Cell Cycle Flashcards
What is the cell cycle overview?
Highly coordinated process that allows the cell to divide into 2 daughter cells in an orderly manner
3 roles of the cell cycle
Reproduction of the organism, growth and development, tissue repair
Somatic cells
All body cells except reproductive cells, during mitosis when cells are dividing and chromosomes are visible, somatic cells contain 46 chromosomes in 23 pairs, DIPLOID
Gametes
Reproductive cells, during phase when chromosomes are visible, gametes contain 23 chromosomes HAPLOID
What is the main purpose of mitosis and meiosis
Distribute genetic material to offspring accurately with few mistakes, genetic material in nucleus is depicted and moved towards poles of cells then plots into two daughter cells
Main series of the cell cycle
Interphase (G1, S, G2) and M-phase (mitosis and cytokinesis), non dividing/resting phase is G0
% of cell cycle stages
40% G1, 39% S, 19% G2, 2% M, G0 is variable, cell enters G1 from G0
Interphase overview
The cell continues to grow during interphase and it may last for hours to weeks depending on the cell type
G1 phase overview
First gap, the cell grows and accumulates the substrates required for DNA replications, movement of one centriole in the centrosome away from the other
S phase overview
DNA synthesis., the amount of DNA present in the cell doubles as the DNA strands are replicated, centrosome divides to give 2 daughter pairs
G2 overview
Second gap, cell continues to grow and produce the proteins and other molecules required for mitosis to occur
Checkpoints in cell cycle (overview)
The cell cycle does not proceed unchecked, various points where the cycle stops until the correct signal s present to allow it to proceed to the next part, cyclic-dependent kinases (CDKs) activate other proteins to allow the next phase to proceed
G1 checkpoint
Cell proceed to S-phase or it leaves the cycle for the G0 phase
G2 checkpoint
Controls entry into the M-have, checks to see if chromosomal DNA is damaged or poorly replicated
M-checkpoint
Presence of correct signals ta this point allows the chromatids to separate (occurs during mitosis)
Control mechanisms of cell cycle
Cyclin-dependent kinases (CDKs) and cyclins
CDK overview
Kinase enzymes that are required for the cell cycle, they DO NOT vary in concentration throughout the cycle, however, they are inactive until the bind with proteins cyclins
Cyclins overview
The concentrations of these proteins do vary throughout the cell cycle, their rate of synthesis varies as the cell cycle progresses, cyclins and CDK bind complexes that control the progression of the cell cycle
Maturation (M-phase) promoting factor (MPF)
Protein allows cell to progress past the G2 checkpoint and enter mitosis, it is formed when cyclin binds to CDK, activated MPF is a kinase and controls some of the processes associated with mitosis, including the breakdown got he nuclear membrane, ONLY a transiently active molecule, it also initiates. Sequence that leads to its separation back into a cyclin and the inactive CDK, cyclin is broken down and levels remain low until correct signal occurs to increase cyclin concentration
kinase activity during cell cycle
MPF activity increases as cyclin concentration increases (same with decreases)
Cell cycle cell componentes involved
Cytoskeleton (micro tubules for cell division and micro filaments), nucleus (contains genetic material and must be replicated faithfully to provide daughter cells with a functional genome)
Microtubules are essential for cell division
Centrosomes are the point at which microtubules are formed in some but not all cells, in animals cells they contain a pair of centrioles that may contribute to for microtubule formation
Nucleus in cell cycle, nucleolus
Ribosomes and RNA, is well developed in cells with a lot of active protein synthesis, site of synthesis of ribosomes
Nucleus in cell cycle, chromatin
Consist of DNA, his tones, other associated proteins, histones are4 structural proteins closely associated with DNA, man regulatory proteins have functions in controlling gene expression
Packaging of DNA non-dividing
in non-diving, DNA not organized into easily visible structure, chromosomes not present DNA found in chromatic, DNA and histones and other protones are found in nucleus of non-dividing cell throughout the cell
Packaging of DNA dividing
Chromatin organized into readily recognizable structures (chromosomes), compromised of single strand of DNA, in somatic cell, two sister chromatids (identical) joined at centromere (where pulled apart), during cell division, the centromere develops a kinetochore (microtubules) attached to and pull chromosome apart
genetic material
Chromatin, chromosomes, sister chromatid
How is DNA organized within the nucleus?
Accomplished y a complex folding process that involves a close association of the DNA with a series of proteins
Packaging of DNA process
DNA couple helix wraps around histones (now nucleosomes) and wrapped tighter (30.nm fiber) then loops and scaffolds (looped domains 300nm fiber) until replicated chromosome (1,4000 nm made up 2 chromatids of 700 nm)