Topic 6 - immunity, infection and forensics

Question 1

What is the role of decomposers?

Answer 1

Secrete enzymes that break down biological molecules in dead tissues

Question 2

Examples of decomposers

Answer 2

Bacteria and fungi

Question 3

What is the order of decomposition?

Answer 3

1) Cells and tissues (hours-days)
2) Tissues and organs (days-weeks)
3) Remaining soft tissue turns to liquid (months-years) until a skeleton
4) Skeleton discentigrates (decades-centuries)

Question 4

What happens to the body when cells and tissues are broken down?

Answer 4

Skin goes a greenish colour

Question 5

What happens when decomposers break down tissues and organs?

Answer 5

• Bloating - as this process produces gases (methane)
• Skin blisters and falls off

Question 6

What are the conditions that affect rate of decomposition?

Answer 6

• Oxygen present (aerobic or anaerobic conditions)
• Temperature (hotter = quicker)

Question 7

What is succession?

Answer 7

Change in the type of organisms found in a habitat overtime

Question 8

What is the habitat?

Answer 8

The dead body

Question 9

What is the order of the organisms?

Answer 9

1) Bacteria
2) Flies
3) Larvae - laid by flies
4) Beetles
5) Flies leave (prefer moisture-rich environment - tissue has dried out)
6) Beetles remain until there is no tissue left

Question 10

How does the succession occur?

Answer 10

Pioneer species is out-competed and disappears as the system matures
- Bacteria arrives immediately
- Flies and larvae leave when the tissue has dried out
- Beetles remain until there is no soft tissue left

Question 11

How do stages of succession differ?

Answer 11

Depending on where the body is located - affects accessibility to insects and availability of oxygen
- Buried in soil
- Buried in a coffin
- Underwater

Question 12

What is forensic entomology?

Answer 12

Study of insect colonies

Question 13

What is PCR?

Answer 13

It is used to amplify DNA for it to be used in DNA profiling

Question 14

What is DNA profiling?

Answer 14

A fingerprint of an organisms DNA

Question 15

What can DNA profiling be used for?

Answer 15

• Identifying individuals
• Determining genetic relationships (through genetic tests - paternity/ maternity tests, ancestry reports)
• Captive breeding programmes (to prevent inbreeding)

Question 16

What is needed in PCR/ reaction mixture?

Answer 16

• DNA sample
• Free nucleotides
• Primers
• DNA polymerase
• Buffer solution

Question 17

What is the process of PCR?

Answer 17

1) Reaction mixture is created
2) DNA mixture is heated to 95 degrees - breaks hydrogen bonds between two strands of DNA
3) Mixture is cooled to between 50-65 degrees so that primers can anneal to the strand
4) Reaction mixture is heated to 72 degrees so that DNA polymerase can work
5) DNA polymerase lines up free nucleotides alongside each template strand
6) Two new copies of the fragment of DNA are formed
7) One cycle of PCR completed
8) Cycle is repeated, this time with double the amount of DNA

Question 18

What are primers?

Answer 18

Short pieces of DNA that are complementary to the bases at the start (start codon) of DNA fragment

Question 19

What is DNA polymerase?

Answer 19

Enzyme that creates new DNA strands

Question 20

What is DNA helicase?

Answer 20

An enzyme that breaks the hydrogen bond between two strands of DNA

Question 21

Anneal

Answer 21

Bind

Question 22

What is the buffer solution used for in gel electrophoresis?

Answer 22

Provides ions that carry a current through the gel and to maintain a constant pH

Question 23

What is the receptor called on the T helper cell that HIV attaches to?

Answer 23

CD4 receptor