Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

forensics chem > Topic 3 Biochemical Analytical Technique Part-2 > Flashcards

Topic 3 Biochemical Analytical Technique Part-2 Flashcards

(42 cards)

Start Studying
1
Q

what is dna?

A

Deoxyribonucleicacidcontain genetic material in its nucleus and contains 23 pairs of chr

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are the monomeric units of DNA and RNA respectively?

A

deoxyribonucleotidesand

ribonucleotides.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what are the 3 components of DNA?

A

a)Nitrogenousheterocyclicbase
(purineorpyrimidine)

b) Pentosesugar
c) Phosphategroup

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what are the 4 types of bases in DNA?

A

Adenine,Thymine,
Cytosine, Guanine
AdeninelinkswithThymine CytosinelinkswithGuanine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what are the 2 diff between dna and rna

A

DNA building block is deoxyribonucleotides while RNA is ribonucleotides

DNA function is for storing and passing down genetic information while RNA converts codes into proteins to carry out cellular functions

Sugar in DNA is deoxyribose sugar while RNA is ribose sugar

bases in DNA Is adenine, thymine, guanine and cytosine.
bases in RNA is adenine, uracil, guanine and cytosine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is a protein?

A 
Madeofaminoacids
Containbothacidiccarboxyl(‐COOH)and
basicamino(‐NH2)
groupattachedtoαcarbonatom.
DifferwithrespecttoRgroup.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

how is a protein formed?

A

Formedbycondensationofaminoacids which form a chain aka polypeptide. 2 or more polypeptides together may acquire a functional form and a 3D structure to become a protein. Proteins are long chains of Aas held together by peptide bonds

**Polypeptideshavemolecularweightof1500orless.Proteinshavemolecularweightof5000ormore.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is a Zwitterionic aminoacids?

A

Whendissolveinwater
theycontainanaminegroup(basic)andacarboxylicgroup(acidic)
Thenetchargeoftheentiremoleculeiszero.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

how to calculate isoelectric pH?

A

IsoelectricpH=(pK1 +pK2 )/2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is the isoelectronic pH?

A

MoleculehasnonetelectricchargeatthispHandwillnotmoveinanelectricfield

aminoacidhastheleastbufferingeffect (no ability to change the pH of a system)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what are some examples where DNA can be collected?

A

Couldbealickedenvelope,dirtylaundry,acigarettebuttorsalivaetc.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what are some Specialprecautionswe should take whenhandlingspecimens:

A

gloves,disposableinstruments,avoidtalkingandsneezing,avoidtouchingsamplewithyourskin,air‐drytheevidencebeforepackagingsomolddoesnotgrow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what degrades evidence?

A

sunlight,hightemperatures,bacteria,

moisture

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is the ideal sample?

A

e:1mLoffresh,wholeblood(whitebloodcells)treatedwithEDTA

**Ethylenediaminetetraaceticacid(EDTA)stronglyandirreversiblychelates(binds)calciumions,preventingbloodfromclotting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what are the 3 bioanalytical techniques for DNA typing?

A

PolymeraseChainReaction(PCR)
RestrictionFragmentLengthPolymorphisms(RFLP)
electrophoresis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is the function for PCR?

A

ToamplifyminutequantitiesofDNAespeciallywhenmoreDNAtemplateisrequiredforfurtherreactions/analysis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what is the function for RFLP?

Study These Flashcards
A

TofragmentDNAsamplesintopieces,utilizeshomologousDNAdifferenceswithinrestrictionenzymebindingsites.

18
Q

what is the function for electrophoresis?

Study These Flashcards
A

Toseparatethefragmentsbasedonchargedandlength/size.

19
Q

what is the PCR test mainly for? what is its main advantage?

Study These Flashcards
A

‐Techniqueformakingcopiesoramplifyinga
specificsequenceofDNAinashortperiodoftime.

‐CellfreeDNAamplification

ConvenientmethodforobtaininglargenumberofDNAcopies.Canbethoughtofasamolecularphotocopier.

advantage:
RobustandworksforsmallamountsofDNAandworkseveniftheDNAisbadlydegraded.

20
Q

what are the basic steps of PCR? (DAE)

Study These Flashcards
A
  1. •Denaturation:
    –DNAfragmentsareheatedathightemperatures(94oC)–DNAdoublehelixreducedtosinglestrands.
  2. •Annealing:
    –Thereactionmixtureiscooleddown.
    –PrimersannealtothecomplementaryregionsintheDNAtemplatestrands
    –Doublestrandsareformedagain.
  3. Extension: TheDNApolymerasesynthesizesthecompletecomplementarystrand.
21
Q

how do we calculate the number of DNA produced in a PCR cycle?

Study These Flashcards
A

No of DNA produced = 2^n

n = no of cycles

22
Q

what is electrophoresis?

Study These Flashcards
A

separation method based on the differential rate of migration of charged species (DNA fragments and other macromolecules) in a buffer solution across which has been applied a dc electric field.

23
Q

what is the rate of migration of a given species dependent on?

Study These Flashcards
A

dependsuponcharge and sizeofions.

24
Q

what is the unique ability of electrophoresis? what is it commonly used for?

Study These Flashcards
A

•Uniqueabilitytoseparatechargedmacromolecules ofinterest. •PopularforanalysisofDNA,RNAandprotein

25
what are the 3 principles of separation of DNA fragments in electrophoresis?
Form of separation used to identify macromolecules of biological compounds e.g. DNA and proteins Movement of charged particles in an electric field. A negatively charged particle will move toward the positive end and vice versa. Proteins are charged at all pH except at their isoelectric point (pI). Differences in size and charge between proteins results in different migration rates when they are in an electric field.
26
what are the 2 apparatus used in electrophoresis?
(a) D. C. power supply with control for both voltage and current output. (b) Electrophoresis unit containing electrodes, buffers reservoir and a solid support for electrophoresis medium.
27
explain the general principles of electrophoresis technique in terms of zwitterions, cations and anions
Zwitterion–remains stagnant, a molecule that contains an equal number of positively-and negatively-charged functional groups. Thus overall is neutral. Cation-a positively charged ion, i.e.one that would be attracted to the cathode Anion–a negatively charged ion, i.e.one that would be attracted to the anode Smaller molecules travel longer distances while heavier molecules travel shorter distances
28
what are the 2 types of electrophoresis?
a) Gel electrophoresis (Supporting medium: Gel): (i) Starch (ii) Agarose (Agarose gel electrophoresis) (iii) Polyacrylamide (Sodium Dodecyl Sulphate –PolyAcrylamide Gel Electrophoresis) b)Capillary electrophoresis (Supporting medium: Capillary)
29
briefly describe starch as a supporting medium for electrophoresis. what is its application, advantage and disadvantage?
Starch as supporting medium: Prepare by heating and cooling mixture of partially hydrolyzed starch in an appropriate buffer. Disadvantage : (1) No way to determine exact pore size of starch gels.  (2) Different batches are inconsistent with respect to pore size for same percentage of starch.  Advantage : Ease of applying histochemical tests.  Application: Analysis of isoenzyme patterns.
30
briefly describe agarose gel as a supporting medium for electrophoresis.
Separation of DNA fragments > 1000 base pairs.  All DNA is of uniform shape and charge‐mass ratio.  Separated by molecular weight/ size and measured as base pairs.
31
what are the steps involved in agarose gel electrophoresis?
•Sample is applied as a spot on a well in supporting medium of electrophoresis kit.  •Apply D.C. and the ions of the sample migrate towards the electrodes of opposite polarity at characteristic rates to form bands  •Migration rate is dependent on charge and on completion of electrophoretogram, the supporting medium is dried and sample components are detected  •Protein molecules can be separated from each other by taking advantage of their overall charged (positive or negative).  •In electric field between two electrodes, a positively charged particle will move toward  negative electrode and a negatively charged particle will move toward positive electrode. 
32
briefly describe polyacrylamide gel as a supporting medium for electrophoresis.
Cross‐linked polymer: suppress convective currents produced by small temperature  gradients, a requirement for effective separation.  •serve as molecular sieves that enhance separation. 
33
why is polyacrylamide a commonly used gel medium?
(a) chemically inert (b) readily formed by polymerisation of acrylamide.  (c) Pore size controlled by choosing various concentrations of acrylamide (0.7 –2%). (d) high degree of reproducibility & resolution
34
describe how the qualitative results of gel electrophoresis comes about
Mobility of proteins is linearly proportional to the logarithm of their mass. 
35
what is the main disadvantages of GE? How do we over come this?
* The main disadvantage of the GE is joule heating.  * Lower voltage passes through the gel medium, thus longer separation time. * Overcome: Capillary electrophoresis (CE) technique (using capillary instead of gel supporting medium
36
briefly describe capillary electrophoresis. What are its main advantages?
•Automated, analytical version of the conventional electrophoresis techniques. •Separation medium :  Gel medium replaced with fused silica capillary tube(10‐100 µm internal diameter, 1 m long) filled with buffer  Main advantages: High efficiency and easy automation (increases reliability of results) DC voltage source delivering up to 30 kV Fast separations with very little band broadening Sample size: can be small but detection sensitivity is still good.
37
what are the steps involved in CE?
(1)Purge capillary with electrolyte to remove previous sample matrix for 1 minute  (2)Move capillary into new sample and allow hydrostatic sample introduction for 30 seconds.  (3)Place capillary back into electrolyte and apply voltage for analysis time. This creates an electric field strength across capillary  (4)Ions separate in capillary as they migrate towards the detector  (5) Separated ions pass through capillary’s UV cell window and are detected as changes in UV absorbance.  (6) Data system produces an electropherogram analogous to chromatogram  (7) Process electropherogram using computer. Area of Peak width and reference peak for identification are used
38
how do the results of CE appear?
 similar to a chromatogram in chromatographic separation migration time is recorded. CE can perform both quantitative and qualitative analysis precisely
39
Why is dna typing performed?
–detects normal variations in a sample of DNA.   To establish identity, parentage, family relationship & appropriate matches for transplantation of organs & tissues
40
what is restriction fragment length polymorphisms?
–1st technique used for forensic DNA typing. DNA cut by restriction enzymes; each person will have different DNA fragments  Separate DNA fragments by gel electrophoresis.
41
what are the steps involved in RFLP?
A.Genomic DNA digestion by restriction enzymes DNA is treated with restriction *endonuclease (enzyme) to cut the DNA at specific points, resulted in different sized of DNA fragments. B1. Electrophoresis DNA fragments are separated according to size. With phosphate groups, thus DNA fragments are negatively charged at an alkaline pH. B2. Denaturation •Soaked in NaOH& NaClsolution  •Double stranded DNA into single stranded DNA C1. Southern Blot Technique  •Single stranded DNA is transferred from the gel to a nylon membrane.  •DNA probe is added to the DNA that is affixed to the membrane.  C2. Probe Hybridization •The probe will attach to a section of DNA (complementary base sequence).  •DNA probe is radioactive & emits particles. •Probe does not bond with the DNA is washed away C3. Visualization by radioactive DNA probe •Autoradiograph: X‐ray (photo) film. •Each DNA sample produces an image as bands located in specific positions; Possible to compare two or more autoradiographs to see if the bands match. •RFLP is less common  ‐It requires large amounts of DNA & can be easily contaminated.
42
Describe how DNA typing can help to solve cold cases now
DNA databases have been made in many countries which contain DNA information of known criminals If biological sample of old cold cases are kept in proper condition, we can perform DNA typing and compare against DNA databases. If culprit has criminal record, a match will be found

forensics chem (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions