DNA and proteins

Question 1

What are proteins made of?

Answer 1

Amino acid chains known as polypeptide chains, coiled up forming its shape.

Question 2

What are the four levels of structure of a protein?

Answer 2

Primary, secondary, tertiary, quaternary.

Question 3

Describe the primary structure of a protein

Answer 3

The chain of amino acids/polypeptide chain. Considered useless at this stage.

Question 4

Describe the secondary structure of a protein

Answer 4

Polypeptide chain begins folding as hydrogen bonds begin forming.
Still can’t do its job.

Question 5

Describe the tertiary structure of a protein

Answer 5

Protein continues coiling further as different kinds of bonds begin forming.
Can maybe now do its job if it doesn’t require the quarternary stage.

Question 6

Describe the quarternary structure of a protein

Answer 6

Some proteins have more than one polypeptide chain. This is where other coiled chains connect.
Haemoglobin is an example of this.
Protein can now do its job.

Question 7

Define what an enzyme is

Answer 7

An enzyme is a biological catalyst

Question 8

What are the two types of enzymes?

Answer 8

Anabolic - enzymes which are building larger complex molecules from simple simpler molecules.
ANTS are BUILDING nests

Catabolic - breaking down large complex molecules into smaller simpler molecules.
CATS are BREAKING things (pushing things off the edge)

Question 9

Define what a gene is

Answer 9

A section of DNA which codes for one specific mRNA molecule

Question 10

What is the active site of an enzyme?

Answer 10

The active site is where the job is done. Where substrates slot into the enzyme to either be broken down or built up.

Question 11

What are inhibitors? and what are the two types?

Answer 11

Inhibitors turn the enzyme on and off as we don’t always need them on.
Inhibitors slow down a reaction, product is still made but just slower. (toxins are inhibitors).

Competitive inhibitors - Sitting in the active site stopping substrates from entering. Competing for the active site.

Non-competitive inhibitors - don’t sit in the active site, inhibitor finds the allosteric site and changes the shape of the active site. Substrate can no longer fit.

Question 12

What are genetic mutations?

Answer 12

A mutation is any change in the codon sequence.

Question 13

What are the different types of genetic mutations?

Answer 13

Substitution
- Nonsense
- Missense
- Silent
Frameshift
- deletion

Question 14

What is a nonsense mutation?

Answer 14

When bond gets damaged by radiation or something else, and wrong letters get put together. Results in a stop codon in the middle of the mRNA strand.
Changes one amino acid.

Question 15

What is a Missense mutation?

Answer 15

When wrong amino acid gets coded for. Still makes sense but the wrong sense. Can result in a change in the proteins shape.
Changes one amino acid.

Question 16

What is a silent mutation?

Answer 16

No change, no big deal. Will change the codon (first letter) but will just change it into a degenerate, so does not actually change the amino acid coded.
Changes one amino acid.

Question 17

What is a deletion mutation?

Answer 17

Changes everything! One letter is taken out, so changes codons all the way down stream. This is almost always bad.
Changes everything.

Question 18

List three factors which increase chances in a mutation occurring.

Answer 18

High radiation
Mutagenic chemicals
Some viruses

Question 19

Define transcription

Answer 19

Using a section of of DNA (gene) to build a complimentary strand of mRNA.
Happens in the nucleus.

Question 20

Define translation

Answer 20

A strand of mRNA to provide the instructions for a ribosome to build a polypeptide chain.
Happens in the endoplasmic reticulum.

Question 21

Explain the lock and key theory

Answer 21

The enzyme’s active site is the lock/hole, substrate is the key.
The wrong key/substrate won’t fit into the lock/active site.
Can have one lock and multiple keys and they will all work. Lock doesn’t get used up.
Eventually the lock/active site may break.

Question 22

Describe protein synthesis

Answer 22

The process of transcribing an mRNA strand from DNA, and building a polypeptide chain/protein through the ribosome enzyme.

Question 23

What is SCNT? (Somatic Cell Nuclear Transfer)

Answer 23

When the nucleus from a somatic cell is placed into an enucleated gamete for cell division to begin.

Question 24

Explain the steps of SCNT

Answer 24

1. Somatic cell’s nucleus is removed
2. Nucleus is then injected into ovum from a second donor
3. That egg can now initiate development through mitosis

Question 25

What is SCNT used for?

Answer 25

Cloning

Question 26

What is gel electrophoresis?

Answer 26

A technique used to seperate DNA fragments according to size

Question 27

Explain the steps of gel electrophoresis

Answer 27

1. restriction enzymes cut up strands of DNA at certain spots, relating to DNA bases.
2. DNA is placed in wells in the gel electro…. machine (in negatively charged side)
3. When the machine is turned on the DNA begins moving through the gel (towards positive side)
4. Shorter pieces move faster so will be closer to positive side than longer pieces.
5. To see DNA the gel must be stained and put under a UV light
6. Similarities in DNA will line up

Question 28

What is gel electrophoresis used for?

Answer 28

Testing relatedness between people (parents and children)

DNA fingerprinting (crime scenes)

Question 29

What is the formula for maths question

Answer 29

bases - introns / 3 - 1 = number of amino acids