Unit 2 KA3 Flashcards
(24 cards)
(a)
Costs of sexual reproduction
- males unable to produce offspring
- only half og each parents genome passed onto offspring
- disrupting successful genomes from parents
(a)
What is the benefit of sexual reproduction
increase in genetic variation in the ppopulation,
this provides raw material required for adaptation,
gives sexually reproducing organisms a better chance of survival under changing selection pressure
red queen hypothesis
(a)
what may coevolutionary interactions between parasites and hosts select for?
why?
sexually reproducing hosts,genetic variability in their offspring reduces the chages that all will be susceptible to infectio by parasites
(a)
Benefits of asexual reproduction
whole genome from parent are passed on from parent to offspring
(a)
where can the benefits of asexual reproduction be seen?
in what enviroment?
narrow, stable niches/ when re-colonising disturbed habitats
(a)
What is vegetative cloning?
in plants and parthegenesis in lower plants and animalls that lack fertilisation
an example of asexual reproduction in eukaryotes
(a)
Parthenogenesis
is reproduction from a female gamete without ferilisation
more common in cooler climates, low parasite density for diversity
(a)
Asexual reproduction
- cannot adapt easily
- mutations help with variation
- use horizontal gene transfer (quicker evolutionary change)
(b)
Meiosis
division of the nucleus that results in the formation of haploif gametes from a diploid gametocyte
(b)
Properties of homologous chromosomes
- same size
- same centromere position
- same sequence of genes at the same loci
(b)
Briefly describe the process of Meiosis 1
- chromosomes (already replicated) consist of 2 identical chromatids attached at the centromere
- chromosomes condense
- homologous chromosomes pair up
- Chiasmata from at points of contact
- sections of DNA are exchanged
- spindle fibres attach to homologous pairs
- lines up at equator of spidle
- each pair are seperated ad move towards opposite poles
- cytokinesis occurs and 2 daughter cells form
b
crossing over
occurs in meiosis 1
results in new combos of alleles in these genes
b
idependent assortment
occurs i meiosis 1
each pair of homologous chromosomes is positioned independently of the other pairs
this is irrespective of their materna and paternal origin
b
Meiosis 2 (II)
each of hte 2 cells from meiosis I undergoes further division during which the sister chromatid of each chromosome are seperated
4 HAPLOID CELLS ARE PRODUCED
c
How is the sex of birds, mammals and some insects determined?
by the presence of sex chromosomes
c
In mammals what determines the development of male characteristics
what can this result in?
the SRY gene on the Y chromosome
* can result in sex-linked patterns of inheritance (look at carrier femalles and affected males)
c
What is X chromosome inactivation
process by which most of one X chromosome is inactivated
occurs in homogametic females (XX).
random inactivation at an early stage
c
What does X chromosome inactivation prevent
how are carriers benefited
prevents a double dose of gene products which could be harful to cells
also, carriers are less likely to be affected by any deleterious mutations on the x chromosomes
c
What is the implicationn of X chromosome inactivation
half of the cells in any tissue will have a working copy of the gene in question
c
Hermaphrodites
species that have functioning male and femae reproductive organs in each individual
usually have a partner that they exchange gametes
c
What is the benefits of a hermaphrodite?
if meeting another partner is uncommon, there is no requiremnt for the partner to be of the opposite sex
c
what can enviromental factors such as temperature change?
sex determination or ration of sex
c
how else may sex change?
- size
- competition
- parasitic infection
- resource availability
