Meiosis Flashcards
Why are normal body cells called diploid cells?
They contain two of each chromosome.
Why are gametes called haploid cells?
They contain half the DNA of a normal body cell and they only have one copy of each chromosome.
Why must gametes have half the number of chromosomes?
So when they fuse during fertilisation the zygote produced has the correct number of chromosomes.
Where does meiosis take place?
reproductive organs
What are the stages of meiosis?
- DNA replication so you get a 4n cell.
- The DNA condenses
- Meiosis 1
- Meiosis 2
What happens during Meiosis 1?
The DNA is replicated so there are two copies of each chromosome. 4n
The DNA condenses.
The homologous chromosomes line up along the equator of the cell and the homologous chromosomes are separated halving the chromosome number. 2n
What happens during Meiosis 2?
The pair of chromatids that make up each chromosome are separated when the centromere divides and we are left with 4 haploid daughter cells that are genetically different from each other. n
What is the crossing over of chromatids and where does it happen?
In meiosis 1 the homologous chromosomes come together and pair up. The chromatids wrap around each other and bits of the chromatids swap over.
Why does genetic crossingover increase genetic diversity?
It means that the four daughter cells produced will contain different combinations of alleles.
What is independent segregation?
In Meiosis 1 when the homologous chromosomes are separated it is random which chromosome will go into what daughter cell.
Why does independent segregation increase genetic diversity?
It means that the four daughter cells produced will have completely different combinations of maternal and paternal genes.
Why does sexual reproduction increase genetic diversity?
In fertilisation, the gametes that fuse are random meaning that the zygotes will have different combinations of paternal and maternal chromosomes.
What are the differences between mitosis and meiosis?
- Mitosis produces two daughter cells and Meiosis produces 4.
- Mitosis produces genetically identical daughter cells and meiosis doesn’t.
- Mitosis produces diploid cells and Meiosis produces haploid cells.
