Mitosis and Meiosis Flashcards
(25 cards)
What is the structure of DNA?
Double helix- coils around nucleosomes>supercoils>chromosomes.
What are the complimentary base pairs?
Adenine-Thymine
Cytosine-Guanine
How many chromosomes are there?
46 chromosomes:
22 pairs- autosomes (i.e. anything that isn’t sex determining).
1 pair of sex chromosomes (XY= male and XX= female).
What is the karyotype?
The number and appearance of chromosomes in a cell.
The spreads are arranged in size order where the biggest is pair 1, the smallest pair is pair 22 and the sex pair is pair 23.
How many base pairs in a chromosome and number of genes we have?
Each chromosome contains a continuous DNA duplex of roughly 10^7 base pairs and contains several hundred gene- we have approximately 30,000 genes.
What is the structure of a chromosome?
Each chromosome has a long arm (q) and a short arm (p like ‘petite’) and is separated by a centromere.
How many genes in humans?
22,000 genes in humans.
What is mitosis?
Process to produce 2 daughter cells that are genetically identical to parent cells and is important for growth and to replace dead cells.
In what context do you use chromatin, chromosomes and chromatids?
Chromatin is a long chain of DNA= when the cell is not in replication.
Chromosomes is rolled up DNA i.e. when the chromatin has condensed= during/when it is going through cell division.
Sister chromatids are the branches of the same chromosome= after
What process must occur in order to enable mitosis?
Cell must be in the cell cycle and interphase must occur- the longest phase of the cycle.
What are the 3 main parts of interphase?
- G1- no visible activity.
- S (synthesis).
- G2.
What occurs in G1 phase interphase?
G1= cell growth phase:
- Rapid growth.
- Normal metabolic function.
- New organelles produced.
- Protein synthesis of proteins involved in spindle formation.
What occurs in the S/Synthesis phase of interphase?
S/synthesis= DNA synthesis:
- DNA doubles via DNA replication.
- Histone proteins double through protein synthesis.
- Centrosome replication.
N.B. At the end of S, there is x2 as much
DNA.
What occurs in G2 phase interphase?
G2= cell growth:
- Chromosomes condense (coil up and become visible).
- Energy stores accumulate.
- Mitochondria and centrioles double.
What are the different stages of the cell cycle?
- Interphase:
- G1
- S
- G2
- Mitosis (PMAT):
- Prophase (and prometaphase)
- Metaphase
- Anaphase
- Telophase
- Cytokinesis.
What happens during prophase?
Chromatin condenses into chromosomes and the centrosomes nucleate microtubules and move to the opposite poles of the nucleus.
What happens during prometaphase?
The nuclear membrane breaks down (chromosomes visible), microtubules/spindle fibres invade nuclear space, chromatids attach to the microtubules/spindle fibres and the cell no longer has a nucleus.
What happens during metaphase?
Chromosomes line up along the equatorial plane (metaphase plate).
What happens during anaphase?
As the spindle fibres contract, centromeres split in two and the sister chromatid separate and are pulled towards opposite poles of the cell (centromere first).
What happens during telophase?
The nuclear membrane reforms, the chromosomes unfold into chromatin and cytokinesis begins.
Steps of mitosis
I Prefer Milk And Tea: I- Interphase. P- Prophase. M- Metaphase. A- Anaphase. T- Telophase.
What happens during cytokinesis?
The cell organelles become evenly distributed around each nucleus. Cell divides (cleavaging occurs?) into 2 daughter cells with a nucleus in each and 46 chromosomes.
What is a clinical relevance of correct cell division process?
Down’s syndrome= 1 extra chromosome at 21 i.e. trisomy 21.
How to identify a cell undergoing mitosis in histology?
If the nucleus is dark (i.e. the chromatin has condensed to chromosomes) and if the nuclei are not the same size.
