Midterm 2 pt.2

Question 1

Prokaryotes vs eukaryotes?

Answer 1

Prokaryotes: a single circular chromosome
Eukaryotes: multiple linear chromosomes

Question 2

genome?

Answer 2

complete genetic material of an organism (DNA) or virus (RNA), the genome is duplicated before cell division.

Question 3

The DNA is wound…

Answer 3

twice around a protein core

Question 4

What do chromosones consist of?

Answer 4

1 centromere: region on each sister chromatid where sister chromatids attach to each other
2 chromatids: identical copies of the same original chromosome joined all along their lengths by protein complexes

Question 5

Phases of mitosis? (5)

Answer 5

prophase, prometaphase, metaphase, anaphase
telophase

Question 6

G2 phase of interphase? mitosis

Answer 6

Presence of the nuclear envelope and one or more nucleoli
Centrosome duplication into 2 centrosomes
Chromosomes, duplicated during S phase are not condensed

Question 7

Prophase of mitosis?

Answer 7

chromatin fibers condensing into chromosomes
nucleoli disappear.
Each duplicated chromosome appears as two identical sister chromatids
The mitotic spindle begins to form
The centrosomes move away from each other

Question 8

Prometaphase of Mitosis?

Answer 8

nuclear envelope fragments.
microtubules extending from centrosome invade the nuclear area
kinetochore, a specialized protein structure has formed at the centromere of each chromatid
microtubules attach to the kinetochores
Microtubules not attached to the kinetochores interact with the microtubules from the opposite pole

Question 9

Metaphase of Mitosis?

Answer 9

The centrosomes are at opposite poles of the cell.
The chromosomes have reached the metaphase plate chromosomes’ centromeres lie at the metaphase plate.

Question 10

Anaphase of Mitosis?

Answer 10

Cohesins that bind sister chromatids are cleaved by a separate protein
Each chromatid now becomes a distinct chromosome.
daughter chromosomes move toward opposite ends of the cell
At the end of anaphase, the two ends of the cell have equivalent and complete collections of chromosomes.

Question 11

Telophase of mitosis?

Answer 11

Two daughter nuclei form in the cell. Nuclear envelopes arise from the fragments of the parent cell’s nuclear envelope
Nucleoli reappear, chromosomes become less condensed.
Any remaining spindle microtubules are depolymerized.

Question 12

Cytokinesis

Answer 12

Formation of a cleavage furrow, which pinches the cell in two

Question 13

cytokinesis in plants?

Answer 13

The division of the cytoplasm is initiated during the late telophase and involves the alignment of vesicles to form a central plate (phragmoplast). These vesicles can reconstitute a cell wall.

Question 14

Binary fission in prokaryotes? 4 steps

Answer 14

1. Cell division is initiated when the DNA of the bacterial chromosome begins to replicate at the origin of replication, producing two origins.
2. One origin moves toward the opposite end of the cell.
3. The cell elongates and double in size.
4. Replication ends and the plasma membrane pinches inward

Question 15

Phases of the cell cycle?

Answer 15

Interphase (including G1, S, and G2 subphases): 90% of the cycle
M phase (including mitosis and cytokinesis): 10% of the cycle

Question 16

S and G phases?

Answer 16

G1/ G2 phase ): metabolically active cell growth
S phase (“synthesis”): duplication of the chromosomes

Question 17

3 checkpoints for regulation of cell cycle?

Answer 17

G1, G2, M phase

Question 18

Two types of regulatory molecules?

Answer 18

Cyclins: proteins whose concentration fluctuate and that bind to specific kinases
Cyclin-dependent kinases : activate other proteins through phosphorylation and using ATP

Question 19

What are MPFs?

Answer 19

The Cdk-cyclin constitutes a maturation promoting factor (MPF) that peaks during the M phase. MPF is a protein that triggers the cell’s passage from the G2 checkpoint into the M phase

Question 20

How do MPFs regulate the signalling pathway? 3

Answer 20

Fragmentation of the nuclear envelope
Chromosome condensation
Spindle formation

Question 21

G1 and S, G2, M checkpoints

Answer 21

G1 checkpoint:
Abundance of resources before proceeding to S, G2 and M
Failure leads to the G0 phase
M phase checkpoint:
Activation of protein complexes that cleaves cohesins

Question 22

RAS protein?

Answer 22

G protein that relays a signal from a growth factor
Cellular response: synthesis of a protein that stimulates the cell cycle
Proto-oncogene: gene coding for a protein that stimulates the normal cell growth and division

Question 23

p53 gene?

Answer 23

tumor-suppressor gene, activated when there is damage to the cell’s DNA.
Cellular response: The cell cycle is halted until the damage has been repaired
Tumor-suppressor gene: gene coding for a protein that inhibits the cell cycle and cell division

Question 24

Apoptosis?

Answer 24

programmed cell death. Important process that removes damaged or unnecessary cells and is initiated when a cell is damaged, superfluous, or potentially dangerous to an organism

Question 25

Apoptosis activates?

Answer 25

Activation of…
proteases: enzymes that attack and digests proteins
nucleases: enzymes that attack and digests nucleic acids.

Question 26

What is Meiosis?

Answer 26

type of cell division in sexually reproducing organisms consisting of two rounds of cell division.
Meiosis produces 4 daughter cells, each with half the number of chromosome sets as the original cell
Fertilization brings this number back to to the original number

Question 27

Prophase 1 meiosis?

Answer 27

Chromosome condensation, centrosome movement, spindle formation, and nuclear envelope breakdown
each chromosome pairs with its homologue , and crossing over occurs
Each homologous pair has one or more X-shaped regions called chiasmata
microtubules from the poles attach to the two kinetochores, at the centromeres.

Question 28

Metaphase 1 meiosis?

Answer 28

Pairs of homologous chromosomes are arranged at the metaphase plate.
Both chromatids of one homologue are attached to kinetochore microtubules from one pole

Question 29

Anaphase 1 meiosis?

Answer 29

Breakdown of cohesins, allowing homologues to separate.
The homologues move toward opposite poles
Sister chromatid cohesion persists at the centromere, causing chromatids to move as a unit

Question 30

Telophase 1 cytokensis meiosis?

Answer 30

Each half of the cell has a complete haploid set of duplicated chromosomes
Cytokinesis is initiated , forming two haploid daughter cells.

Question 31

Prophase 2 meiosis?

Answer 31

Duplication of the centrosomes and formation of a spindle apparatus
Chromosomes , move toward the metaphase II plate

Question 32

Metaphase 2 meiosis?

Answer 32

two sister chromatids of each chromosome are not genetically identical.
The kinetochores of sister chromatids are attached to microtubules extending from opposite poles.

Question 33

Anaphase 2 meiosis?

Answer 33

Breakdown of cohesins that hold the sister chromatids together at the centromere, allowing the chromatids to separate.
Chromatids separate and move toward opposite poles as individual chromosomes

Question 34

Telophase 2 and Cytokinesis?

Answer 34

Nuclei form, the chromosomes begin decondensing, and cytokinesis occurs.

Question 35

Intra-chromosomal recombination?

Answer 35

crossing over during the prophase I of meiosis produces recombinant chromosomes
Crossing overs contribute to much of the genetic variation within a population of organisms

Question 36

Synapsis?

Answer 36

pairing and physical connection of duplicated homologous chromosomes during
prophase I of meiosis