Mitosis & Meiosis Flashcards
(18 cards)
What is mitosis?
Division of one parent cell into two genetically identical diploid daughter cells
- process of cell duplication
4 phases of mitosis
Prophase
Metaphase
Anaphase
Telophase
What is meiosis?
Division of germ cell into 4 haploid daughter cells
- Also known as reduction division.
- Consists of: meiosis I
meiosis II - Note: Each haploid cell has 23 chromosomes.
What happens during Meiosis I & Meiosis II?
Meiosis I
→ homologous chromosomes separate,
reducing chromosome number by half
Meiosis II
→ Sister chromatids separate,
resulting into 4 haploid cells
Haploid cell v/s Diploid cell
Haploid cell contains one complete set of chromosomes, i.e. 23
Diploid cell contains two complete sets of chromosomes, i.e. 46
→ two copies of each gene, one from each parent
Meiosis I : What happens during prophase I ?
Chromosomes condense & become visible.
Homologous chromosomes pair up.
Crossing over between non-sister chromatids may occur.
Nuclear envelope break down, nucleolus ‘disappears’.
Meiosis I : What happens during metaphase I ?
Pairs of chromosomes line up at equator of spindle, attached by centromere.
- independent assortment may occur
Meiosis I : What happens during anaphase I ?
Pair of homologous chromosomes pulled apart by microtubules,
move towards opposite ends of spindle
Meiosis I : What happens during telophase I ?
Chromosomes reached pole of spindle.
The cell divides into two daughter cells.
Similarities between Mitosis & Meiosis
- Both involve DNA replication
- Both occur in eukaryotic cells
- Both start with diploid cell
Differences between Mitosis & Meiosis
Mitosis:
- only 1 cell divison
- 2 daughter cells produced
- daughter cells are genetically identical
- create diploid cell (i.e. with 46 chromos.)
Meiosis:
- 2 cell divisions occur
- 4 daughter cells produced
- daughter cells are genetically different
- create haploid cell
- crossing over & independent assortment may occur
Which cells undergo Mitosis?
Somatic (body) cells
What is crossing over?
Exchange of genetic material between homologous chromosomes
during prophase I of meiosis I
What is independent assortment?
Random distribution of homologous chromosomes
during metaphase I of meiosis I
Purpose of Meiosis
To produce genetically different haploid gametes for sexual reproduction
How errors arise at meiosis?
Errors, such as nondisjunction, can occur during chromosome separation,
leading to gametes with an incorrect number of chromosomes
Process of monozygotic twins
One fertilized egg splits into 2 embryos
- genetically identical twins
Process of dizygotic twins
Two separate eggs fertilized by two different sperms
- genetically like siblings
