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Genes: Organisation and Function > Lecture 26 > Flashcards

Lecture 26 Flashcards

1
Q

Cells come in different forms:

A
  • Size (2 - 3cm, 200 microns)
  • Shape (highly structured, maintained by the cell wall in plants)
  • Specificity (different types for different things, in different organisms, differing levels of complexity)
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2
Q

Stem cells:

A
  • Totipotent: can differentiate into anything
  • Pluripotent: more limited, but still many possibilities
  • Blood stem cells: will turn into some form of a blood cell
  • Other stem cells: create muscle, nerves, bones etc
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3
Q

Liver regeneration:

A
  • A rat liver can regenerate itself, if part of a liver is chopped off, but will stop at a certain size so that the liver doesn’t take over the body
  • The degree of regeneration varies across the kingdom of life
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4
Q

Cell cycle:

A
  • Cell growth occurs through chromosome duplication via mitosis
  • Chromosomes duplicate, chromosomes segregate
  • Cytokenesis: cells separate
  • Interphase: the nucleus is present, gene activity and cellular metabolism
  • Prophase: chromosomes become visible
  • Prometaphase
  • Metaphase: there is little gene activity as chromosomes are condensed, chromosomes duplicate
  • Anapase: chromosomes separate
  • Telophase
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5
Q

Yeast: sachromyces cerevisiae:

A
  • Budding yeast, a new daughter cell grows from the mother cell
  • During cell division everything within the cell are duplicated (endosomes, ribosomes, nucelus etc)
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6
Q

Yeast: pombe:

A
  • Divide by fission

- Once the cell reaches a certain size a septum forms and the cells divide

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7
Q

Cell growth:

A
  • Cell growth is different from cell division
  • G1: gap phase, the beginning of the cycle
  • S: replication
  • G2: mitosis,
  • M:
  • Cell division without growth means there is no G1 or G2 phase
  • Must be an ordered process
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8
Q

Cell signals promote either cell growth or cell division:

A
  • Cell growth and cell division can occur simultaneously, separately or consecutively, depending on the signal they receive from growth factors, mitogens and external factors
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9
Q

Growth gives shape, how?

A
  • Growth in all directions are created by even growth (yeast growth)
  • Hyphal growth occurs from one end (polarised growth)
  • These two growth mechanisms can occur in different and in the same organisms (dimorphic organisms)
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10
Q

Example of mitosis (cell division) without cell growth:

A
  • In amphibians the oocyte grows without dividing until fertilization
  • After fertilisation the cell divides without growth for some time
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11
Q

Apoptosis:

A
  • Some cells are destined to die
  • The nucleus condenses and the cell is devoured by surrounding cells
  • This is a response to cell damage or normal development (ie, digit formation in the human embryo)
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12
Q

cdc mutants in S. cerevisiae:

A
  • cell cycle mutants
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13
Q

Wee-1 gene:

A
  • leads to very small cells

-

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14
Q

Cell cycle, M phase:

A
  • Mitosis is at the start and is nuclear division
  • Is all DNA replicated?
  • Is the environment stable?
  • G2/M checkpoint
  • Are all chromosomes attached to the spindle?
  • Metaphase to anaphase transition, anaphase is triggered and the cell proceeds to cytokinesis (cell division)
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15
Q

Cell cycle, G1 phase:

A
  • Is the cell cycle ready to be entered?
  • Start checkpoint
  • Is the environment favourable?
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16
Q

S phase:

A
  • Mitosis occurs, nuclear separation occurs here
17
Q

G2 phase:

A
  • At the end we went mitosis, so we check if the cell is ready to divide
  • Is the DNA properly replicted?
  • Is the environment
18
Q

The discovery of cyclins:

A
  • Cyclin’s are key molecules in the cell cycle
  • In amphibians like frogs there are huge eggs.
  • Cell division can be synchronised by synchronising fertilisation with sperm
  • ## Proteins at different levels of the cell cycle can be determines
19
Q

MFP:

A
  • Mitosis promoting factor
  • A cyclin plus cyclin dependent kinase
  • This protein activity peaks at cell division in the middle of mitosis- This can be added to cells to stimulate mitosis
20
Q

Cyclins:

A
  • Proteins that are synthesised and degraded throughout the cell cycle
  • Cyclin is a kinase dependent on the presence of Cdk
  • Cdk enzymes are inactive until bound by a cyclin, Cdk-activation kinase (CAK) makes it fully active by phosphorylation
  • Activity is regulated by the presence of cyclins
21
Q

The activity of Cdks is dependent on what?

A
  • The activity and specificity of Cdk is dependent on what type of cylin has phosphorylated the Cdk enzyme
  • Different stages of the cell cycle have different cyclins present, so a different substrate protein acts at each state

Genes: Organisation and Function (33 decks)

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