Chapter 12 The Cell Cycle

Question 1

Genome

Answer 1

A cells and a minute DNA, it’s genetic information

Question 2

Chromosome

Answer 2

The replication and distribution of so much DNA is manageable because the DNA molecules are packed into structures called chromosomes

Question 3

Chromatin

Answer 3

The entire complex of DNA and proteins that are the building material of chromosomes is referred to as chromatin

Question 4

Gametes

Answer 4

Reproductive cells also sperm and eggs have one set or half as many chromosomes as somatic cells. For humans gametes have one set of 23 chromosomes whereas somatic cells have 46 chromosomes

Gametes have a haploid number of chromosomes meaning half of the amount of chromosomes a somatic cell has

Question 5

Sister chromatids

Answer 5

Each duplicated chromosome has two sister chromatics which are joined copies of the original chromosome

Question 6

Centromere

Answer 6

Each sister chromatid has a centromere, a region of chromosomal DNA where the chromatid is attached most closely to eat sister chromatid. The attachment is mediated by proteins bound to the centromeric DNA, other bound proteins condense the DNA, giving the duplicated chromosome a narrow waist

Question 7

Mitosis

Answer 7

Mitosis is the division of genetic material in the nucleus, is usually followed immediately by cytokinesis.

Question 8

Cytokinesis

Answer 8

Cytokinesis is the division of cytoplasm. One cell has become two, each the genetic equivalent of its parent cell.

Cytokinesis starts usually late in anaphase or sometimes and telophase.

Partitioning of cell must be super accurate to prevent mutation.

Question 9

Interphase

Answer 9

Interphase accounts for about 90% of the cell cycle. It can be divided into sub phases, the G1 phase, the S phase synthesis, and the G2 phase

In interphase DNAs organized around histones. We wrapped it around to be able to fit extremely long molecules into the nucleus.

During interphase we cannot make out individual discrete strands until additional condensation during prophase of mitosis

We only super condense when we are ready to partition to separate cells. Other than this we need access to genes on DNA during interphase

Question 10

Mitosis: The mitotic (M) phase

Answer 10

Mitosis is conventionally broken down into five stages: prophase, prometaphase, metaphase, anaphase, and telophase

Question 11

Mitotic spindle

Answer 11

Mitotic spindle begins to form in the cytoplasm during prophase. The structure consists of fibers made of microtubules and associated proteins

Question 12

Centrosome

Answer 12

A sub cellular region containing materials that function throughout the cell cycle to organize the cells microtubules

Question 13

Kinetochore

Answer 13

These microtubules shorten in order to drag sister chromatins towards the centersome at opposite poles. Motor proteins facilitate this movement and walk the chromosomes towards the pole while the kinetochore microtubules certain behind it.

Question 14

Cleavage Furrow

Answer 14

On the cytoplasmic side of the furrow is a contractile ring of Actin microfilament. the actin microfilaments interact with the myosin molecules causing the ring to contract.

Question 15

Prophase

Answer 15

Chromosome start to condense, spindle starts to be set up, centrosomes move to opposite sides of cell

Question 16

Prometaphase

Answer 16

DNA continues to condense, for easy and accurate separation, spindle is further constructed. Nuclear membrane fragments. Spindle continues to become opposite poles

Question 17

Metaphase

Answer 17

Spindle is complete. Chromosomes are aligned in center of spindle. Each sister chromatid of a dyad is connected to microtubules the emanate from opposite poles. The specific microtubules that connects to the kinetochore proteins on the chromosomes are called kinetochore microtubules

Question 18

Anaphase

Answer 18

Sister chromatins separate and each one of a dyad gets pulled to opposite poles creating a V or checked shape. Cytokinesis can begin in late anaphase some spindle microtubules are lengthening, others are shortening

Question 19

Telophase

Answer 19

DNA condenses. Nuclear membrane starts to form. Spindle is disassembled. Usually cytokinesis is completed.

Question 20

Cyclin dependent kinase molecule

Answer 20

Part of all cycles. But when cyclin is added to the CDK molecule in whatever phase, when these combined, the cell moves to the next phase

Question 21

Cyclin protein

Answer 21

There are several. Each work at different junctions. Cyclin often rises in concentration during a specific time in the cell cycle when they combine with their specific kinases called CDK (cyclin dependent kinases).

They have to be the kinase and phosphorylate a particular protein to drive the cell cycle forward. I E G1-S-G2 etc.

Question 22

Checkpoints

Answer 22

There are three checkpoints
G1 before moving to S
G2 checkpoint before mitosis.
Metaphase checkpoint also

Question 23

G1 checkpoint

Answer 23

Cell size is adequate.
Nutrients are available.
Growth factors (signals from other cells) are present.
Any problem with DNA and it will not move forward DNA must be fixed first

Question 24

G2 checkpoint

Answer 24

Cell size is adequate.

Chromosome replication is completed successfully

Question 25

Metaphase checkpoint

Answer 25

All chromosomes must be attached to the mitotic spindle

Question 26

What happens if the cell is unable to satisfy requirements of the checkpoints

Answer 26

If a cell is unable to satisfy requirements of the checkpoints, the cell must commit suicide. A cell tries to pass checkpoints and fix damage as programmed cell death is a last resort

Question 27

Apoptosis

Answer 27

Chromatin shrink.
Cell shrinkage.
Preservation of organelles and other membranes.
Rapid engulfment by neighboring cells prevents information
Biomechanical hallmark: DNA fragments!

Question 28

Necrosis

Answer 28

Nuclear spelling. 
Cellular swelling. 
Disruption of organelles. 
Rupture of cell and release of salt content. 
Inflammatory response.

Question 29

Mitogens

Answer 29

These are also called growth factors. Mitogens are stimulators extracellular signals causing cell division. Some growth factors can also stimulate and increase cell mass (more proteins/more organelles made)