Meiosis Flashcards
What does each organisms have?
2 copies of each gene, one from the mother and one from the father.
How are these genes carried?
On chromosomes.
Genes are carried on Chromosomes. Therefore what does each nucleus contain?
A matching set of chromosomes-1 maternal and 1 paternal.
What is this matching set known as?
Homologous pairs
What is an allele?
A different version of the same gene.
Why is Meiosis important?
-Production of Gametes
-Creating Variation
What is the first stage in Meiosis?
-Prophase 1
What happens in Prophase 1?
Like in Mitosis
-Chromosomes condense
-Nuclear envelope disintegrates, nucleolus disappears
-Spindle formation begins
What do the homologous chromosomes form?
Pair up which form Bivalents
What happens when these Bivalents form?
Crossing over occurs where genes from the same locus are swapped between the homologous pairs.
Which function of meiosis does this carry out?
Variation
What is the second stage in Meiosis?
Metaphase 1
What happens in Metaphase 1?
Same as Metaphase in Mitosis EXCEPT the homologous pairs line up along the metaphase plate (equator) instead of individual chromosomes.
What is the orientation of each homologous pair?
Random
Which way do the paternal and maternal chromosomes face in this orientation?
They could face either pole.
What is this random orientation and facing called?
Independent (random) assortment.
What does Independent Assortment create?
Variation
How is Anaphase 1 different from Anaphase in Mitosis?
The homologous chromosomes are pulled to opposite poles.
-Maternal chromatids stay together and Paternal chromatids stay together.
What happens in Telophase 1?
Chromosomes assemble at each pole and uncoil.
Nuclear Membrane reforms.
(essentially the same as telophase in mitosis)
What happens in Prophase 2?
-Each chromosome consists of 2 chromatids.
-The chromosomes condense, nuclear envelope disintegrates.
-Spindle formation begins.
What happens in Metaphase 2?
-Individual chromosomes line up on Metaphase plate(equator),
-Independent assortment occurs again
Why does the Independent assortment occur again?
The chromatids are no longer identical.
What does this independent assortment create?
Creates more genetic variation.
What happens in Anaphase 2?
Chromatids of individual chromosomes are pulled to opposite poles.
