molecular biology Flashcards
DNA
deoxyribonucleic acid
What is a gene?
an inheritance unit that helps determine a trait
genome
The complete set of genetic material in an organism
DNA contains 4 different types of bases
adenine
thymine
guanine
cytosine
Explain basic DNA structure in terms of sugars
bases and phosphates,
Nitrogenous bases are attached to a sugar-phosphate backbone
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
transcription
synthesis of RNA from DNA template where the code in the DNA is converted into a complementary RNA code
Explain the steps involved in transcription
- Before transcription can take place, the DNA double helix must unwind near the gene that is getting transcribed. One strand, the template strand, serves as a template for synthesis of a complementary RNA transcript. The other strand, the coding strand, is identical to the RNA transcript in sequence, except that it has uracil (U) bases in place of thymine (T) bases.
- The RNA transcript is read to produce a polypeptide.
- If the gene that’s transcribed encodes a protein (which many genes do), the RNA molecule will be read to make a protein in a process called translation.
translation
synthesis of a protein from an mRNA template where the code in the mRNA is converted into an amino acid sequence in a protein
Explain the steps in translation
- Initiation: in this stage, the ribosome gets together with the mRNA and the first tRNA so translation can begin.
- Elongation: in this stage, amino acids are brought to the ribosome by tRNAs and linked together to form a chain.
- Termination: in the last stage, the finished polypeptide is released to go and do its job in the cell.
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
What is a restriction enzyme?
Enzymes that cut a DNA molecule at a particular location
What is a Ligase enzyme?
Joins DNA strands together
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
- Forensics
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 Electrophoresis
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 will go less distance and short will travel further
smaller molecules travel faster through agarose gel than larger molecules. true or false
true
True or False? “electrophoresis can separate molecules based on both size and charge”
true
What types of molecules can be separated using Electrophoresis?
DNA
A certain type of PAGE can be used to separate denatured proteins. What are denatured proteins?
Denatured proteins are proteins that proteins that have disrupted/destroyed secondary and tertiary structures, and are only left with their primary structure
What is meant by the term “metabolism”?
A sequence of enzyme catalysed chemical reactions in the cell - both anabolic and catabolic reactions
Anabolic and catabolic pathways are different. Explain two of the differences between an anabolic pathway and a catabolic pathway.
Anabolic: Concerned with the processes involved in the assembly of complex organic molecules, requires energy and has divergent pathway
Catabolic: Processes related to degradation of complex substances, with resulting generation of energy, conserves energy and has a convergent pathway
What is an enzyme?
Catalysts that regulate the chemistry of cells and organisms
What is an enzyme active site?
Part of enzyme involved in the catalytic reaction
When referring to an enzymatic reaction what is meant by the term “substrate”?
The reactant in an enzyme-catalysed reaction (Substance acted upon by the enzyme)
When referring to an enzymatic reaction what is meant by the term “product”?
What is produced after the enzyme and substrate have bonded together
List and explain four (4) variables that can effect enzyme activity.
- Temperature: Each enzyme has an optimum temperature, and can only work within a certain range of temperatures.
- pH: Each enzyme has an optimum pH, and can only work within a certain range of pH levels.
- Substrate concentration: The more substrates that bind with available enzymes, the faster the reaction.
- Enzyme concentration: The greater the number of enzymes that are able to bind with a substrate the faster the reaction.
A laboratory assay uses an enzymatic reaction as part of the assay procedure. Explain why the incorrect incubation time for the laboratory assay may effect the results of the assay
This could affect the temperature that the enzyme is working in, and the enzyme may not be able to work effectively.
List 4 different types of biological specimens that may be used in a Biomedical Science or Pathology laboratory.
- Blood
- Urine
- Faeces
- Solid tissue
Name the cellular components of blood
RBC
WBC
platelets
Name 3 components of blood required for clotting
- Ca2+
- Platelets
- Clotting proteins e.g. fibrinogen
Is there a difference between serum and plasma? Explain your answer.
Plasma: liquid portion of blood
Serum: liquid portion of blood without clotting components
What is an anticoagulant?
A substance that allows the plasma portion of blood to be separated from the rest
List one anticoagulant and explain its mode of action.
Heparin: inhibits clotting proteins (eg thrombin)
Why are different anticoagulants used when collecting blood?
Different coagulants have different purposes and modes of action, e.g. sodium fluoride preserves glucose in blood and oxalate joins calcium ions together.
Why is correct identification of a patient sample important?
So that the patient waiting for results does not get an incorrect diagnosis, treatment or intervention.
List 2 reasons that a patient sample may be unsuitable for a laboratory assay necessitating the recollection of a sample
- If the patient is identified incorrectly
- If the sample is damaged while being transported
Haemophilia is a disease studied in a Coagulation laboratory. What is Haemophilia?
A blood disorder where blood is not able to clot properly
Why might a protein need to be separated from a mixture of other proteins?
There may only be one protein that you need in order to complete your analysis/testing
What types of molecules can be separated from a mixture using Chromatography?
DNA
RNA
other organic molecules
List three Chromatography principles that can be used to separate a molecule of interest from a mixture
Ion Exchange: Solid stationary phase and liquid mobile phase
Size Exclusion: Liquid stationary phase and liquid mobile phase
Affinity: Stationary ligand and liquid mobile phase
For each of the 3 chromatography principles what property of the molecule of interest is being utilised (eg size, charge, etc)
Ion exchange: charge
Size exclusion: size
What factors may affect the reliability of a laboratory test result?
Accuracy and precision
Explain the term Accuracy when referring to laboratory results
Closeness of measured value to true value
Explain the term Precision when referring to laboratory results
How close together a set of measurements (of the same parameter) are to each other
