Today: Meiosis, producing genetically diverse offspring, and inheritance

For life to exist, the information (genes) must be passed on. {Meiosis: producing gametes} For life to exist, the information (genes) must be passed on. {Mitosis: producing more cells}

Voles Prairie Monogamous Both parents care for young Montane Nonmonogamous Mother cares for young briefly

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

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 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 Sexual Reproduction vs. extremely low genetic diversity 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

Hi, want to study biology together? In most other species, because females mate with multiple males, introduction of sterile males has little effect. Hi, want to study biology together? F M F M fertile 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 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: …Would you go out with me tonight? = 50% yes Male 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…” 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

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

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 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 Original male (mated 9 times) fathered 46% of offspring The 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

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 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.

What advantage is their for females to accept or solicit EPCs? 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? bye monogamous non-monogamous

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

How does evolution work for a behaviors such as monogamy? bye non-monogamous 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)

better off helping with these kids or should I mate with someone else? 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.

How does sexual reproduction generate genetic diversity? Asexaul Reproduction Sexaul Reproduction vs. extremely low genetic diversity greater genetic diversity How does sexual reproduction generate genetic diversity?

Gene for growth hormone Gene for brown hair pigment Gene for hemoglobin Gene for DNA polymerase Gene for blue eye pigment Haploid chromosomes

Gene for growth hormone Gene for hair color Gene for hemoglobin Allele for low express (short) Allele for black hair Allele for sickle cell Hb Gene for growth hormone Gene for hair color Gene for hemoglobin Diploid chromosomes Allele for high express (tall) Allele for black hair Allele for normal Hb

Fig 1.5 Each pair of chromosomes is comprised of a paternal and maternal chromosome

Fig 1.11 meiosis Diploid Haploid

Meiosis splits apart the pairs of chromosomes. Fig 3.16 X 23 in humans Meiosis splits apart the pairs of chromosomes.

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

Meiosis splits apart the pairs of chromosomes. Fig 3.16 X 23 in humans Meiosis splits apart the pairs of chromosomes.

How does sexual reproduction generate genetic diversity? Asexaul Reproduction Sexaul Reproduction vs. extremely low genetic diversity greater genetic diversity How does sexual reproduction generate genetic diversity?

Crossing-over (aka Recombination) Fig 3.10 DNA cut and religated

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 Crossing-over: Proteins in the cell cut and religate the DNA, increasing the genetic diversity in gametes.

How does sexual reproduction generate genetic diversity? Asexaul Reproduction Sexaul Reproduction vs. extremely low genetic diversity greater genetic diversity How does sexual reproduction generate genetic diversity?

Fig 3.17 Independent Assortment (aka Random Assortment)

2 possibilities for each pair, for 2 pairs Fig 3.17 Independent Assortment 2 possibilities for each pair, for 2 pairs 22 = 4 combinations

2 possibilities for each pair, for 23 pairs Fig 3.17 Independent Assortment 2 possibilities for each pair, for 23 pairs 223 = 8,388,608 combinations

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

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?

In many instances there is a unique pattern of inheritance. Fig 2.6 In many instances there is a unique pattern of inheritance. Traits disappear and reappear in new ratios.

from DNA to Protein: from gene to trait Fig 1.6 from DNA to Protein: from gene to trait

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 B RBC A B RBC 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

Human blood types Fig 4.11

We each have two versions of each gene… RBC A A A So 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. RBC A A A A A A A Genotype could be A and A OR A and O See Fig 4.2

What about… RBC Genotype = ??

What about… RBC Genotype = OO

What about… A B RBC B A A B B A A B

What about… A B RBC B A A B B A A B Genotype = AB

Human blood types Fig 4.11 AA or AO BB or BO AB OO

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 BB or BO Dad=A blood AA or AO possible genotypes

Mom=B blood BB or BO Dad=A blood AA or AO all B / 50% B and 50% O possible genotypes all B / 50% B and 50% O all A / 50% A and 50% O Gametes

Mom=B blood BB or BO Dad=A blood AA or AO Gametes all B / 50% B and possible genotypes Gametes all B / 50% B and 50% O all A / 50% A and 50% O Frank can be BO = B blood …no worries

Mom=B blood BB or BO Dad=A blood AA Gametes all B / 50% B and 50% O Grandparents AB and AB Mom=B blood BB or BO Dad=A blood AA possible genotypes Gametes all B / 50% B and 50% O all A Frank can be BO or BB = B blood …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 Dad = AB Gametes: A or B A or B

Mom = AB Dad = AB A or B A or B Gametes: Dad A or B 25% AA 50% AB 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

Single genes controlling a single trait are unusual 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 Fig 4.11 AA or AO BB or BO AB OO

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