Science (Meiosis and fertilization) Flashcards
What is the purpose of meiosis?
To make gametes for sexual reproduction
Where does this take place?
In the ovaries in women and testes in men
What is meiosis?
process of nuclear division that reduces the # of chromosomes in new cells to half the # in the original cell
How many cellular division are there in meiosis?
2 (meiosis I+II)
What is meiosis I often called?
the reduction division
What is synapsis? What is each pair of chromosomes called?
- when homologous pairs of chromosomes “pair up” before meiosis begins
- tetrads
What happens to chromosomes in prophase I? What disappears and what appears?
- chromosomes become thick and visible
- nucleoli and nuclear envelope disappears
- spindle fibers form
What is crossing over and what’s its result?
WHEN DOES IT OCCUR?
- crossing over is when portions of chromatids break off and attach to adjacent chromatids
- crossing over results in genetic recombination
- CROSSING OVER OCCURS DURING PROPHASE I
What happens during metaphase I?
tetrads line up (still paired together) along the middle of the cell randomly
What happens during anaphase I?
homologous pairs of chromosomes -separate from each other as spindle fibers pull them to opposite ends of the cell
-THE RANDOM SEPARATION IS CALLED INDEPENDENT ASSORTMENT
What happens in telophase I?
Cytokinesis begins
During prophase II, double stranded chromosomes __________ and become _________.
-condense and become visible
During metaphase II, double stranded chromosomes in each haploid cell move…
-to the center of the cell
During anaphase II, the __________ divide and single stranded chromosomes move…
- centromeres
- away from each other toward opposite poles
During telophase II…
haploid cells with single stranded chromosomes are a result
