Unit 5 (Heredity)

Law of Segregation

Mendel's first law, stating that allele pairs separate from one another during gamete formation

Law of Independent Assortment

Mendel's second law stating that genes for one trait are not inherited with the genes of another trait.

Recombinant Offspring

Offspring with phenotypes that are different from the parents - combination

Linked Genes

Genes located on the same chromosome that tend to be inherited together in genetic crosses.

True Breeding

Organisms that, when reproducing, create offspring of all the same variety (purebred).

Phenotype

An organism's physical appearance, or visible traits.

Genotype

An organism's genetic makeup, or allele combinations.

Heterozygous

An organism that has two different alleles for a trait

Allele

Different forms of a gene

Homozygous

An organism that has two identical alleles for a trait

Dominant

An allele that is always expressed (only requires one copy)

Recessive

An allele that is masked when a dominant allele is present (two copies needed)

Karyotype

A picture of all the chromosomes in a cell arranged in pairs

Meiosis

a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores.

Haploid

having a single set of unpaired chromosomes (half the normal amount)

Diploid

an organism or cell having two sets of chromosomes or the full amount of chromosomes

Crossing over

the exchange of genes between homologous chromosomes, resulting in a mixture of parental characteristics in offspring.

Autosomal

Any chromosome that is not a sex chromosome

monohybrid cross

A cross between individuals that involves one pair of contrasting traits

dihybrid cross

Cross or mating between organisms involving two pairs of contrasting traits

Ratio for monohybrid cross (phenotype)

3:1 dominant to recessive

Ratio for dihybrid cross (phenotype)

9:3:3:1

Law of Addition (probability)

The probability of either of two independent events happening is given by adding their probabilities (this OR that can happen)

Law of Multiplication (probability)

the probability of two or more events occurring simultaneously is obtained by multiplying the probabilities of the events occurring individually (this AND that must happen together)

Mendalian Genetics

all the rules associated with dominant vs. recessive genes that Mendel discovered (like the 3:1 ration); support the law of dominance

Non-Mendelian Genetics

inheritance doesn't follow Mendel's law of independent assortment or of complete dominance

Codominant

A heterozygote in which both alleles are fully expressed

incomplete dominance

Situation in which neither allele is fully expressed, heterozygotes have. a unique phenotype

sex-linked gene

gene located on the X or Y chromosome (usually the X)

female carrier

in sex-linked recessive inheritance refers to a female heterozygote

Epistasis

a gene at one locus (location) alters the effects or presence of a gene at another locus

Non-nuclear DNA

mitochondria and chloroplasts contain small amounts of DNA separate from the nucleus, this is inherited maternally

phenotypic plasticity

the ability of an organism to change its phenotype in response to changes in the environment.

chi-square value

the calculated value from the equation (o-e)^2/e

degrees of freedom

the number of possible outcomes minus 1

critical value

The value that the chi-square must exceed in order to reject the null hypothesis.

null hypothesis

the hypothesis that there is no significant difference between specified populations, any observed difference being due to sampling or experimental error.

pedigree

A chart or "family tree" that tracks which members of a family have a particular trait