Section 3 - Genetics - Meiosis, sexual and asexual reproduction Flashcards
Are gametes haploid or diploid cells?
Haploid
What is a zygote? Is it haploid or diploid?
When a male gate fuses with a female gamete to produce a fertilised egg. It is diploid
In meiosis, how many daughter cells are produced, are they identical and haploid or diploid, and where does it occur?
4 daughter cells, not identical to each other, haploid, and happens in reproductive organs; testes and ovaries.
What happens in the 1st division in meiosis?
- Before cell starts to divide, DNA is duplicated with one arm of each X-shaped chromosome an exact copy of other.
- Chromosomes line up in pairs in centre of cell
- Pairs pulled apart so each new cell has one copy of each chromosome. Membrane of nucleus break down
- Cell membrane and cytoplasm divide and two separate cells formed
What happens in the 2nd division in meiosis?
- Chromosomes line up again in centre of cell and arms of chromosomes pulled apart to opposite ends
- Four daughter cells produced
Difference between sexual and asexual reproduction?
Asexual - cells divide by mitosis
Sexual - involves meiosis with genetically different haploid gametes fusing to form a diploid cell at fertilisation
2 advantages of asexual reproduction and how?
- can produce lots of offspring very quickly as reproductive cycle is so fast
- only one parent needed so organisms can reproduce wherever conditions favourable without waiting for mate
Advantage of sexual reproduction and how?
Creates genetic variation so if environmental conditions change then some may survive the change
Disadvantage of asexual reproduction and how?
No genetic variation so if environmental conditions unfavourable, whole population may be affected
2 disadvantages of sexual reproduction and how?
- takes more time and energy than asexual so fewer offsprings in lifetime
- two parents needed so problem if individual isolated