Cell Division

Question 0

Disadvantages of becoming multi cellular?

Answer 0

Specialised organs systems needed

Question 1

Advantages of becoming multi cellular?

Answer 1

• organisms becomes larger
• organisms become more complex
• cell differentiation

Question 2

What do the specialised organ systems of multicellular organisms enable?

Answer 2

• communication between all cells in body
• supply cells with nutrients
• control exchanges with outside environment

Question 3

Describe a unicellular organism

Answer 3

An amoeba consists of one cell. It reproduces by dividing to make 2 clones of the parent cell. It then doubles the genetic information within he cell.

Question 4

What does mitosis produce?

Answer 4

Diploid cells

Question 5

What is a diploid cell?

Answer 5

A cell with 46 chromosomes/ a cell containing 2 copies of each chromosome.

Question 6

What is mitosis used for?

Answer 6

• Growth and repair
• Replacement of worn out cells
• Asexual reproduction

Question 7

What is D.N.A replication?

Answer 7

The process in which genetic information is doubled.

Question 8

Why is D.N.A replication needed?

Answer 8

To ensure that each cell produced by mitosis has 2 copies of each chromosome.

Question 9

Describe D.N.A replication

Answer 9

1. The double helix of a D.N.A molecule unzips to form single strands.
2. New strands are formed by D.N.A bases lining up in complimentary base pairings.

Question 10

What is mitosis?

Answer 10

The process in which new, diploid cells are produced for growth.

Question 11

Describe mitosis

Answer 11

1. A resting cell undergoes D.N.A replication (chromosomes are copied).
2. A spindle forms with the chromosomes aligned along equator of the cell.
3. The spindle splits, dragging the chromosome single strands to opposite poles of he cell.
4. New nuclear membranes form around the new sets of chromosomes, producing 2 new, genetically identical cells.

Question 12

What is a homologous cell?

Answer 12

A cell containing identical, paired chromosomes.

Question 13

What are gametes?

Answer 13

Sex cells, e.g. Sperm and egg cells.

Question 14

What is a haploid cell?

Answer 14

A cell which contains only 23 chromosomes / one chromosome from each pair. (Half the number of chromosomes a normal cell would have).

Question 15

What happens during fertilisation?

Answer 15

1. 23 chromosomes within the mother cell pair up with 23 chromosomes from the father cell.
2. This creates a diploid zygote that is genetically varied from its parents (since it has a mix of the D.N.A).
3. The 23rd chromosome decides the gender of the baby, X + Y = Male, X + X = Female.

Question 16

How is a sperm cell adapted to its function?

Answer 16

• Many produced - increase fertilisation chances.
• Tail - to swim to egg.
• Streamlined body shape - make swimming to egg quicker and easier.
• Acrosome (tip of head) containing enzymes - to break down egg cell membrane.
• many mitochondria - produce energy for long swim.

Question 17

Describe meiosis.

Answer 17

There are 2 divisions (of x-shaped chromosome not of the cell).

1. In the first division, the single strand chromosome is copied to make an x - shaped chromosome ( 2 single strands together) - the x - shape is made of 2 single strand chromosomes with the same genes.
2. Genetic information is swapped between chromosomes.
3. In the second division, the chromosomes from each x - shaped pair split and move to the opposite poles (each corner) of the cell.
4. The cell splits into 4 new haploid cells, all genetically different from each other.