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HL Biology > TOPIC 1.6 > Flashcards

TOPIC 1.6 Flashcards

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1
Q

What is mitosis for?

A 
Growth
Asexual reproduction
Tissue
Embryonic development
(GATE)
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2
Q

What is a haploid

A

Half set of chromosomes

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3
Q

What is a diploid

A

Full set of chromosomes (one set from each parent)

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4
Q

What is a centromere

A

Part of chromosome which links sister chromatids

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5
Q

What are sister chromatids

A

Duplicated chromosomes attached by a centromere. When they split after anaphase, they are called chromosomes

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6
Q

What is the role of centrioles

A

To organise spindle microtubules

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7
Q

What are the phases of interphase?

A

G1, S, G2 and G0

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8
Q

What happens during G1?

A
  • increased volume in cytoplasm
  • organelles produced
  • proteins synthesised
    SA:Vo ratio decreases
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9
Q

What happens during S?

A

Cell replicates all genetic material in its nucleus, so after mitosis both new cells have complete set of genes

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10
Q

What happens during G2?

A
  • increased volume of cytoplasm
  • organelles produced
  • synthesised proteins
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11
Q

What is G0

A

A phase on interphase that occurs sometimes when the cell has left the cycle and stopped dividing. Entered after G1

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12
Q

What is the difference between chromatin, chromosome and sister chromatid?

A

Chromatin refers to the DNA complex spread out in the nucleus of a cell. When a cell is getting ready to divide and the chromatin condenses, then they are called chromosomes. When chromosomes are replicated, each chromosome is called a sister chromatid. Divide, then called chromosomes again.

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13
Q

What happens during prophase?

A
  • chromosomes are supercoiled (chromatin is condensed)
  • sister chromatids formed
  • nucleolus breaks down, as well as nuclear membrane
  • microtubules form on opposite poles of cell between centrosomes
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14
Q

What happens during interphase

A 
Preparing to divide
Mr - Metabolic reactions 
P - protein synthesis, allows cell to function 
O - organelles numbers are increased
D - DNA is replicated
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15
Q

What happens during metaphase?

A
  • Microtubules continue to grow and attach to centromeres on each chromosome (pair of sister chromatids)
  • Sister chromatids attach to microtubules from different poles so they can separate
  • Microtubules tested by shortening at centromere, if attachment is correct, chromosomes remain on an line up on equator of cell
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16
Q

What happens during anaphase?

A
  • Centromeres divide so sister chromatids can separate and be called chromosomes
  • spindle microtubules pull them to opposite poles of the cell, so genetically identical nuclei can form
17
Q

What happens during telophase?

A
  • Chromosomes pulled into MTOC so nuclear membrane can form around them
  • Chromosomes uncoil (decondense to chromatin) and nuclear membrane forms around
  • microtubule spindle fibres disappear
  • cell is dividing and daughter cells enter interphase
18
Q

What is cytokinesis?

A

The division of the cytoplasm and therefore the cell. It begins before mitosis is completed.

19
Q

How does cytokinesis take place in animal cells?

A
  • Plasma membrane is pulled inwards around equator of cell to form cleavage furrow.
  • Accomplished using ring of contractile protein inside plasma membrane at equator
  • when cleavage furrow reaches centre, cell is pinched apart
20
Q

How does cytokinesis take place in plant cells?

A
  • Vesicles from Golgi are moved to equator where they fuse to form tubular structures across
  • Structure and other vesicles merge to form two layers of plasma membrane
  • become plasma membranes of two daughter cells
  • cell plate continues to form until it meets the plasma membrane of the existing cell
  • This completes division of the cytoplasm
  • next vesicles deposit pectins by exocytosis to form middle lamella that links new cell walls
  • Both daugter cells secrete cellulose to form new adjoining walls
21
Q

What are cyclin?

A

A group of proteins with the role of ensuring that tasks are performed at the right time and the cell only moves on to the next stage of the cycle when appropriate.

22
Q

How to cyclins work?

A

They bind to cyclin dependent kinases. The kinases become active and attach phosphate groups to other proteins to become active and carry out tasks specific to one of the phases of the cycle.

23
Q

Aim of cyclin

A

Cells cannot progress to the next stage of the cell cycle unless the specific cyclin reaches it threshold.

24
Q

What is a tumour?

A

An abnormal growth of tissue

25
Q

What is cancer?

A

A malignant tumour named after the part of the body where it develops

26
Q

What is a mutation

A

A change in an organism’s genetic code which can result in cancer

27
Q

What are mutagens?

A

Agents that cause genetic mutations, not necessarily result in cancer

28
Q

What is carcinogen?

A

A mutation which causes cancer

29
Q

What is an oncogene?

A

A gene that tells cells when to stop dividing, control the cell cycle. If there is a mutation in oncogenes, this can cause uncontrolled division and tumours

30
Q

How do primary tumours develop?

A

Cancerous cells detach from primary tumour, some gain ability to penetrate. lymph/ blood vessels and circulate around the body, then invading tissues and divide uncontrollably to cause secondary tumours. This is called metastasis; the movement of cells from primary tumour to set up secondary tumours in other parts of body

31
Q

What is the evidence supporting endosymbiotic theory?

A

organelles like mitochondria and chloroplast have:

  • their own DNA (naked DNA in circular shape)
  • ribososmes similar to those in prokaryotes (70)
  • have double membrane
  • can only be produced by division of pre-existing mitochondria and chloroplasts
32
Q

Describe briefly the endosymbiotic theory

A

Suggests that the first eukaryotic cells came about when small prokaryotic cells/organisms were engulfed by larger prokaryotic cells. Instead of being consumed and digested, they smaller prokaryotic cells survived, and a symbiotic relationship was formed, in which the smaller cell provided the bigger prokaryotic cell with a characteristic that made the organism competitive in its environment, allowing the cell to reproduce and adapt with the cell it consumed as an organelle over time.

33
Q

Give an example of endosymbiotic theory

A

An aerobic prokaryote was engulfed by a larger anaerobic prokaryote. Instead of being digested, the aerobic prokaryote survived and provided the larger one with the ability to aerobically respirate, making it more competitive in its environment and forming a symbiotic relationship. The organism started reproducing by binary fission, and over time, the aerobic prokaryote became a part of the larger one. We now know this as the mitochondria.

34
Q

G0

A

Cell leaving the cell cycle, stops dividing

HL Biology (12 decks)

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