today: meiosis, producing genetically diverse offspring, and inheritance
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Today: Meiosis, producing genetically Today: Meiosis, producing genetically diverse offspring, and inheritancediverse offspring, and inheritance
For life to exist, the information (genes) must be passed on.
{Mitosis:producing more cells}
{Meiosis:producing gametes}
VolesPrairie
• Monogamous
• Both parents care for young
Montane
• Nonmonogamous
• Mother cares for young briefly
VolesPrairie
• Monogamous
• Both parents care for young
• More receptors
Montane
• Nonmonogamous
• Mother cares for young briefly
• Less receptorsSame levels of oxytocin and vasopressin
Why might these voles use different reproductive strategies?
Prairie voles:
Resource poor habitat
• Monogamous
• Both parents care for young
Montane voles:
Resource rich habitat
• Nonmonogamous
• Mother cares for young briefly
haploid
diploid
X 23in humans X 23
in humans
X 23in humans
Sexual Reproduction = The combination of genes inherited from Mom and Dad.
extremely lowgenetic diversity
greater geneticdiversity
vs.Asexual Reproduction
SexualReproduction
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
Sterile male screw worm flies led to decreased populations because of screw worm monogamy.
F M
sterile
Sterile male screw worm flies led to decreased populations because of screw worm monogamy.
In most other species, because females mate with multiple males, introduction of sterile males has little effect.
F
F
M
sterile
M
sterile
In most other species, because females mate with multiple males, introduction of sterile males has little effect.
F M
sterilefertile
FM
Hi, want to study biology together?
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…”
Male answers:…Would you go out
with me tonight?= 50% yes
Female answers:…Would you go out
with me tonight?= 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…”
Male answers:…Would you go out
with me tonight?= 50% yes…Would you come to
my apartment tonight?
= 69% yes
Female answers:…Would you go out
with me tonight?= 50% yes…Would you come to
my apartment tonight?
= 6% 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…”
Male answers:…Would you go out
with me tonight?= 50% yes…Would you come to
my apartment tonight?= 69% yes…Would you go to bed
with me tonight?= 75% yes
Female answers:…Would you go out
with me tonight?= 50% yes…Would you come to
my apartment tonight?= 6% yes…Would you go to bed
with me tonight?= 0% 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.
Original male (mated 9 times) fathered 46% of offspringThe last male that only mated
once fathered 54% of offspring
Last male advantage
To ensure fatherhood males mate guard and produce copious quantities of sperm
Last male advantage
Purple MartinsAfter 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 DogsSexually monogamous female squirrels have a 92% chance of successfully giving birth.
Gunnison’s Prairie DogsSexually monogamous female squirrels have a 92% chance of successfully giving birth.
Non-monogamous females have a 100% chance of giving birth
http://www.pbs.org/wgbh/evolution/library/01/6/l_016_08.html
Can females detect compatible genes?
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
byeHow does evolution work for a behaviors such as monogamy?
monogamous non-monogamous
VolesPrairie
• Monogamous
• Both parents care for young
• More receptors
Montane
• Nonmonogamous
• Mother cares for young briefly
• Less receptorsSame levels of oxytocin and vasopressin
byeHow does evolution work for a behaviors such as monogamy?
monogamous non-monogamous
How does evolution work for a behaviors such as monogamy?
monogamous
non-monogamous
After several generations…
•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)
Is this the best I can do?Maybe I can find someone
with better genes or more genetic diversity.
Am I the only one? Am Ibetter off helping with these
kids or should I matewith someone else?
extremely lowgenetic diversity
greater geneticdiversity
vs.Asexaul Reproduction
SexaulReproduction
How does sexual reproduction generate genetic diversity?
Gene forblue eye pigment
Gene forbrown hair pigment
Gene forgrowth hormone
Haploidchromosomes
Gene forhemoglobin
Gene forDNA polymerase
Gene forhemoglobin
Gene forhair color
Gene forgrowth hormone
Allele forblack hair
Allele forblack hair
Allele forlow express(short)
Allele forhigh express(tall)
Allele for normal Hb
Allele forsickle cell Hb
Diploidchromosomes
Each pair of chromosomes is comprised of a paternal and maternal chromosome
Fig 1.5
meiosisDiploid Haploid
Fig 1.11
Fig 3.16
Meiosis splits apart the pairs of chromosomes.
X 23in humans
haploid
diploid
X 23in humans X 23
in humans
X 23in humans
Inheritance = The interaction between genes inherited from Mom and Dad.
Fig 3.12
sister chromatids= replicated DNA (chromosomes)tetrad= pair of sister chromatids
Fig 3.16
Meiosis splits apart the pairs of chromosomes.
X 23in humans
extremely lowgenetic diversity
greater geneticdiversity
vs.Asexaul Reproduction
SexaulReproduction
How does sexual reproduction generate genetic diversity?
Fig 3.10
DNA cut and religated
DNA cut and religated
Crossing-over(aka Recombination)
Crossing-over:Proteins in the cell cut and religate the DNA, increasing the genetic diversity in gametes.
Fig 3.10
Fig 3.10Crossing-over:Proteins in the cell cut and religate the DNA, increasing the genetic diversity in gametes.
Crossing-over:Proteins in the cell cut and religate the DNA, increasing the genetic diversity in gametes.
Fig 3.10
extremely lowgenetic diversity
greater geneticdiversity
vs.Asexaul Reproduction
SexaulReproduction
How does sexual reproduction generate genetic diversity?
Fig 3.17 Independent Assortment(aka Random Assortment)
Independent Assortment
2 possibilities for each pair,
for 2 pairs22 = 4
combinations
Fig 3.17
Independent Assortment
2 possibilities for each pair, for 23 pairs
223 = 8,388,608
combinations
Fig 3.17
Crossing-Crossing-overover
Meiosis I
Meiosis II
4 Haploid cells, each unique
Meiosis:In humans, crossing-over and independent assortment lead to over 1 trillion possible unique gametes.(1,000,000,000,000)
(Ind. Assort.)(Ind. Assort.)
Fig 3.12
4 haploid cells
Fig 3.12
Sexual reproduction creates genetic diversity by combining DNA from 2 individuals, but also by creating genetically unique gametes.
{Producing more cells}
{Producing gametes}
haploid
diploid
X 23in humans X 23
in humans
X 23in humans
Inheritance = The interaction between genes inherited from Mom and Dad.
Do parents’ genes/traits blend together in offspring?
In many instances there is a unique pattern of inheritance.
Traits disappear and reappear in new ratios.
Fig 2.6
from DNA to Protein:from gene to trait
Fig 1.6
Cellular
Organism
Population
Molecular
from DNA to Protein:from gene to trait
Fig 1.7
Genotype Phenotype
Human blood types Fig 4.11
One gene with three alleles controls carbohydrates that are found on Red Blood Cell membranes
RBC
A A
A
A
AA
AA
A
RBCRBC
B B
B
B
BB
BB
B
Allele A = A carbs Allele B = B carbs Allele O = no carbs
Fig 4.11
Human blood types Fig 4.11
RBC
A A
A
A
AA
AA
A
We each have two versions of each gene…
So
Genotype could be A and AORA and O
RBC
A A
A
A
AA
AA
A
Recessive alleles do not show their phenotype when a dominant allele is present.
Genotype could be A and AORA and OSee Fig 4.2
What about…
Genotype = ??
RBC
What about…
Genotype = OO
RBC
RBC
AA
A
B
A A
B
B
B
What about…
B
RBC
AA
A
B
A A
B
B
B
What about…
B
Genotype = AB
Human blood types
AA orAO
AB
BB orBO
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?
possible
genotypes
Mom=B blood
BB or BO
Dad=A blood
AA or AO
Gametes all B / 50% B and50% O
all A / 50% A and50% O
possible
genotypes
Mom=B blood
BB or BO
Dad=A blood
AA or AO
Mom=B blood
BB or BO
Dad=A blood
AA or AO
Gametes all B / 50% B and50% O
all A / 50% A and50% O
possible
genotypes
Frank can be BO= B blood …no worries
Mom=B bloodBB or BO
Dad=A bloodAA
Gametes all B / 50% B and50% O
all A
possible
genotypes
Frank can be BO or BB= B blood …Uh-Oh
GrandparentsAB and AB
Pedigree, tracing the genetic past
Dom. Rec. Rec. Dom.
Fig 2.11
We can also predict the future
Fig 2.6
Mom = AB Dad = AB
Inheritance of blood types
Mom = AB Dad = AB
Gametes: A or B A or B
Inheritance of blood types
Mom = AB Dad = AB
Gametes: A or B A or B
A or B
A or B
AA
AB BB
AB
Chance of each phenotype for each offspring25% AA50% AB25% BB
Mom
Dad
Inheritance of blood types
Single genes controlling a single trait are unusual. Inheritance of most genes/traits is much more complex…
Dom. Rec. Rec. Dom.
PhenotypeGenotype
Genes code for proteins (or RNA). These gene products give rise to traits…
Human blood types
AA orAO
AB
BB orBO
OO
Fig 4.11
PhenotypeGenotype
Genes code for proteins (or RNA). These gene products give rise to traits…
It is rarely this simple.
Incomplete dominance
Fig 4.3
Fig 4.4
Wednesday: Mapping and EpigeneticsWednesday: Mapping and Epigenetics