Intro Flashcards
What are genetic materials?
Materials that play fundamental roles in the composition of living organisms
What are the two types of genetic materials?
Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA)
Where are genetic materials located?
DNA:
- Located in the nucleus of eukaryotic cells (animals and plants) and the cytoplasm of prokaryotic cells (bacteria)
- Also located in the mitochondria
RNA:
- Located in the Cytosol
- Located in Ribosomes
How does DNA differ from RNA?
Draw the bases in each
What is the difference between a nucleoside and a nucleotide?
A building block of DNA or RNA, a nucleotide is made up of the sugar, nitrogenous bases, and phosphate while the nucleoside is made up of sugar and base only
Draw a table of comparision of the structure, function and length between DNA and RNA
Draw a table of comparison between DNA and RNA
Consider;
- Bases
- Base pairs
- Sugars
- Location
- Reactivity
- Ultraviolet (UV) sensitivity
Demonstrating DNA is the Genetic Material:
Describe the methodolgy of the Pneumococcus bacterium transformation experiment by Fred Griffiths
Virulent Type 1:
- disease causing
- protected by slime capsule
- giving smooth appearance
- Causes pneumonia
Non-virulent Type 2:
- harmless
- lost its slime capsule
- rough appearance
Describe the outcome (findings) of the Pneumococcus bacterium transformation experiment by Fred Griffiths
- He took smooth virulent type 1 bacteria and injected into mouse→The mouse died When examined, live type 1 smooth virulent bacteria was found
- Injected the mouse with type II rough, avirulent bacteria→ The mouse survived Immune system took care of the bacteria
- Griffith took a heat killed sample of the type 1 bacteria and injected it into mouse→ The mouse survived
- A sample of type I heat killed bacteria was mixed with type II rough avirulent bacteria→The mouse died. Live type 1 smooth bacteria was found upon examination
Describe the conclusion of the Pneumococcus bacterium transformation experiment by Fred Griffiths
- Concluded something from heat killed cell converted rough avirulent type II cell to type I one cell
- We now know that something was gene for type I slim capsule
- At the time, the gene was not known
- Griffith just knew something was causing the conversion and he called it ‘ transforming principle’
How did Avery discover the bio-molecule in S (type 1, virulent bacteria) that can transform R (type 2, avirulent bacteria)?
- Remove the lipids and carbohydrates from a solution of heat-killed S cells. Only proteins, RNA and DNA remain
- Subject the solution to treatments of enzymes that destroy either the proteins, RNA or DNA
- Add a small portion of each sample to a culture containig R cells.
- Observe whether transformation has occured by testing the presence to virulent S cells
Conclusion: Transformation cannot occur unless DNA is present. Therfore, DNA must be the hereditary material.
Why do we need to obtain genetic materials?
- To study the genetic causes of disease, e.g. cystic fibrosis
- Development of diagnostics and drugs
- Carrying out forensic science
- Sequencing genomes
- Detecting bacteria and viruses in the environment
- Determining paternity
Why are model systems/organisms important?
Model Systems/organisms for Molecular/Cellular Biology are chosen because they are convenient to study or are of practical importance.
Give examples of model organisms
- Bacteria (E. coli)
- Yeast (Saccharomyces cerevisiae)
- Round worms (Caenorhabditis elegans)
- Fruit fly (Drosophila melanogaster)
- Zebrafish (Danio rerio)
- Animals (e.g. rodents, pigs, primates……)
- Humans
What makes an organism amenable to molecular biology research?
- Location in the tree of life
- Ability to obtain candidate genes via either sequencing or cloning
- Ability to determine gene expression patterns at different stages of the organism’s development
- Ability to grow or obtain large numbers of organisms
- Ability to knockout or functionally inactive genes to ascertain the role of the gene plays in the organism’s growth, development, metabolism etc.
What are some of the different methods of obtaining genetic material from model organisms?
- Breaking open the cells to release DNA/RNA
- Separate DNA/RNA from protein:
Traditional Phenol extraction
Column-based extraction: Silica and anion exchange resins
- DNA purification:
Removal of RNA using ribonuclease
DNA purification via ethanol precipitation
What are some other sources of genetic material (artificial DNA)?
- Amplification
- Reverse transcription of mRNA
What is PCR?
Polymerase Chain Reaction (PCR):
- A laboratory technique for DNA replication that allows a “target” DNA sequence to be selectively amplified.
- PCR can use the smallest sample of the DNA to be cloned and amplify it to millions of copies in a short period of time
Breifly describe how PCR works
First cycle:
- Start with a region of double stranded chromosomal DNA to be amplified
- Separate the DNA strands and add a DNA oligonucleotide primer
- DNA is synthesised in this first cycle to produce two double-stranded DNA molecule
Second cycle:
- Separate the DNA strands and anneal the primer
- DNA is synthesised in this second cycle to produce four double stranded DNA molecules
Third cycle:
- Separate the DNA strands and anneal the primer
- DNA is synthesised in this this third cycle to produc eight double-stranded DNA molecules
What is RT-PCR?
Reverse transcriptase PCR (RT-PCR):
A laboratory technique combining reverse transcription of RNA into DNA (in this context called complementary DNA or cDNA) and amplification of specific DNA targets using PCR.
Briefly describe how RT-PCR works
- From a tissue sample lyse the cells and purify the mRNA
- Hybridise the mRNA with a poly(T) primer
- Make a DNA copy with the reverse transcriptase enzyme
- Degrade RNA with RNase H enzyme
- Synthesise a complementary DNA strand using DNA polymerase; the RNA fragment acts as a primer
- A double stranded cDNA copy of the original mRNA is produced
What are the advantages of using mRNA?
- Represents only contiguous coding material - introns occupy 9/10ths of a eukaryote gene. Hence using mRNA can get a gene into a vector
- mRNA free from wild type promoters
- mRNA represents the genes most actively coding for proteins - only 2% of genomic material is involved in protein coding
