Meiosis Flashcards
What is meiosis
Type of cell division that happens in the reproductive organs to produce four gametes from one normal cell
What is a chromatid
A single chromosome
Process of meiosis
- DNA replicates so there are two identical copies of each chromosome, so four chromatids in each homologous pair(92 chromosomes in cell)
- The DNA condenses to form double-armed chromosomes made from two sister chromatids
- Chromosomes arrange themselves into homologous pairs-pairs of matching chromosomes
- First division-homologous pairs separated halving the number of chromosomes
- Second division- pairs of sister chromatids are separated
- 4new daughter cells are produced that are genetically different from each other called gametes
What is a homologous pair
Two identical chromosomes
What are sister chromatids
Chromatids of the same chromosomes
What are the gametes in flowering plants
Ovaries and anthers
Reason for gametes being haploid cells
-maintains the diploid number of chromosomes after fertilisation
-helps create genetic variation among offspring
What is independent assortment
Only one chromosome from each pair ends up in each gamete which is a source of genetic variation
-it is a random process in which either chromosome from each pair could be in any gamete depending on the alignment of the chromosomes as they line up
What is crossing over of chromosomes
-during first meiotic division, homologous chromosomes come together as pairs and all four chromatids come into contact, it is at these contact points that the chromatids break and rejoin and exchange section of DNA between non-sister chromatids(not in same chromosome), several points of contact and crossing over can occur along the length of each chromosome
-produces chromosomes in gametes that contain new combinations of alleles from both parents
What is the point where chromatids break called
Chiasma (plural chiasmata)
Does crossing over happen on sex chromosomes
No
