Meiosis Flashcards
What is a diploid?
Containing two complete sets of chromosomes, one from each parent.
What is a haploid?
A single set of unpaired chromosomes.
What does homologous mean?
It refers to a diploid cell, and these chromosome pairs have the same genes as each other in the same sequence, but don’t have the same alleles of those genes.
How does the number of chromosomes in a cell become reduced from diploid to haploid?
Through meiosis.
What is meiosis?
A reduction division of a diploid nucleus to form haploid nuclei.
Why do organisims have to halve their chromosome number after sex?
Because the fusion of gametes during fertilization doubles it.
What are eukaryotic chromosomes made of?
DNA and proteins.
What happens during Prophase 1 of meiosis?
The nuclear envelope disappears, spindle microtubules grow from each pole to the equator, and chromosomes pair up as homologs.
What is a homolog pair?
Homologous chromosomes.
What happens during Metaphase 1 of meiosis?
Spindle fibers move chromosomes to equator, the homologs are side by side, but there is independent assortment (random assortment of placement/side of metaphesial pair).
What is the difference between metaphase in mitosis and metaphase one in mieosis?
Mitosis: single file. Meiosis: double line.
What happens during anaphase 1 of meiosis and what does this do?
Homolog split: this halves the chromosome number.
What happens during telophase one of meiosis?
The nuclear envelope appears.
What can meiosis 1 and meiosis 2 be breifly described as?
1: Homolog split. 2: Sister chromatid split.
What is non-disjunction?
The failure of homologous chromosomes to separate normally during nuclear division.
What happens in prophase 2 of meiosis?
Nuclear envelope disappears, no crossing over is allowed, and new spindle microtubules grow from the poles to the equator.
When is crossing over allowed in meiosis?
During Prophase 1, but not Prophase 2.
What happens in metaphase 2 of meiosis?
The chromosomes line up in middle (single file).
What happens in anaphase two of meiosis?
The centromeres have divided making the chromatids into separate chromosomes which move to opposite poles. Also, the cell membrane is pulled inwards again to divide the cells.
What happens in telophase two of meiosis?
Each nucleus has half as many chromosomes as the nucleus of the parent cell, nuclear membranes reform, and both cells have divided to form four haploid cells.
What is an example of a cell in a diploid state?
Somatic cells. Humans: 46 Chromosomes, 23 pairs.
What is an example of a cell in a haploid state?
Gametes. Humans: Eggs and sperm only have 23 chromosomes
What’s the difference between haploid and diploid cells?
Haploid cells have one copy of a chromosome while Diploid cells have two copies of a chromosome.
Can both diploid and haploid cells undergo mitosis?
Oui.
