Inheritance Patterns in a Population

Question 1

DNA sequencing

Answer 1

DNA sequencing: the exact nucleotide sequence (orders of base pairs) of a gene on a chromosome is determined using various methods – sanger method, maxam gilbert method or using a DNA sequencer

Question 2

reason for DNA sequencing

Answer 2

Reason for DNA sequencing: medical research, identifying different sections of gene in terms of their code and association with different diseases.

Question 3

Sanger Method

Answer 3

1. Isolate the DNA from the cells of the organism
2. Isolated DNA is amplified (many copies of it are made, using the polymerase chain reaction method)
3. DNA denaturation: separate double stranded DNA into single strands, done through a series of heating steps
4. A primer is added to the 5’ side (binds to the start of the single stranded DNA). Primed DNA distributed into 4 vessels.
5. DNA polymerase is added to all 4 vessels in order to build complementary DNA strands, including free nucleotides
6. Chain terminating nucleotides (dideoxy nucleotides – ddNTP) which are labelled with fluorescent dye added in the reaction mixture (these stop the DNA building process)
7. Once chain terminating nucleotides are added, no further nucleotides can be added, and the chain is terminated (with different lengths)
8. Capillary gel electrophoresis begins – method used to separate DNA fragments  the dye labelled DNA strands are placed into gel filled capillary tube
9. Electric current is passed through the gel, causing fragments to be pulled through the gel – short strands move quickly and long slowly
10. Fragments which arrive at the end of the cell pass through a laser beam – this information is picked up by the detector (photocell) and displays this on a chromatogram

Question 4

PCR

Answer 4

polymerase chain reaction

• makes a copy of a specific section of DNA
• used in diagnosis of disease or tracking of mutations, in crime scenes

Question 5

PCR method

Answer 5

• 1. Denaturation (using heat to separate the 2 strands of the molecule)
• 2. Annealing (2 strands separated by the heat have now been cooled and bound with primers)
• 3. DNA synthesis (more copies of DNA are being made using DNA polymerase which uses the spare nucleotides to create the complementary strand)

Question 6

DNA fingerprinting

Answer 6

• DNA is extracted from blood cells
• DNA is cut into fragments by a restriction enzyme
• The DNA fragments are separated into bands using electrophoresis
• Use the same restriction enzyme on each sample of blood
• The band pattern is transferred onto a membrane
• The radioactive probe is paired with it to make the pattern visible
• The probe just paired binds to specific DNA sequences on the membrane
• The DNA probe has now dyed the different bits of DNA
• This is then x-rayed, turning it into a reading