Biology Test 4 SG

All material from study guide. Test is on 12/2

purebred

an organism that has the same alleles for a trait

hybrid

an organism that has two different alleles for a trait

punnett square

a helpful diagram of squares used for tracking traits

pedigree

family history that charts a hereditary trait through past generations

simple dominance

inheritance pattern where one allele masks another for a single gene, and heterozygotes express the dominant phenotype

incomplete dominance

blending of alleles resulting in the creation of a third phenotype

codominance

when both alleles are inherited and expressed

multiple alleles

some traits can have more than 2 alleles

polygenic inheritance

two or more genes working together to express a trait

sex-linked traits

traits controlled by sex chromosomes

carriers

people who carry an allele but do not express it (can pass it to offspring)

two main factors that control gene expression

DNA and environment

promoters

accompany every gene and will "turn on" or "turn off" a gene

enhancers

bind a promoter to "turn on"

silencers

found in DNA and bind a promoter to "turn off"

regulatory proteins

bind to enhancers and promoters and are the link to promoters

introns

non-coding sections of DNA

exons

coding sections of DNA used to make a protein

environmental effects could include

hormone-activated, light, temperature, chemicals

cell differentiation

a process that changes cells so that they can perform different and specialized functions

homeotic genes

genes that function to serve as a map for an organism's body structure

stem cells

changeable cells that have not yet differentiated into specialized cells. can be embryonic or somatic

allele frequency

how often a certain allele shows itself in a given population

gene flow

the ebb and flow of genetic variation within a population

genetic equilibrium

the condition of a large population with a stable allele frequency

genetic drift

a change in the allele frequency based on random events

bottleneck effect

dramatic change in a gene pool and allele frequency (for example a large portion of deaths in a population)

founder effect

when a small population moves to a new area and the allele frequency changes as new population grows