chapter 21- manipulating hormones

What is the genome

All of the genetic material that an organism contains

Introns

The non-coding parts of DNA that is removed from mRNA before it’s translated

How many stages are there in DNA profiling

5

What is the first stage of DNA profiling

Extracting the DNA

How do you extract DNA

• must be extracted from a tissue sample using PCR

What is PCR

Polymerase chain reaction

What is the 2nd step in DNA profiling

Digesting the sample

How do you digest a DNA sample

• strands of DNA are cut into fragments using Restriction Endonucleases

• They make two cuts, once through each strand of the DNA helix

• Each cut is at a specific DNA nucleotide sequence known as the restriction site

What us step 3 of DNA profiling

Seperating the DNA fragments

How do you separate DNA fragments

• using electrophoresis

• Gel is immersed in an alkali in order to separate the double strands into single strands

• Single strands are then transferred onto a membrane by southern blotting

What is the 4th step of dna profiling

Hybridisation

What is hybridisation

• radioactive DNA probes are added in excess to the DNA fragments in the membrane

• The DNA probes bind to complementary strands of DNA

What are probes

Short DNA or RNA sequences complementary to a known DNA sequence

What is stage 5 of DNA profiling

Seeing the evidence

How can you see the evidence when DNA profiling RADIOACTIVE

X-rays are taken of the membrane

How can you see the evidence when DNA profiling FLUORESCENT

The membrane is placed under UV light so the tags glow

What are the reactants in PCR

• the DNA

• Excess of the 4 nucleotide bases

• Small primer DNA sequences

• DNA polymerase enzymes

Step one in PCR

• temperature is increased to 90c

• This denatures DNA by breaking the hydrogen binds holding strands together

Step two in PCR

• temperature decreased to 55c

• Primers anneal to the DNA ends

Step three in PCR

• temperature increased to 75c

• This is the optimum temp for DNA polymerase

• DNA polymerases adds bases to the primer building complementary strands of DNA

What is the result of step 1 PCR

A DNA fragment split into its two strands

What is the result if step two PCR

• the two DNA strands are having complementary primers added to each end of the section being copied

What can PCR most commonly be used for

• forensic science

• Can be carried out on traces of DNA so that it can be compared to a sample of the suspect

Where can DNA be found for PCR

• blood

• Semen

• Saliva

What is the result of step 3 PCR

• DNA polymerase attaches nucleotides to produces two new DNA fragments

What are primers

Short DNA molecules which are added to either side of the section being copied in PCR