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Chapter 3: Genetics
Mendel’s Peas
Discreet
Units of
Inheritance
(genes)
Genes
Inherited
Independently
(Independent Assortment)
Cells
Cell
Cytoplasm
Nucleus
Chromosomes
Diploid Organisms
Have
Chromosomes
Organized in
Homologous Pairs
Humans have 46 Chromosomes
(23 Homologous Pairs)
Cell Division
Mitosis
Making
Somatic Cells
Diploid Daughter Cells
Meiosis
Making
Sex Cells
Haploid Gametes
(eggs & sperm)
Genes: DNA
Alleles
(different varieties of genes)
Homozygous
Heterozygous
Terms
• Genotype = the particular genes or alleles
that an individual has
• Phenotype = the observable trait of a
individual’s genotype
• Dominant = individuals with only one copy
of the allele have the same phenotype
• Recessive = individuals need two copies
of the allele, no effect in the heterozygotes
Mendel’s Peas Again
F0 to F1
Parent
Generation
(F0)
True Breeding for Seed Color
Homozygous
Genotypes = AA & aa
Phenotype = Yellow & Green
Meiosis
Haploid
Sex Cells
Sex
Daughter
Generation
(F1)
Heterozygous
Genotype = Aa
Phenotype = Yellow
Mendel’s Peas Again
F1 to F2
Genotype = Aa
Phenotype = Yellow
F1 Generation
Meiosis
Sex
F2
Generation
Punnett Square
A
a
A
AA
Aa
a
Aa
aa
Genotype = 1:2:1
Phenotype = 3:1
Punnett Square
A
a
A
AA
Aa
A
AA
Aa
Genotype = 1:1
Phenotype = 1
Punnett Square
a
a
A
Aa
Aa
A
Aa
Aa
Genotype = 1
Phenotype = 1
Punnett Square
a
a
A
Aa
Aa
a
aa
aa
Genotype = 1:1
Phenotype = 1:1
Punnett Square 2 Genes/Traits
ab
ab
A
B
Aa
Bb
Aa
Bb
A
B
Aa
Bb
Aa
Bb
Genotype = 1:1
Phenotype = 1:1
Punnett Square 2 Genes/Traits
AB Ab
AB
Ab
aB
ab
aB
ab
AA
BB
AA
Bb
Aa
BB
Aa
Bb
AA
Bb
AA
bb
Aa
Bb
Aa
bb
Aa
BB
Aa
Bb
aa
BB
aa
Bb
Aa
Bb
Aa
bb
aa
Bb
aa
bb
Genotype = All Different
Phenotype = 9:3:3:1
Crossover
DNA = Deoxyribonucleic Acid
Bases:
Backbone
Is made of
Phosphates
& Sugars
Adenine
Thymine
Guanine
Cytosine
A
G
T
C
T
C
A
G
Paired
Making an Exact Copy
Making a Protein
DNA
A
T
T
C
G
A
C
C
G
U
A
A
G
C
U
G
G
C
Amino Acid 1
mRNA
Amino Acid 2
tRNA
C G A
U A A G C U G G C
Cytoplasm
mRNA