Flashcards in EXAM2_L21_The_Cell_Cycle Deck (23)
What are MITOGENS?
What are 4 phases of Cell cycle?
What is considered INTERPHASE?
What is considered M phase?
Mitogens are Growth Factors (signaling molecules)
-alter proteins that control initiation of cell cycle
-G1, S, G2, M
Interphase: G1, S,G2
M phase: Mitosis (physical division of the cell)
What is a resting state?
What is a non-proliferating cell called?
- Normal functioning cell (NOT DIVIDING)
-IN ABSENCE OF MITOGEN
if non proliferating cell -"Arrested" in G0
Cells that terminally enter G0?
Gap 1 Phase events
-Stimulated by a mitogen-- enters G1:
Replicates PROTEINS, ENZYMES, METABOLITES
-cellular components required for survival
***-Proteins required for DNA replication
S Phase events
-46 chromosomes (23 maternal 23 paternal) is duplicated
-Daughter stays attached to parent chromosome by centromere
-DNA is Euchromatin state (uncondensed)
After S phase- Cell has 92 chromatids and is 4n.
G2 Phase events
-Cell Growth in size
-makes proteins, organelles, cytoplasm
Makes everything needed so it can DIVIDE in mitosis
(including proteins needed to condense & separate chromatin)
-DOUBLE CHECKS for errors in duplicated Chromosomes
-makes any needed repairs- then enters mitosis
Mitosis Phase events
Cell enters M phase with DOUBLE EVERYTHING
Cell with ONE version of each chromosome (ie: egg/sperm)
-haploid number is 23 (1-22, plus either X or Y)
-ploidy number represented as "n"
Cell with TWO versions of ea. Chromosome
-one copy maternal & one copy paternal
-initially occurs at fertilization of egg/sperm then diploid state maintained in all SOMATIC (body) cells
-46 chromosomes (23 maternal 23 paternal)
-ploidy number is "2n"
Maternal and Paternal chromosomes comprised of the same genes/DNA sequences
in INTERPHASE or G0- microtubules used for organelle and vesicular transport
During M-phase_MT's undergo HUGE transformation to sort mitotic chromosomes
Centrosomes, centromeres, centrioles WHAT ARE THESE?
- organelles made from centrioles and other proteins
- Move to ends of cell & form MITOTIC SPINDLE
Centrioles- make centrosomes
Centromeres- attach sister chromatids
How are chromosomes pulled to opposite ends of the cell?
MT's pull chromosomes apart via kinetochore
What does interphase look like?
Protein complex- HANDLE for MT's
-connects each sister chromatid to the mitotic spindle
Centromere joins sister chromatids and to kinetochore
-Microtubules dispersed throughout cell
-Chromosomes loosley dispersed
-Chromosomes begin to condense at end of g2
P: Chromosomes condensed; MT's organize (tubulin used in mitotic spindle)
PM: nuclear membrane breaks down (MTs extend in) ea. ch has one kinetochore on each side.
M: metaphase plate; line up parallel to MP.
A: shortest: separate chromatids- cytokinesis begins
T: nucleus reforms; chromosomes decondense- cytokinesis
When does cytokinesis begin and end?
What causes cleavage?
what direction is cleavage? Why?
starts anaphase ends telophase
-Contractile Ring (actin microfilaments inner cell surface)
-cleavage furrow- forms perpendicular to mitotic spindle to ensure equal splitting
Mitosis vs Meiosis
asking number of cells and what they turn into:
2n n etc
Mitosis- 1 diploid cell makes two diploid daughter cells
Meiosis- 1 diploid germ cell makes 4 haploid gametes
Spermatogonia develop into..
Oogonia divide to form...
four haploid sperm cells
One haploid egg, and three polar bodies
**In humans only 2 polar bodies
-**(1st doesn't go through meiosis II)
What happens in S of a cell undergoing meiosis?
One Maternal chromosome (two chromatids)
One Paternal chromosome (two chromatids)
bundled together for Homologous recombination
Diploid 2n cell replicated to 4n state then starts meiosis 1
4n (46 chromosomes; 92 chromatids)--
-Tetrads undergo homologous recombination
-TETRADS separate into DYADS and cell splits into two diploid 2n cells (23 recombined and duplicated pairs)
What 2 events cause genetic variability?
TWO diploid 2n Cells divide into FOUR haploid n cells
1. Crossing over/Recombination
2. Random arrangements of chromosomes during metaphase lineup (2^23= 8 million combinations)
Protein that zips all four maternal/paternal chromatids together into a TETRAD
Formation of tetrad stimulates crossing over