Ch 13 - 14 Campbell 11th edition AP biology, genetics and meiosis

Homologous chromosomes

2 chromosomes paired together, one from each parent

Heredity

The passing of traits from parents to offspring

Crossing over

When homologous chromosomes pair up, chromatids are broken, and are reconnected to non sister chromatids

Synapsis

When homologous chromosomes align closely together and form a tetrad

Synaptonemal complex

A structure that forms between homologous chromosomes to hold them in place

Genetics

The study of heredity and genes

Genes

A basic unit of heredity that carries specific DNA

Allele

A variant or different version of the same gene

Meiosis

A process that halves the number of chromosomes of a diploid to create 4 genetically unique haploid cells (gametes)

Gametes

A type of cells that are involved in sexual reproduction (sperm and eggs)

Autosomes

Any chromosomes that isn’t a sex chromosome

Sex chromomes

Chromosomes found in gametes and are involved in sexual reproduction

Genotype

An organism’s genetic makeup, the unique combination of alleles they carry (Hh)

Phenotype

Physical traits that you see (brown hair, blue eyes…)

Homozygous

have 2 of the same allele for the same trait (HH or hh)

Heterozygous

Have 2 different alleles for a trait (Hh)

Dominant allele

(H)A type of gene that is expressed even if there is only one copy present, represented by a capital letter

Recessive allele

(h)A gene variant that is only expressed when 2 copies are present, often masked by dominant alleles, usually represented by a lower case letter

Homozygous dominant

(HH) means that an organism has 2 copies of a dominant allele, expressing the dominant trait

Homozygous recessive

(hh) means that an organism has 2 identical copies of the recessive allele, allowing for expressing the recessive trait

Asexual reproduction

Reproducing without gametes, producing genetically identical clones

Karyotype

Ordered display of chromosomes

Sexual reproduction

A type of reproduction requiring the fusion of gametes (fertilization) to produce genetically unique offspring

Chiasmata

Site of crossing over

Recombinant chromosomes

Chromosomes with mixed parental alleles due to crossing over

Independent assortment

Random alignment of homologous pairs, increasing genetic variation

Character

Heritable feature

Trait

Variant of a character

True-breeding

Organisms producing genetically identical offspring when self-pollinated

Hybridization

Crossing 2 true—breeding varieties

P generation

Parental generation

F1 generation

First fillial offspring (hybrid)

F2 generation

Offspring from f1 self cross

Law of Segregation

Alleles separate during gamete formation, each gamete gets one allele

Law of independent assortment

Alleles for different traits segregate independently

Punnet square

Diagram predicting offspring genotype

Test cross

Cross with homozygous recessive to determine genotype

Monohybrid cross

Cross tracking one character

Dihybrid cross

Cross tracking 2 characters

Complete dominance

Heterozygote matches dominant homozygote

Incomplete dominance

Heterozygote shows intermediate phenotype

Codominance

Both alleles fully expressed

Pleiotropy

One gene affecting multiple traits

Polygenic inheritance

Multiple genes affecting one trait

Haploid

A type of cell that only has 1 set of chromosomes

Diploid

A type of cell that has 2 sets of chromosomes

Polyploid

A type of cell that has multiple sets of chromosomes, mostly in plants

Somatic cell

A type of body cell that is any other cell than a gamete