Sex, Reproductive systems - Lecture 6

Parthenogenesis

Asexual reproduction where the egg is developed without fertilization

(the DNA is only from the mother)

Clonal propogation

Asexual reproduction not involving an egg

Sexual VS Asexual (3)

Sexual -

• meiotic, division to form gametes

• 2 parents involved

• Fusion of Gametes

Asexual -

• No meiotic division

• 1 Parent only

• Genetic offspring are clones

Costs of sexual reproduction (7)

• Two fold cost of meiosis (50% of parent genes)

• Breaks up favorable combinations of alleles

• time energy

• Cost of producing males

• Time and energy

• Time to attract males

• Risk predation or infection

4 Benefits of sexual reproduction

• Favorable combinations quicker

• Eliminating harmful mutations & bringing together beneficial ones

• Tangled bank hypothesis (offsprings thrive in different microenvironments)

• More Genetic Diversity

True Or False: the benefits of asexual reproduction last very long

Not true which is why they go extinct quicker than sexual organisms

Costs of asexual reproduction

• have more stop codons

• Go extinct quicker

• Low genetic variation

Outbreeding VS Inbreeding

Out - Regular, not closely related

In - Closely related

True Or False: There’s no fine line between inbreeding and outbreeding

True, it’s a spectrum

EX. colour mixing: Orange-Yellow-Green

Outcrossing

Mating with someone else

Selfing

Mating with yourself

• Most extreme form of inbreeding

True Or False: selfing is asexual

No, because it doesn’t always produce clones. It’s just another form of inbreeding

Inbreeding depression

Produces less fitness in inbred offspring

Does inbreeding change polymorphism?

No, allele frequencies are not directly changed. distribution of genotypes changes, but the pool of alleles in the population stays the same.

Effects Of Inbreeding On Heterozygosity

• Increases homozygosity

• Decreases heterozygosity

Why do selfers seem more fit than outcrossers?

When the females contribute 100% of her genes while outbreeders only contribute 50

Costs of selfing (3)

• Overtime leads to low diversity & inefficient selection

• Higher extinction rates

• Inbreeding depression