Inheritance patterns

Genotype

Set of alleles in DNA of an individual organism
-controls majority of organisms phenotype
-dominant = always expressed
-recessive = mutation causes DNA code 4 non-func protein

Hemizygous = organism has only one copy of gene
-e.g XY mammals are hemizygous 4 all genes on X + Y chromosomes

Phenotype

Organism’s observable characteristics,
-result of their genotype, influence by environment
-can affect its life, only its genotype passed down + affect offspring

Complete dominance + test crosses

One allele = dominant over other
-traits show discrete variation

-homozygous dominant + heterozygous = same phenotype, to determine genotype, test cross w/ recessive = performed
-if offspring = dominant phenotype, then parent genotype = homozygous dominant
-show both phenotypes, genotype = heterzygous

Test crosses

•Individuals who are heterozygous (Aa) and homozygous dominant (AA) for a trait have the same phenotype

•To determine their genotype, a test cross with a homozygous recessive (aa) individual is performed

Incomplete dominance VS Co dominance

Incomplete dominance = when heterozygotes partially express both alleles in phenotype, neither = dominant
-produces blend of homozygous dom + recessive phenotypes

Co dominance = heterozygotes express both alleles equally, present multiple, independent phenotypic traits

Polygenic inheritance
-more genes involved in trait, more possible different phenotypes

Some traits, individual’s phenotype = influenced by more than 1 gene
-e.g height = control by 50+ genes, 4+ for skin
-traits show continuous variation

Epigenetic factors

Environmental factors e.g. diet, can alter activity some proteins, → changes expression of gene
-affects amount protein produced, alters phenotype

Do not alter actual DNA sequence of gene
-some changes (e.g. drug use) can pass → offspring

Autosomal dominant + recessive

Dominant
-one affected parent = affected offspring
males + females equally affected, every generation

Recessive
-males and females are equally affected, skip generation

X link dominant VS recessive

X link dominant
-all affected sons = affected mother
-affected fathers = affected daughters, every generation

Recessive
-skip generations, males > females affected
-females = carriers, males no
-affected fathers cant pass → sons

Gene linkage

Genes controlling traits = close together + same chromosome, often inherited together, linked
-not assort independently, but occasionally separate in crossing over

If crossing over site = btwn linked genes, can separated, + assort independently

Test crosses gene linkage
-test crosses + examining phenotypic ratios can determine the distance btwn the genes

If proportion of offspring w/ recombinant (non-parental) phenotypes = ↑, gene not linked

If proportion of recombinant phenotypes = ↓, genes = likely linked