CH.5 Mitotic Cell Cycle

Question 1

What is a chromatid?

Answer 1

one of two identical parts of a chromosome, held together by a centromere, formed during interphase by the replication of the DNA strand.

Question 2

Mitosis

Answer 2

the division of a nucleus into two so that the two daughter cells have exactly the same number and type of chromosomes as the parent cell

Question 3

Interphase

Answer 3

the cell grows to its normal size after cell division and carries out its normal functions.
G1, S, G2 phase
centrosome replicates

Question 4

G1 phase

Answer 4

cells make RNA, enzymes and other proteins needed for growth. At the end of G1, the cell becomes committed to dividing or not dividing.

Question 5

S phase

Answer 5

synthesis of DNA
a signal is received that the cell should divide again
DNA in the nucleus replicates so that each chromosome consists of two identical chromatids
short phase

Question 6

G2 phase

Answer 6

cell continues to grow
new DNA that was made during the S phase is checked
any errors are usually repaired
preparation for cell division also made
ex. sharp increase in the production protein tubulin which is used to make microtubules for mitotic spindle

Question 7

Mitosis phases

Answer 7

prophase
metaphase
anaphase
telophase

Question 8

Importance of mitosis in the production of
genetically identical daughter cells during

Answer 8

• growth of multicellular organisms
• replacement of damaged or dead cells
• repair of tissues by cell replacement
• asexual reproduction

Question 9

How does the behaviour of chromosomes in plant cells differ from that of animal cells?

Answer 9

plant cells don’t contain centrosomes
after the nuclei division of a plant cell, a new cell wall must form between the daughter nuclei

Question 10

Early prophase and late prophase

Answer 10

Early prophase
two centrosomes produced by replication of original centrosomes during the S phase
chromosomes start to appear as chromatin coils up and becomes shorter and thicker

Late prophase
nuclear envelope breaks into small vesicles that are not visible with a light microscope
nucleolus disappears (forms part of several chromosomes)
chromosomes are seen to consist of two identical chromatids
centrosomes moving towards opposite ends of the nucleus

Question 11

Metaphase

Answer 11

each centrosome reaches a pole
centrosomes help to organise the production of spindle microtubules
chromosomes line up across the equator of the spindle; they are attached by their centromeres to the spindle

Question 12

Anaphase

Answer 12

chromatids move to opposite poles, centromeres first, pulled by the microtubules

Question 13

Telophase

Answer 13

nuclear envelope re-forming
nucleolus re-forming
chromatids have reached the poles of the spindle, they will now uncoil again

Question 14

cytokinesis

Answer 14

division of the cytoplasm and the cell into two by constriction from the edges of the cell

Question 15

Kinetochore

Answer 15

a protein structure found at the centromere of a chromatid to which microtubules attach during nuclear division

Question 16

Telomere

Answer 16

repetitive sequence of DNA at the end of a chromosome that protects genes from the chromosome shortening that happens at each cell division

Question 17

Role of telomeres

Answer 17

prevent the loss of genes during cell division and to allow continued replication of a cell
telomerase enzymes are used

Question 18

stem cell

Answer 18

a relatively unspecialised cell that retains the ability to divide an unlimited number of times, and which has the potential to become a specialised cell (such as a blood cell or muscle cell)

Question 19

give examples for each cell type
totipotent
pluripotent
multipotent

Answer 19

zygote stem cells
embryonic stem cells
adult stem cells

Question 20

mutation

Answer 20

a random change in the base sequence of DNA, or in the structure and/or number of chromosomes

Question 21

Cancer

Answer 21

a group of diseases that result from a breakdown in the usual control mechanisms that regulate cell division; certain cells divide uncontrollably and form tumours, from which cells may break away and form secondary tumours in other areas of the body (metastasis)