Using Genome Projects (A Level only) (AQA A Level Biology): Flashcards
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What is a genome?
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What is a genome?
A genome contains all of the genes within an organism.
How does a genome project create a reference genome?
DNA samples are collected from many individuals of a species.
These samples are sequenced and compared to create a reference genome.
More than one individual is used because a single organism may carry anomalies atypical of the species.
More than one individual is used to create a reference genome because one organism may have in its DNA sequence that are atypical of the species.
The proteome is all of the proteins that can be produced by a cell.
What was the Human Genome Project (HGP) and when did it begin?
The Human Genome Project began in 1990 as an international, collaborative research programme to sequence the human genome.
Why was the Human Genome Project publicly funded?
So that there would be no commercial interests or influence, and the results would be made publicly available.
This meant data could be shared rapidly between researchers and used by anyone to maximise human benefit.
By 2003 the human genome had been sequenced to accuracy.
By 2003 the human genome had been sequenced to 99.9% accuracy.
Roughly how long is the human genome, and how many genes does it contain?
The finished genome was over 3 billion base pairs long.
It contained only about 25,000 genes, much fewer than expected.
What is the proteome?
The proteome is all of the proteins that can be produced by a cell.
Why are there many more proteins in the proteome than genes in the genome?
Because of processes such as alternative splicing and post-translational modification.
What is the epigenome?
The epigenome consists of the inherited changes in DNA that do not involve a change in the DNA base sequence.
Once the genome of a simpler organism is known, what can scientists do with it?
Use bioinformatics to identify genes
Predict the amino acid sequences of proteins
Study which proteins are actively expressed in different conditions
Why are the genomes of simpler organisms (e.g. bacteria and viruses) easier to sequence and interpret?
They have smaller genomes
They have no introns (especially in prokaryotes)
They have less complex gene regulation
Large databases store information about an organism's gene sequences and its sequences.
Large databases store information about an organism's gene sequences and its amino acid sequences.
In vaccine production, what is an antigen?
An antigen is a protein on the surface of a pathogen that triggers an immune response.
Outline the steps used to identify a suitable antigen for a vaccine from a pathogen's genome
Sequence the genome of the pathogen
Use computational tools to predict the proteome
Identify proteins that are on the surface, are unique to the pathogen, and can stimulate an immune response
Use these proteins as antigens in the vaccine
Which parasite causes severe malaria, and how were its antigen genes identified?
Plasmodium falciparum causes severe malaria.
Thousands of parasites were genome sequenced and compared to find the genes with the highest variation between individuals.
High variation suggests strong selective pressure, indicating these genes could code for antigen proteins.
The first malaria vaccine approved for human use is (Mosquirix), which targets a surface protein of Plasmodium falciparum.
The first malaria vaccine approved for human use is RTS,S (Mosquirix), which targets a surface protein of Plasmodium falciparum.
True or False?
A gene showing a high level of variation between individuals is likely to be under strong selective pressure
True.
A high level of variation suggests the gene is under strong selective pressure; such genes could code for the antigen proteins found on the parasite.
Why does knowing the proteome of a pathogen help vaccine development?
It enables scientists to identify antigens – the surface proteins that trigger an immune response – which can then be used in vaccines.
Why is it difficult to translate the genome of a complex organism into its proteome?
Large amounts of non-coding DNA (introns and repetitive sequences) are present and are hard to distinguish from coding DNA.
Simply knowing the sequence doesn't tell you which regions are coding or expressed.
Which types of sequence make up the non-coding DNA of the human genome?
Introns
Repetitive sequences
Proteins are made from the regions of the genome, via transcription and translation.
Proteins are made from the coding regions of the genome, via transcription and translation.
What is the role of regulatory genes?
Regulatory genes control the expression of other genes.
They do not code for proteins directly, but influence which genes are transcribed and translated.
Give two reasons why the proteome is larger than the genome
Alternative splicing
Post-translational modification of proteins
What is post-translational modification?
The modification of a protein molecule after translation, which often takes place in the Golgi apparatus or endoplasmic reticulum.
True or False?
The proteome is the same in all cells and stays constant over time
The modification of a protein molecule after translation, which often takes place in the Golgi apparatus or endoplasmic reticulum.
Regulatory genes do not code for proteins directly, but they influence which genes are transcribed and .
Regulatory genes do not code for proteins directly, but they influence which genes are transcribed and translated.
Why does simply knowing a DNA sequence not reveal the proteome of a complex organism?
It is very hard to identify the non-coding sections (introns and repetitive sequences) from the coding DNA.
The sequence alone does not tell you which regions are coding or expressed.
What is DNA sequencing?
DNA sequencing is the process of determining the exact order of nucleotide bases (A, T, C, G) in a DNA molecule.
How have modern DNA sequencing methods changed?
They are continuously evolving and becoming faster.
Most methods are now automated, allowing scientists to rapidly sequence whole genomes.
What is done with the data obtained from sequencing?
It is entered into computers running specialised programmes that compare the base sequences of different organisms.
Which type of nucleotide do all DNA sequencing methods use?
All methods use dideoxyribose nucleotides, which are very similar to deoxyribose nucleotides but have one less oxygen atom.
A dideoxyribose molecule has one less oxygen atom than a deoxyribose molecule and fewer oxygen atoms than a ribose molecule.
A dideoxyribose molecule has one less oxygen atom than a deoxyribose molecule and two fewer oxygen atoms than a ribose molecule.
Why does DNA replication stop when a dideoxyribose nucleotide is added to the new strand?
When DNA polymerase encounters a dideoxyribose nucleotide on the developing strand, it stops replicating.
This is the chain-termination technique used for DNA sequencing.
An automated DNA sequencing machine can read roughly different DNA sequences within 2 hours.
An automated DNA sequencing machine can read roughly 100 different DNA sequences within 2 hours.
True or False?
Automated DNA sequencing can detect fragments differing by just one base
True.
The process is extremely accurate and can detect fragments differing by just one base.
In DNA sequencing, is it the template strand or the new strand that is sequenced?
It is the new (test) strand that is sequenced, not the original template strand.
Because bases pair specifically (A–T, C–G), the template strand can be worked out from the test strand.
Dideoxyribose nucleotides can pair with deoxyribose nucleotides on the template strand that have a base.
Dideoxyribose nucleotides can pair with deoxyribose nucleotides on the template strand that have a complementary base.
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