exam 2 ch 8 Flashcards
Bdelloid rotifers reproduce ?
without sex
Daughters are ______ of their mother
clones
Reproduction from unfertilized eggs, Requires chromosome changes before or during meiosis
Parthenogenesis
When a cell exits the mitotic cell cycle in G2 phase and undergoes multiple S phases without entering mitosis and undergoing cytokinesis
Premeiotic endoreplication
2 methods of parthenogenesis
Premeiotic endoreplication
fusion of egg and polar body
During Meiosis instead of being degraded, the polar bodies add their DNA to the egg
fusion of egg and polar body
Asexual reproduction that requires the presence of sperm without the actual contribution of its DNA for completion
- Paternal DNA is destroyed before fusion.
-Males, do not pass on their DNA
gynogenesis
2 methods of Gynogenesis
- ameiosis
- premeiotic endoreplication
Suppression of one of the meiotic division
ameiosis
premeiotic endoreplication
Is a type of gynogenesis
The opposite of gynogenesis is
Androgenesis
Elimination of the female genome after fertilization.
Androgenesis
-Evolutionary advantageous to individual male (normally only gives ½ of chromosomes).
-It is deleterious to the population as a whole.
-Egg-producing individuals become rare & the population can decline to extinction.
-Seen in some insects, trees, clams.
androgenesis
Ejection of the chromosomes from one parent before an endoreplication phase before meiosis or ameiosis.
Hemiclonal Reproduction
why is sexual reproduction used by 99% of eukaryotes?
Searching for a mate takes time and energy.
-Increases risk of being eaten by a predator.
-Once found, a potential mate may demand additional exertion or investment before agreeing to cooperate.
-Sex itself may expose the parties to sexually transmitted diseases.
-And for all that, the mating may prove to be infertile
So asexual reproduction is?
- Faster.
- More energy efficient.
- Only requires one parent
In the absence of recombination, an accumulation of irreversible deleterious mutations occurs (Because everyone inherits the same alleles)
mulers ratchet
Reduction in the mean fitness of a population due to the presence of deleterious alleles
genetic load
Frequently the most lethal thing for most lifeforms is?
infection
Surface proteins on immune cells (antigen-presenting B cells and T cells) and enable the immune system to recognize pathogens
Major histocompatibility complex (MHC)
the non-random association of alleles at adjacent loci
linkage disequilibrium
Over time, a pair points on a chromosome in the population move from linkage __________ to
linkage ____________, as recombination events eventually occur between___________________________________
disequilibrium, equilibrium; every possible point on
the chromosome
Genotypes at one locus are randomly distributed with respect to genotypes at
another locus
linkage equilibrium
set of DNA variants along a single chromosome that tend to be inherited together
- Recombinations between these variants are rare
haplotype
can increase linkage disequilibrium in a population
natural selection and drift
is the main mechanism that reduces disequlibroum in a population
sexual reproduction
Variations of nucleotides at a specific loci in the genome
Single Nucleotide Polymorphisms (SNPs)
Natural selection and drift can _________ linkage disequilibrium in a population
Sexual reproduction is the main mechanism that __________ it
increase, reduces
