SAC 2 (cell cycle) Flashcards
Interphase
- G1,S,G2
- cell spends most of it’s life in interphase
G1
- cell growth
- chromosomes exist as chromatin (open form)
S phase (Synthesis)
- DNA replication
- chromosomes exist as chromatin (open form)
G2
- prepares for divison
- chromosomes exist as chromatin (open form) at the start of G2
- chromosomes condense (closed/coiled form) during G2 and finish condensing in prophase
Mitosis - Prophase
- chromosomes finish condensing (closed/coiled form)
- condense for protection
- spindle fibres produced
Mitosis - Metaphase
- chromosomes line up along the equatorial plate (any order)
- spindle fibres attach to the centre of each chromosome
Mitosis - Anaphase
- spindle fibres pull chromosomes towards opposite poles of the cell
- chromatids are pulled apart from each other
Mitosis - Telophase
- nuclear membrane reforms
- chromosomes decondense
- chromosomes revert back to chromatin to form nuclear membrane
Cytokinesis
- cyto means cell
- cells splits into 2 daughter cells
Apoptosis
- programmed (deliberate) cell death
- is to prevent cells with DNA damage from continuing replication
- INTERNAL - enzymes (capases) are released from the mitochondria
- EXTERNAL - a signal (death ligand) binds to the outside of the cell and then capases are triggered
Apoptosis steps
- capases released break down DNA and the cell cytoskleteton
- cell starts to bleb (blebbing)
- cell blebs break up into vesicles
- vesicles are engulfed by immune cells by endocytosis
Nucleotide structure
- subunit - monomer
- phosphate (circle)
- deoxyribose sugar (pentagon)
- nitrogen base (A,T,C,G) (rectangle)
DNA structure
- is a polymer
- made up of many subunits (monomer is the subunit)
- the monomer is a nucleotide
complementary base pairing rule
- Adenine bonds with Thymine (2 hydrogen bonds)
- Cytosine bonds with Guanine (3 hydrogen bonds)
- hydrogen bond is attraction between the base pairs
rungs and backbone
rungs - base pairs
backbone - sugar and phosphate
DNA is antiparallel
- anti parallel because the backbones run in opposite directions
5’ 3’
I I
I I
I I
3’ 5’
phosphodiester bond
- phosphodiester bond joins the sugar of the previous nucleotide with the next phosphate
- the condensation reaction joins the sugar and the phosphate
- it requires an enzyme called DNA polymerase to occur
- when the bond is formed a H2O molecule is released
DNA replication steps
- unwind helix by helicase (enzyme)
- unzip DNA by breaking hydrogen bonds between bases
- free nucleotides form hydrogen bonds with opposite nucleotides of DNA
- DNA polymerase joins the sugar and phosphates in the backbone by forming phophodiester bond
- the process continues until the entire length of each DNA strand is copied
stem cell definition
undifferentiated cells found in multicellular organisms
stem cells (source)
- sperm and ovum create the zygote
- zygote is the very first cell
- zygote going through mitosis help you grow
- the cells splits from one cells to two then four the eight
- at the eight cell stage differentiation occurs (and cells become specialised)
stem cells (potency)
Totipotent - any cell type possible - can become any cell type of an organism
v
Pluripotent - any cell type BUT a placental cell (embryonic stem cells)
v
Multipotent - many but not all cell types
v
Unipotent - a single type of cell
Necrosis
the death of the cells in your body tissues. Necrosis can occur due to injuries, infections or diseases.
e.g lack of blood flow to the tissue
stem cells ethics
- unethical
- the stem cells destroys the blastocyst
- embryonic stem cells are unethical due to when having to obtain them the embryo has to be destroyed.
- researchers have bias towards the stem cells (earning money from the research) (stakeholder)
- the stem cells getting tested and killed are also another stakeholder
binary fission
- division of prokaryotic cells
- produces two new cells with identical genetic information
- warm temp faster, cold temp slower
binary fission steps
- parent prokaryotic cell
- cell elongates and circular chromosomes are copied
- cell wall and capsule begins to separate
- two new bacterial cells produced
ethical decision making
consequence - aims to maximise positive outcomes and minimise negative outcomes
duty/rule - promotes responsibility (doctors have to follow doctor law) over all else, obligation
virtue - acting in accordance with values of a moral person, honesty
blastocyst definition
- is a cluster of dividing cells made by a fertilised egg.
- It’s the early stage of an embryo
checkpoint - G2
G2
- ensures all replication of chromosomes is complete
- all chromosomes have started to condense
- no DNA is missing
apoptosis malfunctions
- failure to initiate apoptosis following DNA damage may cause cancer
- lead to uncontrolled cell division
- lead to tumours
checkpoint - mitosis
MITOSIS
- ensures spindle fibres has attached to the centromere
- ensures chromosomes will separate equally
checkpoint - G1/S
G1/S
- ensures cells are large enough to proceed to S phase
- check for DNA damage before replication
