Unit 2 - Cell cycle/ differentiation Flashcards
what occurs during the stages of interphase?
G1: cell growth, copying organelles
S: DNA replication
G2: more cell growth, protein and organelle synthesis - reorganise contents in prep for mitosis
where are the checkpoints in the cell cycle and how are they regulated?
after M, G1 and g2
- regulated by cyclins and cyclin-dependent kinases
- cyclins - act as control switch and bind to the kinases to form complexes - if check is normal, the cell is allowed to transition to next phase
what are the roles of:
S-Cdk
M-Cdk
Cdk-1
S-Cdk - initiates DNA replication and ensures only one copy (after G1)
M-Cdk - drives cell into mitosis assembles spindle fibres (after G2)
Cdk-1 - catalyse the phosphorylation of nuclear lamins in order to break down nuclear envelopes
what is the role of the kinetochore?
protein on chromosome that attach to centrosome and microtubules attach to it which allow chromosomes to line up during metaphase and in anaphase kinetochore fibers shorten and grip fibres tightly to pull chromosomes apart
explain how cytokinesis occurs
actin microfilaments contract so form cleavage furrow so cytoplasm splits in half
what is the difference between apoptosis and necrosis?
- apoptosis - programmed cell death - chromatin condenses, shrinkage of cytoplasm, cell fragmentation and blebbing - phagocytes ingest parts
- necrosis - compromised membrane so swelling leads to lysis -release of intracellular components leads to inflammation triggering cellular response
what are the three stages to cell differentiation?
specification - fate not absolute/ identity can change
determination - fate fixed/ irreversible
differentiation
how do transcriptional factors influence gene expression?
- bind to promoter region and initiation factors
- bind DNA/chromatin alter its structure
- affect activity of second factor - regulate own production to maintain expression of particular set of genes
what are stem cells?
undifferentiated cells that divide and give rise to cells that differentiate into specialised cells of tissues
- they are self renewing
embryonic cells are totipotent. what does this mean and how do cells lose totipotency?
totipotency: all types of body cells as well as placental cells loss of DNA/ rearrangement of DNA terminal differentiation (entered G0 phase - post mitotic e.g. glial cells, muscle cells. neurons) altered gene expression
describe what type of cells haemopoetic cells divide into?
divide into blood cells - pluripotent (limited number)
how can haemotopoesis be regulated?
by cytokines released from stromal cells in bone marrow - allows rapid expansion of cells for immune responses -e.g. erythropoetin (EPO), thrombopoetin (TPO), granulocyte-stimulating factor (GSF), granulocyte-macrophage stimulating factor (GMSF)
what is the role of telomeres?
sections of DNA at end of sequences of same repeated short sequence (TTAAGGG) forms a molecular cap preventing chromosomal rearrangement and protects DNA as bases removed from cap rather than coding DNA
what is a gametogonium? give different types and what they develop into as well as ploidy states
gametogonium - stem cell for gametes in gonads
male: spermatogonium (diploid) - mature into spermatozoa (haploid)
female: oogonium (diploid) - mature into primary oocyte (diploid) and then secondary oocyte (haploid)
give classes of proteins considered to be housekeeping genes
ribosomal proteins RNA polymerase related proteins citric acid cycle related proteins mitochondrial proteins cytoskeleton proteins
