biol+4+standard+glossary+aos1

 Due to popular demand you have the opportunity to create a glossary together.It really is important that you use your own words and please add your own definition to one that has been done. There is no one answer to any particular term.

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**DNA:** Deoxyribonucleic acid. Composed of four different types nucleotides; Adenine, Thymine, Cytosine and Guanine. Found in the nucleus of a cell. Contains the genetic information of the organism.
 * RNA:** Ribonucleic acid. Three different types: mRNA, tRNA and rRNA. Composed of the bases Adenine, Guanine, Cytosine and Uracil (as opposed to Thymine).
 * Complimentary base pairing:** Involves Adenine and Thymine (or Uracil in the case of RNA) always bonding together and Cytosine and Guanine always bonding together.
 * Nucleotides:** are organic substances comprised of a ribose sugar, phosphate group and nitrogenous base

__**DNA replication**__ **Semi-conservative:** Refers to each newly synthesized DNA strand having one parent strand and one new strand.
 * Helicase:** Enzyme responsible for unwinding the double helix of the parent DNA strand
 * DNA polymerase:** Is an enzyme responsible for adding free nucleotides to the parent strand, based on the complimentary base pairing rule, in order to create a new complementary strand.
 * DNA ligase:** Enzyme responsible for joining the Okazaki fragments together.
 * Okazaki** **fragments:** Fragments formed when nucleotides are added to the lagging strand due to it being 3’ to 5’.
 * Leading strand:** The DNA strand that is continuously synthesized as it is in the 5’ à 3’ direction.
 * Lagging** **Strand****:** 3’ à 5’, Synthesized discontinuously.
 * RNA primer:** added at intervals along the lagging strand to allow formation of Okazaki fragments and ultimately the DNA strand.
 * Chromosome:** chromosomes are packages of DNA that are tightly coiled so that large amounts of DNA can fit into a nucleus.
 * Hydrogen bonds:** Hydrogen bonds are the bonds that link the complementary nucleotides together such as guanine to cytosine. They are easily broken by helicase when it is time for DNA replication.
 * Parent DNA:** This is the original DNA from the parent cell that is copied during the S section of interface.

Transcription:** This is the process whereby the part of the DNA that codes for a protein (i.e. gene) is unwound and free floating nucleotides that are complementary to the template strand of the gene are joined to form a pre-mRNA molecule. This occurs in the nucleus.
 * __Gene Expression__
 * Translation:** This is the process whereby the mRNA molecule containing the code for a polypeptide is passed through a ribosome and tRNA moleucles with the correct anti-codon 'drop off' the amino acid that they carry. The amino acids are linked by peptide bonds to form a polypeptide. This occurs in the cytosol or on endoplasmic reticullum.
 * Ribosome:** A ribosome is a structure made from two subunits of rRNA and protein. It is the site for protein synthesis. Two tRNA molecules can act at the ribosome at any one time.
 * Pre-mRNA:** This is the original mRNA that is created during transcription before it undergoes splicing.
 * Splicing:** Splicing is the process in which parts of the pre-mRNA that do not code for the desired protein (introns) are eliminated/detached/cut off from the mRNA strand.
 * Intron:** Parts of the pre-mRNA that are excluded/cut off as they do not code for the desired protein.
 * Exon:** The parts of the pre-mRNA that are kept as they code for the desired protein.
 * RNA polymerase:** RNA polymerase acts like DNA polymerase. Its role is to attach the free floating nucleotides together o form an RNA moleucle.
 * Transfer RNA (tRNA):** This is an RNA molecule that carries amino acids to the ribosome and drops them off to form a polypeptide.
 * Amino acid:** Is the monomer of a polypeptide.
 * Anti-codon:** The codon carried by a tRNA molecule that is complementary to the mRNA codon thus being identicle to the original DNA triplet except that uracil replaces thymine.
 * Triplets:** Sets of three nucletides in the DNA that code for an amino acid.
 * Gene:** Section of the DNA that codes for a protein.
 * The redundant nature:** This is the concept that multiple codons code for the same amino acid since there are only 20 amino acids but 64 combinations for a codon.

Meiosis:** The process that produces haploid gametes (sex cells) from germ cells.
 * __Meiosis__
 * Homologous pairs:** Are chromosomes that contain the same alleles and genes in the same position. They are similar in length.
 * Gametes:** Are sex cells that are haploid - contain one set of chrmosomes (23) and are the product of meiosis.
 * Germ cells:** The cells that undergo meiosis. THey are diploid.
 * Diploid:** Cells that contain 2 sets of chromosomes = 46.
 * Haploid:** Cells that contain 1 set of chromosomes = 23
 * Meiosis 1:** The process where chromosomes find their homologous pairs, line up facing each other at the equator and are seperated from each other by the spindle fibres. The result is two intermediate cells.
 * Meiosis 2:** The chromosomes of the intermediate cells line up on the equator and are seperated to create 4 haploid cells. This is a mitotic division.
 * Intermediate cells:** These are the products of meiosis 1 that undewrgo meiosis 2.
 * Crossing over:** When the homologous pairs line up facing eachother, a part of the chrosome comes into contact with the other. IN this even, DNA information is exchanged which leads to greater variety and difference in the gametes from the original germ cells. (this is what i understand it to be, please correct me if i'm wrong)

__**Mutations**__ - Point:** Involve a change in a single base of DNA. There are three types - insertion, deletion and substitution.
 * Mutation:** A mutation is any change in the base sequence of a DNA molecule. They occur when repair mechanisms fail during DNA replication.
 * Mutagens:** Are factors that cause mutations. Examples are high temperature, pathogens, radiation and life style habits.
 * Types of mutations:
 * - Insertion:** A nucleotide is added into the gene's sequence of bases causing all subsequent triplets to be inaccurate in relation to the polypeptide it is suppose to code for.
 * - Deletion:** A nucleotide is deleted from the sequence of the gene's bases causing all subsequent triplets to be inaccurate in relation to the polypeptide it is suppose to code for.
 * - Substitution:** One base is replaced by another base causing that triplet to be incorrect, no other triplets are affected.
 * - Frame shift:** Another name for insertion and deletion mutations probably because the triplets are shifted to code for different amino acids.
 * - Silent:** If the substituted base codes for the same amino acid as the original due to the redundant nature, it is called a silent mutation because there is no impact on the organism.
 * - Nonsence:** If the substituted mutation codes for a STOP codon, it is called a nonsence mutation.
 * - Block:** These mutations involve large scale changes in the DNA sequence of a chromosome. Large proportions or even enire genes can be involved in these mutations. There are four types - deletion, translocation, duplication and inversion.
 * - Deletion:** As the name suggests, a section of the chromosome is broken off and is lost.
 * - Translocation:** A segment of chromosome or gene is removed and added to another chromosome.
 * - Duplication:** This is the same as translocation however it is specific to homologous pairs. One segment joins the other homologous chromosome.
 * - Inversion:** A segment of a gene or chromosome rotates 180 degrees thus flipping the information around then it rejoins the chromoosme. When this occurs, no information is lost from the mutated gene.
 * - Chromosomal:** These mutations can have extremely dramatic effects on the individual. They involve the loss or gain of an entire chromosome and can arise due to non-disjunction during meiosis or translocation.
 * Non-disjuntion:** In anaphase II, the sister chromatids do not seperate and so an entire chromosome is pulled to one side of the cell while the other side recieves no chromatids.
 * Translocation:** This refers to what has already been discussed i.e an entire chromosome is attached to another.
 * Aneuploidy-** A chromosome abnormality in which there is a missing or extra chromosome

Stuctural genes -** produce protins that become part of the structure of an organism
 * __Gene regulation__
 * Regulatory genes** **(general)** - produce protein that control the action of other proteins
 * Master genes -** play an important role in embryonic development by regulating the actions of hundred of other genes.
 * Regulatory protein -** This protein binds to the promoter region of a gene and prevents RNA polymerase from attaching and transcribing mRNA.
 * Promoter region -** RNA polymerase binds to this region when it wants to transcribe some mRNA. It is just infront ot the gene.
 * Regulatory gene (specific) -** A section of the gene just infront of the promoter region tha produces a protein to bind to the promoter region of we want the gene to be turned off.
 * Terminator region** - signals the end of the gene and RNA polymerse cannot continue to add nucleotides to form mRNA because it has reached the terminator region.

Transgenic Organsism -** An organism that has obtained the DNA of another organism through genetic modification.
 * __Gene Technology__
 * Recombinant DNA -** DNA that is composed of two organism's DNA being put together.
 * Plasmid** - A seperate ring of DNA found in bacteria and yeast.
 * Polymerase Chain Reaction -** A process that involves the cloning of a DNA molecule mulriple times very quickly. (see course notes 3 for good explanation or p252 of textbook)
 * Taq polymerase -** The enzyme used to attach nucleotides to make a copy of DNA during PCR that comes from bacteria that live in hot springs.
 * Primer -** A small section of DNA that attaches to the seperated strands of DNA and provides a side for Taq polymerase to work off.
 * Probes -** SIngle stranded piices of DNA or RNA that are used to target specific sections of a DNA molecule by binding to it. Often they will be radioactively labelled.
 * Restriction enzymes -** enzymes that are able to cut DNA after finding their recognition site.
 * Recognition zone -** a specific set of bases in a sequence of DNA tha is recognised by a specific restiction enzyme and cut.
 * Blunt end -** The term given to the ends of a DNA fragment cut in two if each end has complimentary base pairing. Two equal strands.
 * Sticky end -** The term given to the end of a DNA fragment cut be a restriction enzyme that has one strand longer than the other hence no complimentary base pairing on the end.
 * Gel electrophoresis** - A technique to seperate DNA fragments of various size with the smaller fragments travelling the furthest on a slate of gel that has a positive and negative charge. Helps to detect mutations, identify biological parents, solve crimes.
 * Restriction Fragment Length Polymorphisms -** Differences in alleles of a particular gene.
 * DNA sequencing -** A process whereby we can determine the order of nucleotides that compose a gene or entire DNA molecule
 * Chain termination method** - the actual method of sequencing DNA (see course notes 3 for good explanation or p256 of textbook)

Allele -** Alleles are variations of a gene. When a gene comes in different forms, these forms are said to be alleles. Most genes have two alleles.
 * __Inheritance__
 * Dominant -** A reference to the phenotype of an individual. When an individual contains two different alleles (is heterozygous), the trait that is expressed is said to be the dominant one.
 * Recessive -** A reference to the phenotype of an individual. An individual with two different alleles expresses only one trait. The trait that is not expressed or hidden is reffered to as recessive. The recessive trait will only be expressed an individual is homozygous for that trait.
 * Heterozygous -** The individual contains two different alleles.
 * Homozygous -** The indivdual contains two identicle alleles.
 * Homologous Pairs -** Chromosomes that contain the same genes in the same location. During meiosis, they line up against eachother/side by side in metaphase.
 * Locus -** the position of the gene.
 * Genotype -** The alleles received from an individuals parents.
 * Phenotype -** The charateristics displayed by an individual's genotype.
 * Lethal Alleles -** These are mutations of a gene that produce a gene product that may affect an organism's survival. This means that if two particular alleles of a gene come together, the product will be lethal to the organism.
 * Codominance -** If neither allele is dominant over the other, both characteristics will be displayed and this is codominance.
 * Incomplete Dominance -** Neither allele is dominant over the other but te characteristic displayed is a mixture of the two.
 * Sex-Linked**- Genes whih are present on the sex chromosomes (usually the X in mammals)
 * Test Cross-** Crossing an individual showing the dominant phenotype with a homozygous recessive individual in order to determine its genotype.

//__**AREA OF STUDY TWO**__


 * EVOLUTION:**//
 * Adaptation:** inherited characteristic that increases the likelihood of survival and reproduction of an organism in its environment.
 * Analogous Structures:** Structures whose functions are similar but have different evolutionary origins
 * Artificial selection:** organisms with favourable traits are selectively bred and others prevented from breeding
 * Cline:** continuous variation in the phenotype of a species over its range due to differences in selection pressures in different environments
 * Co-evolution:** evolution in two interdependent species were each acts as the selecting agent for the other
 * Convergent evolution:** the process by which two groups of organisms (which do not share a recent ancestor but live in similar environments with similar selection pressures) develop similar phenotypes.
 * Cultural Evolution:** changes in the human way of life since the evolution of biologically modern humans.
 * Divergent Evolution:** the evolution of many organisms from a common ancestor. AKA Adaptive radiation
 * Extinction:** the permanent loss of a species. The term also applies to the loss of a population or higher taxon (e.g. family)
 * Fossil:** the remains of an organism or direct evidence of its presence (footprints, casts, moulds etc) which have been preserved
 * Founder Effect:** genetic drift which results from non-representative allele frequencies in a small founding population
 * Gene Flow:** the movement of alleles out of (emigration) or into (immigration) a population. Gene flow between populations of plants can occur by the dispersal or seeds or spores.
 * Gene Pool:** The total genetic material of all members of a population
 * Genetic bottle neck:** the loss of genetic variability when population size is severely reduced
 * Genetic drift:** changes in allele frequencies due to small population size and random causes
 * Half- life:** the time in which half of a sample of a radioactive isotope will decay to a stable form
 * Homologous structure:** structures which have a common evolutionary origin and similar underlying anatomy, but have evolved in different ways in different groups to different selection pressures.
 * Macroevolution:** the evolution of species or high taxons (e.g. family)
 * Microevolution:** changes in allele frequencies in a population of organisms
 * Polyploidy:** the presence of additional full sets of chromosomes (3n, 4n...)
 * Reproductive isolation:** mechanisms preventing gene flow between species. Mechanisms may be prezygotic or postzygotic
 * Selection pressures or selecting age:** factors which act to favour one phenotype over another. A selecting agent may be abiotic or biotic
 * Selective advantage:** relative advantage
 * Vestigial:** any structures that have, over time, lessened in function that it no longer has purpose within the organism.