•Homework #3 is due 11/19
•Bonus #2 is posted
•No class W 11/21
•Today: Meiosis, producing genetically
diverse offspring, and inheritance
{Meiosis:
producing gametes}
For life to exist,
the information
(genes) must be
passed on.
{Mitosis:
producing more cells}
Gene for
growth
hormone
Gene for
brown hair
pigment
Gene for
blue eye
pigment
Gene for
hemoglobin
similar to Fig 2.18
Gene for
DNA polymerase
Haploid
chromosomes
Allele for
low express
(short)
Gene for
growth
hormone
Allele for
high express
(tall)
similar to Fig 2.18
Allele for
black hair
Gene for
hair color
Allele for
black hair
Allele for
sickle cell Hb
Gene for
hemoglobin
Allele for
normal Hb
Diploid
chromosomes
Each pair of
chromosomes
is comprised
of a paternal
and maternal
chromosome
sister chromatids= replicated DNA (chromosomes)
tetrad= pair of sister chromatids
Fig 2.41
Meiosis splits apart the
pairs of chromosomes.
Fig 2.19
X 23
in humans
haploid
X 23
in humans
X 23
in humans
diploid
X 23
in humans
Inheritance = The interaction between genes
inherited from Mom and Dad.
Asexaul
Reproduction
extremely low
genetic diversity
vs.
Sexaul
Reproduction
greater genetic
diversity
How does sexual reproduction generate
genetic diversity?
Meiosis splits apart the
pairs of chromosomes.
Fig 2.19
X 23
in humans
Fig 4.3
Crossing-over
(aka Recombination)
DNA cut and
religated
DNA cut and
religated
Crossing-over:
Proteins in the cell cut and religate the DNA,
increasing the genetic diversity in gametes.
Fig 4.5
Crossing-over:
Proteins in the cell cut and religate the DNA,
increasing the genetic diversity in gametes.
Fig 4.4
Crossing-over:
Proteins in the cell cut and religate the DNA,
increasing the genetic diversity in gametes.
Fig 4.5
Asexaul
Reproduction
extremely low
genetic diversity
vs.
Sexaul
Reproduction
greater genetic
diversity
How does sexual reproduction generate
genetic diversity?
Independent Assortment
(aka Random Assortment)
Fig 3.8
Independent Assortment
2 possibilities
for each pair,
for 2 pairs
22 = 4
combinations
Fig 3.8
Independent Assortment
2 possibilities
for each pair,
for 23 pairs
223 =
8,388,608
combinations
Fig 3.8
Box 2.2
Crossingover
Meiosis:
In humans,
crossing-over and (Ind. Assort.)
independent
assortment lead to
over 1 trillion
possible unique
gametes.
(1,000,000,000,000)
Meiosis I
Meiosis II
4 Haploid cells, each unique
Box 2.2
Box 2.2
4 haploid cells
{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 6.4
In many
instances there
is a unique
pattern of
inheritance.
Traits
disappear and
reappear in
new ratios.
Fig 2.12
Genotype
Pg 23
Phenotype
Human blood types
Pg 225
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
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
A
B
A
RBC
B
A
B
B
A
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
If Frank has B blood type,
his Dad has A blood type,
And his Mom has B blood type…
Should Frank be worried?
•Homework #3 is due 11/19
•Bonus #2 is posted
•No class W 11/21
•Today: Meiosis, producing genetically
diverse offspring, and inheritance