chapter 21. genetic inheritance

Genotype

Refers to the genes of an individual

Genes

Are segments of DNA on a chromosome that code for a trait. They are units of heredity

Locus

Position on a chromosome

Dominant alleles

Mask the expression of recessive alleles. Only one copy of the allele needs to be present for a trait to appear.

Recessive

Both chromosomes must possess this allele for it to be expressed

Homozygous dominant

Individuals that have dominant phenotypes. AA

Homozygous recessive

Individuals that have recessive phenotypes. aa

Heterozygous

Individuals have a dominant and recessive phenotype. Aa

Phenotype

Physical appearance of a trait. Determined by the expression of the alleles in the genotype

Monohybrid cross

A cross between individuals who are heterozygous

Meiosis

The chromosome number of the cells that will form the gametes is divided in half. This is accomplished by the separation of homologous chromosomes

Punnet square

All possible alleles that may be found in the sperm are lined up vertically, and all possible alles for the eggs are lined up horizontally. Every possible combination of gametes occurs within

One short and one long

A gamete will receive ______ chromosome for each kind

dihybrid cross

Cross involves two traits. The individual is heterozygous in two regards

Pedigree

Shows the pattern of inheritance for a particular condition

Carriers

They carry the recessive trait in their DNA but their phenotype is dominant

Lysosome

What enzyme causes tay Sachs disease

Genotype for colorblind male

X^b Y

Sex linked traits

Color blindness, muscular dystrophy, Fragile X syndrome, hemophilia

Cystic fibrosis

Autosomal recessive disorder that occurs among all ethnic groups but is most prevalent in Caucasians. Caused by defective chloride ion channel. Lack of water causes mucus in the bronchial tubes and pancreatic ducts.

Sickle-cell disease

Autosomal recessive disorder in which blood cells are sickle or boomerang shaped. This causes them to stack up and clog vessels

Marfan syndrome

Autosomal dominant disorder is caused by a defect in the elastic connective tissue protein called fibrin.

Osteogenesis imperfecta

Autosomal dominant genetic disorder that results in weakened brittle bones due to a lack of collagen

Huntington disease

Autosomal dominant disorder that leads to degeneration of the brain cells. Caused by a mutated protein gene.

Polygenic traits

Such a as skin color and height are governed by several sets of alleles.

Melanocytes

Skin color is a result of pigmentation produced by cells called

Multi factorial traits

Polygenic traits are subject to environmental influences.

Pleiotrophy

Occurs when a single mutant gene affects two or more seemingly unrelated traits

Incomplete dominance

Occurs when the heterozygote is intermediate between the two homozygotes

Codominance

Occurs when alleles are equally expressed in the hterozygote

X and Y

Males have these chromosomes

XX

Female chromosomes

Du Henne muscular distrophy

An x linked recessive disorder characterized by the degeneration of muscles

Fragile X syndrome

Most common cause of metal impairment. Most common cause of autism.

Anticipation

That the number repeats in the gene that can increase in each successive generation

Hemophilia

An x linked recessive disorder. Effects blood clotting.