Unit 5: Mutations and Biotechnology

Question 1

Define

Mutation

Answer 1

Any change to DNA / genetic information

Question 2

Two general categories of mutations

Answer 2

Small scale, or “point” mutations which affect one or a few nucleotides and only one gene

Large scale mutations, which affect overall chromosomal structures / arrangement, thereby affecting many genes

Question 3

Two types of small scale mutations

Answer 3

Substitutions
Insertions / Deletions

Question 4

Define and list the types of

Substitution Mutations

Answer 4

A change of a nucleotide for another

Types:
* Missense
* Nonsense
* Silent

Question 5

Describe

Silent mutation

Answer 5

Change of a nucleotide that results in the same amino acid as in the original

Happens because of the redundancy of the genetic code - multiple codons can code for the same amino acid (see “wobble”)

The protein that forms is identical to the non-mutated but there may be slight differences in the expression of genes after a silent mutation

Question 6

Describe

Missense mutation

Answer 6

Change of a nucleotide that results in the change of an amino acid

Effects can vary based on the properties of the amino acid (size, polarity) and what part of the protein is affected (ex: active site of an enzyme)

Can be harmful or have minimal effect. Can even be beneficial (rarely)

Question 7

Describe

Nonsense mutation

Answer 7

Change of a nucleotide that results in a stop codon instead of an amino acid

Severity depends on where in the sequence the mutation occurs

Less detrimental nearer to the end of a protein (generally) but will result in nonfunctional protein if it happens closer to the start of the protein

Question 8

Describe

Frameshift mutations

Answer 8

The insertion or deletion of nucleotides that results in a change to the reading from of the gene

All downstream amino acids are changed

Severity depends on where in the sequence the mutation occurs

Less detrimental nearer to the end of a protein (generally) but will result in nonfunctional protein if it happens closer to the start of the protein

Question 9

What is important about mutations?

Answer 9

They are the source of all genetic variation, which is the basis of evolution by natural selection

The mutations themselves happen randomly BUT beneficial variations are favored by natural selection

Question 10

When do spontaneous mutations happen?

Answer 10

During DNA replication
(Reminder: DNA polymerases add new nucleotides AND help proofread the new DNA to ensure proper base pairing)
Incidence rate of around 0.000 000 000 1

Question 11

What are the results of mutations?

Answer 11

In normal body cells, mutations occur each time cell divides
These accumulate and eventually can lead to cancer and other age-related outcomes

Mutations can only be passed on to new generations if the error happens in the cell that produces the sperm or egg cell that is fertilized

Question 12

Define

Mutagen

Answer 12

Any physical or chemical agent that causes mutations

Question 13

List examples of

Mutagens

Answer 13

Radiation (such as UV, Xray, or nuclear radiation)
Chemical agents, which are often carcinogenic

Question 14

Define

Genetic engineering

Answer 14

Alteration of genes for practical purposes

Question 15

List some uses of genetic engineering

Answer 15

Medicine / health
Research
Criminal law
Agriculture

Question 16

What is the basis for all genetic engineering?

Answer 16

Complementary base pairing

Understanding how bases pair together and how to break up stretches of DNA allows scientists to take DNA from different sources and join it together

Question 17

Define

DNA cloning

Answer 17

The production of multiple copies of a specific DNA segment

Question 18

What are two ways of cloning DNA?

Answer 18

Using plasmids to make recombinant bacteria, which copy the DNA each time it reproduces

PCR

Question 19

Why is DNA cloning important?

Answer 19

Isolates just the gene / segment of DNA that is important
Makes a lot of copies so that it can be studied / manipulated more easily

Question 20

Define

Restriction Enzyme

Answer 20

Restriction endonuclease
Enzyme that cuts DNA at specific location (based on sequence)
Found naturally in bacteria as a type of defense
Used in genetic engineering by acting as “molecular scissors”

Question 21

Where do restriction enzymes work?

Answer 21

At specific restriction sites
These are usually palindromic / have the same sequence when read 5 -> 3 on either strand
Ex: 5’-GGATCC-3’, whose opposite strand is 3’-CCTAGG-5’
The restriction enzyme then cuts it to either make blunt or sticky ends

Question 22

Define

Sticky End

Answer 22

A piece of DNA that was cut by a restriction enzyme in a way that left some of the nucleotides unpaired
This can allow for the joining of DNA from different sources

Question 23

Summarize the process of making recombinant bacterial cultures

Answer 23

1. Identify the gene of interest (GOI)
2. Find a restriction site outside of the GOI
3. Find a plasmid that has the same restriction sites
4. Combine the GOI, plasmid, and restriction enzyme
5. Use DNA ligase to rejoin the sticky ends
6. Get bacteria to take up the plasmid
7. Culture the bacteria
8. Test bacteria to ensure it has taken up the GOI

Question 24

Define

Competent

In reference to bacterial transformation

Answer 24

Competent bacteria are those able to take up plasmids from their environment
Usually requires causing some type of stress to the bacteria, such as by heat-shocking

Question 25

What is gel electrophoresis?

Answer 25

A method of separating DNA fragments (usually cut into fragments by restriction enzymes) by size

Question 26

Outline the process of gel electrophoresis

Answer 26

Solution containing DNA fragments are injected into wells within an agarose gel slab
A gel electrophoresis chamber applies a current through the gel, with a + electrode at one end
Small fragments of DNA are attracted to the + electrode and travel quickly through the agarose gel
Larger fragments are attracted to the + electrode but travel more slowly through the agarose

Question 27

What is PCR?

Answer 27

Polymerase chain reaction
A method of amplifying a small quantity of DNA to make a huge number of copies

Question 28

Describe the steps of PCR

Answer 28

DNA gene of interest, RNA primers, polymerase, and DNA nucleotides are placed into a test tube then go through repeated cycles of:
1. Heating, which separates the strands of DNA (denaturation)
2. Cooling, which allows primers to bind to the DNA (annealing)
3. Waiting, which allows the polymerase to build onto the primers and make new DNA strands

Each cycle doubles the amount of the gene present