The mitotic cell cycle

Question 1

Chromatids

Answer 1

• 1 of 2 identical parts of a chromosome
• held together by a centromere
• formed during interphase by the replication of a DNA strand

Question 2

Centromere

Answer 2

region of the chromosome to which the microtubules of the spindle attach during cell division

Question 3

Kinetochores

Answer 3

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

Question 4

Telomere

Answer 4

protective sequence of nucleotides found at the ends of the chromosomes

Question 5

Function of telomeres

Answer 5

• needed for successful cell division
• permit continued replication
• prevent loss of genes

Question 6

Cell Cycle

Answer 6

• G1 phase
• S phase
• G2 phase
• Mitosis
• Cytokinesis

Question 7

Cell cycle definition

Answer 7

sequence of events taking place from one cell division until the next

Question 8

Interphase phases

Answer 8

• G1 phase
• S phase
• G2 phase

Question 9

Interphase

Answer 9

• longest phase
• normal cell functions
• cell grows to its normal size
• time spent between cell divisions

Question 10

G1 phase

Answer 10

• cells make RNA, enzymes & other proteins needed for growth
• at the end, cell becomes committed to dividing or not

Question 11

S phase

Answer 11

• DNA replication so that each chromosome consists of 2 identical chromatids

Question 12

G2 phase

Answer 12

• cell continues to grow
• new DNA is checked & any errors are repaired
• preparations are made to start cell division

Question 13

Mitosis

Answer 13

nuclear division that produces 2 genetically identical daughter cells

Question 14

Roles of mitosis

Answer 14

• maintains genetic stability
• ensures cells retain function
• maintains chromosome number

Question 15

Functions of mitosis

Answer 15

• growth
• cell replacement
• repair of tissues
• asexual reproduction
• immune response

Question 16

Stages of mitosis

Answer 16

• Prophase
• Metaphase
• Anaphase
• Telophase

Question 17

Prophase

Answer 17

• centrosomes migrate to opposite poles of mitotic spindle
• chromatin starts to condense
• nuclear envelope & nucleolus begin to disappear

Question 18

Metaphase

Answer 18

• centrosomes are at poles of the cell and organise the production of spindle microtubules
• chromosomes line up across equator of spindle
• each chromosome splits at centromere
• chromosomes start to be pulled apart by microtubules

Question 19

Anaphase

Answer 19

• chromatids move to opposite poles, centromeres are first pulled by microtubules
• spindle fibres contract and chromosomes are pulled to the opposite ends

Question 20

Telophase

Answer 20

• nuclear envelope and nuceolus start reforming
• nucleus divides
• chromosomes are at poles of cell

Question 21

Cytokinesis

Answer 21

division of cytoplasm

Question 22

Cytokinesis in plant cells

Answer 22

• cell plate forms across equator of cell ; cellulose, cell wall laid down
• cytoplasm is hence divided into 2

Question 23

Cytokinesis in animal cells

Answer 23

• contractile ring forms, pushing the equator of cell inwards, forming a cleavage furrow
• cleavage furrow deepens as active filaments in the ring contract
• cell eventually splits into 2

Question 24

Differences in plant & animal cell mitosis

Answer 24

• plant cells don’t have any visible centriole
• in plant cells, daughter cells get separated by cell plate, there is no cleavage furrow

Question 25

Centrosome

Answer 25

• an organelle found in animal cells that acts as the MTOC for construction of the spindle
• present at the poles of cell

Question 26

Centrioles

Answer 26

• act as MTOCs
• assemble/form spindle fibres during prophase
• contraction of spindle fibres during anaphase separates sister chromatids

Question 27

Stem cell

Answer 27

a relatively unspecialised cell that retains the ability to divide an unlimited amount of times and has the potential to become a specialised cell

Question 28

Potency

Answer 28

extent of the power of a stem cell to produce different cell types

Question 29

Stem cell therapy

Answer 29

introduction of new adult stem cells into damaged tissue to treat a disease or injury

Question 30

Totipotent

Answer 30

stem cells that can produce any type of cell

Question 31

Pluripotent

Answer 31

stem cells that form all the cells that will lead to the development of the embryo and later the adult

Question 32

Multipotent

Answer 32

stem cells that are only able to produce a few types of cells

Question 33

Cancer

Answer 33

a result of uncontrolled mitosis, due to a mutation ; cancerous cells divide repeatedly and form a tumour

Question 34

Benign

Answer 34

a tumour that will not spread, safe, and will break down after some time

Question 35

Malignant

Answer 35

tumours that spread throughout the body, invading & destroying tissues, causing cancer

Question 36

Metastasis

Answer 36

cells that break off and spread through the blood and lymphatic system to other parts of the body to form secondary growths

Question 37

Risk of metastasis

Answer 37

most dangerous characteristic of cancer because it can be very hard to find the secondary growths and remove them

Question 38

Carcinogen

Answer 38

a substance or environmental factor that can cause cancer

Question 39

Mutation

Answer 39

a random change in the base sequence of DNA or in the number of chromosomes

Question 40

Cellular changes that occur in the development of cancer

Answer 40

• mutation occurs in gene responsible for cell division ; formation of oncogene
• causes uncontrolled cell division
• coordination of cell cycle is lost
• loss of function and lack of specialisation occurs
• a tumour is formed, an irregular mass of cells showing an abnormal change in shape