CH 10. How Cells Divide

Question 1

Cell Division in Prokaryotes

Answer 1

• Called binary fission
  -DNA replicated-prokaryotes possess single, circular chromosomes

Question 2

Cell Division in Eukaryotes

Answer 2

Two Types:
Mitosis- produces genetically identical diploid cells
Meiosis- produces genetically unique, haploid cells

Question 3

Chromosome

Answer 3

A threadlike structure of nucleic acids and proteins found in the nucleus of most living cells, carrying genetic information in the form of genes.

Question 4

Chromatin

Answer 4

The material of which the chromosomes of organisms other than bacteria (i.e., eukaryotes) are composed. It consists of protein, RNA, and DNA.

Question 5

Chromosome Replication

Answer 5

Chromosome replication and segregation are key events during the microbial cell cycle that must be completed before a cell divides. To reproduce successfully, every cell must replicate its chromosome(s) and distinguish nascent sister chromosomes from one another.

Question 6

Ploidy

Answer 6

The number of sets of chromosomes in the cells of an organism

Question 7

Diploid

Answer 7

Two sets of chromosomes (2n)

Question 8

Haploid

Answer 8

One set of chromosomes (1n or n)

Question 9

Somatic vs Gamete

Answer 9

Somatic (Body) Cells- Contains DNA but it is not the DNA that is passed to offspring
Gamete (Sex) Cells- Are usually haploid (e.g Sperm and Eggs), Have one sets of chromosomes

Question 10

Gametes have one set of chromosomes

Answer 10

For humans: n=23

Question 11

Chromosomes and Chromatid numbers at various points

Answer 11

Similarly, in humans (2n=46), there are 46 chromosomes present during metaphase, but 92 chromatids. A quick tip: notice that during the stages of meiosis and mitosis, the chromatid count never changes. Only the number of chromosomes changes (by doubling) during anaphase when sister chromatids are separated.

Question 12

Purpose and products of Mitosis

Answer 12

-Cell division that creates somatic cells (body cells)
-One division to create two daughter cells
-Cells produced are diploid (2n)
-Cells produced are genetically identical
-New cells used for growth, wound repair, and cell replacement
-Some eukaryotes (mostly single-celled) reproduce asexually by mitosis

Question 13

The Cell Cycle

Answer 13

Cell cycle is the name we give the process through which cells replicate and make two new cells. The cell cycle has different stages called G1, S, G2, and M.

Question 14

Interphase

Answer 14

Period when a cell is not actively dividing

Question 15

G1 Phase

Answer 15

Cell groups and serves its function
-Most time is spent in this phase
-Upon receiving a signal to divide, the cell prepares by making key proteins

Question 16

S Phase

Answer 16

DNA synthesis (DNA Replication)
-Chromosomes replicated to produce sister chromatids connected at centromeres

Question 17

G2 Phase

Answer 17

Cell finishes preparing for division and checks for proper DNA replication

Question 18

G0 Phase

Answer 18

Some cells never divide
-For example: Neurons, cardiac, muscle cells

Question 19

M Phase

Answer 19

Period of cell division

Question 20

Centromere

Answer 20

The region of a chromosome to which the microtubules of the spindle attach, via the kinetochore, during cell division.

Question 21

Sister Chromatid

Answer 21

Sister chromatids are duplicated copies of a single chromosome that are attached to each other and are identical

Question 22

Kinetochore

Answer 22

These are large protein assemblies that connect chromosomes to microtubules of the mitotic and meiotic spindles in order to distribute the replicated genome from a mother cell to its daughters.

Question 22

Phase 1: Prophase

Answer 22

-Chromosomes condense into chromatids
-Start forming spindle apparatus
-Nuclear envelope breaks down

Question 23

Phase 2: Prometaphase

Answer 23

-Microtubules of spindle apparatus bind them to kinetochores on each sister chromatid

Question 24

Phase 3: Metaphase

Answer 24

• Sister chromatid pairs line up in the middle of the cell
  -Driven by microtubule movement cell

Question 25

Phase 4: Anaphase

Answer 25

-Sister chromatids are separated
-Individual chromosomes pulled to opposite ends
-Each pole ends with a full chromosome set

Question 26

Phase 5: Telophase

Answer 26

-Nuclear envelope reforms (into the nuclei)
-Chromosomes decondensed (not shown below)
-Cell now contains two nuclei

Question 27

Cytokinesis

Answer 27

Cytoskeleton divides the cell into 2 new cells

Question 28

G1/S Checkpoint

Answer 28

Is cell division needed?
Is DNA undamaged?
Does the cell have needed materials?

Question 29

G2/M

Answer 29

Was DNA replicated properly?
Does the cell have the needed materials?

Question 30

Spindle Checkpoint

Answer 30

Did the microtubule attach properly to the sister chromatids?
Ensures chromosomes separate properly