Meiosis Flashcards
What happens before meiosis starts?
Dna replicates to form duplicated chromosomes?
What are the stages of meiosis I?
Prophase I: Homologous chromosomes pair and recombine.
Metaphase I: Homologs line up at the center.
Anaphase I: Homologs are pulled apart.
Telophase I: Two haploid cells form.
What happens in meiosis II?
Chromosomes line up again.
Sister chromatids are separated.
Four unique haploid cells are produced.
What is separated in Meiosis I vs Meiosis II?
Meiosis I: Homologous chromosomes
Meiosis II: Sister chromatids
How many divisions in mitosis vs meiosis?
Mitosis: 1 division
Meiosis: 2 divisions
How many cells result from mitosis?
Mitosis: 2 identical diploid cells
Meiosis: 4 unique haploid gametes
Does recombination occur in mitosis?
No — only in meiosis during Prophase I
What aligns on the metaphase plate in mitosis?
Single chromosomes
What aligns on the metaphase plate in meiosis I?
Pairs of homologous chromosomes (bivalents).
When does spermatogenesis start and end?
Starts at puberty, continues throughout life.
How long does it take to make sperm?
64 days
How many gametes result from one precursor in males?
4 sperm cells
When does oogenesis start?
Begins during fetal development
When is female meiosis arrested?
Prophase I: From fetal stage until ovulation
Metaphase: Until fertilisation
How many gametes result from one precursor in females?
1 egg + 2 polar bodies
What are 3 sources of genetic diversity in meiosis?
- Independent assortment
- Recombination
- Random fertilization
What is recombination and when does it happen?
Exchange of DNA between homologs during Prophase I.
What is a chiasma?
The point where crossing over happens between homologous chromosomes.
What is a Holliday junction?
A structure that forms during recombination when strands are swapped and rejoined.
What determines how likely genes are to be inherited together?
Their physical distance on the chromosome.
What is non-disjunction?
Failure to separate chromosomes properly during MI or MII.
What is anaphase lag?
A chromosome/chromatid is left behind and lost from the nucleus.
what does uniparental disomy mean?
Receiving both copies of a chromosome from one parent.
What is the difference between heterodisomy and isodisomy?
Heterodisomy: Two different copies from one parent (MI error)
Isodisomy: Two identical copies (MII error)
