Transcript 7/21 - Utexas

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}
Voles
Prairie
Montane
• Monogamous
• Nonmonogamous
• Both parents care • Mother cares for
for young
young briefly
Voles
Prairie
• Monogamous
• Both parents care
for young
Montane
• Nonmonogamous
• Mother cares for
young briefly
Same levels of oxytocin and vasopressin
• More receptors
• Less receptors
Why might these voles use different
reproductive strategies?
Prairie voles:
Montane voles:
Resource poor
Resource rich
habitat
habitat
• Monogamous
• Nonmonogamous
• Both parents care • Mother cares for
for young
young briefly
haploid
X 23
in humans
X 23
in humans
diploid
X 23
in humans
Sexual Reproduction = The combination of
genes inherited from Mom and Dad.
Asexual
Reproduction
extremely low
genetic diversity
vs.
Sexual
Reproduction
greater genetic
diversity
Asexual Reproduction
genetically identical to parent
(this tree can reproduce both sexually and asexually)
Why does sexual reproduction
exist?
Cons:
• Need two individuals
• Hard to find mate
• Diseases/Competition
Pros:
• Genetic diversity
Screw worm
flies
F
M
sterile
Sterile male screw worm
flies led to decreased
populations because of
screw worm monogamy.
F
M
sterile
In most other species,
because females mate
with multiple males,
introduction of sterile
males has little effect.
Sterile male screw worm
flies led to decreased
populations because of
screw worm monogamy.
F
M
sterile
In most other species,
because females mate
with multiple males,
introduction of sterile
males has little effect.
Hi, want to study
biology together?
M
F
fertile
F
M
sterile
10-40% of offspring in “monogamous” bird
species are fathered by an extra-pair male
•Social Monogamy = pair lives/works together,
but not “faithful”
•Sexual Monogamy = pair raise young and
only copulate with each other
In mammals, child-rearing is most commonly
done by the female. She provides milk.
Less than 0.01% of mammals are monogamous
Do Males and Females have different
attitudes toward sex and relationships?
On a college campus an attractive male or female
asked the opposite sex: “I have been noticing you
around campus. I find you very attractive…”
Female answers:
Male answers:
…Would you go out
…Would you go out
with me tonight?
with me tonight?
= 50% yes
= 50% yes
On a college campus an attractive male or female
asked the opposite sex: “I have been noticing you
around campus. I find you very attractive…”
Female answers:
Male answers:
…Would you go out with …Would you go out with
me tonight?
me tonight?
= 50% yes
= 50% yes
…Would you come to
…Would you come to
my apartment
my apartment
tonight?
tonight?
= 6% yes
= 69% yes
On a college campus an attractive male or female
asked the opposite sex: “I have been noticing you
around campus. I find you very attractive…”
Female answers:
Male answers:
…Would you go out with …Would you go out with
me tonight?
me tonight?
= 50% yes
= 50% yes
…Would you come to
…Would you come to
my apartment tonight?
my apartment tonight?
= 6% yes
= 69% yes
…Would you go to bed …Would you go to bed
with me tonight?
with me tonight?
= 0% yes
= 75% yes
Why do Males and Females have
different attitudes toward sex and
relationships?
The male
perspective on
monogamy
Eggs require
large resource
input.
A clutch of bird
eggs can be ~20%
of bird’s weight.
Sperm are
cheap.
Human
Females:
~1 egg/month
Human
Males:
250,000,000
sperm/
ejaculation
The female reproductive system
Sperm competition:
Sperm can survive for several days in a
woman’s reproductive tract.
In Great Britain in a survey of 4,000
women…
0.5% had sex with 2 different men within
30 minutes…
30% within 24 hours
= sperm competition.
The female reproductive system
Female mammals
provide additional
resources in form of
milk.
Mating pairs share genetic information and possibly
help in child-rearing
What are the consequences of the different
male and female attitudes toward sex and
relationships?
Zebra Finch
Zebra finch pairs were allowed to mate ~9 times
Then a new male was brought in and allowed to
mate with the female once.
Last male advantage
The last male that only mated
once fathered 54% of offspring
Original male (mated 9 times)
fathered 46% of offspring
Last male advantage
To ensure fatherhood males mate guard and produce copious
quantities of sperm
Purple Martins
After successfully
mating, male purple
martins call and
attract younger males
The older males then
cuckold the younger
male’s females
Younger males with
nests near older males
only father 29% of
eggs in their nests.
Older males produce
4.1 offspring with
their mate and 3.6 by
younger neighbor’s
mate.
Younger males with
nests near older males
only father 29% of
eggs in their nests.
Older males produce
4.1 offspring with
their mate and 3.6 by
younger neighbor’s
mate.
What advantage is
their for females
to accept or solicit
EPCs?
Gunnison’s Prairie Dogs
Sexually
monogamous
female squirrels
have a 92% chance
of successfully
giving birth.
Gunnison’s Prairie Dogs
Sexually
monogamous
female squirrels
have a 92% chance
of successfully
giving birth.
Non-monogamous
females have a
100% chance of
giving birth
Can females detect compatible genes?
http://www.pbs.org/wgbh/evolution/library/01/6/l_016_08.html
How can a female know which male
has successful genes?
Females may choose traits, like large
displays, that are disadvantageous for
male survival.
How can females determine “good” males?
Color:
Bright coloring can be correlated with health…
But a male
with a
mate is
judged as
being high
quality
even if he
is less
colorful
How does evolution work for a
behaviors such as monogamy?
monogamous
bye
non-monogamous
Voles
Prairie
• Monogamous
• Both parents care
for young
Montane
• Nonmonogamous
• Mother cares for
young briefly
Same levels of oxytocin and vasopressin
• More receptors
• Less receptors
How does evolution work for a
behaviors such as monogamy?
monogamous
bye
non-monogamous
How does evolution work for a
behaviors such as monogamy?
After several generations…
monogamous
non-monogamous
•Males must choose between having more offspring
(more mates) or helping to raise fewer offspring
(sperm do not require many resources)
•Females choose males that can provide “good”
genes or resources for offspring
(eggs, gestation, and/or lactation require high
resource input)
Am I the only one? Am I
better off helping with these
kids or should I mate
with someone else?
Is this the best I can do?
Maybe I can find someone
with better genes or
more genetic diversity.
Asexaul
Reproduction
extremely low
genetic diversity
vs.
Sexaul
Reproduction
greater genetic
diversity
How does sexual reproduction generate
genetic diversity?
Gene for
growth
hormone
Gene for
brown hair
pigment
Gene for
blue eye
pigment
Gene for
hemoglobin
Gene for
DNA polymerase
Haploid
chromosomes
Allele for
low express
(short)
Gene for
growth
hormone
Allele for
high express
(tall)
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
Fig 1.5
Each pair of
chromosomes
is comprised
of a paternal
and maternal
chromosome
Fig 1.11
Diploid
meiosis
Haploid
Fig 3.16
Meiosis splits apart the
pairs of chromosomes.
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.
sister chromatids= replicated DNA (chromosomes)
tetrad= pair of sister chromatids
Fig 3.12
Fig 3.16
Meiosis splits apart the
pairs of chromosomes.
X 23
in humans
Asexaul
Reproduction
extremely low
genetic diversity
vs.
Sexaul
Reproduction
greater genetic
diversity
How does sexual reproduction generate
genetic diversity?
Fig 3.10
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 3.10
Crossing-over:
Proteins in the cell cut and religate the DNA,
increasing the genetic diversity in gametes.
Fig 3.10
Crossing-over:
Proteins in the cell cut and religate the DNA,
increasing the genetic diversity in gametes.
Fig 3.10
Asexaul
Reproduction
extremely low
genetic diversity
vs.
Sexaul
Reproduction
greater genetic
diversity
How does sexual reproduction generate
genetic diversity?
Fig 3.17
Independent Assortment
(aka Random Assortment)
Fig 3.17
Independent Assortment
2 possibilities
for each pair,
for 2 pairs
22 = 4
combinations
Fig 3.17
Independent Assortment
2 possibilities
for each pair,
for 23 pairs
223 =
8,388,608
combinations
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
Fig 3.12
Fig 3.12
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 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
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
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
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
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
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
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
Wednesday: Mapping and Epigenetics