B3 Cell Division

Question 1

B3.1 The Cell Cycle : Chromosomes GN

Answer 1

-Each cell has 23 pairs of chromosomes in the nucleus
-They are coiled up lengths of DNA
-The X and Y chromosome determines your sex
-Each chromosome carries a larger number of genes which control all characteristics about a persons physical characteristics

Question 2

B3.1 The Cell Cycle : Stages of the cell cycle

Answer 2

1) The cell grows bigger
=> DNA replicates (Chromosomes turn into the X shape as they duplicate)
=> Increase of sub-cellular structures (ribosomes and mitochondria)
2) Mitosis
=> A complete set of chromosomes go to each pole of the cell
=> nucleus divides
3) Cytoplasm and cell membrane divide
=> Two identical daughter cells formed

Question 3

B3.1 The Cell Cycle : Mitosis

Answer 3

-Chromosomes line up at centre of cell
-Cell fibres pull each arm (duplicated part of X chromosome)
-The arms go to opposite poles of the cell
-New nuclei formed around the chromosomes
-cytoplasm and cell membrane divide

Binary Fission V.Similar, but far quicker

Question 4

B3.3 Stem Cells : Stem Cell def

Answer 4

A stem cell is an undifferentiated cell that can develop into one or more types of specialised cell.

Question 5

B3.1 The Cell Cycle : Adult Stem Cells GN

Answer 5

-Found in the bone marrow
-Can only differentiate to form certain types of cell (bone marrow stem cells can only differentiate into different blood cells)

Question 6

B3.1 The Cell Cycle : Adult Stem Cells uses in medicine

Answer 6

ADVANTAGES
-Fewer ethical issues (adults can consent)
-Established technique for treating diseases such as leukaemia
-Relatively safe treatment & donors recover quickly
DISADVTAGES
-Requires a donor
-Can only differentiate into a few cells => less possible treatments using

Question 7

B3.1 The Cell Cycle : Embryonic Stem Cells GN

Answer 7

-Early human embryos (entirely stem cells)
-Taken from spare embryos from fertility clinics
-Can differentiate into any type of specialised cell