today: meiosis, producing genetically diverse offspring, and inheritance

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