)

Cyclin

Family of proteins that control the progression of cells through the cell cycle by binding to and activating cyclin-dependent kinase (Cdk)

Cyclin graph

Apoptosis

Programmed cell death

Cancer

When cells begin dividing at an uncontrolled rate and become invasive

Mitosis

Division of the nucleus in eukaryotic cells

Consists of 4 stages- prophase, metaphase, anaphase, & telophase

Results in two genetically identical cells

Meiosis

Cell division in sexually reproducing organisms that forms gametes

Consists of two rounds of cell division but only one round of DNA replication

Results in four cells with haploid chromosome number

Mitosis diagram

Meiosis diagram

Homologous chromosomes

Paired chromosomes; the same size, shape, and carry genes for the same traits

Diploid

Complete set of paired chromosomes

# found in somatic (body) cells

2n

Haploid

Set of unpaired chromosomes

# found in reproductive cells

1n

Autosomes

All other chromosomes except sex chromosomes

Sex chromosomes

Determines gender

Male= XY

Female= XX

Gamete

Reproductive cell

Contains haploid # of chromosomes

Generated during meiosis

Somatic cell

Body cell

Contains diploid # of chromosomes

Generated during mitosis

Crossing over

Exchange of genetic material between homologous chromosomes

Chromosomal Theory of Inheritance

Genes are carried from parents to their offspring on chromosomes

Zygote

Diploid cell produced by the union of haploid gametes (egg and sperm) during fertilization

True-breeding

Organisms that produce offspring of the same variety over many generations of self-pollination; homozygous

P generation

True-breeding (homozygous) parent individuals from which F1 hybrid offspring are derived; "p" stands for parental

F1 generation

Hybrid (heterozygous) offspring arising from a parental (P generation) cross

F2 generation

Offspring of a hybrid cross resulting in a 3:1 ratio of dominant to recessive phenotypes

Hybrid

Heterozygous

Allele

Different versions of a gene

Ex: A or a

Genotype

Genetic makeup of an individual

Phenotype

Physical traits

Heterozygous

Having different alleles for a gene

Ex: Aa

Homozygous

Having identical alleles for a gene

Ex: AA or aa

Law of Segregation

Two alleles for a trait separate (segregate) during gamete formation and end up in different gametes

Law of Independent Assortment

Each pair of alleles segregates independently of each other pair of alleles during gamete formation

Traits are independent and require own Punnett square

Testcross

Crossing an organism with recessive individual

Monohybrid cross

A cross between two organisms that are heterozygous resulting in 3:1 ratio of dominant to recessive phenotypes

Dihybrid cross

A cross between two organisms that are heterozygous for TWO traits resulting in a 9:3:3:1 ratio

Polygenic

Traits that involve multiple genes

Ex: eye, skin, and hair color

Multiple allele traits

Traits that have more than two alleles contributing to phenotype

Ex: blood type

Sex-linked traits

A gene located on either sex chromosome

Most sex-linked genes are on the X chromosome

Wild-type

Phenotype that most commonly observed in natural populations

Recombinants

Offspring with non-parental phenotypes (new combinations of traits) due to crossing over between linked genes

Recombination frequency

Divide total number of recombinants (non-parental phenotypes) by the total number of offspring

Linked genes

Genes located close enough together on a chromosome that they tend to be inherited together

Linkage map

A genetic map of a chromosome based on recombination frequencies

Map units

Distances between genes; one map unit represents a 1% recombination frequency