genetic fingerprinting and gel electrophoresis

give and explain 5 uses of genetic fingerprinting:

• forensic science - comparing samples of DNA collected from crime scenes to samples of DNA from possible suspects

• medical diagnosis - screening/identifying genetic diseases

• animal and plant breeding - finding evolutionary relationships to prevent inbreeding

why may someone use genetic fingerprinting over sequencing?

• sequencing more time consuming and expensive

• fingerprinting eliminates these issues while maintaining accuracy

what are VNTRs? describe their key features:

• variable number tandem repeats - short base sequence made up of introns repeated multiple times

• inherited!

• no. and length unique so diff in all individuals

describe the steps of genetic fingerprinting:

1. DNA extracted from donor - use PCR to amplify

2. DNA digested using restriction endonucleases

3. electrophoresis

4. DNA transferred onto membrane and hybridised with complementary radioactive/fluorescent DNA probes which bind

5. position compared to other samples - often using radiography/UV light

what is gel electrophoresis?

technique used to separate molecules e.g. DNA/RNA/proteins based on size by using an electric current applied to an agarose gel matrix

describe the process of gel electrophoresis:

1. DNA mixture placed into a well in a slab of gel and covered in a buffer solution that conducts electricity

2. electrical current passed through gel - DNA fragments negatively charged so move towards +ve electrode at far end of gel

3. small DNA fragments move faster and travel further through the gel so DNA fragments separate according to size

what is the ladder in gel electrophoresis? what is its purpose?

• mixture of DNA fragments of known lengths that allows you to work oout the length of the bands in electrophoresis

• allows comparison and identification of DNA bands

soybean cells were screened for the presence of the P34 protein. this process involved the use of gel electrophoresis to separate proteins extracted from soybean cells.

suggest 2 features of the structure of different proteins that enable them to be separated by gel electrophoresis (2)

• mass/no. of AAs/polypeptides

• charge

• R groups differ