BMS 110 Basics of Genetics

Gene

Encodes for a protein or RNA and contains the instructions for all human traits

Locus

Specific location of a gene on a chromosome

Allele

Each version of a gene

Genome

the complete set of genes and alleles in a certain organism

Homozygous

identical alleles copies for a trait

Heterozygous

Different alleles copies for a trait, one dominant one recessive

Genotype

Genetic makeup of an organism (DNA)

Phenotype

the physical features

Monohybrid cross

used to predict the likely outcome of offspring

segregation

pairs of alleles separated during gamete formation (disjunction)

linkage

genes that are close together on the chromosome, best friends and travel together

independant assortment

A given chromosome and its genes move randomly into gametes

Dihybrid Cross

between individuals heterozygous for two traits yield sixteen different gametes unions

Pleiotrophy

wide-ranging effect of one gene

Multiple allele system

a gene that has 3 or more alleles (ex: blood types)

Penetrance

probability that someone who inherits an allele will have the phenotype associated with it

codominance

both dominant alleles are expressed (ex: AB blood type)

Polygenic traits

combined expression of several genes (ex: skin color, eye color)

Sex-influenced traits

appear more often in one sex than the other

Sex-limited genes

males and females inherit the same X chromosome, only the genes appropriate for the sex are turned on

Natural selection (3 parts)

1. Stabilizing 2. Disruptive 3. Directional

Stabilizing selection

average phenotype is favored, loss in extreme phone types

Disruptive selection

both extreme phenotypes are favored, allele frequency shifts away from mean

Directional Selection

ONE extreme is favored, causing allele frequency shift toward the extreme phenotype

multifactorial trait

phenotypes shaped by one or more genes and affected by the environment

chromosome mutation types (4)

1. deletion 2. duplication 3. Translocation 4. inversion

Deletion

permeant loss of genetic material

Duplication

gene sequences are related (ex: Huntingtons)

Translocation

moves one segment of a chromosome to a different chromosome

Translocation Non-reciprocal

loses information

translocation reciprocal

information is retained, just moved

inversion

a segment of a chromosome is inverted 180 degrees