Unit 4: Genetics and Inheritance

mitosis, meiosis, cyclins

mitosis- interphase

• G1 phase is cell growth

• S phase is DNA synthesis

• G2 phase is further cell growth

• interrupted by mitosis and cytokinesis

• cells that do not reproduce remain in G0

these phases are controlled by cyclins

mitosis- prophase

chromosomes visible, unordered

mitosis- metaphase

chromosomes separating

mitosis- anaphase

chromosomes line up and are drawn to poles by spindle fibres

mitosis- telophase

chromosomes grouped in two at poles of cell

mitosis- cytokinesis

cell splits in two by closing off membrane down cleavage, chromosomes less distinct as they uncoil, returns to interphae

cytokinesis in animal cell

ends not touching

cytokinesis in plant cell

ends touching

cyclins

proteins that contribute to the regulation of the cell cycle. They reach a threshold concentration and prevent reproduction of cell until needed.

• C gradually increases and decreases across the cell cycle

• E triggers G1 → S

• A triggers S → G2

• B triggers G2 → mitosis

Cyclin Dependent Kinases (CDKs)

• phosphorylate other proteins, activating them to carry out specific tasks

• Apoptosis- if a cell fails a checkpoint during Interphase or Mitosis, it self destructs

substrate — (kinases) → substrate P

phosphofructokinase (enzyme)

histone proteins

basic proteins: their positive charges allow them to associate with DNA, which is negatively charged. Some function as spools for the thread-like DNA to wrap around.

tumours