Meiosis Flashcards
What 2 ways does meiosis lead to an increase in genetic diversity?
- crossing over
- independent segregation
What is the first stage of crossing over?
Homologous chromosomes align and the chromatids become twisted around each other
When does independent segregation occur?
in Meiosis I
How does independent segregation increase genetic diversity?
It is random which side of the equator the paternal and maternal chromosomes lie. Therefore, when these are separated, there is a larger number of combinations that are possible
How can you calculate the possible number of chromosome combinations following meiosis?
2^n
When does crossing over occur?
in meiosis I
What happens after the chromatids are twisted around each other?
It puts tension on the chromatids, causing them to break
What happens once parts of the chromatid are broken off?
they recombine, often with the chromatids of other chromosome
What is exchanged in crossing over?
equivalent sections of DNA/homologous chromosomes
What does crossing over produce?
a new combination of alleles
What does meiosis produce?
gametes
What is 2 differences between meiosis and mitosis?
- mitosis; genetically identical daughter cells
meiosis; genetic variation in daughter cells - mitosis; 1 nuclear division
meiosis; 2 nuclear divisions - mitosis; diploid
meiosis; haploid
How does genetic variation increase with fertilisation?
as the gametes that fuse are random
What happens in meiosis II?
- independent segregation of chromatids
- each cell divides again (4 cells produced)
