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Asexual
Reproduction
extremely low
genetic diversity
vs.
Sexual
Reproduction
greater genetic
diversity
Crossing-over and independent assortment
generate genetic diversity during sexual
reproduction.
Why does sexual reproduction
exist?
Cons:
• Need two individuals
• Hard to find mate
• Diseases/Competition
Pros:
• Genetic diversity
or
• Replace damage DNA
CB 29.8 and .12
Haploid
dominant
(algae)
Diploid
dominant
(fern)
Why does sexual reproduction
exist?
Cons:
• Need two individuals
• Hard to find mate
• Diseases/Competition
Pros:
• Genetic diversity
or
• Replace damage DNA
Does a stressful environment lead to sexual
reproduction?
Asexual
Reproduction
extremely low
genetic diversity
vs.
Sexual
Reproduction
greater genetic
diversity
CB 26.20
Environmental
changes occur slowly
Asexual
Reproduction
extremely low
genetic diversity
vs.
Sexual
Reproduction
greater genetic
diversity
CB 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}
Each pair of
chromosomes
is comprised
of a paternal
and maternal
chromosome
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?
CB 14.3
In many
instances there
is a unique
pattern of
inheritance.
Traits
disappear and
reappear in
new ratios.
CB 14.6
Genotype
Phenotype
Human blood types
CB tbl 14.2
CB tbl 14.2
One gene with three alleles controls carbohydrates
that are found on Red Blood Cell membranes
A
A
A
A
A
RBC
A
A
A
A
Allele A = A carbs
B
B
B
B
B
RBC
B
RBC
B
B
B
Allele B = B carbs
Allele O = no carbs
Human blood types
CB tbl 14.2
CB tbl 14.2
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
CB tbl 14.2
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
CB tbl 14.2
What about…
RBC
Genotype = ??
CB tbl 14.2
What about…
RBC
Genotype = OO
CB tbl 14.2
What about…
B
A
A
B
A
RBC
B
A
B
B
A
CB tbl 14.2
What about…
B
A
A
B
A
RBC
B
A
B
Genotype = AB
B
A
Human blood types
AA or
AO
BB or
BO
AB
OO
CB tbl 14.2
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
genotypes
Mom=B blood
Dad=A blood
BB or BO
AA or AO
Gametes all B / 50% B and all A / 50% A and
50% O
50% O
possible
genotypes
Mom=B blood
Dad=A blood
BB or BO
AA or AO
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
genotypes
Gametes all B / 50% B and
50% O
Frank can be BO or BB
= B blood
Dad=A blood
AA
all A
…Uh-Oh
Some simple dominant/recessive relationships
in humans
Dom.
Rec.
Rec.
Dom.