the evolution of sex

Question 1

isogamy

Answer 1

sexual reproduction by the fusion of identical gametes

Question 2

anisogamy

Answer 2

sexual reproduction by the fusion of asymmetrical

Question 3

binary fission

Answer 3

asexual reproduction by a separation of the body into two new bodies

1. DNA replication
2. growth of a cell
3. segregtion of DNA (cell elongates with a septum forming at the middle. 2 chromosomes seperate)
4. splitting of the cells (2 daughter calls)

e.g bacteria, protists and some unicellular fungi

Question 4

budding

Answer 4

asexual reproduction

e. g reproduction in hydra (genus of small, freshwater organisms) by budding
1. tiny bumps appears on parent hydra
2. parent hydra develops bud
3. bud grows
4. bud breaks off to become inderpendent hydra

also yeast and anemone

Question 5

vegetative reproduction

Answer 5

asexual reproduction

a new plant grows from a fragment of the parent plant or grows from a specialized reproductive structure (such as a bulb, corm, rhizome, runner, tuber)

Question 6

sporogenesis

Answer 6

mitotic sporogenesis is asexual reproduction in some fungi and some algae

reproduction via spores

(some fungi produce spores sexually as well)

Question 7

fragmentation

Answer 7

asexual reproduction

where an organism is split into fragments. Each of these fragments develop into mature, fully grown individuals that are clones of the original organism

e.g. lichens, annelids, sea stars, plants

Question 8

parthenogenesis

Answer 8

asexual reproduction

spontaneous development of an embryo from an unfertilized egg cell.

e.g rotifers, insects, reptiles, amphibians

Question 9

potential advantages of sex

Answer 9

• sex leads to unique combination of alleles:
- alleles segregate independently into gametes
- fertilization combines alleles from different lineages
- crossing over shuffles alleles between chromosomes
• generate genetic diversity in offspring
• eliminate costly mutations quickly
• allow beneficial allels to combine

Question 10

deleterious mutations

Answer 10

A genetic alteration that increases an individual’s susceptibility or predisposition to a certain disease or disorder

Question 11

muller’s ratchet

Answer 11

a process through which, in the absence of recombination, an accumulation of irreversible deleterious mutations results

Question 12

asexual vs sexual pressure

Answer 12

•asexual
- reuires less energy 
- no costly non-reproducing sex
- quicker 
- offspring are clones of parents 
  = genes are not diluted 
• sexual 
- requires more time and energy 
- two-fold cost of producing males 
- offspring are genetically diverse

Question 13

sexual dismorphism

Answer 13

systematic difference in form between individuals of different sex in the same species

Question 14

environmnetal sex determination

Answer 14

the establishment of sex by a non-genetic cue (environment)

e.g spotted turtles
temp dependent
23-27 ºC - mostly male
30 ºC - female

Question 15

Wolbachia

Answer 15

genus of intracellular bacteria that infects mainly arthropod species and some nematode species

transmission via host egg, but not sperm

Question 16

infection-induced sex determination

Answer 16

armadillidium vulgare

• isopod crustacean
• androgenic gland
  •increase by Z chromsome
  •decrease by W chromosome (ZW = female)
• male hormone

ferminsation of wolbachia

• degradation of gland
• suppression of ‘male’ gene

Question 17

hermaphrodites

Answer 17

condition of having both male and female reproductive organs

frequent in invertebrates, occasional in vertebrates, usual in plants

Question 18

gametes

Answer 18

organism’s reproductive cell
- fertilization

carry one set of chromosones (haploid)

• gametes contain mix of genes from parents
  
  • recominbination

Question 19

anisogamy

Answer 19

form of sexual reproduction wherein males and females produce sex cells, or gametes, of different sizes

larger produced by female ( egg )
smaller produced by male ( sperm )

Question 20

isogamy

Answer 20

form of sexual reproduction that involves gametes of the same morphology, found in most unicellular eukaryotes. Because both gametes look alike, they generally cannot be classified as male or female.

Question 21

mitochondrial DNA (mtDNA)

Answer 21

one or more circular

multiple copies

animals : 32 genes, 12 code for polypeptides

Question 22

mitochondrial binary fission

Answer 22

initation of constriction site

constriction of protein comples contains:
• Drp-1/hFis1
or
• Dnm1p/Mdv1p/(Caf4p)/Fis1p

completition of fission

Question 23

Uniparental inheritance of mtDNA

Answer 23

non-mendellian inheritance
- input bias
- unequal cytokinesis
- disappearance of mtDNA
- sperm organelles fail to enter the egg
- selective destruction of mitochondria in
zygotes

usually mitochondria are maternally inherited

Question 24

mtDNA : parents

Answer 24

by definition female is the ‘parent’ whose mtDNA is retained at fertilisation and male is the ‘parent’ whose mtDNA is excluded