6.7 Production of haploid gametes Flashcards
How many chromosomes are in a somatic cell?
46
What is reduction division?
Production of gametes through dicision in meiosis that reduces the chromosome umber from diploid to haploid
What is crossing over?
When non-sister chromatids of homologous chromosomes exchange corresponding segments
What is independent assortment?
The formation of random chromosomes combinations during meiosis that contributed to variation
When does crossing over occur?
Prophase I
What is bivalent?
A pair of homologous chromosomes that are held together by at least one crossover
Name the stages of meiosis
Interphase, prophase 1, metaphase 1, anaphase 1, telophase 1, prophase 2, metaphase 2, anaphase 2, telophase 2
What happens before meiosis?
A diploid cell has 4 chromosomes (2n=4)
What happens during interphase?
DNA is replicated, results in sister chromatids
What happens during prophase 1?
Chromosomes condense and nucleur envelope degrades, crossing over occurs
What happens during metaphase 1?
Homologous chromosomes line up alongside each other down the equator of cell
What happens during anaphase 1?
Seperated from each other, centromeres are pulled to opposite poles by spindle fibres
What happens during telophase 1?
Nuclear envelope reforms around each set of chromosomes, fibres disappear, cytokenisis occurs, forms two new cells
What happens during prophase 2?
Re-condense if necessary and nuclear envelope breaks down
What happens during metaphase 2?
Chromosomes line up along the equator