Topic 5 Mitotic cell cycle Flashcards
What is a DNA
- double helix DNA is associated with histone proteins
- DNA wraps and coils around histone proteins
Structure of chromosomes
- 1 chromosomes has several thousand genes
- Genes: DNA that codes for a polypeptide
- Alleles: different form of one gene
What is a Homologous chromosome
- pair of chromosomes found in diploid cells
- 1 maternal, 1 paternal
- similar centromere’s position, chromosome size and shape
- same genes (may have different alleles)
What are sister chromatids?
- (during interphase) DNA replication occurs in the nucleus
- 1 chromatid become 2
- two identical chromatids
What is a telomere
A region of repetitive nucleotide sequences
- to prevent DNA loss during mitotic division
- telomerase (enzyme) repairs telomeres
- telomerase active in stem cells and cancer cells
Mitotic cell cycle
Interphase
- G1 phase
- S phase
- G2 phase
Mitosis
- Prophase
- Metaphase
- Anaphase
- Telophase
Cytokinesis
Importance of mitosis
Result in 2 genetically identical daughter cells
- maintaining number of chromosomes
- growth of multicellular organisms
- cell replacement/ tissue repair
- asexual reproduction
Interphase
G1 phase:
- growth of cell
- synthesis of protein & other organelles
S phase:
- DNA replication
- result in sister chromatids
G2 phase:
- growth
- duplication of centrioles
- repair of DNA replication errors from S phase
Mitosis
Prophase:
- condensation of chromatin
- spindle fibre formation
- centriol moves to opposite side
- nuclear envelope & necleolus breaks down
Metaphase:
- centriole reaches the opposite side
- spindle fibre fully formed
- chromosomes line up at the equator
- chromosome attached to spindle fibre at centromere
Anaphase:
- centromere of each chromosome divides
- sister chromatids split at the centromere
- spindle fibre shorten
- chromatids pulled to opposite poles
Telophase:
- chromatids reach the pole
- chromosomes decondense
- nucleolus & nuclear envelope reassembles
- spindle fibre break down
- cytokinesis starts
Cytokinesis (animal/plant)
Animal:
- cell membrane drown together
- cell membrane fuses
- divided into two
Plant:
- vesicles transported to the equator
- cell wall laid down
- cytoplasm divided into two Plant
Stem cell
- undifferentiated cells
- able to continuously divide by mitosis
- telomeres do not shorten (telomerase present)
- produce stem cells
- produce specialised cells
Stem cell role
- form cells that can differentiate
- continuous supply of stem cells
for: cell replacement, tissue repair, growth
Level of cell potency
- totipotent: all type of cells (unlimited capability)
- Pluripotent: most type of cells
- Multipotent: related cells (eg blood stem cells -> blood related cells)
Cancer cells
- result of uncontrolled mitosis
- short interphase (error in DNA replication)
What are the mutagens
Subtances that causes mutation
- ionising radiation
- UV light
- free radicals
- chemicals
- virus infection
Cancer process
- Oncogene transformed by carcinogens
- Cancerous cell doesn’t respond to signals from other cells; continuous division
- Mitosis
- cancerous cells not removed by immune system
- Absorp nutrients; rapid mitosis
- Tumour gets bigger
- Tumour supplied with blood and lymph vessels; spread across the body
- Metastasis (invade other tissues)
