Learning Objectives• Understand basic genetics vocabulary• Predict outcomes of monohybrid crosses• Predict outcomes of dihybrid crosses
Using Punnett Squares
B
B b
b
BB Bb
Bb bb
Different DNA (genetic material)
Why do people look different from one another?
What is Genetics?
Different proteins(appearances)
Genetics Vocabulary
Traita version of a character
Charactera recognizable feature controlled by genetics
fur color seed shape white fur wrinkled seeds
Genetics Vocabulary
Genotypean organism’s genetic makeup for a character
Phenotypean organism’s appearance for a character
white fur wrinkled seedshomozygous
recessiveheterozygous
bb Ww
Genetics Vocabulary - Genotype
Heterozygous“different”
Homozygous“same”
RRhh
BB
ww ss
TT
RrHh
Bb
Ww Ss
Tt
Phenotypes of heterozygous individuals can vary
• Complete dominance – same as
homozygous
• Incomplete dominance – an intermediate
• Codominance – both phenotypes shown
Genetics Vocabulary - Dominance
Genetics Vocabulary - Genotype• Individuals can be homozygous for some
characters and heterozygous for others• What determines an organism’s
genotype?
hh
ww
TT
Rr
Bb
Ss
Test Cross
A homozygous red-flowering plant is crossed with a homozygous white-flowering plant. What genotype will the offspring have?
RR rr
Rr
Test Cross
A homozygous red-flowering plant is crossed with a homozygous white-flowering plant. If red is dominant, what phenotype will the offspring have?
RR rr
Rr
red flowers
Monohybrid Cross
Two heterozygous red-flowering plants are crossed. What genotypes could the offspring have?
Rr Rr
R rR
r
RR Rr
Rr rrRR, Rr,
rr
Monohybrid Cross
Rr Rr
Two heterozygous red-flowering plants are crossed. If red is dominant over white, what is the most likely phenotype in the offspring?
R rR
r
RR Rr
Rr rrRed
Monohybrid Cross
Rr Rr
Two heterozygous red-flowering plants are crossed. If red is dominant over white, what are the average genotypic and phenotypic ratios?
R rR
r
RR Rr
Rr rr
Genotypes1 RR : 2 Rr :
1rrPhenotype
s3 red : 1 white
Monohybrid Cross
Rr Rr
Two heterozygous red-flowering plants are crossed. If red color is incomplete dominance, what is the most likely phenotype in the offspring?
R rR
r
RR Rr
Rr rrPink
Dihybrid Crosses
Two heterozygous red-flowering and heterozygous tall plants are crossed. If both characters are completely dominant, what fraction of their offspring will be tall and red-flowering (on average)? RrTt x RrTt
RT Rt rT rt
RT
Rt
rT
rt
RRTT
RRTt
RRTt
RrTT
RrTt
RrTT
RrTt
RRtt RrTt
RrTt rrTT
rrtt
Rrtt
rrTt
rrTtRrtt
9/16
Dihybrid Crosses
Two heterozygous red-flowering and heterozygous tall plants are crossed. If both characters are completely dominant, what are the average genotypic and phenotypic ratios?RT Rt rT rt
RT
Rt
rT
rt
RRTT
RRTt
RRTt
RrTT
RrTt
RrTT
RrTt
RRtt RrTt
RrTt rrTT
rrtt
Rrtt
rrTt
rrTtRrtt
Phenotypicred/tall red/shortwhite/tall white/short
- 9- 3- 3- 1
GenotypicRRTTRRTtRRttRrTTRrTtRrttrrTTrrTtrrtt
- 1- 2- 1- 2- 4- 2- 1- 2- 1
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