Ella Middlemiss
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Ella Middlemiss
Created by Ella Middlemiss almost 9 years ago
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DNA Profiling

Question 1 of 20

1

Fill the blank spaces to complete the text.

(STRs) are short DNA sequences repeated many times. They're found within (intragenic regions) that are non-coding. They're inherited in the same way as genes in the coding regions - (expressed regions). STRs occur at the same on both chromosomes of a pair. The number of repeats on each of the homologous chromosomes can be different. The number of repeats at a locus varies between individuals. There's a large amount of variation in the number of repeats at each locus. Therefore 2 individuals are highly unlikely to have the same combination of STRs.

Explanation

Question 2 of 20

1

STRs are inherited in the same way as alleles of a gene, with offspring receiving one repeated sequence randomly from each parent.

Select one of the following:

  • True
  • False

Explanation

Question 3 of 20

4

What can DNA profiling be used for?

Select one or more of the following:

  • identification purposes

  • settling paternity disputes

  • identifying stolen animals

  • looking at variation and evolutionary relationships between organisms

  • finding the meaning of life

Explanation

Question 4 of 20

1

DNA profiling is widely used in . It is generally thought to produce a result that is almost to the individual and a near indication of guilt in criminal trials. This is true even for due to the accumulation of mutations during a person's life. But because the DNA profile only analyses a few , it is less likely to be completely unique. This is a particular problem if individuals being tested are closely . In court, a forensic scientist estimates the chance of seeing the same DNA profile in the general population; this is usually in excess of .

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    legal proceedings
    unique
    certain
    twins
    repeated sequences
    related
    1 billion

Explanation

Question 5 of 20

1

DNA samples can come from almost all - animal or plant.

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    biological tissue

Explanation

Question 6 of 20

4

Examples of sources of DNA samples:

Select one or more of the following:

  • cells in cheek swab

  • white blood cells in blood smear

  • bone marrow in a skeleton

  • sperm left after a sexual assault

  • bacteria sample taken from a body

Explanation

Question 7 of 20

1

Fill the blank spaces to complete the text.

The tissue sample is broken down in a solution (includes salt and detergent) to disrupt the cell membranes. The small suspended particles, including the DNA, are separated from the rest of the cell debris by filtering or . enzymes are incubated with the suspension to remove proteins. Then, cold is added to precipitate out the DNA. Several stages of washing the DNA in buffer solution follow.

Explanation

Question 8 of 20

1

cut a DNA sample into fragments only where their occurs. The names of the restriction enzymes reflect the from where they originate. If restriction sites are either side of an sequence, that fragment of DNA will remain intact, but it will cut away the rest of the . The repeated sequences remain . They only cut at specific base sequences, usually 4 or 6 base pairs long. Restriction enzymes are found naturally in bacteria where they cut up invading . means they cut the DNA at sites within a strand of DNA.

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    specific restriction sequence
    Restriction enzymes
    bacteria
    STR
    genome
    intact
    viral DNA
    Endonucleases

Explanation

Question 9 of 20

1

Fill the blank spaces to complete the text.

Polymerase Chain Reaction: The sample is placed in a reaction tube with DNA , DNA primers and . The reaction tube goes into the PCR thermal cycler. It's heated to degrees C which separates the double stranded DNA. It's then cooled to degrees C which optimises the binding of the to the target DNA sequence in the sample. It's then heated to degrees C which is the temperature for the heat stable DNA polymerase. The polymerases attach and are added, extending the DNA from the primer. After 2 cycles, copies that are just the sequence fragment are produced. As the cycle continues, huge numbers of the targeted DNA fragments are produced.

Explanation

Question 10 of 20

1

What are DNA primers?

Select one of the following:

  • heat stable enzyme

  • short DNA sequences complementary to the DNA adjacent to the STR (marked with fluorescent tags)

  • free DNA bases

  • a short section of DNA with a base sequence complementary to the target DNA sequence that needs to be located

Explanation

Question 11 of 20

1

In gel electrophoresis, DNA fragments are separated according to their colour

Select one of the following:

  • True
  • False

Explanation

Question 12 of 20

1

Fill the blank spaces to complete the text.

Gel Electrophoresis: DNA placed on or polyacrymalide, which provide a stable medium through which the fragments can move (porous). The gel is submerged in a solution, and connected to that produce a potential difference (voltage across the gel). The charged DNA fragments migrate through the gel according to their overall size and . In a given time, smaller fragments end up closer to the electrode. A reference sample with fragments of known length may be added to the gel. This is known as a ladder or marker. The fragments are measured in base pairs.

Explanation

Question 13 of 20

1

The gel is quite and the DNA fragments are after electrophoresis if restriction enzymes have been used.

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    fragile
    double stranded

Explanation

Question 14 of 20

1

What is DNA probe?

Select one of the following:

  • a short section of DNA with a base sequence complementary to the target DNA sequence that needs to be located

  • short DNA sequences complementary to the DNA adjacent to the STR

  • a heat stable enzyme

Explanation

Question 15 of 20

1

Fill the blank spaces to complete the text.

Southern blotting is used to transfer the fragments to a more resilient or nitrocellulose membrane. The membrane is placed directly onto the gel and a wad of dry absorbent is placed on top. This acts as a wick to draw up through the gel, carrying onto the membrane. During this process, the fragments maintain their positions relative to each other and are denatured into strands, exposing the base sequences. The membrane is then incubated with an excess of DNA . After allowing time for the probe to bind to any complementary sequences (hybridise), any unbound probe is washed away.

Explanation

Question 16 of 20

1

Probes may be radioactive, labelled with , or labelled with a .

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    radioactive phosphorous
    fluorescent marker

Explanation

Question 17 of 20

1

With a radioactive probe...

Select one of the following:

  • the membrane is dried and placed next to X-ray film - the film blackens wherever the probe has bound with the DNA to form double-stranded fragments

  • it's position on the membrane can be visualised under UV light

Explanation

Question 18 of 20

1

With a fluorescent probe...

Select one of the following:

  • it's position on the membrane can be visualised under UV light

  • the membrane is dried and placed next to X-ray film - the film blackens wherever the probe has bound with the DNA to form double-stranded fragments

Explanation

Question 19 of 20

1

A band occurs on the profile where a person's maternal and paternal chromosomes have the number of repeats at a particular locus. bands occur on the profile if the 2 chromosomes have a number of repeats at the same locus. There must be a for comparison. The reference profile may come from a suspect in a murder investigation, a relative in the case of identifying a corpse, or from the parents when establishing paternity.

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    single
    same
    2
    different
    reference profile

Explanation

Question 20 of 20

1

Select from the dropdown lists to complete the text.

The DNA ( primers, probes ) have a fluorescent tag attached to them which allows the system to be automated. As the DNA fragments with their fluorescent tags move through the gel, they pass a ( laser, gun ), the ( dye, DNA ) in the tag fluoresces and the coloured light is detected. This effectively gives a time that it has taken for the fragments to pass through the gel. Passing a separate set of fragments of known length through the gel allows the length of time for passage through the gel to be calibrated with fragment size. Several STR loci can be analysed at once by using tags that fluoresce at different ( wavelengths, times ) giving different colours for each of the STR loci. A computer processes the information from the detector displaying the results of the gel electrophoresis as a ( graph, kymograph ).

Explanation

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