Cell Division - Mitosis

Question 1

What are the two types of cell division in eukaryotes?

Answer 1

1. Mitosis

2. Meiosis

Question 2

In mitosis, the parent cell divides to produce what?

Answer 2

Two genetically identical daughter cells

Question 3

Why is mitosis needed?

Answer 3

Mitosis is needed got the growth of multicellular organism and for repairing damaged tissue

Question 4

What is the cell cycle

Answer 4

The cell cycle consists of a period of cell growth and DNA replication called interphase. Mitosis happens after that. Interphase can be divided into three separate growth stages - G1, S and G2

Question 5

Explain the 4 stages of the cell cycle

Answer 5

1. Mitosis - the cycle starts and ends here
2. G1 (gap phase 1) - cell grows and new organelles and proteins are made
3. Synthesis - cell replicates its DNA, ready to divide by mitosis
4. G2 (gap phase 2) - cell keeps growing and proteins needed for cell division are made

Question 6

What are the four stages of mitosis?

Answer 6

1. Prophase
2. Metaphase
3. Anaphase
4. Telephase

Question 7

Describe interphase

Answer 7

The cell carries out normal functions, but also prepares to divide. The cell’s DNA is unravelled and replicated, to double its genetic content. The organelles are also replicated so it has spare ones, and its ATP content is increased (ATP provides the energy needed for cell division)

Question 8

Describe prophase

Answer 8

The chromosomes condense, getting shorter and fatter. Tiny bundles of protein called centrioles start moving to opposite poles of the cell, forming a network of protein fibres called the spindle. The nuclear envelope breaks down and chromosomes lie free in the cytoplasm

Question 9

Describe metaphase

Answer 9

The chromosome (each with two chromatids) line up along the middle of the cell and become attached to the spindle by their centromere

Question 10

Describe anaphase

Answer 10

The centromeres divide, separating each pair of sister chromatids. The spindles contract, pulling chromatids to opposite poles of the spindle, centromere first. This makes the chromatids appear v-shaped

Question 11

Describe telophase

Answer 11

The chromatids reach the opposite poles on the spindle. They uncoil and become long and thin again. They’re now called chromosomes, so there are now two nuclei. The cytoplasm divides - cytokinesis. There are now two daughter cells that are genetically identical tot he original cell and each other. Mitosis is finished and each daughter cell starts the interphase part of the cell cycle to get ready for the next round go mitosis

Question 12

Describe the chromosomes at the beginning and end of mitosis

Answer 12

As mitosis begins, the chromosomes are made of two strands joined in the middle by a centromere. The separate strands are called chromatids. There are two strands because each chromosome has already made an identical copy of itself during interphase. When mitosis is over, the chromatids end up as one-strand chromosomes int he daughter cells

Question 13

What are mitosis and the cell cycle controlled by?

Answer 13

Genes

Question 14

What happens to cells if there is a mutation in the gene?

Answer 14

Normally, when cells have divided enough times to make enough new cells, they stop. If there is a mutation in the gene that controls cell division, the cells can grow out of control. The cells keep on dividing which forms a tumour. Cancer is a tumour which invades surrounding tissue

Question 15

What are some treatments for cancer designed to control?

Answer 15

They are designed to control the rate of cell division in tumour cells by disrupting the cell cycle. This kills the tumour cells

Question 16

Can cancer treatments distinguish between normal cells and tumour cells?

Answer 16

Cancer treatments cannot distinguish tumour cells from normal cells - they also kill normal body cells that are dividing. However, tumour cells divide much more frequently than normal cells, so the treatments are more likely to kill tumour cells

Question 17

Some cell cycle targets of cancer treatment include:

Answer 17

1. G1 - some chemical drugs (chemotherapy) prevent the synthesis of enzymes needed for DNA replication. If these aren’t produced, the cell in unable to enter the synthesis phase (S), disrupting the cell cycle forcing it to kill itself
2. S - radiation and some drugs damage DNA. At several points in the cell cycle the DNA in the cell is checked for damage. If severe damage is detected, the cell will kill itself - preventing further tumour growth