genetics Flashcards
(19 cards)
benefit of sexual reproduction
mutations can originate independently and join in fertilisation, speeding up a populations ability to adapt
What came first, DNA or RNA? how did this start?
Possible solution: RNA can do the functions of both DNA and RNA, having half the template so can replicate itself
- RNA can do chemical reactions DNA cant
Chicken and Egg question
-use a phylogeny
- Eggs are a common ancestor that has been lost in some lineages, which is before the evolution of chickens
definition of sex
genetic recombination, bringing together and mixing DNA from 2 different parents, producing offspring with a mixed genome
Issue with asexual reproduction
every generation is a clone of the previous, only adaptations are through mutations which then have to be fixed 100%
anisogamous
gametes are not the same size
isogamous
gametes are the same size
Evolution of anisogamous
- one type of gamete
- multicellularity evolves, specialised cells
- divergence in the size of gametes
- loss of flagella in egg
Why would sex evolve if organisms could reproduce 2x faster with all female offspring? Two-fold cost of sex
Hypothesis one: this is beneficial for disease adaptation and becoming fixed, cant be reversed
Hypothesis two: sexual selection enhances survival of species over the survival of asexual species
Hermaphrodite
both sexes in one body, both gametes produced
Gonochorism
bodies specialised to produce 1 gamete
X chromosome
maternal
Y chromosome
paternal
Genetic sex determination (GSD)
determination of the gonads
XX female
XY male
SRY gene
Sex-determining-rgion-Y
- started after monotremes branched as they have a different system and gene
- 200mya
- gene regulation, turns on and off certain genes
What does the SRY gene do?
starts development pathway to make testosterone
Dimorphism
the existence of 2 different forms for male and female
evolutionary sex determination sequence
anisogamy, hermaphrodite, gonochorism, GSD, SRY, Y chromosome
