Collinearity of the Gene and the Protein

Question 1

What is a gene ?

Answer 1

Segment of a DNA molecule

Question 2

What does a gene specify ?

Answer 2

A protein

Question 3

What is the function of most genes ?

Answer 3

to instruct the cell how to make a protein

Question 4

What do you need to know to understand how genes work ?

Answer 4

Some simple protein biochemistry

Question 5

Whats the process to get from DNA to cell ?

Answer 5

DNA - mRNA - Protein - function - cell organism

Question 6

How are proteins made ?

Answer 6

-By joining together amino acids to form polypeptide chains
- The chains fold up to make a 3D structures
- Each amino acid in a protein has the same chemical structure except for its R group

Question 7

What are the groups bonded to a central carbon atom in an amino acid ?

Answer 7

• Amino group
• Carboxyl group
• Hydrogen Atom
• R group ( different in each amino acid )

Question 8

What are the 4 different classes of R groups ?

Answer 8

1. Neutral and non-polar : 9
2. Neutral and polar : 6
3. Acidic : 2
4. Basic : 3

Question 9

What do amino acids join to form ?

Answer 9

peptide bonds

Question 10

What is the primary structure and what is it determined by ?

Answer 10

Primary structure is an amino acid sequence and its determined by the genetic code of the mRNA

Question 11

What is the secondary structure and what’s bonds and interactions does it have in it ?

Answer 11

-Folding and twisting of a single polypeptide chain
Results pf weak H-bonds and electrostatic interactions

Question 12

What is the tertiary structure and what bonds does it contain?

Answer 12

Three dimensional shape of a polypeptide chain
Function of R-groups contained in the polypeptide

Question 13

What is the quarternary structure and what does it occur in ?

Answer 13

Association between polypeptides in multi-subunit proteins

Occurs only with two or more polypeptides

Question 14

Where did the first detailed evidence of how genes specify proteins come from ?

Answer 14

Studies on the oxygen binding protein found in red blood cells - haemoglobin

Question 15

What is the structure of haemoglobin ?

Answer 15

It is made of four polypeptide chains ; two a-chains and two b-chains

Question 16

What occurs to people with inherited disorders such as anaemia and thalassemia ?

Answer 16

1. All of the sufferers have altered haemoglobin or more specifically a globin
2. These disorders are caused by semi-dominant mutations obeying mendelian laws.

Question 17

What occurs to the haemoglobin when a person has sickle cell anaemia ?

Answer 17

• When the gene defect is in homozygous form HbsHbs all of the haemoglobin is altered
  -Some of the haemoglobin forms insoluble deposits in the red blood cells which become sickle shaped.

Question 18

If the sickle cell anaemia gene defect is in heterozygous form hBShba does the person still suffer with the disease ?

Answer 18

Yes because the protein is a tetramer

Question 19

What occurs to the haemoglobin in sickle cell anaemia - what does this change cause ?

Answer 19

-The sixth amino acid is changed from glutamine to valine
- This is a drastic change from an acidic, negatively charged, hydrophilic amino acid to a neutral, uncharged, hydrophobic one.

Question 20

Why do changes of one amino acid for another destroy the function of a protein ?

Answer 20

1. If the protein is an enzyme, the amino acid that carries out the reaction may be changed.
2. The altered amino acid may have been involved in pairing with another amino acid to maintain the shape of the protein

Question 21

What is a mutation that doesn’t affect the function of the gene ?

Answer 21

Silent mutations

Question 22

What has the study of haemoglobin shown ?

Answer 22

That mutations in a gene can cause specific changes in a protein

Question 23

What does it mean if the genetic map and the amino acid sequence are collinear ?

Answer 23

The mutations in the gene and the changed amino acids in the protein appear in the same relative positions.

Question 24

How can 4 nucleotides ( G,A,T,C) encode for 20 different amino acids ?

Answer 24

In fact, each amino acid is specified by a triplet of nucleotides, known as a codon.

Question 25

What can a mutation in a gene where one amino acid is changed for another cause ?

Answer 25

A mutation in a gene that causes a change of one amino for another can affect the function of a protein and can result in disease.

Question 26

What are the protein sequence and the genetic map ?

Answer 26

Collinear