Topic 4 - Meiosis [5] Flashcards
Zygote
sperm cell + egg cell joined together at fertilisation.
Gametes
Sex Cells
sperm cells + egg cells
they join together forming a zygote.
Why does Mitosis not have genetically different daughter cells
No crossing over or independent segregation involved unlike Meiosis.
Mitosis vs Meiosis
Mitosis
Produces cells with SAME NUMBER of chromosomes as parent cell.
Meiosis
Produces cells with HALF the number of chromosomes as parent cll
Mitosis
Daughter cells identical to each other and to parent cell
Meiosis
Daughter cells are different from one another and parent cell
Mitosis
2 daughter cells
Meiosis
4 daughter cells
What happens in Meiosis I
homologous pairs of chromosomes line up at equator of cell
it is COMPLETELY RANDOM which side of equator the paternal and maternal chromosomes go. This means the 4 d cells will have completely different combinations of m and p chromosomes. (loads of genetic variation)
the pairs are separated so one of each pair end up in a daughter cell (dc)
Two mechanisms which introduce variation in Meiosis
occur in what stage of Meiosis?
independent segregation of homologous chromosomes
crossing over between homologous chromosomes
both occur in meiosis i
What does Meiosis Produce?
Meiosis produces 4 haploid daughter cells that are genetically different from each other
involves 2 nuclear divisions.
What is Crossing Over?
during meiosis i, chromosomes come together and pair up. chromatids can twist around each other and bits of chromatids break off and then recombine with bits swapped over. loads of different combinations of alleles.
What is Meiosis?
what Cells does it start with?
What does it end up with?
Meiosis is a type of Cell Division.
Takes place in reproductive organs.
start- Cells that divide by Meiosis are diploid
end - Haploid. chromosome number halves.
What happens to the Gametes during fertilisation?
Both haploid gametes join, making a cell with the normal diploid number of chromosomes.
How do Gametes differ from normal body cells?
Normal body cells - diploid number of chromosomes (2 of each chromosome 1 mum 1 dad)
Gametes - Haploid number of chromosomes. 1 copy of each chromosome.
Zygote
sperm cell + egg cell joined together at fertilisation.
