Unit 1 section 3: The cell Cycle and mitosis

Question 1

The cell cycle

Answer 1

The process all multi-cellular organisms use to grow.

Consists of Cell growth and DNA replication (interphase) and cell division (Mitosis)

Question 2

interphase

Answer 2

sub-divided into three growth stages: G1,S & G2
Gap phase 1 : Cell grows and new organelle and proteins are made
Synthesis : Cell Replicates it’s DNA and Checks for mutations ( If there are mutations the cell may kill itself to prevent mutations being passed on)
Gap Phase 2 : Cell keeps growing and proteins made for cell division are made.

During interphase normal cell functions are carried out as well as preparations to divide. The DNA is unravelled and replicated. ATP content is increased.

Question 3

Mitosis

Answer 3

needed for the growth of multicellular organisms an for repairing damaged tissue. One continuous process described as series of divisions:
Prophase
Metaphase
Anaphase 
Telophase.

Question 4

Chromosomes in mitostis

Answer 4

*initially the chromosomes are two Strands (chromatids) joined in the middle by a centromere. each of the strands are called Sister chromatids. there are two strands as each chromosome has already made a copy of itself during interphase. when mitosis has finished the chromatids end up as one stranded chromosomes in the new daughter cells.

Question 5

Order of mitosis

Answer 5

Prophase
Metaphase
Anaphase
Telophase

(PMAT or Purple Mice Are Tasty)

Question 6

1. Prophase

Answer 6

• chromosomes condense getting shorter and fatter
• Centrioles start moving towards opposite ends of the cell, forming a network of Protein (spindle) fibres between them
• The nuclear envelope Breaks down leaving chromosomes freein the cytoplasm

Question 7

2.Metaphase

Answer 7

The chromosomes line up along the middle of the cell at the spindle equator and become attached to the spindle by their centromere

Question 8

3. Anaphase

Answer 8

• The centromers divide separating each pair of sister chromatids
• the spindles contract pulling chromatids to opposite ends of the cell

Question 9

4. Telophase

Answer 9

• once the chromatids reach opposite poles they uncoil becoming long and thin again (now called chromosomes)
  *a nuclear envelope forms around each group of chromosomes (now have two nuclei)
  *The cell membrane constricts, pinching and splitting the cell into two daughter cells (process of Cytokinesis)
  The daughter cells are genetically identical to the original cell and each other.

Question 10

mitosis in plants

Answer 10

is similar to in animals with a few differences:

• in plants only cells in the meristem can divide by mitosis
• Plant cells don’t have centrioles so the spindle formed during prophase forms without them
• Cytokinesis begins in the cenre of a plant cell, with a cell plate. the cell wall forms in the centre and moves outwards until they meet the perimeter

Question 11

cell plate

Answer 11

a double membrane which secretes materials needed to make two cell walls.