1.6

Question 1

mitosis

Answer 1

division of the nucleus into two genetically identical daughter nuclei

Question 2

cell cycle

Answer 2

interphase, mitosis and cytokinesis

Question 3

cell division

Answer 3

mitosis and cytokinesis

Question 4

interphase

Answer 4

a very active phase of the cell cycle with many processes occurring in the nucleus and cytoplasm, the longest phase, G1, S and G2

Question 5

***G1

Answer 5

in cytoplasm
1. the cell grows and functions normally undergoing everyday processes
2. rapid protein synthesis takes place allowing the cell to grow in size
3. proteins required for DNA synthesis are made
4. mitochondria and chloroplasts (in case of plant cells) are replicated (this continues in S phase)

Question 6

***S

Answer 6

in nucleus
1. the amount of DNA doubles as DNA replication takes place
2. the genetic material is duplicated, but no chromosomes are formed yet

Question 7

***G2

Answer 7

in cytoplasm
1. protein synthesis occurs to produce the proteins needed for cell division, such as microtubule proteins that will make up a mitotic spindle
2. the cell is actively preparing for cell division

Question 8

condensation of chromosomes

Answer 8

packaging chromosomes into much shorter and wider structures (because human nuclei are less then 5 micrometers in diameter, but DNA molecules are more than 50,000 micrometers long) during the 1. stage of mitosis; histones and enzymes help

Question 9

supercoiling of chromosomes

Answer 9

repeatedly coiling DNA molecule to make chromosomes shorter and wider

Question 10

mitosis

Answer 10

the division of the nucleus into 2 genetically identical daughter nuclei; involves the separation of sister chromatids into individual chromosomes which are then distributed among the daughter nuclei; after G2

Question 11

4 stages of mitosis

Answer 11

prophase, metaphase, anaphase and telophase

Question 12

***prophase

Answer 12

1. DNA supercoils, causing the chromatin to condense (chromatids become shorter and fatter)
2. nucleolus disappears (nuclear membrane disintegrates)
3. spindle fibres (made for microtubules that grow from structures called microtubule organizing centers MTOC) start to form and are completely formed by the end of prophase
4. centrioles (absent from plant cells) move to the opposite poles

Question 13

***metaphase

Answer 13

1. spindle fibres bind to the centromere of sister chromatids and cause their movement towards the equatorial plate
2. the microtubules are all put under tension to test whether the attachment is correct, by shortening microtubules at the centromere; if the attachment is correct, chromosomes remain on the center
3. sister chromatids are separated at the equatorial plate at the end of metaphase

Question 14

***anaphase

Answer 14

the shortest phase
1. each centromere divides, allowing the pairs of sister chromatids to separate
2. spindle microtubules pull them rapidly towards the poles of the cell
3. mitosis produces two genetically identical nuclei

Question 15

***telophase

Answer 15

1. chromatids have reached the poles and are now called chromosomes
2. nuclear membrane starts to reform at each pole
3. nucleolus appears in each new nucleus and chromosomes uncoil
4. spindle fibres disintegrate
5. cell elongates, in preparation for cytokinesis
6. in some cases, invagination of membrane is also visible (marking the beginning of cytokinesis)

Question 16

mitotic index

Answer 16

the ratio between the number of cells in mitosis in a tissue and the total number of observed cells

Question 17

mitotic index formula

Answer 17

(P + M + A + T) / total cells

Question 18

cytokinesis

Answer 18

occurs after mitosis and is different in plant and animal cells, due to existence of cell wall in plant cells

Question 19

***cytokinesis in animal cells

Answer 19

1. a ring of protein (microfilaments) located beneath the plasma membrane at the equator pulls the plasma membrane inwards
2. the inward pull on the plasma membrane produces the characteristic cleavage furrow
3. when the cleavage furrow reaches the center of the cell, it is pinched apart to form 2 daughter cells

Question 20

***proteins used in cytokinesis in animal cells

Answer 20

actin and myosin

Question 21

***cytokinesis in plant cells

Answer 21

1. Golgi apparatus forms vesicles that consist of material to build anew cell wall
2. vesicles merge and form cell plate
   3, the cell plate divides into 2 daughter cells
   pectins and other substances have to be brought in vesicles by exocytosis between 2 new membranes; this forms the middle lamella that will link the new cell walls;

Question 22

cyclins

Answer 22

a group of proteins that ensure that required tasks are performed at the correct time and that the cell moves on to the next stage of the cycle with it’s appropriate

Question 23

cyclin-dependent kinases

Answer 23

enzymes that cyclins bind to; they become active and attach P groups to other proteins in the cell; the attachment triggers other proteins to become active and carry out tasks specific to one of the phases of the cell cycle

Question 24

***cyclin D

Answer 24

triggers cells to move from G0 to G1 and from G1 to S

Question 25

***cyclin E

Answer 25

prepares cell for DNA replication in S phase

Question 26

***cyclin A

Answer 26

activates DNA replication inside nucleus in S phase

Question 27

***cyclin B

Answer 27

promotes the assembly of the mitotic spindle and other tasks in the cytoplasm to prepare for mitosis

Question 28

tumorigenesis

Answer 28

the formation of a tumor

Question 29

tumor

Answer 29

mass of cells that divide uncontrollably; develop in any stage of life, any par of body

Question 30

benign tumor

Answer 30

usually localized, doesn't spread to the other parts of the body; most respond well to treatment

Question 31

maligant tumor

Answer 31

cancerous growth that is often resistant to treatment; may spread to toher parts of the body and sometimes recur after it has been removed = carcinomas

Question 32

cancer

Answer 32

diseases due to maligant tumors

Question 33

carcinogens

Answer 33

chemicals and agents that cause cancer: some viruses, chemical mutagens, high energy radiation - cancerogenic

Question 34

cancerogenic viruses

Answer 34

hepatitis B

Question 35

***cancerogenic chemical mutagens

Answer 35

osbestos, dioxin

Question 36

cancerogenic high energy radiations

Answer 36

X-rays, short-wave ultraviolet light

Question 37

mutagens

Answer 37

agents that cause gene mutation and mutations CAN cause cancer

Question 38

mutation

Answer 38

change in organism's genetic code; CAN result in tumor formation

Question 39

***oncogene

Answer 39

gene that has undergone a mutation that will contribute to the development of a tumor

Question 40

***proto-oncogenes

Answer 40

oncogenes in their normal, non-muted state; they can assist in regulation of cell division

Question 41

***metastasis

Answer 41

the development of cells from a primary tumor to other parts of the body where they develop into secondary tumors

Question 42

***metastising of a tumor

Answer 42

1. cancerous cells detach from the primary tumor 2. some cancerous cells gain the ability to penetrate the walls of lymph or blood vessels and so circulate around the body 3. circulating cancerous cells invade tissues at different locations and develop by uncontrolled cell division into secondary tumor

Question 43

p53

Answer 43

protein in cell cycle that mutates and causes a tumor formation (over 50% of tumors have a mutation of p53 gene)

Question 44

what happens when a mutation in one of the cyclins happen

Answer 44

CDKs, tumor can form