Cell Devision

Question 0

What does a chromosome consist of?

Answer 0

One coiled D.N.A molecule encased in a protective protein coat.

Question 1

What are the two types of cell division found in eukaryotic cells?

Answer 1

Mitosis and meiosis.

Question 2

What is the life cycle of a cell called?

Answer 2

The cell cycle.

Question 3

What do chromosomes form out of?

Answer 3

The chromatin found within the nucleus.

Question 4

How many chromosomes are found in humans?

Answer 4

23 identical chromosome pairs (46 in total).

Question 5

What is a diploid cell?

Answer 5

A cell containing 2n chromosomes, where “n” is the number of pairs of chromosomes found in the organism.

Question 6

Why are two identical sets of chromosomes?

Answer 6

Because the Zygote as formed through the fusion(fertilisation) of two haploid(n) gametes.

Question 7

What happens once a zygote has formed?

Answer 7

The zygote copies itself billions of times to create genetically identical clones.

Question 8

What is mitosis used for?

Answer 8

Growth and repair.

Question 9

Why do the cells of the body need to be constantly replaced?

Answer 9

Because the lifespan of the organism is about 7 times that of the individual cell.

Question 10

What is the name given to the genes responsible for controlling the lifespan of the cell and how fast the cell divides?

Answer 10

Onco genes.

Question 11

What is interphase?

Answer 11

It is the time between cell divisions in which the cell grows due to protein synthesis, produces a “store” of A.T.P and replicates its organelles.

Question 12

What happens right at the very end of interphase?

Answer 12

The chromosomes are copied resulting in a two stranded structure also called a chromosome consisting of two chromatids joined together by a centromere. By the end of interphase, D.N.A mass has doubled and 46 chromosomes become 92.

Question 13

What are the stages of cell division in chronological order?

Answer 13

Prophase
Metaphase
Anaphase
Teilophase

Question 14

Outline what happens in Prophase.

Answer 14

This begins when chromosomes become visible as a pair of chromatids held together with a centromere. In ANIMAL CELLS ONLY The centrioles then Migrate to opposite poles of the cell which then make protein fibres that grow around the nucleus and join with fibres from the other centriole. Creating a rugby ball shaped protein spindle. Finally the nucleus and nucleolus break down, releasing chromosomes into the spindle.

Question 15

What is spiralisation?

Answer 15

He process by which a chromosome coils itself to form a short, fat chromosome.

Question 16

Outline what happens in Metaphase.

Answer 16

The centrioles of each chromosome become attached to one spindle fibre, depending on weather they are attached below or above the cell’s equator they move up or down until they reach the equator and the chromosomes spin until their arms are at right angles to the spindle fibres.

Question 17

What happens during Anaphase?

Answer 17

During anaphase the protein fibres contract and the chromatids are separated. As the spindle contracts it pulls each centromere to one of the poles of the cell causing the arms of the chromosomes to form a “V” shape.

Question 18

What are the two main features of Mitosis?

Answer 18

One cell division resulting in two daughter cells. Both cells have the same chromosome number as each-other and the parent cell.

Both cells have the same combination of dominant and recessive genes I.e they are genetically identical clones.

Question 19

What are the uses of Mitosis?

Answer 19

Growth from zygote to adult

Repair of damaged or old tissues.

For A-sexual reproduction, e.g strawberry plants.

Question 20

What are the advantages and disadvantages of A-sexual reproduction?

Answer 20

Advantage - it is very fast.

Disadvantage - A lack of genetic variation.

Question 21

What are the features of Meiosis?

Answer 21

Two cell divisions (Meiosis 1 and Meiosis 2) resulting in four daughter cells.

Because there are two cell divisions the chromosome number is halved.

During prophase1 homologous chromosomes pair up and swap genetic information in the process called “crossing over”. Resulting in genetic variation.

Creates genetically individual organisms.