Today: Meiosis, producing genetically diverse offspring, and inheritance

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Today Meiosis, producing genetically diverse
offspring, and inheritance
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Meiosis producing gametes
For life to exist, the information (genes) must
be passed on.
Mitosis producing more cells
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Voles

• Prairie
• Monogamous
• Both parents care for young

• Montane
• Nonmonogamous
• Mother cares for young briefly

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Voles

• Prairie
• Monogamous
• Both parents care for young
• More receptors

• Montane
• Nonmonogamous
• Mother cares for young briefly
• Less receptors

Same levels of oxytocin and vasopressin
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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

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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.
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Asexual Reproduction
Sexual Reproduction
vs.
extremely low genetic diversity
greater genetic diversity
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Asexual Reproduction
genetically identical to parent
(this tree can reproduce both sexually and
asexually)
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Why does sexual reproduction exist?

• Cons
• Need two individuals
• Hard to find mate
• Diseases/Competition

• Pros
• Genetic diversity

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Screw worm flies
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F
M
sterile
Sterile male screw worm flies led to decreased
populations because of screw worm monogamy.
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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
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In most other species, because females mate with
multiple males, introduction of sterile males has
little effect.
Hi, want to study biology together?
F
F
M
M
sterile
fertile
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10-40 of offspring in monogamous bird species
are fathered by an extra-pair male
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• Social Monogamy pair lives/works together, but
  not faithful
• Sexual Monogamy pair raise young and only
  copulate with each other

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In mammals, child-rearing is most commonly done
by the female. She provides milk.
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Less than 0.01 of mammals are monogamous
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Do Males and Females have different attitudes
toward sex and relationships?
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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
• Would you go out with me tonight?
• 50 yes

• Male answers
• Would you go out with me tonight?
• 50 yes

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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
• Would you go out with me tonight?
• 50 yes
• Would you come to my apartment tonight?
• 6 yes

• Male answers
• Would you go out with me tonight?
• 50 yes
• Would you come to my apartment tonight?
• 69 yes

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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
• 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

• 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

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Why do Males and Females have different attitudes
toward sex and relationships?
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The male perspective on monogamy
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Eggs require large resource input. A clutch of
bird eggs can be 20 of birds weight. Sperm
are cheap.
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Human Males 250,000,000 sperm/ ejaculation
Human Females 1 egg/month
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The female reproductive system
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Sperm competition

• Sperm can survive for several days in a womans
  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.
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The female reproductive system
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Female mammals provide additional resources in
form of milk.
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Mating pairs share genetic information and
possibly help in child-rearing
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What are the consequences of the different male
and female attitudes toward sex and relationships?
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Zebra Finch
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Zebra finch pairs were allowed to mate 9 times
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Then a new male was brought in and allowed to
mate with the female once.
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Last male advantage
Original male (mated 9 times) fathered 46 of
offspring
The last male that only mated once fathered 54
of offspring
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Last male advantage
To ensure fatherhood males mate guard and produce
copious quantities of sperm
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After successfully mating, male purple martins
call and attract younger males
Purple Martins
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The older males then cuckold the younger males
females
Younger males with nests near older males only
father 29 of eggs in their nests.
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Older males produce 4.1 offspring with their mate
and 3.6 by younger neighbors mate.
Younger males with nests near older males only
father 29 of eggs in their nests.
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Older males produce 4.1 offspring with their mate
and 3.6 by younger neighbors mate.
What advantage is their for females to accept or
solicit EPCs?
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Gunnisons Prairie Dogs
Sexually monogamous female squirrels have a 92
chance of successfully giving birth.
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Gunnisons Prairie Dogs
Sexually monogamous female squirrels have a 92
chance of successfully giving birth. Non-monogamo
us females have a 100 chance of giving birth
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Can females detect compatible genes?
http//www.pbs.org/wgbh/evolution/library/01/6/l_0
16_08.html
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How can a female know which male has successful
genes?
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Females may choose traits, like large displays,
that are disadvantageous for male survival.
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How can females determine good males?
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Color Bright coloring can be correlated with
health
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But a male with a mate is judged as being high
quality even if he is less colorful
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How does evolution work for a behaviors such as
monogamy?
bye
monogamous
non-monogamous
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Voles

• Prairie
• Monogamous
• Both parents care for young
• More receptors

• Montane
• Nonmonogamous
• Mother cares for young briefly
• Less receptors

Same levels of oxytocin and vasopressin
51
How does evolution work for a behaviors such as
monogamy?
bye
non-monogamous
monogamous
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How does evolution work for a behaviors such as
monogamy?
After several generations
monogamous
non-monogamous
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• 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)

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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.
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Asexaul Reproduction
Sexaul Reproduction
vs.
extremely low genetic diversity
greater genetic diversity
How does sexual reproduction generate genetic
diversity?
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Gene for brown hair pigment
Gene for growth hormone
Gene for hemoglobin
Gene for DNA polymerase
Gene for blue eye pigment
Haploid chromosomes
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Allele for low express (short)
Allele for black hair
Allele for sickle cell Hb
Gene for growth hormone
Gene for hemoglobin
Gene for hair color
Diploid chromosomes
Allele for black hair
Allele for high express (tall)
Allele for normal Hb
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Fig 1.5
Each pair of chromosomes is comprised of a
paternal and maternal chromosome
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Fig 1.11
meiosis
Diploid Haploid
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Fig 3.16
X 23 in humans
Meiosis splits apart the pairs of chromosomes.
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haploid
X 23 in humans
X 23 in humans
diploid
X 23 in humans
Inheritance The interaction between genes
inherited from Mom and Dad.
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sister chromatids replicated DNA
(chromosomes) tetrad pair of sister chromatids
Fig 3.12
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Fig 3.16
X 23 in humans
Meiosis splits apart the pairs of chromosomes.
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Asexaul Reproduction
Sexaul Reproduction
vs.
extremely low genetic diversity
greater genetic diversity
How does sexual reproduction generate genetic
diversity?
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Fig 3.10
Crossing-over (aka Recombination)
DNA cut and religated
DNA cut and religated
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Fig 3.10
Crossing-over Proteins in the cell cut and
religate the DNA, increasing the genetic
diversity in gametes.
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Fig 3.10
Crossing-over Proteins in the cell cut and
religate the DNA, increasing the genetic
diversity in gametes.
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Fig 3.10
Crossing-over Proteins in the cell cut and
religate the DNA, increasing the genetic
diversity in gametes.
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Asexaul Reproduction
Sexaul Reproduction
vs.
extremely low genetic diversity
greater genetic diversity
How does sexual reproduction generate genetic
diversity?
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Fig 3.17
Independent Assortment (aka Random Assortment)
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Fig 3.17
Independent Assortment
2 possibilities for each pair, for 2 pairs 22 4
combinations
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Fig 3.17
Independent Assortment
2 possibilities for each pair, for 23 pairs 223
8,388,608 combinations
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Crossing-over
Meiosis In humans, crossing-over and independent
assortment lead to over 1 trillion possible
unique gametes. (1,000,000,000,000)
Meiosis I
(Ind. Assort.)
Meiosis II
4 Haploid cells, each unique
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Fig 3.12
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Fig 3.12
4 haploid cells
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Producing gametes
Sexual reproduction creates genetic diversity by
combining DNA from 2 individuals, but also by
creating genetically unique gametes.
Producing more cells
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haploid
X 23 in humans
X 23 in humans
diploid
X 23 in humans
Inheritance The interaction between genes
inherited from Mom and Dad.
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Do parents genes/traits blend together in
offspring?
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Fig 2.6
In many instances there is a unique pattern of
inheritance. Traits disappear and reappear in
new ratios.
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Fig 1.6
from DNA to Proteinfrom gene to trait
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from DNA to Proteinfrom gene to trait
Fig 1.7
Molecular
Cellular
Organism
Population
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Genotype
Phenotype
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Human blood types
Fig 4.11
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Fig 4.11
One gene with three alleles controls
carbohydrates that are found on Red Blood Cell
membranes
A
A
B
RBC
A
RBC
B
RBC
B
A
B
A
B
A
A
B
B
A
A
B
B
Allele O no carbs
Allele A A carbs
Allele B B carbs
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Human blood types
Fig 4.11
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We each have two versions of each gene
A
A
RBC
A
A
A
So
A
A
A
A
Genotype could be A and A OR A and O
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Recessive alleles do not show their phenotype
when a dominant allele is present.
A
A
RBC
A
A
A
A
A
A
A
Genotype could be A and A OR A and O
See Fig 4.2
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What about
RBC
Genotype ??
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What about
RBC
Genotype OO
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What about
A
B
RBC
B
A
A
B
B
A
A
B
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What about
A
B
RBC
B
A
A
B
B
A
A
B
Genotype AB
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Human blood types
Fig 4.11
AA or AO
BB or BO
AB
OO
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If Frank has B blood type, his Dad has A blood
type, And his Mom has B blood type Should Frank
be worried?
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MomB blood BB or BO
DadA blood AA or AO
possible genotypes
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MomB blood BB or BO
DadA blood AA or AO
possible genotypes
all A / 50 A and 50 O
all B / 50 B and 50 O
Gametes
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MomB blood BB or BO
DadA blood AA or AO
possible genotypes
all A / 50 A and 50 O
all B / 50 B and 50 O
Gametes
Frank can be BO B blood
no worries
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Grandparents AB and AB
MomB blood BB or BO
DadA blood AA
possible genotypes
all B / 50 B and 50 O
Gametes
all A
Frank can be BO or BB B blood
Uh-Oh
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Pedigree, tracing the genetic past
Dom.
Rec.
Rec.
Dom.
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Fig 2.11
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We can also predict the future
Fig 2.6
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Inheritance of blood types
Mom AB
Dad AB
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Inheritance of blood types
Mom AB
Dad AB
A or B
Gametes
A or B
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Inheritance of blood types
Mom AB
Dad AB
A or B
A or B
Gametes
Dad
A or B
Chance of each phenotype for each offspring 25
AA 50 AB 25 BB
AA
A or B
AB
Mom
AB
BB
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Single genes controlling a single trait are
unusual. Inheritance of most genes/traits is
much more complex
Dom.
Rec.
Rec.
Dom.
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Phenotype
Genotype
Genes code for proteins (or RNA). These gene
products give rise to traits
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Human blood types
Fig 4.11
AA or AO
BB or BO
AB
OO
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Phenotype
Genotype
Genes code for proteins (or RNA). These gene
products give rise to traits It is rarely this
simple.
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Fig 4.3
Incomplete dominance
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Fig 4.4
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Wednesday Mapping and Epigenetics