Topic 8 Flashcards
Gene mutation
change in base sequence of DNA
occurs during DNA replication
includes addition, deletion, substitution, inversion, duplication and translocation of bases
Mutagenic agents
chemical or radiation that increases mutation rate
Addition mutation
One extra base is added to the DNA sequence
causes all subsequent codons to be altered (frameshift)
Deletion mutation
One base is deleted in the DNA sequence.
causes all subsequent codons to be altered (frameshift)
Substitution mutation
One base in the DNA sequence is changed
no frameshift
only one codon changes
may have no impact due to degenerate genetic code
Frameshift
A change in all the codons after the point of mutation
each base shifts left or right one position
Inversion mutation
A section of bases detach from the DNA sequence and re-join inverted
results in different amino acids being coded for in this region
Duplication mutation
One base is duplicated at least once in the sequence
causes a frameshift to the right
Translocation of bases mutation
A section of bases on one chromosome detaches and attaches to a different chromosome
Non-functioning protein
a protein with a different primary and tertiary structure therefore the shape is changed it cannot carry out its function
Benign tumour
a mass of cells as a result of uncontrolled cell division
can be benign or malignant
non-cancerous tumour
grows large but at a slow rate
produce adhesive and are surrounded by a capsule so they cannot spread
Malignant tumour
Malignant tumours that form due to uncontrolled cell division
cancer cells breaking off from the tumour
spreading to form secondary tumours in different tissues or organs
Oncogene
a mutated version of a proto-oncogene
results in constant initiation of DNA replication and mitotic cell division
causes tumour formation
Tumour suppressor genes
genes that produce proteins to slow down cell division and cause cell death if DNA copying errors are detected
Epigenetics
the heritable change in gene function without changing the DNA base sequence caused by changes in the environment
can inhibit transcription
Hypermethylation
an increased number of methyl groups attached to a gene results in the gene being deactivated
results in cancer if happens to a tumour suppressor gene
inhibits transcription
Methylation of DNA
methyl groups attach to the cytosine base on DNA prevents transcriptional factors from binding
condenses the DNA-histone complex
How can oestrogen increase the risk of breast cancer?
Oestrogen is a steroid hormone it binds to a receptor site on a transcriptional factor causing a change in shape so it can bind to the DNA to initiate transcription
can result in uncontrolled cell division
Stem cell
undifferentiated cells that can continually divide and become specialised
Totipotent stem cell
occur for a limited time in early mammalian embryos
can differentiate into almost any body cell
Pluripotent stem cell
occur in embryos
can differentiate into almost any body cell
But not placenta cells
Multipotent stem cell
can differentiate into a limited number of cells
found in mature mammals bone marrow
What is a unipotent stem cell?
Stem cell that can differentiate into one type of cell
found in mature mammals
What is an induced pluripotent stem cell?
Stem cell produced from adult somatic cells
using protein transcriptional factors
Turns on all genes which were switched off to make it specialised therefore regaining state of pluripotency
overcomes ethical issues of using embryonic stem cells
What is a transcriptional factor?
Proteins that can bind to different base sequences on DNA to initiate transcription of genes
What is RNA interference (RNAi)?
Inhibition of the translation of mRNA by small interfering RNA (siRNA)
siRNA destroys mRNA molecules to prevent translation
An enzyme breaks a long double stranded rna into siRNA
One of the two strands of siRNA joins with an enzyme
siRNA inside navigates the enzyme to a mRNA and binds to complimentary bases and now the enzyme breaks down mRNA into smaller fragments and these cannot be translated
Therefore gene not expressed
What is a vector?
A DNA molecule used as a carrier of isolated DNA fragment e.g. plasmids/viruses
What is acetylation of histones?
Process where decreased acetylation inhibits transcription by making histones more positive and attracting the negative phosphate group on DNA
Decreased acetylation forms heterochromatin
Increased acetylation forms chromatin
What is recombinant DNA technology?
Combining different organisms’ DNA to manipulate and alter genes for industrial processes and medical treatment
What are sequencing projects?
Reading the full genome of organisms to screen DNA for potential medical problems
How can you create a DNA fragment?
By using a gene machine, reverse transcription with reverse transcriptase, or restriction endonucleases
What is reverse transcriptase?
An enzyme that makes cDNA single-stranded copies of DNA from mRNA
What is a restriction endonuclease?
Enzymes that cut up DNA to create fragments by cutting at specific recognition/restriction sequences
What is in vivo cloning?
Creating DNA fragments using bacteria and restriction endonuclease enzymes
What is in vitro cloning?
Using PCR to create a large number of copies of a DNA fragment
What are the uses of PCR?
Widely used in gene technology for forensics, genotyping, cloning, paternity tests, and microarrays
What is gel electrophoresis?
Separation of DNA samples using an electrical voltage to separate different lengths of DNA VNTRs
Why does DNA move in gel electrophoresis?
DNA is negatively charged and moves towards the positive end of the gel; shorter DNA pieces move faster and further
What is genetic screening?
Testing DNA to identify the presence of alleles that can cause/increase the risk of developing a disease
What is genetic counselling?
Type of social work giving people advice following the screening of disease-causing alleles
What is cDNA?
Complementary, single-stranded DNA strands created by reverse transcriptase
What are the advantages of using the gene machine?
Very quick, accurate, and can create intron-free DNA
What are the advantages of using reverse transcription?
Create intron-free cDNA
What are the advantages of using restriction endonucleases?
Create sticky ends on DNA to enable DNA fragments to join with complementary base pairs
What are oligonucleotides?
Short DNA molecules used in gene machines to create DNA fragments
What are sticky ends?
Exposed staggered ends of bases created by restriction endonuclease enzymes
What is a palindromic sequence?
Sequences of bases that read the same forwards as they do backwards
What is a blunt end?
When a restriction endonuclease cuts the DNA double-strand in the same position without overhang of bases
What are the two methods to amplify DNA?
In vivo and in vitro (PCR)
What is a promoter region?
A sequence of DNA that is the binding site for RNA polymerase to enable transcription to occur
What is a terminator region?
Added at the end of the gene to cause RNA polymerase to detach and stop transcription
What is a plasmid?
A circular DNA molecule used as a vector in recombinant DNA technology
What is a recombinant plasmid?
A plasmid that has had foreign DNA inserted into it for cloning purposes
What happens when a restriction endonuclease cuts the DNA double-strand in the same position?
There is no overhang of bases
Example sentence: The restriction endonuclease EcoRI cuts the DNA double-strand in the same position, resulting in no overhang of bases.
What is the Promoter region?
A sequence of DNA that is the binding site for RNA polymerase to enable transcription to occur
Additional information: The promoter region plays a crucial role in initiating the transcription process.
What is the Terminator region?
A region added at the end of the gene that causes RNA polymerase to detach and stop transcription to ensure one gene is copied into mRNA at a time
What is a Plasmid?
A small loop of bacterial DNA that contains only a few genes
Additional information: Plasmids are commonly used in genetic engineering for gene cloning purposes.
What is a Recombinant plasmid?
A small loop of bacterial DNA with the DNA from another organism inserted into it
What is Transformation?
The process of getting a plasmid to re-enter a bacterium, involving calcium ions and temperature shocking
How can transformed cells be identified?
Using marker genes such as antibiotic resistance genes, genes coding for fluorescent proteins, or enzymes
What is a DNA probe?
Short, single-stranded pieces of DNA labelled radioactively or fluorescently so that they can be identified
What is DNA hybridisation?
DNA is heated to separate the double helix into single strands, mixed with complementary sequences of single-stranded DNA, and then cooled for complementary strands to anneal
What are VNTRs?
Variable number tandem repeats sequences of bases in introns that are unique to each person
How can DNA samples be collected?
From blood, body cells, or hair follicles
How is DNA extracted from cells so that it can be examined?
Through cell fractionation and ultracentrifugation
How is DNA digested in genetic fingerprinting?
Restriction endonucleases are added to cut the DNA into smaller fragments, followed by the addition of enzymes that cut close to the target VNTRs
Why can the genome not be easily translated into the proteome in complex organisms?
Due to the presence of non-coding DNA and regulatory genes
What is the role of DNA ligase in making recombinant DNA?
DNA ligase is used to stick the DNA fragment to create recombinant DNA
