Chapter 8.8 Flashcards

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1
Q

Explain the Sanger method of DNA sequencing

A

Also called SANGER’S CHAIN TERMINATOR TECNIQUE”

It uses the DNA polymerase enzyme to generate a series of DNA fragments that are complimentary to the DNA being sequenced.

4 solutions contain:

  1. A primer
  2. An unknown DNA sequence
  3. Replication Enzymes
  4. Normal nucleotides (A, C, T, G)
  5. And a small amount of a terminator nucleotide ( A or C or T or G)
  6. To sequence the DNA, it must first be separated into two strands.
  7. The strand to be sequenced is copied using chemically altered bases.
  8. These altered bases ( terminator) cause the copying process to stop each time one particular letter is incorporated into the growing DNA chain.
  9. This process is carried out for all four bases,
  10. The result is a group of fragments that differ in length from one another by one end base.
  11. Once a collection of such pieces is generated a technique called ELECTROPHORESIS can be used to separate the fragments by size
  12. Reading the end bases in order by size reveals the sequence of the compliment the deriving the the original /unknown sequence is easy.

5 the fragments are put together like a jigsaw to reveal the sequence of the original piece of DNA.

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2
Q

DNA MICROARRAYS

A

( also called DNA chip)

. it offers a way to sequence DNA on smaller scale

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3
Q

POLYMERASE CHAIN REACTION (PCR)

A

It replicates millions of copies of a DNA sequence of interest ( in a test tube)

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4
Q

The requirements of PCR replication

A
  1. Target DNA sequence to be replicated
  2. Taq polymerase ( a heat stable DNA polymerase derived from bacterium that occupies hot springs)
  3. 2 types of laboratory made DNA primers that are complimentary to the sequences known o occur at each end of the target sequence. The PRIMERS are necessary because DNA polymerase can only attach to an existing strand.
  4. a supply of 4 types of DNA nucleotides
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5
Q

Why are Primers necessary

A

he PRIMERS are necessary because DNA polymerase can only attach to an existing strand.

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6
Q

The steps of PCR

A
  1. heat ( from a thermal cycler) separates the 2 strands of the target Dna
  2. The temperature is then lowered - short primers attach to the separated target strands by complementary pairings.
  3. Tag DNA POLYMERASE adds nucleotides to the primers and builds sequences complimentary to the target
    sequence
  4. the heat is raised again: The newly synthesized strands act as templates in the next round of replications which are are separated.
  5. The number of pieces of DNA doubles with every round of PCR
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7
Q

What is PCR’s greatest strength

A

it works on tiny samples: a trace amount of dan from a few skin cells ar a strand of hair can filed enough material for profiling.

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8
Q

How is PCR used in forensics

A

to amplify DNA needed to establish genetic relationships, identify remains, convict criminals, and exonerate the falsely accused

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9
Q

What is PCR greatest sensitivities

A

Its it’s extreme sensitivity. Contimination from stray DNA can lead to a false result

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10
Q

DNA PROFILING

A

uses just the most variable parts of the genome to detect genetic differences between individuals

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11
Q

SHORT TANDEMS REPEATS

A

one approach to DNA profiling that, which are sequences of few nucleotides that are repeated in noncoding regions of Dna( silent DNA)

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12
Q

The uniqueness of short tandem repeats

A

For each of the accepted 13str sites each person will have different/unique number of repeats for each nucleotide

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13
Q

How is a DNA profile generated

A

1.DNA is extracted from a person’s cell
2.PCR is used to amplify the DNA at each of the 13 STR sites.
Electrophoresis is then used to determine the number of repeats at each site
by measuring the length difference in the fragments

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14
Q

what are the statistics that of the chance of any two unrelated individuals have the same pattern in all of the 13 STR markers

A

one in 250 trillion

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15
Q

From who is mitochondrial DNA inherited . How is it useful in DNA profiling

A

only from one’s mother. Although it is not useful to distinguish amon siblings, however it is useful to verifying the relationship between woman and child

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16
Q

How is father son relationship verified

A

STRS on the Y chromosome

17
Q

. How do researchers use the Sanger method and DNA microarrays to deduce a DNA sequence?

A

The Sanger method uses 4 test tubes with the materials needed to replicate many copies of DNA. Included in each test tube are special terminator nucleotides which result in replicated strands of various lengths indicating the positions of A, C, T, and G in the unknown DNA. When the replicated strands are added to a gel electrophoresis plate the complimentary DNA sequence can be determined. Microarrays also determine unknown DNA sequences as the small segments bind to complimentary sequences on the microarray chip. A computer then pieces together the overlaps in sequences to determine the original sequence.

18
Q

How do target DNA, primers, nucleotides, and Taq DNA polymerase interact in PCR

A

The primers attach to both ends of the target DNA to give the DNA polymerase the necessary nucleotides. The Taq form of the polymerase is not denatured by the heating process that occurs in PCR, and the nucleotides provide the raw material the polymerase needs to replicate the strand.

19
Q

Why is PCR useful

A

PCR creates many copies of a tiny DNA sequence for analysis, especially in forensics. It can also be used to increase the amount of DNA recovered from a microorganism to aid in diagnosis or from a fossil to aid in evolutionary classification

20
Q

What are STRs, and how are they used in DNA profiling

A

Short tandem repeats are a series of just a few repeating nucleotides that occur in noncoding portions of DNA. Each individual varies in the number of repeats they possess, so by combining analysis of several STR sites between individuals, a DNA profile can be produced.

21
Q

Why does mitochondrial DNA provide different information from nuclear DNA?

A

Mitochondrial DNA is much shorter than nuclear DNA and exists in many copies between all the mitochondria in a cell. It is inherited only from the female parent and does not contain a recombination of male and female nuclear DNA. For this reason it cannot be used to distinguish between siblings.