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A Level Biology > Topic 6 > Flashcards

Topic 6 Flashcards

1
Q

What does DNA profiling rely on

A

The fact that everyone’s DNA bar twins is unique

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2
Q

What are introns

A

They are non-coding blocks and are inherited in the same way as genes

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3
Q

What do introns contain

A

They contain STR satellites that are repeated several times

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4
Q

Although the same str occur at the same loci on both chromosomes of a homologous pair how do they differ

A

They differ in the number of times they are repeated

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5
Q

Why is the variation in the number of repeats of str on a loci good

A

Scientists use this to create unique DNA profiles

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6
Q

Gives the steps in obtaining a Tissue sample

A

A sample of DNA is collected from biological tissue i.e. Blood smear

The tissue sample is broken using a buffet solution that contains a salt and detergent the cell memebranes are disrupted

The DNA is separated from the rear of the cell debris by flirtation and centrifuging

Proteins are removed due the fact that protease enzymes are incubated and cold ethanol is used to precipitate the DNA

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7
Q

What two ways can be used in creating DNA fragments

A

Restriction enzymes or Polymerase chain reaction

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8
Q

Where do restriction enzymes come from

A

They are found in bacteria and its name is reflected by the bacteria it comes from

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9
Q

What do restriction enzymes do

A

They cut DNA at specific recognition sites at either side of the DNA which means the fragment is intact but cut from the rest of the genome

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10
Q

When do restriction enzymes cut a DNA sample

A

When their specific restriction sequence occurs

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11
Q

What are DNA primers

A

They are DNA sequences that contain fluorescent tags and are complementary to the DNA adjacent to the str

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12
Q

Describe the steps of PCR

A

A the DNA from a sample along with DNA polymerase, DNA primers with markers and nucleotides are added to a reaction tube

At 95 degrees the DNA separates into two strands

At 55 the DNA primers attach to the start of the str repeated sequence on each strand

At 70 DNA polymerase attach the two nucleotides together which extends the extend the DNA from the primer and the str repeated sequence along with the DNA adjacent are replicated DNA polymerase is attached

This cycle repeats its self producing a large number of DNA fragments

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13
Q

What method is used to separate the DNA fragments

A

Gel electrophoresis or southern blotting

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14
Q

What technique is used to separate DNA fragments

A

Gel electrophoresis Its done accordance to size

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15
Q

Describe what occurs in gel electrophoresis

A

The DNA fragments are placed in a gel of garose or polyacrylamide

The gel has electrodes connected to it and it produces a Pd across it and it’s placed in a buffer solution

The DNA fragments are negative charged and move through the gel in accordance to size and charge, so smaller sequences travel to the positive electrode faster

Fragments are measured in base pairs

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16
Q

What technique is used to visualise fragments

A

Southern blotting or

Gel electrophoresis

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17
Q

What is southern blotting used for

A

To transfer DNA fragments to a more resilient nylon membrane as gel is to fragile

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18
Q

Describe stages in southern blotting and when it’s used

A

After restriction enzymes

The membrane and dry absorber paper are place on the gel directly to draw the buffer solution up alive with DNA fragments denatures strands from double to single

  1. The membrane is incubated with excess of labelled DNA probe (either radioactive or fluroescent
  2. to visualise with a radioactive probe, the membrane is dried first and placed to an X ray film,if the probe has bound with DNA, the film go black

If the probe is fluorescent,the postion on the membrane is visualised under uv light

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19
Q

In southern blotting what is the DNA probe and what does it do

A

It’s a short DNA section complementary to the base sequence of target DNA and they are either radioactive or labelled with fluorescent marker

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20
Q

In a DNA profile why does a single bond occur

A

When a persons maternal and paternal chromosome have the same number of stars in a certain locus

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21
Q

When do 2 bands occur on a DNA profile

A

If the two chromsomes have a different number of repeats at a locus

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22
Q

In visualising DNA when do we use gel electroresis

A

After PCR

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23
Q

Describe the stages in Gel electrophoresis in analysing DNA fragments

A

The DNA primers have fluorescent tags

The DNA fragments with their tags pass through a laser in the gel,this causes the the dye in the tags to fluoresce and the coloured light is detected

This gives a time taken fragments to pass through the gel and the time length can be calibrated with the fragment size

Str loci can be analysed by using the tags that fluroresce at different wavelengths as they give different colours for each str loci

A computer processes this info from the sector and displays the results of this on s graph

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24
Q

What determines the size of the fragment t

A

Number of base pairs

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25
Q

How is time of death measured

A

Using temperature of the body

State of decomposition

Degree of rigor mortis

Entomology

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26
Q

How can body temperature be used to determine time of death and how is it measured

A

When the body dies it cools as their is no more heat being produced by chemical reactions

An abdominal stab or measuring via rectum is how core body temp is measured

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27
Q

Why isnt a normal clincal thermometer used

A

It’s to short and has too small temperature range

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28
Q

What factors affect post mortem cooling

A

Clothing -reduces heat loss as it insulates the body
Body postion -curled up would reduce heat lose
Air movement -cools the body down faster
Body size
Humidity
Temperature of surroundings
Water

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29
Q

What is rigor mortis

A

The stiffening of muscles,with joints becoming fixed

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30
Q

What happens after RM

A

It passes and muscles relax again

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31
Q

Name the stages of Rigor mortis

A
  1. after death,muscle cells become deprived of oxygen and oxygen dependent reactions stop
  2. Anaerobic respiration occurs in cells and lactic acid is produced
  3. the ph in cells drop,which inhitbs enzymes and so anaerobic respiration is inhibited
  4. ATP is no longer produced and its needed for muscle production, this results in the bonds between muscles proteins becoming fixed
  5. The proteins can no longer shorten muscle as they can’t move over one another,it means muscle and joints are now fixed
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32
Q

How long does rigor mortis normally take and what muscle stiffen first

A

It lasts 6-9 hours and smaller muscles stiffen first

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33
Q

What are the first stages of decomposition

A

Autolysis occurs first which is when cells are broken down by the body’s own enzymes,from lysosomes

After death tissues are invaded by bacteria from the gut,the release of enzymes result in decomposition

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34
Q

What are the stages and signs of decomposition

A

The greenish discolouration in the lower abodonm,it’s caused by sulfhaemoglobin occurring in the blood and it spreads and chanted colour from purple to black

The formation of Co2,NH4,H,CH4,H2S in tissues and intestines causes the body to smell and become bloated

The body will deflate due to the tissues further decomposing and gases being released

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35
Q

How can autolysis be delayed

A

If the heat is to intense as enzymes involved are denatured

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36
Q

What are antigens

A

Molecules that are recognised by the hosts immune system and they are recognised as foreign

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37
Q

Give the differences between viruses and bacteria

A

Bacteria are prokaryotes
And they don’t have any memebranes bound organelles

And they reproduce via binary fissions,so they divide into two

Bacteria have double strand DNA virus have single

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38
Q

In bacteria what is the cell wall made from and give the two types of cell wall

A

It’s made from a polysaccharide called protideoylycan which is crossed linked by peptide bonds

Two types are gram positive cell wall and gram negative cell wall

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39
Q

Distinguish between gram positive and gram negative cell wall

A

Gram postive cell wall have thicked walls as they have additional proteins and polysaccharides that are cross linked

Gram negative have thinner walls and a surface layer of proteins and lipids from protection

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40
Q

How do viruses replicate

A

They enter the the cells of the host and uses its metabolic system to make more viruses

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41
Q

Describe the stages of viral infection

A

Viruse attaches to the host of the cell

It’s nucleic acid is inserted into the cell

The viral nucleic acid replicates

Viral protein coats synthesis

New virus particles are formed

Cell lysis releases the virus particles

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42
Q

What is lysis

A

The bursting of a cell

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43
Q

What are pathogens

A

Bacteria and viruses that cause disease

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44
Q

Give examples of barriers in the our body that help prevent infection

A

Stomach acid
Skin
Lysozyme
Gut and skin flora

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45
Q

In what ways does the skin act as a barrier in protection from infection

A

It contains keratin which is a protein and it’s a hard outer layer that stops entry of microorganisms

Blood clots form if the skin is broken,wounded so it seals the wound so no microorganisms and enter

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46
Q

How does gut and skin flora provide protection

A

Flora are harmless microorganisms found in skin and the gut and they compete with pathogens for nutrients and space so they limit they amount of pathogens that can grow

They are produced by lactic acid

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47
Q

How do mucous membranes protect us

A

They are produced by goblet fells and trap any particles and microbes that are carried away by beating clia to be swallowed

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48
Q

How does lysozyme protect us

A

They are produced in our eyes,mouth nose

They damage the bacterial cell walls causing it to burst which kills it

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49
Q

What are the two responses that the immune system produces

A

Non specific response

Specific response

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50
Q

Distinguish between the non specific and specific response

A

Non specific helps in destroying any invading pathogen

Sordid response is directed at a specific pathogen

52
Q

Give the 4 ways that the non specific immune system responds to infection

A

Lysozyme
Inflammation
Phagocytosis
Interferon

53
Q

When does the inflammatory response occur

A

When we receive a cut to the body

54
Q

Describe the inflammatory response

A

Histamines are released by damaged mast cells

They cause dilation of arterioles in the area and they cause increased permeability of the capillary walls so this results in increase in blood flow to the capillaries at the infected site and the white blood cells in the blood at the time act and destroy the pathogen

55
Q

What is a problem with histamines and the inflammatory response

A

They can cause swelling in tissues like odema due to the fact histamines increase permeability in capillary wallls

56
Q

What happens in phagocytosis

A

When white blood cells engulf bacteria and other foreign in blood and tissues these white blood cells are called phagocytes

The ingested material is enclosed within a vacuole the vacuole fuses with lysosomes which release digestive enzymes which destroy bacteria or foreign material

57
Q

Name the 3 types of white blood cells

A

Neutrophils
Lymphocytes
Monocytes

58
Q

What are neutrophils

A

They last only a few day

Ingest and destroy bacteria

59
Q

What are the two types of lymphocytes and what are they involved in

A

B cells and T cells

They are involved in the immune response i.e. Immunity

60
Q

What are monocytes and what are their roles

A

They become macrophages which engulf bacteria and cell debris and foreign matter

61
Q

What are lymphocytes

A

White blood cells involved in the specfic immune response they help defend against specfic diseases

62
Q

What’s the role of the lymphatic system

A

They help in preventing the spread of bacteria, macrophages are present in lymph nodes

63
Q

Describe the stages that occur when preventing the spread of infection in the non specfic immune system

A

Tissue fluid is drained into lymphatic vessels

The fluid known as lymph flows along these lymph nodes and its passes through them via thoracicducts and lymphatic as it returns to the blood

As lymph passes through lymph nodes lymphocytes and macrophages become activated if any pathogens are present and they destroy it

64
Q

What is interferon and what is its role

A

It’s and antimicrobial protein

It produced by cells that are infected with viruses and diffuses to other cells to prevent spread of infection

It inhibits viral proteins synthesis but has side effects

65
Q

What are B cells covered in and where are they produced

A

They are covered in proteins called antibodies and they are produced in bone marrow

66
Q

Once activated what occurs with the B cells

A

Antibodies are secreted by a B cell when it’s activated

They bind onto antigens and label them which enables phagocytes to recognise and destroy the cell

67
Q

Give the stages that in phagocytosis

A

Neutrophils arrive and they engulf bacteria and they become inactive

Macrophages are next and they destroy 100 bacteria by phagocytosis they ingest debris from damaged cells along with any foreign matter

The ingest material is enclosed within a vacuole and it fuses with lysosomes which released digestive enzymes which destroy bacteria

Pus forms as a result due to the area being now filled with dead cells

68
Q

What do T cells contain and where they are produced

A

In the bone marrow and they contain a specific antigen receptor which binds to an antigen with a complementary shape

69
Q

What are the two types of T helper cells

A

T helper cells

T killer cells

70
Q

What are t helper cells

A

They stimulate B cells to divide and they become capable of producing antibodies and they inhance phagocytes activity and they contain cd4 receptors

71
Q

What are t killer cells

A

Any cell that has a foreign antigen is killed by these cells

72
Q

Describe the process in the activation of t helper cells in the primary immune response

A

Once a macrophage engulfs a pathogen they present themselves as a antigen presenting cell

This acts as s signal to the immune system m

The CD4 receptor on a t helper cell bind on to the antigen in the APCs

And this binding activates the t helper cells causing them to divide and produce a clone of active T cells and a clone memory cell

These clones remain in the body for years meaning they can react faster if the same antigen is occurs again

73
Q

What are the two types of B cells

A

B memory cells

B effector cells

74
Q

Describe the stages of clonal selection and what are the two things are produced

A

B cells become APCs

They bind with active t helper cells

This binding results in the releasing of cytokines by t helper cells

These chemicals stimulate division and differentiation of B cells into B memory and b effector cells

75
Q

What are B effector and B memory cells ( part of primary immune response)

A

B effector cells -they differntiate to produce plasma cells and these release antibodies into lymph and blood last for a few days

B memory cells- they remain for years in the body which allows individuals to respond more quickly to the same antigen

76
Q

Describe the stages in t killer cells activation and state their role

A

B cell is infected with bacterium and it becomes and antigen presenting cell and a t killer cell with a complementary receptor binds on to it

This binding causes the T cells to divide into t killer and t memory cells cytokines helps in this reaction

They cause pores to occur in infected cell membranes by releasing enzymes to create these pores this causes lysis
Which causes the pathogen to
Be released which means it can be labelled by antibodies from B cells

77
Q

When does the secondary immune response occur

A

When the same bacterium arrives again and the response occurs faster and it involves memory cells

78
Q

Give symptoms of the disease tb

A

Shortness of breath
Loss of appiette and weight

Fever and fatigue

Coughing

79
Q

In the primary response to Tb how does the immune system respond and what is formed

A

Macrophages engulf the bacteria and a granuloma forms

The conditions in the tissue mass anaerobic and they contain dead bacteria and macrophages

This controls the infection

80
Q

How can bacteria survive from the attacks of the immune system (tb)

A

They contain thick waxy cell walls which are hard to break down and it means they can lay dormant for years in the tubercules

81
Q

What is latent tb

A

When a person has inactive form of tb

82
Q

State the ways active tb may form

A

Mulnutrition
Old age
Aids
Poor living conditions

83
Q

What does active tb do

A

The bacteria multiply rapidly and destroy lung tissue creating holes in in the lung

84
Q

State how a fever occurs

A

An inflammatory response in which substances are released by neutrophils and macrophages these chemical cause our hypothalamus to alter our core body temperature to a higher temperature in which effectors warm up the body to a new point

85
Q

What are the benefits of the raised temperatures

A

It enhances immune function and phagocytosis

The bacteria and viruses reproduce at at a slower rate at high temperatures

86
Q

Give two ways to tb can be diagnosed

A

Skin and blood tests

87
Q

How does skin testing work for tb

A

A small amount of tuberculin is injected into a person

A positive result will show an inflamed area of skin around the injection site,this caused by antibodies indicating the presence of Tb antigens

88
Q

How can HIV be spread

A

Via sex
Bodily fluid salvia,
Sperm

89
Q

State the parts of a HIV virus

A

Glycoproteins pg 120
Viral proteins,which contain reverse transcriptase and integrase

Capside molecules made of protein United

Layer of viral proteins

90
Q

State how HIV viruses invade our cells

A

Gp 120 binds onto the CD4 receptor on a t helper cell surface

The virus fuses with the CSM membrane of the t helper which allows virus RNA and enzymes to enter the cell

Once inside the cell reverse transcriptase is used to make a complementary strand of DNA from the viral RNA template

A double strand of DNA is made that is inserted in to the human DNA by the HIV enzyme intergrase

Once inside the human genome it transcripts and translated

91
Q

As a result of HIV give two ways that t helper cells are destroyed and killed

A

As the HIV virus is being made it buds out of the t helper cell which kills it

As a result of HIV the t helper cell is infected and is destroyed by t killer cells

92
Q

What happens in mrna splicing and what does this means

A

When mrna is edited between translation and transcription

In this process some sections called introns are removed they are non coding

The remaining sequences are called exons and can be spliced in various ways,(these sequences can be expressed)

It means several proteins can be made from the same mrna

93
Q

What happens in the acute phase of HIV

A

HIV antibodies appear in the blood

The symptoms that occur are fever sweats,headaches,sore throat,

after a few weeks T killer cells destroy infected cells

94
Q

What is the latent phase in HIV

A

When the symptoms aren’t present as the virus is under check by the immune system

Can last up to 20 years

95
Q

What is the diease phase in HIV

A

When HIV is now aids by the increase of number of viruses in the blood

The immune system is now weakened by the decline in t helper cells

96
Q

State the four types of immunity

A

Active natural immunity
Active artificial immunity

Passive natural immunity
Passive artificial immunity

97
Q

What is active immunity and state the difference between the two types

A

This is when our immune system makes its own antibodies by stimulation by an antigen

Natural is when after catching the disease you become immune

Artificial- when your given a vaccine contains a harmless dose of antigens

98
Q

What’s passive immunity

A

When we receive antibodies from an other organsims

Natural ie when baby because immune after receiving antibodies from mother via breast milk

Artificial when antibodies are injected into another organism

99
Q

What may a vaccine contain

A

A toxin that is in harmless form

Killed bacteria

Antigen bearing fragments

100
Q

How do we gain immunity

A

By vaccination in which we are Injected with dead or inactive pathogens

101
Q

What is herd immunity

A

When are large percentage of the population ie immmue to an infection

102
Q

What is ambient temperature

A

The temperature of the surroundings and it determines core body temperature

103
Q

What is infection

A

When a pathogen invades a cells

104
Q

Give 3 ways HIV evades our immune system

A

It reduces the number of immune system cells so it has less chance of being detected

HIV has a high mutation rate which causes new strain of the virus to appear means memory cells are unable to recognise different types of antigens produce by HIV

It disrupts antigen presentation in cells meaning the immune system can’t recognise and kill it

105
Q

How does Tb evade detection

A

It disrupts antigen presentation in infected cells which prevents them being killed by infected phagocytes

When engulfed by pathogens they produce substances that prevent lysozyme fusing and killing it meaning it can multiply and divide

106
Q

What are antibiotics and state the two types

A

Chemical that kill the or inhibit the growth of microorganisms

Bateriocidal and bateriostatic

107
Q

State which ways antibiotics inhibit bacteria and metabolism

A

They disrupt their cell membrane which can lead to lysis due to change in permeability

Inhibit the cell wall synthesis

They prevent cell division it inhibits nucleic acid synthesis replication and transcription

It inhibits protein synthesis meaning enzymes and other proteins are produced so it can’t carry out important metabolic processes

108
Q

What are antiviral drugs

A

These are drugs that reduce HIV production and they are used in combination

109
Q

State the two main types of antiviral drugs and their function and state other antiviral drugs

A

Reverse transcriptase inhibitors they prevent viral RNA from making DNA that would be integrated into host genome

Protease inhibitors that inhibit protease which catalyse the cutting down of larger proteins into small polypeptides which are used in constructing new viruses

Integrase inhibitors and fusion inhibitors

110
Q

In terms of the evolution what do antibiotics and the immune system provide bacteria

A

They act as a selection pressure

111
Q

How can bacteria develop resistance to antibiotics in terms of natural selection

A

Random mutations occur in the gene in a bacteria, with antibiotics acting as a selection pressure it means that a gene could become advantageous,these bacteria are able to survive and when they reproduce via binary fisson or a sexual reproduction the gene is passed onto the new bacteria formed increasing allel frequncy

112
Q

What is conjugation

A

This is when bacteria cell to cell contact and its aids in evolution

113
Q

What are hospital acquired infections

A

These infections are caught while a person is in hospital

114
Q

How are HAI transmitted

A

Cough and sneezes not being contained

Hospital staff and visitors not washing their hands before and after visiting someone

Equipment and surfaces not being disinfected after use

115
Q

State ways to prevent and control Hai

A

Hospital staff and visitors should be encouraged to wash their hands before and after they have been with patient

Equipment should be disinfected after use

116
Q

State way to control hai caused by antibiotic resistant

A

Antibiotics shouldn’t prescribe antibiotics to prevent infections

Patients should complete there full course of prescription

Doctors should rotate the use of different antibiotics

Doctors should use narrow spectrum antibiotics when possible(only affect specfic bacterium)

117
Q

Name differences between viruse and bacteria

A

Bacteria have a cytoplasm virus don’t

Bacteria have double strand DNA,virus have a single strand

Some bacteria have plasmid virus don’t

Bacteria have ribosomes,plasma membrane not virus

118
Q

Name the structures in a bacteria and their roles

A

Flagellum allows them to move

Ribosomes-produce proteins from mrna

Pilli-They allow bacteria to stick to cells used in gene transfer

Plasmid small loops of DNA

slime capsule- helps protect bacteria from attack

119
Q

Describe the structure of an antibodies and state their functions

A

Hinge region-enables flexibility when binding to antigens

Disulfide bridges-holds the polypeptide chains together

Has 4 polypeptide chains two heavy and two light chains

Variable region- they are antibody binding sites and its shape is complementary to a specific antigen and this region is different between antigens

Constant region-its the same in all antibodies and it allows binding to receptors of immune system cells

120
Q

Describe the ways antibodies help to clear infections

A

Agglutination of pathogens- this is when they clump pathogens together as the antibodies have two bindings sites so they can bind to two pathogens at the same time (allows phagocytosis to occur)

Neutralising toxins-the toxins that are produced by pathogens are binded onto by antibodies neutralising them meaning they can’t damage human cells

Inhibiting then from binding to human cells - when antibodies bind to antigens on pathogens they block the cell surface receptors from pathogens meaning the pathogen can’t bind to the host cell

121
Q

State the difference between active immunity and passive

A

Active you are able to stimulate your own antibodies

Passive you are injecting with antibodies

122
Q

What is an infection

A

When a pathogen evades barriers and is inside tissues/cells

123
Q

What is meant by the immune system being non specific

A

It’s reacts against any microorganism/pathogen and it involves,inflammation,phagocytosis,lysozyme

124
Q

Explain how macrophages present antigens to t helper cells

A

Macrophages bind on to a t helpers cell CD4 receptor it’s also becomes an antigen presenting cell

A Level Biology (9 decks)

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