AP BIO - unit 5: Heredity

Heredity

The passing of traits from parents to offspring

Genes

Segments of DNA that code for specific traits

Mutations

Changes in the DNA sequence that can create new traits

Homologous chromosomes

Pairs of chromosomes with the same genes, one from each parent

Asexual Reproduction

Reproduction involving one parent producing genetically identical offspring

Sexual reproduction

Reproduction involving two parents producing genetically diverse offspring

Karyotype

A display of an individual’s complete set of chromosomes

Somatic cell

A body cell that is diploid

Gametic cell

A sex cell (sperm or egg) that is haploid

Diploid

A cell with two sets of chromosomes (2n)

Haploid

A cell with one set of chromosomes (n)

Autosomes

Chromosomes that are not sex chromosomes

Sex Chromosome

Chromosomes that determine biological sex (X and Y)

Life Cycle

The sequence of stages in an organism’s reproduction

Zygote

A fertilized egg cell formed by the fusion of gametes

Genetic

Relating to genes or heredity

Clones

Genetically identical copies of an organism

Meiosis

Cell division that produces haploid gametes

Synapsis

Pairing of homologous chromosomes during meiosis

Tetrad

A group of four chromatids formed during synapsis

Chiasmata

Points where crossing over occurs between chromatids

Crossing Over

Exchange of genetic material between homologous chromosomes

Independent Assortment

Random distribution of homologous chromosomes during meiosis

True Breeding

Organisms that produce offspring identical to themselves when self-fertilized

P Generation

The parental generation in a genetic cross

F1 Generation

The first generation of offspring from the P generation

F2 Generation

The second generation of offspring from crossing F1 individuals

Punnett Squares

Diagrams used to predict genetic crosses

Monohybrid Cross

A cross examining one trait

Dihybrid Cross

A cross examining two traits

Phenotype

The observable traits of an organism

The Multiplication Rule

Probability rule stating that the chance of two events both occurring is the product of their probabilities

Law of Segregation

Alleles separate during gamete formation

Law of Independent Assortment

Genes for different traits assort independently

The Addition Rule

Probability rule used to calculate the chance of one of multiple events occurring

Recessive

An allele expressed only when two copies are present

Alleles

Different forms of a gene

Heterozygous

Having two different alleles for a trait

Genotype

The genetic makeup of an organism

Dominant

An allele expressed even if only one copy is present

Homozygous

Having two identical alleles for a trait

Pedigrees

Diagrams that track inheritance of traits through generations

Incomplete Dominance

A blend of phenotypes in heterozygotes

Polygenic inheritance

Traits controlled by multiple genes

Multiple alleles

More than two allele options for a gene in a population

Epistasis

One gene affects the expression of another gene

X-linked

Traits associated with genes on the X chromosome

Codominance

Both alleles are fully expressed in heterozygotes

Y-linked

Traits associated with genes on the Y chromosome

Hemizygous

Having only one allele for a gene (common in X-linked genes in males)

Barr body

An inactivated X chromosome in female cells

Recombinants

Offspring with new combinations of traits not seen in parents

Linkage Map

A map of gene positions based on recombination frequencies

Chi Square

A statistical test used to compare expected vs observed results

Phenotypic plasticity

The ability of an organism to change phenotype due to environment

Nondisjunction

Failure of chromosomes to separate properly during meiosis