Molecular Biology and Gel Electrophoresis
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What does the abbreviation DNA stand for?
Deoxyribonucleic acid
What is a gene?
A small section of a chromosome which determines a characteristic or trait
What is a genome?
The complete set of genetic material in an organism
DNA contains 4 different types of bases, what are these bases?
Adenine, thymine, cytosine, guanine
Explain basic DNA structure in terms of sugars, bases and phosphates
• 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
Explain the central dogma of molecular biology
Involves DNA replication, transcription and translation in order to make proteins
Explain “the information for making a new strand of DNA comes from an old strand of DNA”
In DNA replication, An old strand of DNA becomes a template to create a new complementary strand
Explain transcription
Copying a double strand of DNA to a single strand of RNA in the nucleus
Explain translation
The synthesis of proteins from mRNA that takes place in the ribosomes
What is a codon
A sequence of three nucleotides which together form a unit of genetic code in DNA or RNA
What is meant by genetic code?
The genetic information carried by DNA and RNA in living cells
What are two differences between RNA polymerases and DNA polymerases?
• RNA polymerase does not need a primer but DNA polymerase does • DNA polymerase synthesises DNA for transcription and RNA polymerase synthesises mRNA during transcription
Restriction enzyme
Enzymes that cut a DNA molecule at a particular location
Ligase enzyme
Joins DNA strands together
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.
Yes
Ligase enzyme
Joins DNA strands together by catalyzing the formation of a phosphodiester bond
How can PCR be used in sex determination?
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
What are 3 other applications of PCR?
• 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)
Describe the steps of PCR
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
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.
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
Describe an application of electrophoresis
Paternity and maternity testing
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?
Longer; smaller molecules travel faster through agarose gel than larger molecules
True or False? “electrophoresis can separate molecules based on both size and charge”
True
What types of molecules can be separated using Electrophoresis?
DNA