4_Single Gene Inheritance Bio025

Ch. 4 Human Genetics Lewis; Some terms are from previous chapters--we are still using them.

allele

Alternative form of a gene;

one of a pair of genes that

occupies the same position

on homologous chromosomes

autosomal dominant

inheritance pattern where only one copy of a dominant allele is necessary for the expression of a trait, affecting both sexes equally.

autosomal recessive

inheritance pattern where two copies of a recessive allele are necessary for the expression of a trait, affecting both sexes equally but may skip generations.

carrier

An individual who has one copy of a recessive allele for a trait but does not express the trait, often able to pass the allele to offspring.

compound heterozygote

an individual with two different recessive alleles in the same gene. This condition can lead to recessive disorders if both alleles are defective.

consanguinity

blood relatives having children together (increases the risk of recessive genetic disorders due to shared alleles).

dominant allele

version of a gene that can mask expression

of recessive version--only one copy required to produce the trait. Written with a capital letter (A).

genotype

genes of an individual for a particular trait

ex: BB or Aa

heterozygous

Possessing two different alleles of a gene.

ex: Aa

homozygous dominant

Possessing two copies of the dominant allele

ex: AA

homozygous recessive

Possessing two identical alleles for a particular trait that are only expressed in this situation

ex: aa

mode of inheritance

pattern in which a gene variant passes to offspring such as dominant, recessive, autosomal, X-linked or Y-linked.

monogenic

Trait or disorder caused by mutation of a single gene (Ex. Tay Sach's, Sickle Cell Disease, Cystic Fibrosis)

monohybrid cross

A cross of two individuals who are heterozygous for a single gene.

mutant

an allele that differs from the most common allele in a population and alters the phenotype.

pedigree

A diagram that shows the genetic relationships and inheritance patterns within a family across generations.

phenotype

visible expression of a genotype

Punnett square

a diagram used to follow and combine parental gene contributions to offspring (and to calculate the probability of certain outcomes).

recessive

version of a gene that causes a phenotype only when two copies are present; its expression is

masked by the dominant version of the gene. Written with a lowercase letter (a)

segregation

Mendel’s first law: the alleles of a gene are distributed into separate gametes during meiosis.

sex chromosome

one of the pair of chromosomes that determine the sex of an individual

test cross

a breeding experiment used to determine the genotype of an individual with a dominant phenotype by crossing it with a homozygous recessive individual.

wild type

the most common phenotype or allele in a population for a particular gene. Often considered the standard or typical form.

Cystic Fibrosis

autosomal recessive disease that results in thick, mucous secretions that do not drain normally affecting many body systems

Huntington Disease

Autosomal dominant disease that causes progressive degeneration of brain cells

autosome (autosomal, adjective)

Chromosome that is not a sex chromosome (on a non-sex chromosome).

sex chromosome

one of the pair of chromosomes that determine the sex of an individual

genetic disorder

A disease caused by abnormalities in an individual's DNA, which can be inherited or arise spontaneously, often leading to specific health issues.

genetic trait

a characteristic that can be inherited from parents to offspring.