The control of gene expression Flashcards
What is insertion?
when a nucleotide is randomly inserted into a DNA sequence
affects function of the polypeptide due to causing a frameshift
causes Huntington’s disease
What is deletion?
when a nucleotide is randomly deleted in a DNA sequence
affects function of the polypeptide due to causing a frameshift
causes Cystic fibrosis
What is substitution?
where a DNA nucleotide is swapped for a different one
It is:
silent - doesn’t alter amino acid sequence
missense - alters a single amino acid
nonsense - can create a premature stop codon
causes sickle-cell anaemia
What is inversion?
when a single gene is cut in 2 places, inverted 180 degrees and re-joined
results in a non- functional protein
causes haemophilia A
What is duplication?
where one or more nucleotides are duplicated in a DNA sequence
original gene is not gene
causes Charcot-Marie tooth disease
What is translocation?
when a section of a chromosome is added to another chromosome that isn’t its homologous partner
Philadelphia chromosome that’s found in leukaemia cancer
What is a cause of mutations?
chemical mutagents
ionising radiation
errors in DNA replication
What are stem cells?
Stem cells are undifferentiated cells which can keep dividing to give rise to other cell types
What is a totipotent stem cell?
cells that are able to differentiate into any type of cell found in body and into
extra embryonic cells such as those in the placenta.
What are pluripotent cells?
cells that can form any cell type in the body, however cannot form extra embryonic cells.
What are multipotent cells?
can differentiate into other cells
types but are more limited
What are unipotent cells?
these cells can only differentiate
into one type of cell
How can oestrogen alter transcription?
-The lipid soluble nature of oestrogen means that is can freely diffuse across the cell
membrane where is binds to a receptor molecule on a transcription factor
-The binding alters the shape of the DNA binding site on the transcription factor and makes it
able to bind to the DNA.
-The transcription factor therefore enters the nucleus via the nuclear pore where it binds to DNA. This stimulates the transcription of the gene that makes up the DNA.
What are transcriptional factors?
molecules that bind to a specific site on DNA to begin the
process of transcription
What is small interrupting RNA and what does it do?
silencing DNA that ‘switches off’ genes by binding onto strands and preventing transcription
What is genomics?
the study of the whole set of genetic information in the form
of the DNA base sequences that occur in the cells of organisms of a particular species
What is a genome?
the complete set of genetic information contained within an organism / cell
What is a proteome?
the full range of proteins that the cell can produce
Why is determining the proteome of a simple organism easy?
-They have just one, circular piece of DNA that is not associated with histones
-There are no non-coding portions of DNA which are typical of eukaryotic cells
Why is determining the proteome of a complex organism difficult?
-There are many non-coding genes
-Many genes have a role regulating other genes
-Individuals (except identical twins) have different base sequences on their DNA, therefore mapped DNA will differ, slightly, from everyone else’s DNA
What is the Human genome
project?
International research initiative with the primary goal of mapping and
sequencing the entire human genome.
It aimed to determine the order of all the nucleotide bases in human DNA, identify all the genes, and understand their functions.
The project, which began in 1990, was officially completed in
2003.
How were the sections of the human genome cloned in the
Human Genome Project?
introduced into bacteria, allowing the fragments to be
cloned and amplified.
The amplified DNA was then sequenced and pieced together using computational techniques.
What advances have been made as a result of
publishing the research of the Human Genome Project?
-Identification of genes linked to diseases: such as cystic fibrosis,
Huntington’s disease, and certain cancers.
-Advances in personalized medicine: Development of targeted therapies based on individual genetic profiles.
-Biotechnology advancements: Use of genomic data in drug development and agricultural improvements.
-Evolutionary insights: Understanding human evolutionary history and comparing genomes across species.
What is recombinant DNA (rDNA)?
where fragments of foreign DNA are inserted into other sections of DNA
What is genetic engineering?
an area of research that studies the design and construction of different biological pathways, organisms and devices, as well as the redesigning of existing natural biological systems
Describe the steps of genetic engineering:
- Identification of the DNA fragment or gene
- Isolation of the desired DNA fragment
- Multiplication of the DNA fragment (using polymerase chain reaction - PCR)
- Transfer into the organism using a vector (e.g. plasmids, viruses, liposomes)
- Cloning-Identification of the cells with the new DNA fragment (by using a marker), which is then cloned
What is needed to modify an organism?
Enzymes (restriction endonucleases, ligase and reverse transcriptase)
Vectors - used to deliver DNA fragments into a cell (eg. plasmids, viruses and liposomes)
Markers - genes that code for identifiable substances that can be tracked (eg. GFP - green fluorescent protein which fluoresces under
UV light or GUS - β-glucuronidase enzyme which transforms colourless or non-fluorescent substrates into products that are coloured or fluorescent)
What are types of GM crops?
-herbicide-resistant crops
-disease-resistant crops
-crops with increased nutritional
value e.g. Golden Rice
What are 3 methods of creating fragments of DNA?
-Using restriction enzymes
-Reverse transcriptase
-Gene machine
What are restriction endonucleases?
They separate the two strands of DNA at the specific target base sequence or recognition sequence by ‘cutting’ the sugar-phosphate backbone in two ways. Either leaving ‘blunt’ or ‘sticky ends’
Describe mRNA and reverse transcriptase
-Once isolated, the mRNA is then combined with a reverse
transcriptase enzyme and nucleotides to create a single
strand of complementary DNA (cDNA).
-Reverse transcriptase enzymes are sourced from
retroviruses and they catalyse the reaction that reverses
transcription. The mRNA is used as a template to make
the cDNA
-DNA polymerase is then used to convert the single
strand of cDNA into a double-stranded DNA molecule
which contains the desired code for the gene.
-This technique for isolating the desired gene is considered
advantageous as it is easier for scientists to find the gene
because specialised cells will make very specific types of
mRNA
What is the gene machine used for?
-If the amino acid sequence is known, it is possible to synthesise genes artificially.
-Scientists use computers to generate the nucleotide sequence (rather than an mRNA template) to produce the
gene.
-Short fragments of DNA are first produced one nucleotide at a time, which are joined to make longer sequences
of nucleotides and then inserted into vectors (eg. plasmids). This method is being used to create novel genes
contained in vaccines.
What is recombinant DNA (rDNA)?
is a form of DNA that has been artificially created by combining genetic material from two
or more different sources. This technology is used in genetic engineering to produce transgenic/genetically modified
organisms (GMOs).
What is meant by a palindromic recognition sequence?
a specific sequence of DNA bases that reads the same in both directions when looking at complementary strands. These sequences are recognised by restriction enzymes, which cut the DNA at or
near these sites.
