All Cells Arise From Other Cells Flashcards
What is cell division for?
- replace old, dying or dead cells in eukaryotes
- for growth of an organism
What is the cell cycle?
A sequence of events that occurs during cell division as one parent cell divides to form 2 genetically identical daughter cells
What are the 3 phases of the cell cycle?
- interphase
- mitosis
- cytokinesis
What are the 3 stages of interphase?
G1
S
G2
What happens in G1 of interphase?
- cell grows + makes a new set of organelles and proteins for the daughter cells
What happens in S of interphase?
- cellular DNA is replicated + the 2 daughter cell each get one set of DNA
What happens in G2 of interphase?
- cell growth continues + there is synthesis of special proteins in preparation for mitosis
What is mitosis?
Mechanism of cell division that occurs in somatic cells
What is meiosis?
Cell division process that occurs only in gametes
Characteristics of chromosomes in humans
- 23 pairs
- diploid organisms so 2 sets of each chromosome
- large structure of DNA + proteins
- made up of 2 chromatids held together by a centromere
What is each copy of a particular chromosome called?
A chromatid
What do histones result in?
DNA wrapped around histones results in chromatin which coils into chromosomes
What are the 4 stages of mitosis?
Prophase
Metaphase
Anaphase
Telophase
What happens in prophase of mitosis?
- chromosomes become shorter + thicker and become visible as sister chromatids
- centrioles split + move to opposite poles of the cell + produce mitotic spindle which extends across the cell
- nuclear envelope disintegrates + chromosomes are freed into the cytoplasm
What happens in metaphase of mitosis?
- nuclear envelope is completely gone
- spindle fibres attach to the centromeres of each chromosome
- spindle fibres pull the chromosomes lining them up at the equator/metaphase plate
What happens in anaphase of mitosis?
- chromosomes break apart at the centromere
- spindle fibres begin pulling the sister chromatids to opposite poles of the cell
- form 2 v-shaped chromatid structures
What happens in telophase of mitosis?
- spindle fibres pull chromatids to opposite poles of the cell
- chromatids uncoil
- nuclear envelope reforms around each set of chromosomes
- cell now has 2 nuclei each with a full set of identical DNA
- prepares to split + forms a cleavage furrow
What happens in cytokinesis?
- final step of mitosis
- cell will completely divide into 2 daughter cells
- each daughter cell is identical to each other and their parent cell
Why do cells have checkpoints in cell division?
Because a mutation could have formed so transitions from one phase to the next are highly regulated by checkpoints
What happens if the cell is damaged during the cell cycle?
The cell will try to repair the damage by stopping the cell cycle, if its irreversible apoptosis happens
What are the checkpoints regulated by?
Cyclins and cyclin dependent kinases which monitor the rate of progression through the cell cycle as well as tumour suppressor proteins which check for mutations
Why is apoptosis important?
Since it prevent mutations from being passed down
What 2 mutations can cause cancer?
- mutant tumour suppressor gene
- mutant oncogene
Why can a mutant tumour suppressor gene cause cancer?
- cannot prevent a mutated cell from carrying out cell division and growing
Why can a mutant oncogene cause cancer?
- oncogenes promote cell division + growth
- so a mutant oncogene will force cell to rapidly divide + proliferate
What are tumours?
- group of rapidly growing cancer cell which forms a rapidly growing tissue
- unable to control their growth
- acquire even more mutations as they grow so become more uncontrollable
Why can tumours be lethal?
- outcompete nutrients to fuel their growth
- if organs can’t obtain necessary nutrients they stop functioning + eventually die
What are some treatment dangers with cancer?
- non-specific since it targets all fast growing cells including hair, gut & skin
- very toxic in high doses so needs to be limited
- mutagenic + can result in the formation of new cancers
What parts of the cell cycle does chemotherapy usually target?
- G1 + prevent protein/enzyme synthesis
- DNA replication
- mitosis (e.g prevent spindle fibres from forming)
