DNA and gene technologies essay plan Flashcards
(5 cards)
3.8.4.1 PCR (polymerase chain reaction)
-The PCR process requires DNA strands that include the gene of interest, activated nucleotides and a thermocycler
-Primers are short, single-stranded DNA sequences used to locate the genes of interest
-Taq polymerase is a heat stable enzyme from bacteria living in hot springs
1) DNA strands are separated by increasing the temperature to 95ºC
2) Primers anneal at 55ºC, complimentary base pairing occurs at the specific DNA sequence of interest, primers also prevent the two strands rejoining
3) At 72ºC the DNA is synthesised by the Taq polymerase, which forms the phosphodiester bonds. DNA is extended in both directions and the cycle repeats
-PCR is an important process because it is a relatively simple and quick method of DNA amplification compared to using bacteria. The DNA produced can be used to create genetically modified organisms for insulin production. It also helps to diagnose genetic disorders and can allow for personalised medicine/genetic counselling
3.8.4.3 Gel electrophoresis and genetic fingerprinting
-Variable Number Tandem repeats are analysed, as there is a very low likelihood of two individuals having the exact same VNTRs, the closer two individuals are related the more similar they will be
-Genetic fingerprinting begins with Gel electrophoresis, where DNA samples are collected and cut into the VNTRs using restriction endonucleases, they are then loaded into wells on agar gel and a buffer solution and electrical current are applied. Smaller pieces move further and faster, separating the VNTR lengths
-DNA probes are added, with the hybridised DNA transferred to a nylon sheet that is observed under X-ray or UV light to see the position of the probes
-These can then be analysed and compared to establish genetic relationships, or the presence of specific genes
-Genetic fingerprinting is important in the medical field to identify if a person has disease-causing alleles that may be passed onto their children, or can affect the individual themselves. This can also help to match a patient to specific medications. This is also important as it can be used in both paternity testing, or matching unknown samples-specifically in the context of a crime scene
3.1.5.1 DNA structure
-DNA is a double-helix polynucleotide
-The nucleotides are made up of a phosphate group, deoxyribose ( a pentose sugar), and a nitrogen-containing base
-The bases are adenine, thymine, cytosine and guanine
-The double helix structure is formed by hydrogen bonds between complimentary paired bases (c-g, a-t)
-A condensation reaction between the phosphate group and sugar of two adjacent nucleotides forms a phosphodiester bond, which forms the sugar backbone
-DNA is important as an information-carrying molecule because its stable and replicable allows for inheritance, specifically of favourable alleles which can be passed on to offspring, allowing for continued survival and reproduction. DNA also has a universal code, this allows for gene transfer across different species in gene technologies
3.1.5.2 DNA replication
-DNA helicase ‘unzips’ the hydrogen between nucleotides to form two template strands
-Free nucleotides bind to the exposed strand by complementary base pairing (adenine-thymine, cytosine-guanine)
-DNA polymerase synthesises phosphodiester bonds between the phosphate and sugar of two adjacent nucleotides
-Two identical strands are formed
-Replication is semi-conservative as each new strand contains a strand from the original DNA molecule and one new strand
-Semi-conservative replication is important because it ensures the sequence of bases is faithfully copied during interphase, and can then be passed onto daughter cells during mitosis. Semi-conservative replication is also a base principle for gene technologies, such as PCR, which can amplify specified genes
3.8.2.2 Regulation of transcription by transcriptional factors
-In eukaryotes, transcription of DNA can be stimulated by transcriptional factors
-These are proteins that move from the cytoplasm to the nucleus to bind to DNA
-For example: oestrogen is a steroid hormone that is lipid soluble, so can enter the cell via facilitated diffusion. It then binds to the transcriptional factor, altering its shape so that it can enter the nucleus through nuclear pores, and bind to the DNA molecule.
-Transcriptional factors are important as they stimulate mRNA transcription, once bound to the DNA, RNA polymerase is then able to bind to the transcription factor to begin transcription
-This is important as the mRNA can then be translated to then form essential proteins for life, such as enzymes involved in respiration and photosynthesis
-Transcriptional factors turn genes on/off when binding, which is what allows cells to become specialised
