B3D- Cell Division

Question 1

When do cells divide?

Answer 1

Whenever the body needs to grow , replace worn out cells and to repair damaged tissue.

Question 2

What is a unicellular organism ?

Answer 2

When its whole body is a single cell.

Question 3

What asexual reproduction?

Answer 3

To reproduce the cell just divides to form two new cells.

Question 4

What is multicellular?

Answer 4

Organisms that can grow large

Question 5

What is cell differentiation?

Answer 5

When cells become different shape or sizes to carry out specialised jobs.

Question 6

What are homologous pairs ?

Answer 6

The chromosomes in a pair that look the same and carry similar information.

Question 7

When a cell has pairs of chromosome what is it called?

Answer 7

A diploid cell

Question 8

What type of cell division makes new cells during growth?

Answer 8

Mitosis

Question 9

Describe the process of mitosis and chromosomes

Answer 9

First the cell is resting
Then each chromosome is copied, the single strand forms a double stranded ‘x’ shape
Next spindle forms, chromosomes are arranged along the equator
The chromosome single strand move to poles of the cell
Then two genetically identical cells are produced

Question 10

Describe DNA replication

Answer 10

When DNA replicates, the base pairs separate and the strand ‘unzips’ to form two single strands
Then new bases pair up with their complementary base to form two new double strands
The cross links DNA are formed from four bases called a, t, c and g. Base a always links with base t. Base c always links with base g

Question 11

Describe sexual reproduction

Answer 11

Eggs or sperm are called sex cells or reproductive gametes. Gametes join during fertilisation.To increase the chance of one sperm reaching the egg a male releases millions of sperm at a time.
The gametes have half the number of chromosomes of a body cell.so when they join the new cell has the full number of chromosomes.
The individual that develops from the cell will have inherited genes from big parents. This means they have their own unique set of genes.

Question 12

What is a haploid ?

Answer 12

When gametes have half a set of chromosomes.

Question 13

What is a zygote?

Answer 13

When gametes join to form a zygote- which is diploid and can develop into an embryo

Question 14

What is meiosis?

Answer 14

A special type of cell division that produces gametes

Question 15

How are sperm adapted to travel a long way to get inside an egg?

Answer 15

It has large numbers of mitochondria to release energy for motion
A structure called an acrosome on the sperm head releases enzymes that digest the cell membrane of an egg allowing the sperm inside.

Question 16

Describe the process of meiosis

Answer 16

1- homologous chromosomes pair up
2- one from each pair moves to each pole
3- the strand of each chromosome are pulled apart to opposite poles
4- four new haploid cells form, all genetically different from each other