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AP Biology Unit 7: Genetics Cheat Sheet by

Ch 13: Meiosis; Ch 14: Mendelian Genetics; Ch 15: Chromosomes



genetic or chromo­somal (deletion, inversion, transl­oca­tion, polypl­oidy) abnorm­ality
diagram that shows size, #, & shape of chromo­somes
failed separation of homologous chromosomesaneuploidy(trisomy, polyploidy

Chromosome Mutations


Mendelian Laws

Law of Dominance
offspring of 2 organisms that are homozygous for 2 opposing traits will be hybrid but will only exhibit the dominant trait and not the recessive trait
Law of Segreg­ation
during formation of gametes, the 2 traits carried by each parent will separate
Law of Indepe­ndent Assortment
alleles of a gene for one trait segregate indepe­ndently from alleles of a gene for another trait (applies w/dihybrid cross)


genes on the same chromosome
traits carried on X chromosome
linkage mapping
distance between genes on chromosome=chance of separation by crossing over
recomb­ination frequency
=total recomb­ina­nts­/total # offspring x100
used to determine how traits are inherited
Barr body
inacti­vated X chromosome in each female mammal's somatic cellgenetic mosaic

Types of Crosses

monohybrid cross
Tt x Tt; phenotype ratio=3:1; genotype ratio=­1:2:1
B/__ x b/b to determine B/__'s genotype
dihybrid cross
TtYy x TtYy; can produce 4 types of gametes & phenotype ratio=­9:3:3:1

Dihybrid Cross

Types of Inheri­tance

incomplete dominance
hybrids show blending of traits
hybrids show both traits
multiple alleles
more than 2 allelic forms
1 gene affects an organism in severa­l/many ways
2 genes, 1 trait; 1 masks expression of the other
blending of several genes that vary along a continuum

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