Genetic screening, protein synthesis and DNA profiling

Question 1

Why would genetic screening be necessary

Answer 1

When DNA replication does not work how it should and a gene is not copied correctly. When a gene will not carry the correct code for a protein they intend to produce.

Question 2

Give an example of a genetic disorder and the consequences of it

Answer 2

Cystic Fibrosis- results in the build up of mucus in the lungs.

Question 3

Define genetic screening

Answer 3

A test for the presence of altered or abnormal genes.

Question 4

how genetic screening is carried out

Answer 4

Can be done on adults to see if they are carriers of a defective gene
It can also be carried out on a foetus by removing cells from the placenta. Treatment can be given when the child is born.

Question 5

An example of genetic screening

Answer 5

The heel prick is done to detect the disorder PKU a disorder of protein metabolism leading to mental retardation.

Question 6

Ethical issues of genetic screening [3]

Answer 6

• May lead to discrimination from life insurance companies against people who are more likely to develop a disease
• Employers may ot give employment to those with a disorder.
• It may lead to more abortions if the disease is untreatable

Question 7

How do genes make protein

Answer 7

A gene works when its code us sent out in to the cytoplasm and a protein is assembled according to the code.

Question 8

What are the 3 types of RNA

Answer 8

Messanger RNA [mRNA] Transfer RNA [tRNA] and Ribosomal RNA [rRNA]

Question 9

Describe mRNA

Answer 9

It carries the information for a specific protein
Its made up of codons
Each codon is specific for one amino acid

Question 10

Describe tRNA

Answer 10

It picks up an appropriate amino acid floating in the cytoplasm.
Transports amino acids to mRNA in ribosome
It has anti codons which are complimentary to mRNA codons.

Question 11

Describe the process of transcription

Answer 11

The piece of DNA which codes for a protein is rewritten onto a new molecule mRNA taking place in the nucleus.
- The double helix unwinds.
- The exposed DNA bases are matched up with RNA bases in the nucleus to form mRNA. Done by enzyme RNA polymerase.
The mRNA leaves the nucleus into the cytoplasm and attaches to a ribosome

Question 12

Describe the process of translation

Answer 12

tRNA containing an anti codon brings an amino acid to the codons on mRNA.
The anticodon on the tRNA links with 3 unpaired bases on the mRNA.This keeps happening and as a result the correct sequence of amino acids are joined together by peptide bonds forming a particular protein. The process continues until a stop codon is reached.

Question 13

What is the last step in protein synthesis. [NB]

Answer 13

when the polypeptide is complete it is released from the ribosome and undergoes folding and the addition of bonds. This allows the protein to reach its 3D folded globular shape which influences the function of the protein

Question 14

What is DNA profiling?

Answer 14

A method of making a unique pattern of bands from the DNA of a person. This pattern can be used to distinguish that DNA from another persons.

Question 15

4 steps of DNA profiling

Answer 15

1. Releasing DNA from cells.
2. DNA is cut into fragments.
3. These fragments are separated according to size.
4. The pattern of fragment distribution is analysed.

Question 16

Describe the first step in DNA profiling

Answer 16

DNA is released- cells usually blood and semen are broken down to release DNA

Question 17

What is a polymerase chain reaction [PCR]

Answer 17

If the dna sample is too small it can be increased by replicating the DNA using special enzymes.

Question 18

Describe the 2nd step in DNA profiling

Answer 18

The DNA is cut into fragments at specific base sequences using restriction enzymes

Question 19

Why are DNA fragments different lengths?

Answer 19

The base sequences being cut maybe close together or far apart on the DNA strand. If the base sequences are close togeether then the fragment is short. If they are far apart its long.

Question 20

describe step 3

Answer 20

the fragments are separated on a gel according to size using gel electrophoresis. The DNA bands created are transferred onto a nylon membrane and a radioactive probe is applied to the membrane producing a fluorescent image.
An Xray film is placed over the image and once developed reveals a pattern of bands [DNA profile]

Question 21

Describe electrophoresis

Answer 21

DNA fragments are placed on a gel. An electric current is applied along the gel drawing the DNA to one end of the gel. Small DNA fragments move faster through the gel separating the DNA into bands.

Question 22

What is the importance of DNA fingerprinting?

Answer 22

• Establishes whether or not the DNA found at a crime scene matches the DNA of a suspect
• It can determine the paternity/maternity of a child. This may be needed in cases of financial/property inheritance or immigration cases.

Question 22

What is the importance of DNA fingerprinting?

Answer 22

• Establishes whether or not the DNA found at a crime scene matches the DNA of a suspect
• It can determine the paternity/maternity of a child. This may be needed in cases of financial/property inheritance or immigration cases.