TOPIC 6

Question 1

normal body temperature

Answer 1

36.2 degrees celsius to 37.6 degrees celsuis

Question 2

how long can temp. of body be used to estimate time of death

Answer 2

24hours

Question 3

factors affecting rate of cooling (at least 4 marks)

Answer 3

body size, humidity, body position, surrounding temp. of environment , clothing

Question 4

describe rigor mortis process

Answer 4

• muscles starved of oxygen and reactions stop
• respiration in cells becomes anaerobic and lactic acid produced
• pH falls, inhibiting enzymes that stop anaerobic respiration
• ATP no longer produced
• bonds between muscle proteins fixed
• muscles &joints fixed in place

Question 5

give time length of rigor mortis

Answer 5

• happens about 6-9 hours after death

- whole process wears off after 36 hours

Question 6

autolysis

Answer 6

enzymes, in body from the digestive tract, and lysosomes break down cells

Question 7

7. process of body decompostion (6 marks)

think acronym and backstory

Answer 7

1.skin&lower abdomen turn green-sulhaemoglobin production(between 36&72 hours
after death)
2. body becomes reddish green then purplish black.
3. gas blisters appear on skin
4.body begins to smell and become bloated(due to gases e.g. CO2, CH4 etc) - 1
week after death
5. gas released and body deflates
6. fluid drains away and soft tissues shrink.

Question 8

8. forensic entomology-any details known to

help with generally graph questions

Answer 8

-succession of species of insect on body along with species present on body allows
stage of succession to be determined&time of death to be estimated

Question 9

why is everyone’s DNA unique?

Answer 9

because of variety of sections of DNA not used to code for proteins (introns)

Question 10

10. exons

Answer 10

coding regions of DNA

EXPRESSED

Question 11

introns

Answer 11

non-coding regions of DNA

Question 12

Short Tandem Repeats (STRs)

Answer 12

• short DNA sequences are repeated many times.
• located within introns
• sequence of repeated bases

Question 13

why are STRs unique to each individual?

Answer 13

-number of times STRs are repeated on homologous chromosomes at a single locus
varies between individuals
ALTHOUGH … some STRs occur at the same place on both chromosomes of a
homologous pair

Question 14

Steps of DNA Profiling (5 marks)

think acronym and backstory

Answer 14

1. obtain tissue sample
2. extract sufficient amount of DNA
3. cut DNA into different sized fragments using RESTRICTION ENDONUCLEASES
   #only cut DNA at specific base sequences
4. separate DNA fragments using gel electrophoresis
   5.compare sample with reference sample

Question 15

5. why do scientists use PCR?

POLYMERASE CHAIN REACTION

Answer 15

-samples obtained by forensics scientists at crime scene are too small to be
manipulated and experimented with.
- PCR amplifies tiny samples of DNA so they can be used in DNA profiling

Question 16

what does PCR require

Answer 16

• DNA Fragments
• DNA polymerase
• DNA Primers
• Free Nucleotides
• Thermocycler

Question 17

describe how small samples of dna can be

amplified

Answer 17

-PCR machine
-DNA polymerase enzyme added
-need for primers/ nucleotides
-heat to 95 degrees celsius, then cool down to 50 degrees celsius&then heat up
DNA to 70 degrees celsius
-cycle needs to be repeated several times to make several copied of DNA

Question 18

non overlapping genetic code

Answer 18

Each codon is non-overlapping

Question 19

codon.

Answer 19

The genetic code is formed from the
sequence of bases along the coding
strand of the DNA. We read the
genetic code as a series of three bases(CODON)

Question 20

degenerate nature of the

genetic code

Answer 20

Because there are 64 possible codons and only 20 amino acids quite
a few amino acids have more than one codon coding for them.
-MORE THAN 3 BASES CODE FOR ONE AMINO ACID

Question 21

. PCR Process (7 marks)

Answer 21

Polymerase Chain Reaction:
1. Heat sample of DNA to 95°C - H bonds break & it becomes
single-stranded.
2. Add free nucleotides - they will H bond with complimentary
partners in DNA
3. Add RNA Primers - short lengths of single-stranded RNA
that bind to the DNA and stop it annealing
4. Cool to 37°C - allows H bonds to form between nucleotides
5. Add DNA Polymerase
6. Heat to 72°C - optimum temp for thermophilic bacterium (not denatured at
high temp.)
7.REPEAT 20-30 TIMES TO FORM CYCLES

Question 22

steps in DNA fingerprinting technique?

Answer 22

obtain DNA sample
-amplify DNA sample using PCR
-cut DNA into fragments using restriction endonucleases
-dna fragments separated by gel electrophoresis according to their size
-dna placed on agarose gel, which is submerged in a buffer solution and
connected to electrodes
-dna current applied
-southern blotting used
-dna radioactive probe added to membrane
-x ray film placed next to membrane
-x ray film developed

Question 23

features of bacteria DEFFO

Answer 23

ribsosomes (70s)
circular DNA
plasmids
cytoplasm

Question 24

Ribosomes -bacteria

Answer 24

Same function as eukaryotic cells ( site of protein synthesis),
but are smaller (70s rather than 80s)