Variation and Sexual Reproduction Flashcards
Costs of sexual reproduction?
males unable to produce offspring
only half of each parent’s genome passed onto offspring, disrupting successful parental genomes
Benefits of sexual reproduction?
increase in genetic variation in the population
Why can asexual reproduction be a successful reproductive strategy?
whole genomes are passed on from parent to offspring
When is maintaining the genome of the parent an advantage?
particularly in very narrow, stable niches or when re-colonising disturbed habitats
Examples of asexual reproduction in eukaryotes
vegetative cloning in plants and parthenogenesis in lower plants and animals that lack fertilisation
Advantage of asexual reproduction?
offspring can be produced more often and in larger numbers
Parthenogenesis is more common in
cooler climates, which are disadvantageous to parasites, or regions of low parasite density or diversity
What is parthenogenesis?
reproduction from a female gamete without fertilisation
What is meiosis?
The division of the nucleus that results in the formation of haploid gametes from a diploid gametocyte
In diploid cells, chromosomes typically appear as
homologous pairs
What are homologous chromosomes?
Same size, same centromere position, same sequence of genes at same loci
What are linked genes
those on the same chromosome
What can crossing over result in?
new combinations of the alleles of these genes
How many haploid cells are produced during meiosis?
4
What is the independent assortment?
Each pair of homologous chromosomes is positioned independently of the other pairs, irrespective of their maternal and paternal origin
What gene in most mammals determines the development of male characteristics?
The SRY gene on the Y chromosome
What happens In homogametic females?
one of the two X chromosomes present in each cell is randomly inactivated at an early stage of development
What does X chromosome inactivation prevent?
a double dose of gene products, which could be harmful to cells
What are hermaphrodites?
Species that have functioning male and female reproductive organs in each individual.
Other features of hermaphrodites?
They produce both male and female gametes and usually have a partner with which to exchange gametes
Benefit of being a hermaphrodite?
If the chance of encountering a partner is an uncommon event, there is no requirement for that partner to be of the opposite sex
In some species sex can change as a result of…?
size, competition, parasitic infection
How is environmental sex determination controlled in reptiles?
temperature of egg incubation
What is X chromosome inactivation?
A process by which most of one X chromosome is inactivated
