Cell Cycles

Question 1

What is mitosis ?

Answer 1

Produces 2 cells
Each cell is genetically identical
Occurs during growth, repair of cells and asexual reproduction
Each cell has the same number of chromosomes as the original

Question 2

What are homologous chromosomes ?

Answer 2

A pair of replicated chromosomes

Question 3

What is the cell cycle?

Answer 3

Interphase - Cell growth
Nuclear division
Cytokinesis

Question 4

What is interphase

Answer 4

-DNA content doubles via DNA replication
-Increased protein synthesis
- Cell organelles are replicated and mitochondria and ATP content is increased as cell division is an active process
- Longest time period of the cell cycle

Question 5

Prophase - Mitosis

Answer 5

• Chromosomes are made up of 2 sister chromatids joined by a centromere
• The chromosomes condense - shorten and thicken
• Centrioles move to opposite poles
• The nucleolus and the nuclear membrane disintegrates
  ->this allows the chromosomes to move freely

Question 6

Metaphase - Mitosis

Answer 6

Centrioles form spindles across the cell
Chromosomes line up at the equator of the spindle and attaches via its centromere
Sister chromatids are orientated at opposite poles of the cell

Question 7

Anaphase - Mitosis

Answer 7

The centromere splits and the sister chromatids separate
The separated sister chromatids (now called chromosomes) are pulled to opposite poles by the spindle fibres

Question 8

Telophase - Mitosis

Answer 8

-The chromosomes arrive at opposite poles of the cell and begin to uncoil
-The nuclear membrane begins to reform around each set of chromosomes and the spindle fibres break down
Cytokinesis begins

Question 9

Cytokinesis

Answer 9

The cytoplasm splits into 2
2 new genetically identical daughter cells are formed

Question 10

Evidence for the stages of mitosis
Interphase

Answer 10

-Chromosomes are not visible - only
chromatin threads
- Nuclear membrane and nucleolus still present

Question 11

Evidence for the stages of mitosis : Prophase

Answer 11

Chromosomes are still visible

Question 12

Evidence for the stages of mitosis: Metaphase

Answer 12

All chromosomes are in the middle of the cell

Question 13

Evidence for the stages of mitosis : Anaphase

Answer 13

There are a set of chromatids on both cells of the cell

Question 14

Evidence for the states of mitosis: Telophase

Answer 14

2 Cells appearing
2 Nuclei visible

Question 15

What is binary fission

Answer 15

A process prokaryotes use to reproduce
Asexual reproduction
One cell divides —> 2 daughter cells
- replication of the circular DNA and plasmids
- division of the cytoplasm to produce 2 daughter cells, each with a single copy of the circular DNA and a variable number of copies of plasmids

Question 16

Steps of binary fission

Answer 16

Parent cell elongates and dna is replicated
Cell wall and plasma membrane begin to divide
Cross wall forms commended around divided DNA
Cells separate

Question 17

Generation time

Answer 17

time taken for a bacterial population to double
Population in the nth generation = 2^n

Question 18

Steps of Viral Replication

Answer 18

1) The virus attaches to attachment protein using complementary receptors in the cell surface membrane of the host cell
2) The virus injects their DNA or RNA into the host cell
3) The host cell uses the viral nucleus acids to produce viral proteins
4) Viral proteins assemble to produce viral particles which are released from the host cell