DAT - Heredity

Penetrance

The proportion of individuals who have a phenotype associated with a specific allele

Epistasis

One gene affects how another is expressed (ex. with a gene for bald and blonde hair, bald takes precedence)

Polygenic Inheritance

Many genes contribute to one trait (continuous variation); Traits happen gradually from one extreme to another

Pleiotropy

One gene produces many traits (ex. Cystic Fibrosis)

Mendel’s Laws

1. Law of Dominance (completely dominant alleles mask recessive expression)

2. Law of Segregation (homologous gene copies separate during Anaphase 1 in Meiosis)

3. Law of Independent Assortment (homologous pairs line up independently during Metaphase 1, so alleles separate randomly)

Nondisjunction in Meiosis 1

Homologous chromosomes incorrectly split; Half haploid daughter cells have n+1 and half have n-1 (24, 24, 22, 22)

Nondisjunction in Meiosis 2

Sister chromatids incorrectly split; One haploid daughter cell has n+1, one n-1, and 2 are normal (24, 22, 23, 23)

Nondisjunction in Mitosis

Sister chromatids incorrectly split; Diploid parent cells split into 2 daughter cells with one being 2n+1 and one 2n-1 (45, 47)

Aneuploidy

Abnormal number of chromosomes in daughter cells; Disomy (2n), Trisomy (2n+1), Monosomy (2n-1)

Monohybrid Genotype Ratio

AA:Aa:aa → 1:2:1

Dihybrid Crosses

F1 individuals crossed are heterozygous for 2 traits on 2 different genes; F2 = 9:3:3:1

Recombination Frequencies

If < 0.5, the genes are considered linked; Random assortments of unlinked genes have RF values of 0.5

Haplotype

Group of genes close together that are usually inherited together