Molecular Biology and Gel Electrophoresis

Question 1

What does the abbreviation DNA stand for?

Answer 1

Deoxyribonucleic acid

Question 2

What is a gene?

Answer 2

A small section of a chromosome which determines a characteristic or trait

Question 3

What is a genome?

Answer 3

The complete set of genetic material in an organism

Question 4

DNA contains 4 different types of bases, what are these bases?

Answer 4

Adenine, thymine, cytosine, guanine

Question 5

Explain basic DNA structure in terms of sugars, bases and phosphates

Answer 5

• Nucleotides joined by phosphodiester bonds with sugar phosphate backbone
• A nitrogenous base attached to a sugar group and a phosphate group makes up a nucleotide

Question 6

Explain the central dogma of molecular biology

Answer 6

Involves DNA replication, transcription and translation in order to make proteins

Question 7

Explain “the information for making a new strand of DNA comes from an old strand of DNA”

Answer 7

In DNA replication, An old strand of DNA becomes a template to create a new complementary strand

Question 8

Explain transcription

Answer 8

Copying a double strand of DNA to a single strand of RNA in the nucleus

Question 9

Explain translation

Answer 9

The synthesis of proteins from mRNA that takes place in the ribosomes

Question 10

What is a codon

Answer 10

A sequence of three nucleotides which together form a unit of genetic code in DNA or RNA

Question 11

What is meant by genetic code?

Answer 11

The genetic information carried by DNA and RNA in living cells

Question 12

What are two differences between RNA polymerases and DNA polymerases?

Answer 12

• RNA polymerase does not need a primer but DNA polymerase does
• DNA polymerase synthesises DNA for transcription and RNA polymerase synthesises mRNA during transcription

Question 13

Restriction enzyme

Answer 13

Enzymes that cut a DNA molecule at a particular location

Question 14

Ligase enzyme

Answer 14

Joins DNA strands together

Question 15

Are there any infectious disease causing agents that can not be detected using a PCR type reaction? If so, name one such agent or disease.

Answer 15

Yes

Question 16

Ligase enzyme

Answer 16

Joins DNA strands together by catalyzing the formation of a phosphodiester bond

Question 17

How can PCR be used in sex determination?

Answer 17

Set up a PCR reaction as normal, attach appropriate primers to female DNA and male DNA. The annealing sites of these primers means that the female DNA (including XX chromosomes) will produce 1 band of 488 base pairs, and male DNA (including XY chromosomes) will produce one band of 488 base pairs, and one pair of 340 base pairs

Question 18

What are 3 other applications of PCR?

Answer 18

• Diagnosis of genetic disease
• Archaeology to identify human or animal remains
• Research (creating copies of DNA in order to host microbes and discover how they work)

Question 19

Describe the steps of PCR

Answer 19

Denaturing: Heating DNA to approx 95 degrees to break the hydrogen bonds between the double strands of DNA and create two single strands
Annealing: Attaching primers to the DNA strands to determine where polymerase will start attaching base pairs at 50-75 degrees
Extension: Polymerase adds base pairs to each strand in order to create two double stranded DNA molecules at 72 degrees

Question 20

Are there any infectious disease causing agents that can not be detected using a PCR type reaction? If so, name one such agent or disease.

Answer 20

Yes, PCR is used to amplify DNA, so disease causing agents that do not have DNA (e.g. prions) are hard to detect with PCR

Question 21

Describe an application of electrophoresis

Answer 21

Paternity and maternity testing

Question 22

When electrophoresed over a given period of
time, will a small DNA molecule usually migrate
a shorter distance or a further/longer distance
through an agraose gel, compared to a large
DNA molecule?

Answer 22

Longer; smaller molecules travel faster through agarose gel than larger molecules

Question 23

True or False? “electrophoresis can separate

molecules based on both size and charge”

Answer 23

True

Question 24

What types of molecules can be separated

using Electrophoresis?

Answer 24

DNA

Question 25

A certain type of PAGE can be used to
separate denatured proteins. What are
denatured proteins?

Answer 25

Denatured proteins are proteins that proteins that have disrupted/destroyed secondary and tertiary structures, and are only left with their primary structure