[review]

Facultative adaptations

(e.g., sun tanning, mate guarding): track environmental variation and adjust phenotype to maximize fitness prospects.

Heritability

Norm of reaction: Evolved pattern of response to environment.

Different from susceptibility.

Ambient UVb

Mela

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Two nature/nurture questions!

1.Why is my skin this color?

causes of development (interaction)

2. Why do people differ in skin color?

causes of variation

(partition the variance)

If we want to know how heritable a trait is…

h2 = Vg/Vp, thus

h2 = Vg/(Vg+Ve)

h2 varies from 0 to 1.

Selection is more effective when heritability is significant; but selection typically reduces heritability as it works.

Today Goals:

1. Gain an understanding of basic Mendelian genetics.

2. Gain a basic understanding of molecular genetics.

Mendel’s Peculiar results:

Bred pure strains of wrinkled and round together.

wrinkled x round Offspring were all round

Hence, no blending…

Breed these round offspring among themselves.

round x round

¾ round : ¼ wrinkled

What the heck!?!

Mendel’s hypothesis about the stuff of heredity:

1. Particles, not fluids (genes).

2. Adults have a double dose of particles (diploid adults).

3. Adults give only half of their double dose to each offspring (haploid gametes).

4. Some particles have stronger effects than others (dominance).

The model:

1. Particles

2. Diploid adults

3. Haploid gametes

4. Dominance

Model able to predict other outcomes:

F1 hybrid x pure wrinkled ?

Model able to predict other outcomes:

F1 hybrid x pure wrinkled ?

S s

s

s

Ss

Ss

ss

sswrinked:round

1:1

Not the same result as the initial wrinkled x round cross.

Why not?

What does that show?

genotype: the genes themselves.

phenotype: the outward expression of those genes.

allele: variant of a gene, for example: wrinkled allele and round allele of the seed-shape gene

homozygous: two matching alleles.

heterozygous: two different alleles.

recessive allele: expressed only when homozygous

dominant allele: expressed even when heterozygous

M2 P2

Diploidy: Each chromosome is paired, with one from Mom and one from Dad.

Loci match, but alleles may not

But sex cells (gametes, eggs and sperm) are haploid, not diploid.

Sex cells (gametes) could be formed by simply giving either your paternal or maternal chromosome to each gamete.

But they aren’t…

Gamete formation involves recombination (crossing-over):

Exchange of genetic material between maternal and paternal chromosomes

Result is increased genetic diversity