Cell Cycle and Cell Division

Question 1

What is genetic information carried in the form of?

Answer 1

Genes

Question 2

What is a gene?

Answer 2

A section of DNA coding for one polypeptide

Question 3

What is a chromosome?

Answer 3

It is an independent DNA molecule which has been supercoiled into a condensed form. Chromosomes contain many different genes

Question 4

What happens during semi-conservative replication?

Answer 4

. Two genetically identical copies of the DNA molecules are made
. They remain attached at a central point called the centromere
. Each copy of DNA supercoils (using histone proteins to help them fold)
. While they are still joined the two DNA molecules are called ‘sister chromatids’
. The whole structure is the chromosome

Question 5

What is the chromosome number?

Answer 5

It is the number of chromosomes possessed by an organism and is represented a ‘n’

Question 6

What is a diploid cell?

Answer 6

They have their chromosomes in homologous pairs

Question 7

How is the number of homologous pairs of a chromosomes represented?

Answer 7

2n - 2 x The number of chromosomes possessed by an organism

Question 8

What is a haploid cell?

Answer 8

They have one copy of each chromosome and are gametes

Question 9

Why is it important gametes are haploid?

Answer 9

It restores the chromosome number when gametes fuse to make a zygote

Question 10

What is the loci of a gene?

Answer 10

The location of the gene on the chromosome

Question 11

What is an allele?

Answer 11

The variant form of a gene (e.g. Alelle for blue eyes and the allele for brown eyes)

Question 12

What are the stages of the cell cycle?

Answer 12

I - Interphase
P - Prophase
M - Metaphase
A - Anaphase
T - Telophase
C - Cytokinesis

Question 13

What happens during interphase?

Answer 13

Cell spends the majority of it’s time in interphase so during this time the cell performs it’s normal function.
At G1 phase the cell increases in size and a new biomass is made
At S phase the DNA replicates
At G2 phase the cell gets ready for division, it makes stores of ATP and new organelles

Question 14

What is nuclear divison?

Answer 14

The period when the nucleus divides into two

Question 15

What happens during prophase?

Answer 15

The chromosomes supercoil and become visable

Question 16

What happens during metaphase?

Answer 16

Chromosomes line up at the equator of the cell

Question 17

What happens during anaphase?

Answer 17

Spindle fibres get shorter and the centromere splits. The identical chromatids seperate

Question 18

What happens during telophase?

Answer 18

Two nuclei form

Question 19

What happens during cytokinesis?

Answer 19

The cell divides into two, each daughter cell receiving one of the nuclei

Question 20

What is mitosis used for?

Answer 20

. Increasing cell numbers and growth of an organism
. Repair of damaged tissue
. Replacement of dead cells

Question 21

What is produced in mitosis?

Answer 21

Two genetically identical daughter cells

Question 22

What is the definition of cancer?

Answer 22

Cells that undergo uncontrolled mitosis and from tumours that spread into the tissue

Question 23

What is one method used to treat cancer?

Answer 23

Drugs that can stop cell division

These drugs could stop: DNA replication, spindle formation, cytokinesus or other processess linked to mitosis

Question 24

How do prokaryotes reproduce?

Answer 24

Asexually through binary fission

Question 25

What does binary fission in bacteria involve?

Answer 25

. The DNA (which is often attached to a fold at a fold of the cell membrane) must be replicated before cell division
. The cell elongates, separating the DNA
. A new cell wall is formed down the middle which eventually meets, dividing the cell into two

Question 26

How do virus’ reproduce?

Answer 26

They cannot undergo cell division, however they reproduce inside host cells

Question 27

What is the first step in viral replication?

Answer 27

The protein molecules on the capsid attach to the cell surface membrane of the host cell

Question 28

What is the second step in viral reproduction?

Answer 28

The virus enters the cell

Question 29

What is the third step in viral reproduction?

Answer 29

The viruses DNA in encorporated into the host cells DNA

Question 30

What is the fourth step in viral reproduction?

Answer 30

The viral DNA is transcribed and translated into proteins

Question 31

What is the fifth step in viral reproduction?

Answer 31

The cell copies the viral DNA

Question 32

What is the sixth step in viral reproduction?

Answer 32

The genetic material and proteins coats are assembled into virions

Question 33

What is the seventh step in viral reproduction?

Answer 33

Eventually these virions burst out of the cell, destroying the host cell

Question 34

What kind of cells are produced through meiosis?

Answer 34

Four genetically different daughter cells, that are haploid gametes

Question 35

Why is meiosis important?

Answer 35

Without meiosis gametes would have 2n and when two gametes fuse they would form a cell with 4n, double that of a normal organsim

Question 36

What is the process of meiosis

Answer 36

The chromosomes go through two divisions
In the first meiotic division, the homologous chromosomes pair up and are separated
In the second division, the chromatids are separated

Question 37

Random fertilisation

Answer 37

Haploid gametes produced by meiosis cause variation in a population

Question 38

Crossing over

Answer 38

During prophase and metaphase of the first division:
1. The homologous pairs associate (Bivalent)
2. Chiamata form
3. Equal lengths of chromatids are exchanged
4. Producing new alleles
All the cells at the end are genetically different

Question 39

Independent segregation

Answer 39

During metaphase of the first division, the homologous chromosomes attach to the spindle fibres and they pair up and are reshuffled in any combination
To calculate the number of different combinations of chromosomes use 2^n