EXAM2_L21_The_Cell_Cycle Flashcards Preview

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Flashcards in EXAM2_L21_The_Cell_Cycle Deck (23)
1

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)
-Stimulate mitosis
-alter proteins that control initiation of cell cycle

-G1, S, G2, M
Interphase: G1, S,G2
M phase: Mitosis (physical division of the cell)

2

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

3

Cells that terminally enter G0?

Neurons

4

Gap 1 Phase events

-Stimulated by a mitogen-- enters G1:
Replicates PROTEINS, ENZYMES, METABOLITES

-cellular components required for survival
***-Proteins required for DNA replication

not chromosomes!

5

S Phase events

DNA REPLICATION
-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.

6

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

7

Mitosis Phase events

Cell enters M phase with DOUBLE EVERYTHING
PMAT
Cell divides

8

Haploid Cell

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"

9

Diploid Cell

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"

10

Homologous Chromosomes

DIPLOID
Maternal and Paternal chromosomes comprised of the same genes/DNA sequences

11

Microtubules

in INTERPHASE or G0- microtubules used for organelle and vesicular transport

During M-phase_MT's undergo HUGE transformation to sort mitotic chromosomes


12

Centrosomes, centromeres, centrioles WHAT ARE THESE?

Centrosomes- MTOC's
- organelles made from centrioles and other proteins
- Move to ends of cell & form MITOTIC SPINDLE

Centrioles- make centrosomes

Centromeres- attach sister chromatids

13

How are chromosomes pulled to opposite ends of the cell?

MT's pull chromosomes apart via kinetochore

14

Kinetochore
Centromere

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

Interphase( g1,s,g2)
-Microtubules dispersed throughout cell
-Chromosomes loosley dispersed
-Chromosomes begin to condense at end of g2

15

PMAT


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

16

When does cytokinesis begin and end?
What causes cleavage?
What formed?
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

17

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

18

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)

19

Tetrad


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

20

MEIOSIS I

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)

21

MEIOSIS II

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)

22

Synaptonemal complex

Protein that zips all four maternal/paternal chromatids together into a TETRAD

Formation of tetrad stimulates crossing over

23

Chiasmata in human oogenesis

7th month of development female fetus oogonia begin meiosis I and arrest after replication & before division of prophase I (now called primary oocytes 4n).

Now crossing over occurs and synaptonemal complex breaks down.

Primary oocytes contain chiasmata for years b/c primary oocyte paused until puberty/ovulation.