Unit 4 DNA

What is DNA? DNA is one of the chromosomes’ components and is responsible for hereditary traits. It is a molecule made up of two chains that are faced creating a double helix. These chains are respectively formed by the union of nucleotides, organic molecules made up of a fosforic group, a deoxyribose and a nitrogenous base. There are four different nitrogenous bases: adenine, thymine, cytosine and guanine. The nucleotides are named depending on the initial letter of their nitrogenous base and the A ones can only be joined together with the T, the same happens with the nucleotides C and G, being called complementary bases.  

2. What is the importance of Rosalind Franklin in the discovery of DNA? Rosalind Franklin’s important contribution on the discovery of the DNA was due to a photography  known as the “photograph 51” that she took in which it was firstly observed this molecule and its structure  

3. What is the nucleotide sequence? It’s the way in which nucleotides organize in the DNA causing that, despite being only four of them, every organism is different from each other.   

4. Gene and its functions   A gene is a fragment of DNA that codificates the information for a specific hereditary trait. Its functions are: Carrying the genetical information  Controlling the apparition of traits  Transmitting the information from a mother cell to a daughter cell during cellular division    

5. Gene-protein-trait and genetic code Genes themselves don't produce a trait’s phenotype. What they do is provide the data necessary for the creation of a protein that causes that phenotype.However, despite the fact that a gene contains a protein’s whole genetic information the process in which this is translated is really complex. In fact, it wasn’t until the second half of the twentieth century thanks to the work of scientists like Severo Ochoa that the genetic code, the way in which genes are translated into proteins, was discovered. This code says that three nucleotides form an amino acid, an organic molecule that forms a small part of proteins. The structure of three nucleotides that codificates a specific amino acid is called triplet or codon and depending on the three nucleotides that are used the amino acids can change causing the creation of a different protein that will variate the trait’s phenotype.      

6. Transcription and translation To obtain the creation of a specific protein in the ribosomes with the genetic information (DNA) being in the nucleus two different processes must happen: Transcription: is the first process and it happens in the nucleus. It consists of creating a copy of the DNA segment that contains the information necessary for the creation of a specific protein and moving it to the cytoplasm. This copy is made in RNAm, a molecule that differs from the DNA in the fact that it’s made up from just one chain and that instead of thymine it has umine (U) therefore when making the copy this nucleotide is adenine complementary one. Translation: this process takes place in the cytoplasm, where ribosomes are, and consists of creating the protein joining the amino acids in the order that the RNAm says   

7. Replication To carry out this process the DNA separates into the two strands that make it up and, due to the nucleotides’ complementarity, each strand acts as mould for the other chain that has to have the complementary nucleotides of the original. This process ends up in two DNA’s molecules that are made up of one original strand and another new.    

8. Type of mutations - Molecular: It only affects a gene Bases’ replacement Bases’ lost or inversion - Chromosomic: It affects a chromosomes’ segment (various genes) Change of place Lost (delection) Duplication - Genomic: It affects entire chromosomes Changes the number of chromosomes’ sets Disrupts the number of individual chromosomes in a set    

9. Mutagenic agents Mutations can be produced spontaneously, in a natural way, or can be provoked by some agents called mutagenic agents, which can be of two types: Radiations: X rays, ultraviolet light or atomic radiations Chemical substances: Nitrous acid and orange agent 

 10. Are mutations inherited? The inheritance of mutations depends on where its produced On somatic cells: the mutation will disappear when the cell dies, therefore it isn’t inherited. However they can cause tumours, like cancer ones, that belong to cells that have suffered several mutations that lead them to reproduce uncontrollably causing it.   On reproductive cells (gametes): the mutation will be inherited with reproduction since the cell formed by the carrier’s gamete will transfer the mutation to all the cells from the new organism, causing that the mutation can be inherited again.   

 11. Are mutations the key for genetic diversity? Genetic diversity is the variety of the genes’ composition of organisms of the same species and mutations are responsible for it. This is due to the fact that when comparing the nucleotides' sequence of two allele genes, it is usual to find that the difference is of only one or two nucleotides, which are caused by one or various mutations therefore they are responsible for the existence of various alleles in every trait.  

12.  Genetic engineering and genetic recombination Genetic engineering is the group of processes that allow us to move away, modify or add genes to an organism’s DNA molecule to change the information it contains. This manipulation produces new combinations in chromosomes, which is also known as genetic recombination, so the ensemble of the techniques used in genetic engineering is called recombinant DNA technology.  

13.  How to transfer genes? This process is formed by the following steps: Locate the gene that wants to be transferred (transgene) Isolate the gene by using enzymes that cut the DNA by the specific place  Insert the gene in other DNA that acts as a vehicle or vector, this DNA is known as recombinant or recombined Introduce the recombinant DNA in a receptor cell  Make sure that the cell can translate the message contained in the transgene and make the wished protein Clonate the gene

14. What is PCR? PCR or Polymerase chain reaction is a method used to obtain millions of copies of a DNA fragment in a quick and technically easy way. To carry out this process, first the DNA is divided by the action of warmth into the two chains that form it and act as molds for creating its complementary. Then, these molecules are divided again so when the PCR is over the result is 2ⁿ copies of DNA being n the numbers of times the process has been carried out. 

15. What are transgenic organisms? Which are their applications? Transgenic organisms are eukaryotic ones that have been genetically modified to improve their qualities. Their improvements can vary from being able to resist plaques and harder conditions and increasing the production in the cases of transgenic plants to being able to grow faster in animal ones.    

16. How are transgenic organisms produced? In the production of transgenic organisms two phases can be distinguished:  Transformation phase: the transgene is introduced in a cell of the organism that wants to be modified Regeneración phase: an organism made with the modified cell has to be obtained

17. Main fields of genetic engineering Human Genome Project: it was founded in 1990 with the objective of sequencing the whole amount of genes that chromosomes have  Genographic Project: it was created National Geographic Society and IBM to obtain the biggest DNA collection to know how the world was populated Forensic technology: this technology allows the identification of lost people, criminal's suspects and victims, among others and the determination of the molecular fingerprint will be the key of the forensic investigations since it allows the obtention of proofs from blood, hair… Medical investigation: it includes the use of transgenic animals to create organs that can be transplanted and genic therapy, which consists on replace an “ill” gene for its healthy allele Food industry: it includes the improve in the efficiency of process in which microorganisms are involved and the creation of foods with special characteristics Pharmaceutical industry: it employs the medicines and vaccines created by bacteria that have been implanted with a human gene and transgenic organisms Agriculture and livestock: In agriculture, improved plants that grow faster can resist harder conditions are used, whereas in livestock thanks to biotechnology animals that can produce more milk and meat are used Environment: it uses genetically modified organisms to transform contaminants into not toxic substances (bioremediation) and generate biodegradable materials from renewable resources 

18. Risks of genetic engineering Environmental: the GMO can transfer its genetic material on an accidental way to natural organisms altering them and causing that its competence with its natural relatives may lead to a biodiversity loss Human health: genetically modified foods must be perfectly labelled so that allergic people can know if a product contain genes from their allergy Social and economic context: the biggest risks come from the market monopolization from different companies.