Mitosis and Binary Fission Flashcards
Define mitosis
Mitosis is a type of nuclear division that produces cells which are genetically identical. The parent cell divides to produce 2 daughter cells that contain an identical copy of the DNA in the parent cell.
Describe Interphase. Is it a part of nuclear division?
In late interphase, there’s an increase in protein synthesis: DNA content is doubled (S phase) and cell organelles are replicated, such as mitochondria and ATP as cell division is an active process. Interphase ISN’T a part of nuclear division, just the cell cycle. It has 3 phases, G1, S, G2 (G1 & G2). Only chromatics are visible
Describe Prophase
➣Due to DNA replication, each chromosome consists of 2 identical sister chromatids joined by a centromere
➣Each chromosome shortens and thickens
➣The centrioles move to opposite poles and the nuclear membrane breaks down
Describe Metaphase
➣Centrioles form spindle fibres across the cell, consisting of protein microtubules
➣Each chromosome moves to the equator of the spindle and attaches via the centromere. Sister chromatids are pulled to opposite poles.
Describe Anaphase
➣Centromere splits, sister chromatids separate
➣Sister chromatids pulled to opposite poles of the cell by the spindle fibres
Describe Telophase
➣Chromatids are at opposite poles of the cell and being to uncoil, nuclear membrane reforms.
➣The 2 cells are genetically identical to each other and the parent cell
➣They’re now chromosomes
What causes cancer? How does it spread?
Uncontrollable growth and rapid cell division, often due to damage of genes that regulate the cell cycle, result in a tumour. Cells may break away and move to other areas of the body leading to the spread of cancer.
How do we stop cancer?
By drugs that stop cancerous cells diving by inhibiting the enzymes DNA helicase or DNA polymerase or inhibiting the formation of the spindle. However, these disrupt healthy cell’s cycle and normal cells that also divide rapidly are heavily affected
What does the diploid number represent?
(2n) represents the total number of chromosomes in a normal body cell
What does the haploid number represent?
(n) represents a single set of chromosomes, one member from each homologous pair.
Describe the cell cycle.
➣Interphase= cell growth occurs
➣Nuclear division= nucleus divides into 2 or 4
➣Cell division= cell divides into 2 or 4 separate cells
What is a centromere?
Joins chromatids together to form chromosomes
What is a centriole?
These form spindle fibres which equally divides the chromosomes
How do prokaryotic cells divide?
By binary fission. They can’t carry out mitosis as they don’t have chromosomes
Outline binary fission.
➣The circular DNA molecule replicates and both copies attach to the cell membrane. The plasmids also replicate
➣The cell membrane grows between the 2 DNA molecules and pinches inward, diving the cytoplasm into 2
➣A new cell wall forms between the 2 molecules, dividing the original cell into 2 identical daughter cells, each with a single copy of circular DNA and a variable number of plasmid copies
