Genetics

Gene

section of DNA that provides the instructions for making a protein.

Alleles

different versions of the same gene.

Homologous Chromosomes

the matching chromosomes from our mom and dad.

Gregor Mendel

Austrian monk who used pea plants to learn about genetics. He is known as the "Father of Genetics".

3 Laws of Inheritance

Law of Dominance

Law of Segregation

Law of Independent Assortment

Purebred

type of organism whose ancestors are genetically uniform.

Cross

mating of 2 organisms

P = parental generation

F1 = first generation

F2 = second generation

Homozygous

2 of the SAME alleles.

Heterozygous

2 DIFFERENT alleles

Genotype

the actual alleles inherited.

Phenotype

the physical traits/characteristics seen in an organism.

Law of Dominance

A dominant (strong) allele will express itself over a recessive (weak) allele.

Dominant

if present, allele will always have that trait expressed (seen).

Recessive

allele will only have that trait expressed (seen) when the dominant allele is NOT present.

Law of Segregation

When chromosomes separate in meiosis, each gamete (egg or sperm) will receive only one chromosome from each pair.

Law of Independent Assortment

The assortment of chromosomes for one trait doesn't affect the assortment of chromosomes for another trait.

Punnett Square

a diagram that shows the probability of inheriting traits from parents with certain genes.

Exceptions to Mendel's Laws

Some alleles are neither dominant nor recessive, and many traits are controlled by multiple alleles or multiple genes.

Incomplete Dominance

- The heterozygous phenotype is somewhere between the two homozygous phenotypes.

- Neither allele is completely dominant or recessive.

Codominance

Both traits are fully and separately expressed.

- Ex. Red and white flowers make red and white speckled flowers.

Multiple Alleles

Having more than two alleles for one gene (ex. blood type)

Polygenic Inheritance

A trait produced by two or more genes.

Epistasis

When one gene overshadows all of the others.

Chromosome Theory of Inheritance

Genes are located on chromosomes and the behavior of chromosomes during meiosis accounts for inheritance patterns.

Linked genes

genes that are physically located on the same chromosome will be inherited together.

Sex-Linked genes

genes on sex chromosomes

- If on the X, they are "X-linked"

- If on the Y, they are "Y-linked"

(Most are found on X)

X-Linked Genes

- Females inherit X-linked genes as normal & principle of dominance applies.

- Males inherit the gene on the X, but not the Y. (inherit it regardless)

Carrier

someone who carries the recessive trait, but doesn't show it due to having a dominant X to mask it.