Meiosis, Cell Cycle and Cancer (Lecture 2) Flashcards
Meiosis gives rise to which cells?
Haploid
How much DNA does a haploid cell have compared to a diploid?
Haploid cell (n); (1⁄2 the amount of DNA as a diploid cell)
How much DNA does a diploid cell have compared to a haploid?
Diploid cell (2n); 2X more DNA than a haploid cell.
How many chromosomes do humans have?
Humans have 23 pairs of chromosomes, for a total of 46 chromosomes
Click to see the mitosis/meiosis haploid vs. diploid
How many interphases are there in meiosis?
There is only 1 interphase, similar to mitosis
What does the first division do in meiosis that does not happen in mitosis?
The first division randomly separates homologous chromosomes. This does not happen in mitosis
What does the second division of meiosis result in? (similar to mitosis)
The second division results in the splitting of sister chromatids, similar to mitosis.
What is the end result of meiosis? (unlike mitosis)
The end result is 4 genetically unique daughter cells, unlike mitosis.
In meiosis are the daughter cells haploid or diploid?
Each genetically unique daughter cell is haploid, unlike mitosis
Mitosis occurs in the bodies _________, while meiosis occurs in the ______________
Mitosis occurs in the bodies stem cells (eg., colon)
Meiosis occurs in the mature germ (sex) cells
Mitosis occurs in __________________ (to increase #’s)
Mitosis occurs in immature germ (sex) cells (to increase #’s)
Mitosis results in two _____ daughter cells
Meiosis results in four ______ daughter cells
Mitosis results in two diploid daughter cells
Meiosis results in four haploid daughter cells
What is different about the daughter cells produced in mitosis vs. meiosis?
In mitosis, each daughter cell is genetically identical
In meiosis, each daughter cell is genetically unique
In meiosis, how many chromosomes does the daughter cell have?
Each daughter contains half the number of chromosomes as the parent
What is the chromosomal alignment in mitosis and meiosis?
In mitosis, all 46 chromosomes aligned in one plane
In meiosis, 23 pairs of homologous chromosomes aligned in one plane
Where do mitotic spindles attach in mitosis and meiosis?
In mitosis, mitotic spindles attached to kinetochores orientated opposite each other on both sister chromatids
In meiosis, mitotic spindle attached to mono- orientated kinetochores on the sister chromatids
Does recombination occur in mitosis and meiosis?
In mitosis, no recombination occurs
In meiosis, recombination occurs between homologous chromosomes
What events occur in Prophase I of meiosis I?
- Chromosomes first become visible as thin threads. DNA replication is already complete.
- Homologous chromosomes continue to condense and undergo synapsis (gene-for- gene pairing).
- When synapsis is complete, each pair of homologous chromosomes forms a bivalent. Each chromosome consists of two sister chromatids.
- The chromosomes continue to shorten and thicken and the chiasmata between non-sister chromatids become apparent
- The nuclear envelope begins to break down
Explain the process of crossing over
Crossing over is the exchange of genetic material between non-sister chromatids of homologous chromosomes during meiosis, which results in new allelic combinations in the daughter cells
What are paternal and maternal homologs?
One of these chromosomes is derived from the male parent (parental chromosome) and one from the female (maternal chromosome). The chromosomes in this pair are called homologs - there is one paternal and one maternal homolog
What is bivalent?
During the prophase of meiosis I, homologous chromosomes pair and form synapses. The bivalent has two chromosomes and four chromatids, with one chromosome coming from each parent
What is a chiasma?
The chiasma is a structure that forms between a pair of homologous chromosomes by crossover recombination and physically links the homologous chromosomes during meiosis
What are recombinant chromatids?
Crossing over occurs between prophase I and metaphase I and is the process where two homologous non-sister chromatids pair up with each other and exchange different segments of genetic material to form two recombinant chromosome sister chromatids
What events occur in Prometaphase I and Metaphase I?
Prometaphase I: Spindles attach to kinetochores on chromosomes
Metaphase I: Homologous pairs line up in center of cell, with bivalents oriented randomly with respect to each other
What is a kinetochore?
A complex of proteins associated with the centromere of a chromosome during cell division, to which the microtubules of the spindle attach
What events occur in Anaphase I and Telophase I?
Anaphase I: Homologous chromosomes separate, but sister chromatids do not separate
Telophase I and cytokinesis: Daughter cells are ready to move into prophase II
Explain the process of Meiosis II?
Prophase II: The nuclear envelope breaks down and the chromosomes condense.
Prometaphase II: Spindles attach to kinetochores on chromosomes.
Metaphase II: Chromosomes align in center of cell.
Anaphase II: Sister chromatids separate.
Telophase II and cytokinesis: The nuclear envelope re- forms and the cytoplasm divides.
Comparing Mitosis and Meiosis
(Information slide)
What is cytoplasmic division?
Cytoplasmic division or Cytokinesis separates the original cell, its organelles and its contents into two more or less equal halves. While all types of eukaryotic cells undergo this process, the details are different in animal and plant cells.
