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Biology - The Fundamentals of Genetics Cheat Sheet by

Biology

Gregor Mendel­-1860s

The "­Father of Geneti­cs"
His jobs
Austrian monk, teacher, scientist, and gardener
Used peas because
easy to grow, relatively short time period per generation (3 months), self-p­oll­ina­ting, and created purebreds
 
scientist
True-b­reeding
7 simple traits without genetic variation
Used brushes to pollinate
 
P1
parental generation

Punnet Squares - Monohybrid Cross

Punnet Squares - Codomi­nance

Chromo­somes and Genes

Homologous chromo­somes contain genes for the same traits
Traits are controlled by alleles
The genotype is the alleles received at fertil­ization
Phenotype is the physical appearance
 

Principle of Dominance

F1 plants resembled one parent
F1 hybrids contained two factors for each trait
1.Dominant
masks recessive
2.Rece­ssive
"­dis­app­ear­s" with dominant allele

Inheri­tance Patterns

Homozygous Dominant
two dominant alleles (BB)
Homozygous recessive
two recessive alleles (bb)
Hetero­zygous
one dominant and one recessive allele (Bb)

Punnet Squares - Dihybrid Cross

two pairs of contra­sting traits

Polygenic Traits

When 2 or more genes control a trait
Skin color
4-7 genes + melanin
Eye Color
blue (light melanin) + brown (a lot of melanin)
Height

Test Crosses

Unknown genotype x known genotype
important to breeders
performed with homozygous recessive
 

Probab­ility

The mathem­atical chance of an event occuring
3 ways to express
percent, decimal, or fraction
Law of Probab­ility
in the case where there are several possible outcomes and the chances are equally likely, they will even out to follow the predicted probab­ility in large sample sizes

Incomplete Dominance

Ex.) red + white = pink
3 phenotypes
neither alleles are completely dominant
Alleles
homozygous dominant
RR
homozygous recessive
R'R'
hetero­zygous
RR'

Codomi­nance

neither allele is dominant or recessive
Ex.) white + red = red & white
3 phenotypes
Alleles
red coat
RR
white coat
RR
mixed
RW

Punnet Squares - Incomplete Dominance

                                           
 

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helpful! thanks<3

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