1.3 Cell Division

Question 1

To reproduce:

Answer 1

Cells copy their genetic material and divide to form two new daughter cells

Question 2

The purpose of cell division:

Answer 2

• Permits genetic information
• Allows unicellular organisms to reproduce
• Provides a way for multicellular organisms to grow and develop from a fertilised ovum
• Makes new cells available in multicellular organisms to replace dead skin

Question 3

A cell that divides is called a:

Answer 3

Parent cell

Question 4

For cells to divide and form two new functional cells:

Answer 4

One copy of the parent cell’s DNA must be passed to both cells

Question 5

The three events that must occur to pass DNA from one generation of cells to the next are:
And what does this mean?

Answer 5

1. Copying of the parent cell DNA (DNA replication)
2. The two copies move to opposite ends of the parent cell
3. The parent cell must divide into two cells

Cells produced in this way are genetically identical to the parent cell and each other

Question 6

Does binary fission occur in prokaryotes or eukaryotes?

Answer 6

Prokaryotes

Question 7

Explain step 1 of binary fission

Answer 7

Step 1: Circular chromosome attaches to the inside of the cell membrane and the chromosome is replicated identically

Question 8

During step four of binary fission, how is the cell membrane and cell wall formed?

Answer 8

The parent cell membrane grows inwards, and a new cell wall is formed over the outside of it.

Question 9

Does mitosis and meiosis occur in prokaryotes or eukaryotes?

Answer 9

Eukaryotes

Question 10

What are the four distinct phases of mitosis?

Answer 10

PMAT
Prophase
Metaphase
Anaphase
Telophase

Question 11

Mitosis is the division of what in a eukaryotic cell?

Answer 11

Nucleus

Question 12

What happens in prophase?

Answer 12

The nuclear membrane of the parent cell breaks down. The already copied chromosomes (from interphase before mitotic division) condense and become visible under the microscope. Each chromosomes consist of a pair of chromatids joined by a centromere. Long protein filaments called spindle fibres are assembled to form a structure called a spindle.

Question 13

What happens in metaphase?

Answer 13

The pairs of chromatids move to the equator of the cell. Spindle fibres start to form then attach themselves to the centromere of each chromosome.

Question 14

What happens in anaphase?

Answer 14

Chromatids pairs are seperated by spindle fibres pulling them from the centromeres. The pairs are separated to create two identical sets of daughter chromosomes.
Each daughter chromosome is moved to the poles of the spindles by the spindle fibres.

Question 15

What happens in telophase?

Answer 15

The spindle fibres break down. The set of chromosomes at each spindle de-condense. Both sets become enclosed by a nuclear membrane.

Question 16

The product of mitotic division is called:

Answer 16

Diploid cells

Question 17

Why are diploid cells called diploid?

Answer 17

Because of the presence of two complete sets of chromosomes (23) meaning they contain a full set of chromosomes (46 in humans)

Question 18

All human cells are diploid except for what?

Answer 18

Ova and sperm

Question 19

In diploid cells chromosomes are in:

Answer 19

Pairs

Question 20

When one chromosome originated from the mother, and the other from the father they are called:

Answer 20

Paternal chromosomes

Question 21

The two chromosomes that form the pair in diploid cells are called:

Answer 21

Homologous chromosomes

Question 22

How does cancer occur?

Answer 22

When cells divide in an uncontrolled way and are replicated with an error, tumors are created. AKA cell cycle is disturbed

Question 23

How many pairs of chromosomes do diploid cells carry in humans and what are they classified as?

Answer 23

23 pairs total
22 pairs are homologous
1 pair are sex chromosomes
Together this is called the karyotype.

Question 24

In females, the pair of sex chromosomes are what?

Answer 24

Two X chromosomes

Question 25

In males, the pair of sex chromosomes are what?

Answer 25

One X and one Y chromosome

Question 26

Karyotyping is:

Answer 26

Photographing and arranging the chromosomes

Question 27

What are haploid cells?

Answer 27

Haploid cells have one chromosome from each homologous pair meaning they carry 23 chromosomes not 23 pairs. Sperm and ova are haploid cells meaning they do not carry a full set of chromosomes.

Question 28

Haploid cells are also called:

Answer 28

Gametes or sex cells

Question 29

What is a unicellular eukaryotic cell and its characteristics?

Answer 29

Amoeba - which uses binary fission to replicate itself, has organelles and is more complex yet is still a single cell.

Question 30

When does cytokinesis begin?

Answer 30

In anaphase and continues into telophase

Question 31

What is cytokinesis?

Answer 31

The division of the cytoplasm near the end of mitosis which results in daughter cells forming

Question 32

What happens in cytokinesis regarding to cleavage furrow?

Answer 32

The protein fibres in the cell membrane begin to constrict to form a cleavage furrow. The cleavage continues to constrict until it leads to two genetically identical daughter cells

Question 33

Cells use DNA replication:

Answer 33

Prior to cell division to make identical copies of DNA

Question 34

What happens in interphase?

Answer 34

The cells grow and the nuclear DNA is replicated. The cell gets itself ready for mitosis

Question 35

Explain step 2 of binary fission

Answer 35

Step 2: The bacterium starts to grow larger in preparation for binary fissions. Cytoplasm increases. Each chromosome attaches itself to the inside of the parent cell.

Question 36

Explain step 3 of binary fission

Answer 36

Step 3: The two chromosomes are moved to opposite ends of the parent cell as it grows lengthways.

Question 37

Explain step 4 of binary fission

Answer 37

Step 4: A new cell wall and cell membrane form (known as the cross wall) through the centre of the cell.

Question 38

Explain step 5 of binary fission

Answer 38

Step 5: The cell divides into two daughter cells, each one with one identical circular chromosome.