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A level biology - Edexcel > Topic 6 > Flashcards

Topic 6 Flashcards

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1
Q

DNA Profiling - stages

A
  1. tissue sample obtained + DNA extracted
  2. (not enough DNA - PCR)
  3. fragments of different lengths created but cutting up DNA
  4. fragments separated and visualised
  5. DNA profile compared w/ another
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2
Q

Obtaining DNA - process

A
  1. tissue sample broken down in buffer solution to disrupt membranes
  2. filtering/ centrifuging - small suspended particles separated
  3. protease added - removes proteins
  4. cold ethanol added to precipitate out DNA
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3
Q

Polymerase Chain Reaction - process

A
  1. DNA sample placed in reaction tube w/ DNA polymerase, DNA primers and nucleotides
  2. cycle of temperature changes
    • 95 - separate DNA strands
    • 55 - primers attach at start of STR
    • 70 - DNA adjacent replicated
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4
Q

Creating DNA Fragments - process

A
  1. add restriction enzymes (endonucleus)
  2. recognise specific DNA sequence
  3. cuts section out
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5
Q

Separating DNA Fragments - process

A

Gel Electrophoresis

  • DNA placed in arose in buffer
  • connected to electrodes
  • neg charged fragments migrate through gel
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6
Q

Visualising Fragments - how?

A

Southern Blotting

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7
Q

Uses of DNA Profiling

A
  • identification
  • paternity disputes
  • evolutionary relationships
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8
Q

Time of Death - stages

A
  1. Temperature
  2. Degree of Rigor Mortis
  3. State of Decomposition
  4. Entomological Evidence - insects
  5. Stage of Succesion
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9
Q

Temperature - death

A
  • cools due to lack of chemical reactions

- rate varies due to , body size/position, clothing, in water

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10
Q

Rigor Mortis - process

A
  • muscles starved of O2 - anaerobic resp - lactic acid
  • pH cell falls - inhibiting enzymes
  • ATP production stops + bonds btwn muscle proteins fix
  • muscles can’t contract or relax - become fixed
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11
Q

Decomposition - time of death

A
  1. autolysis occurs (enzymes break down tissues)
  2. bacteria from gut and gas exchange system invade tissue
  3. anaerobic bacteria grow
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12
Q

Signs of Decomposition

A
  • greenish lower abdomen
  • gas/liquid blisters on skin
  • body bloated + smelly
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13
Q

Forensic Entomology

A
  • take samples of insects in/around the body

- see what stage of growth/ development they’re in

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14
Q

Succession on Corpses

A
  • different insects colonise the body at different times

- can also determine if body been moved

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15
Q

Humoral Response – process

A
  1. antigen presenting cell produced (phagocytosis)
  2. T-helper cell binds to APC and releases cytokine
  3. B-cell (which has already bound to antigen) activated
  4. proliferation
  5. memory cells and B-effector/ plasma cells produced
    • plasma cells produce non-cell bound antibodies and so destroy complementary antigens
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16
Q

Cell Mediated Response – process

A
  1. antigen presenting cell produced (phagocytosis)
  2. T-helper cell binds to APC and releases cytokine
  3. T-cell (which has already bound to antigen) activated
  4. proliferation
  5. T-memory and T-killer cells produced
    • T-killer cells cause lysis to occur in any cells carrying specific antigen
17
Q

HIV attacking T-helper cells

A

HIV binds w/ CD4 receptors on T-helper cell and then fuses with it - its RNA then enters the cell

18
Q

HIV replication in T-helper cell - process

A
  1. Reverse normal transcription and make DNA from RNA template (use reverse transcriptase)
  2. HIV DNA strand integrated into hosts DNA by HIV enzyme integrase
  3. It can then be transcribes + translated to make new virus proteins
19
Q

AIDS - phases

A
  1. ACUTE phase
    • HIV antibodies appear in blood (3-12 weeks)
    • flue like symptoms
    • rapid replication of hiv and loss of T-helper cells
  2. CHRONIC phase
    - no symptoms - however easily infected by other illnesses
  3. DISEASE PHASE
    • very low no. T-helper cells
    • high chance of opportunistic infections
20
Q

Types of Antibiotic

A

BACTERIOCIDAL - kill bacteria

BACTERIOSTATIC - prevent multiplication then destroyed

21
Q

Ways antibiotics disrupt bacteria growth (5)

A
  1. inhibition of cell wall synthesis = lysis
  2. disruption of cell membranes = lysis
  3. inhibition of nucleic acid synthesis, replication and translation = prevents division/ synthesis of enzymes
  4. inhibition of protein synthesis = essencial proteins not produced
  5. inhibition of specific enzymes found in bac cell

A level biology - Edexcel (9 decks)

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