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Today: Inheritance
for 1 gene
Fig 13.5
{Producing gametes}
Sexual reproduction
creates genetic
diversity by
combining DNA
from 2 individuals,
but also by creating
genetically unique
gametes.
{Producing more cells}
haploid
X 23
in humans
X 23
in humans
diploid
X 23
in humans
Inheritance = The interaction between genes
inherited from Mom and Dad.
Do parents’ genes/traits blend together in offspring?
Fig 14.3
In many
instances there
is a unique
pattern of
inheritance.
Traits
disappear and
reappear in
new ratios.
Fig 14.6
Genotype
Phenotype
Human blood types
Fig 14.11
Fig 14.11
One gene with three alleles controls carbohydrates
that are found on Red Blood Cell membranes
A
A
A
B
A
A
A
A
A
Allele A = A carbs
B
B
B
RBC
A
B
RBC
RBC
B
B
B
B
Allele B = B carbs
Allele O = no carbs
Human blood types
Fig 14.11
We each have two versions of each gene…
A
So
A
A
A
A
RBC
A
A
A
A
Genotype could be
A and A
OR
A and O
Recessive alleles do not show their phenotype
when a dominant allele is present.
A
A
A
A
A
RBC
A
A
A
A
Genotype could be
A and A
OR
A and O
What about…
RBC
Genotype = ??
What about…
RBC
Genotype = OO
What about…
B
A
B
A
A
RBC
B
B
A
B
A
What about…
B
A
B
A
A
RBC
B
B
A
B
Genotype = AB
A
Human blood types
Phenotyp
Phenotype Genotype
e
AA or
AO
BB or
BO
AB
OO
Fig 14.11
Result of transfusion
If Frank has B blood type,
his Dad has A blood type,
And his Mom has B blood type…
Should Frank be worried?
Mom=B blood
possible BB or BO
genotypes
Dad=A blood
AA or AO
possible
Mom=B blood
Dad=A blood
BB or BO
AA or AO
genotypes
Gametes all B / 50% B and all A / 50% A and
50% O
50% O
possible
Mom=B blood
Dad=A blood
BB or BO
AA or AO
genotypes
Gametes all B / 50% B and all A / 50% A and
50% O
50% O
Frank can be BO
= B blood
…no worries
Grandparents
AB and AB
Mom=B blood
possible
BB or BO
Dad=A blood
AA
genotypes
Gametes all B / 50% B and
50% O
Frank can be BO or BB
= B blood
all A
…Uh-Oh
Some simple dominant/recessive relationships
in humans
Dom.
Rec.
Rec.
Dom.
Fig 14.15
We can also
predict the
future
Fig 14.3
Inheritance of blood types
Mom = AB
Dad = AB
Inheritance of blood types
Mom = AB
Gametes:
A or B
Dad = AB
A or B
Inheritance of blood types
Mom = AB
Gametes:
A or B
A or B
Dad
A or B
A AA
Mom or
B AB
Dad = AB
AB
BB
Chance of each
phenotype for
each offspring
25% AA
50% AB
25% BB
Testcross:
determining
dominant/
recessive and
zygosity
Fig 14.7
Sickle-cell anemia is caused by a point mutation
Fig
17.22
Sickled and normal red blood cells
Sickle-Cell Anemia:
A dominant or recessive allele?
Mom = HS
S=sickle-cell
H=normal
Dad = HS
Dad
H or S
H HH
Mom or
S HS
HS
SS
possible offspring
75% Normal
25% Sickle-cell
Fig
23.17
Coincidence of malaria
and sickle-cell anemia
Sickle-Cell Anemia:
A dominant or recessive allele?
Mom = HS
Dad
H or S
H HH
Mom or
S HS
HS
SS
S=sickle-cell
H=normal
Dad = HS
possible offspring
Oxygen transport:
75% Normal
25% Sickle-cell
Malaria resistance:
75% resistant
25% susceptible
2 genes, each coding for a trait:
Variation in pea shape and color
Phenotype
Genotype
Fig 14.8
The
inheritance
of genes on
different
chromosomes is
independent.
Fig 14.8
Approximate position of seed color and shape genes
in peas
Y
y
Gene for seed color
r
Chrom. 1/7
R
Chrom. 7/7
Gene for
seed shape
The inheritance of genes on different
chromosomes is independent:
independent assortment
Fig 15.2
Fig 15.2
meiosis I
Fig 15.2
meiosis I
meiosis II
The
inheritance of
genes on
different
chromosomes
is
independent:
independent
assortment
Fig 15.2
Fig 14.8
Next: more
complex inheritance