Cell Division

Question 1

What is the cell cycle?

Answer 1

Events that take place as one parent cell divides to produce 2 new daughter cells, can be life cycle for some organisms

Question 2

Where are chromosomes and what do they contain?

Answer 2

In the nucleus of eukaryotic cells, contains 1 mol of DNA including specific lengths: genes

Question 3

How many chromosomes in the nucleus of human cell?

Answer 3

46

Question 4

Before a cell can divide, what must happen?

Answer 4

DNA from each chromosome must be replicated, stay held together at the centromere

Question 5

What are the DNA replicates called?

Answer 5

Pair of sister chromatids, cant be seen under a light microscope

Question 6

What happens to sister chromatids when the cell divides?

Answer 6

Each one will end up in a different new daughter cell

Question 7

What does the super coiling of the chromatids do?

Answer 7

Forms visible chromosomes, each is then short and sturdy enough to moved around more easily, can be stained and seen under light micrscope

Question 8

How thick are the chromatid threads before and after coiling?

Answer 8

30nm thick to 500nm thick

Question 9

What cant super coiled chromatids do? How long should they be super coiled?

Answer 9

Chromosomes cant perform normal function so need to be coiled for shortest amount of time

Question 10

What are daughter cells?

Answer 10

Genetically identically to each other and the parent cell

Question 11

What happens when the chromosomes are being replicated?

Answer 11

Proof reading enzymes move along the new DNA strands and check that copying was successful

Question 12

What can happen if genes aren’t copied properly?

Answer 12

Mutations, new cells may not function

Question 13

How fast is the cell cycle?

Answer 13

Varies between species and cell type, availability of nutrients

Question 14

What are the 4 stages to the cell cycle?

Answer 14

interphase: DNA replicates, mitosis: nucleus divides and chromatids separate, cytokineses: cytoplasm divides/cleaves, growth phase: each new cell grows to full size

Question 15

What are G1 and G2?

Answer 15

G1: biosynthesis (proteins and organelles made)
G2: growth

Question 16

What do the new daughter cells also need?

Answer 16

Membranes, cytoplasm, organelles, enzymes and other proteins

Question 17

Mitosis definition?

Answer 17

process of nuclear division where 2 genetically identical nuclei are formed from one parent cell nucleus

Question 18

Why do new cells need to be made?

Answer 18

Asexual reproduction: to produce new organisms, multicellular organisms grow by producing new cells, damaged/dead cells need to be replaced (RBCs and skin cells)

Question 19

In what order are the 4 stages of mitosis?

Answer 19

1. prophase, 2. metaphase 3. anaphase 4. telophase

Question 20

What happens in prophase?

Answer 20

Replicated chromosomes shorten and thicken (super coil), nuclear envelope breaks down, centriole divides in 2 and moves to opposite poles of cell forming spindle

Question 21

What happens in metaphase?

Answer 21

Chromosomes move to equator of spindle and becomes attaches by its centromere

Question 22

What happens in anaphase?

Answer 22

Sister chromatids are separated when their centromere splits, each of the ‘sisters’ is an individual chromosome again. Spindle fibres shorten again pulling sisters towards the poles (they are a v-shape, centromere pulls them)

Question 23

What happens in telophase?

Answer 23

As the sister chromatids reach each pole, anew nuclear envelope forms around each set. Spindle breaks down and chromosomes uncoil

Question 24

What is cytokinesis?

Answer 24

whole cell splits into 2 new cells (after telophase)

Question 25

3 differences between the cell cycle in animals and plants?

Answer 25

Only meristem cells in plants can divide by mitosis and cytokinesis, plant cells don’t have centrioles (tubulin protein threads made in cytoplasm), in plants cytokinesis starts with formation of cell plate