Unit 2- Variation And Sexual Reproduction Flashcards
(14 cards)
What are costs of sexual reproduction?
Males are unable to produce offspring. Only half of each parents genome are passed onto offspring, disrupting successful parental genomes.
Why do the benefits outweigh the costs in sexual reproduction?
There’s an increase in genetic variation which increases survival chances in changing selection pressures.
Describe asexual reproduction.
Reproduction by which offspring arise from a single parent, and inherit the genes of that parent only.
Does not involve fusion of gametes.
Describe parthenogenesis.
Reproduction from a female gamete without fertilisation. Common in cooler climates, which are disadvantageous to parasites.
Describe horizontal gene transfer.
Organisms that reproduce principly by asexual reproduction also often have mechanisms for horizontal gene transfer between individuals to increase variation.
Describe prokaryotes and horizontal gene transfer.
Prokaryotes can exchange material horizontally, resulting in faster evolutionary change than in organisms that only use vertical transfer (reproduction).
Describe homologous chromosomes.
Chromosomes of the same size, centromere position and sequence of genes at the same loci.
What is the name of the cell at the before meiosis?
Diploid gametocyte.
What is the name of the point of contact between non sister chromatids?
Chiasmata.
Describe the stages of meiosis 1.
- Chromosomes condense and homologous chromosome pair up. Chiasmata form and sections of DNA are exchanged.
- This crossing over of DNA is random and produces genetically different recombinant chromosomes.
- Spindle fibres attach to the homologous pairs and line them up at the equator of the spindle.
- The orientation of the pairs of homologous chromosomes at the equator is random.
- The chromosomes of each homologous pair are separated and move to opposite poles.
- Cytokinesis occurs and 2 daughter cells form.
Describe meiosis 2.
Each of the 2 cells produced in meiosis 1 undergo a further division during which the sister chromatids of each chromosome are separated.
4 haploid cells are produced.
What is the name of the sex determining gene?
SRY gene on the Y chromosome. (Determining development of male characteristic).
What is hermaphroditism?
Species which have functioning male and female reproductive organs. They produce male and female gametes and usually have partners to exchange with.
What is the benefit of hermaphroditism?
If the chance of encountering a partner is uncommon, there is no requirement for the partner to be of the opposite sex.
