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Bonus #2
due 4/21
Inheritance
Asexual
Reproduction
extremely low
genetic diversity
vs.
Sexual
Reproduction
greater genetic
diversity
How does sexual reproduction generate
genetic diversity?
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
{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 2.6
In many
instances there
is a unique
pattern of
inheritance.
Traits
disappear and
reappear in
new ratios.
Fig 1.6
from DNA to Protein:
from gene to trait
Fig 1.7
from DNA to Protein:
from gene to trait
Molecular
Cellular
Organism
Population
Genotype
Phenotype
Human blood types
Fig 4.11
Fig 4.11
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 4.11
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
See Fig 4.2
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
AA or
AO
BB or
BO
AB
OO
Fig 4.11
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
Mom=B blood
Possible
genotypes BB or BO
Dad=A blood
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
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
Pedigree, tracing the genetic past
Dom.
Rec.
Rec.
Dom.
Fig 2.11
We can also
predict the
future
Fig 2.6
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
Single genes controlling a single trait are unusual.
Inheritance of most genes/traits is much more
complex…
Dom.
Rec.
Rec.
Dom.
Genotype
Phenotype
Genes code for
proteins (or RNA).
These gene
products give rise
to traits…
Human blood types
AA or
AO
BB or
BO
AB
OO
Fig 4.11
Genotype
Phenotype
Genes code for
proteins (or RNA).
These gene
products give rise
to traits…
It is rarely this
simple.
Fig 4.3
Incomplete
dominance
Fig 4.4
Sickle-cell anemia is caused by a point mutation
Fig
4.7
Sickle and normal red blood cells
Fig
4.7
Sickle-Cell Anemia:
A dominant or recessive allele?
Mom = HS
S=sickle-cell
H=normal
Fig
4.7
Dad = HS
Dad
H or S
H HH
Mom or
S HS
HS
SS
possible offspring
75% Normal
25% Sickle-cell
Coincidence of malaria
and sickle-cell anemia
Fig 24.14
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
Fig
4.7
Dad = HS
possible offspring
Oxygen transport:
75% Normal
25% Sickle-cell
Malaria resistance:
75% resistant
25% susceptible
The relationship between genes
and traits is often complex
Complexities include:
• Complex relationships between alleles
Fig 3.18
Sex determination is
normally inherited by
whole chromosomes or
by number of
chromosomes.
X/Y chromosomes in humans
105 males : 100 females (live births)
Why?
105 males : 100 females (live births)
Why?
Ratio of Males to Females, by Age Group
(number of males per 100 females, total resident population)
Age
1950 1960 1970 1980 1990 2000 2004
Under
103.7 103.4 103.9 104.6 104.9 104.9 104.7
14 years
14 to 24 98.2 98.7 98.7 101.9 104.6 105.1 105.8
years
25 to 44 96.4 95.7 95.5 97.4 98.9 100.2 101.4
years
45 to 64 100.1 95.7 91.6 90.7 92.5 94.8 95.0
years
65 years 89.6 82.8 72.1 67.6 67.2 70.8 71.7
and over
All ages 98.6 97.1 94.8 94.5 95.1 96.3 96.9
The X
chromosome
has many
genes; the Y
chromosome
only has genes
for maleness.
Sex-linked traits are genes located on the X
chromosome
Color Blind Test
Sex-linked traits: Genes on the X chromosome
A= normal;
a= colorblind
normal
similar to Fig 4.13
colorblind
No one affected,
female carriers
Sex-linked traits: Genes on the X chromosome
A= normal;
a= colorblind
normal
normal
50% of males
affected,
0 % females
affected
similar to Fig 4.13
Sex-linked traits: Genes on the X chromosome
A= normal;
a= colorblind
normal
similar to Fig 4.13
colorblind
50% males
affected,
50% females
affected
Sex-linked traits: Genes on the X chromosome
A= normal ; a= colorblind
No one affected,
female carriers
similar to Fig 4.13
50% of males
affected, 0 %
female affected
50% males
affected, 50%
females affected
Fig 3.18
For Th:
Males and females may
have different numbers
of chromosomes. This
must be compensated
for.