MCAT Biology 2- Biochemistry Part 2
MCAT Biology 2- Biochemistry Part 2 CHEM 2223
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This 6 page Test Prep (MCAT, SAT...) was uploaded by ShayD on Wednesday January 13, 2016. The Test Prep (MCAT, SAT...) belongs to CHEM 2223 at University of Missouri - St. Louis taught by John Gutweiler in Fall 2015. Since its upload, it has received 62 views. For similar materials see Quantitative Analysis in Chemistry at University of Missouri - St. Louis.
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Date Created: 01/13/16
MCAT Biology 2 Review: *** This study guide will refresh and enhance your knowledge, however it assumes you have a basic understanding of biology and chemistry*** DNA Structure Made up of nucleic acids (since they are found in the nucleus and possess acidic phosphate groups) Nucleic acids (N. A.) o Ribose sugar Become deoxy, with OH group o Nitrogenous bases A, G, C, T A & G= purine “pure as silver (Ag)” C, U & T= pyrimidines o Phosphate group Bind to ribose sugar of another nucleic acid to form the backbone Polynucleotides o Multiple N. A. are covalently linked together via phosphodiester bonds Connected from the 5’ carbon of the phosphate group to the 3’ carbon of the sugar Watson Crick Model of DNA o DNA structure is composed of a double stranded very long polynucleotides They are held together via hydrogen bonds to form antiparallel orientation a right handed double helix Hydrogen bonding is very specific: Purine+ pyrimidine o A=T 2 hydrogen bonds (weaker) o G=C3 hydrogen bonds (strongest) 10 bases every full turn Chromosome Structure and Packing o Eukaryotes large pieces of linear DNA is Called a chromosome Genome sum total of an organisms Genetic information o Prokaryotes single circular chromosome o Viral may be either linear or circular Chromosome Packing o Prokaryotes is maintained by DNA gyrase, it twists the DNA to form supercoils o Eukaryotes DNA is wrapped around globular proteins called histones; fully packaged DNA is called chromatin Centromeres o Region where spindle fiber attaches Telomeres o The ends of chromosomes, that prevent fusion from with neighboring chromosomes Guanine rich repeated segment that knots up to stabilize the ends Genomic structure Nucleotide variation o Some variation are called single nucleotide polymorphisms, are essential for mutations, present as both large scale and harmless or small scale and harmful PTC taste sensitivity Sickle cell anemia Transposons o These are short segments that can “jump around the genome,” causing mutations o Three types of transposons: IS element which is composed of transposase gene flanked by inverted repeated sequences Complex transposons may also have additional genes Composite Transposons composite transposons have 2 similar IS elements with a central region in between They use transposase enzyme that cuts and pastes the segments The Genetic Code DNA is not directly exerted its influence on cells o Instead it contains a sequence of nucleotides (genes), that are templates that produce another nucleic acid (RNA) The process of reading DNA and writing RONA is called transcription Will be The process of synthesizing proteins using RNA is known as translation covered in o Via ribosome microbiology Central Dogma DNA RNA protein (fundamental law of microbiology) o This is where inherited information is used to create objects (enzyme/proteins) Exceptions: o Retroviruses o Other pathways to transferred in other ways (methylation and post translational modifications) Genetic Code The language used by DNA and mRNA to specify building blocks of proteins (amino acids) o Uses 4 letters Genetic code is written by 3 letter words Codons o Codon chart will not be provided on the MCAT and amino acid properties should be memorized Some numbers worth knowing o There are 64 codons o They only code for 61 amino acids, since 3 will code for STOP codons **DNA Replication During cell division DNA needs to be duplication, it does so through a process known as replication o This occurs during the SPhase Big Picture o Since the new DNA (daughter DNA) is synthesized using the old DNA (parental DNA) using the semiconservative model Memorize Molecular level o Due to its structure (DNA), DNA needs to unwound via an enzyme called helicase Helicase orients itself by identifying a specific sequence of nucleotides known as the Origin of replication (ORI) o Helicase causes strand strain, which is relieved by topoisomerase o The now single strands are stabilized by Singlestrand binding proteins (SSBPs) o RNA must be synthesized for each template Via primase o Replication occurs in the replication bubble At the replication fork o Due to their nature antiparallel structure One strand is replicated continuously (leading strand) The other strand is replicated discontinuously (lagging strand) Small chunks called Okazaki fragments Must memorize o Polymerization (elongation) occurs from the 5’ 3’ Always o DNA polymerase requires a template o DNA polymerase requires a primer o Replication fork grow away from origin in both direction o Eukaryotes have several origins points causing several “replication bubbles” Prokaryotes have only one point of origin (theta replication) o RNA primers are replaced by DNA and the fragments are later joined by ligase DNA polymerase There are several types of enzyme with complicated mechanisms (you DO NOT need to worry about these) only know DNA polymerase I & DNA polymerase III: o DNA polymerase I 5’3’ polymerase activity Superfast, superaccurate elongation of leading strand Proofreading function Has repair functions corrects errors o DNA polymerase III5’3’ polymerase activity Poor processivity (slower), It removes RNA primer as replaces it (exonuclease activity) while leaving behind new DNA (endonuclease activity) Telomeres Are disposable repeats at the end of the chromosome o Since after each cell division DNA is shortened Telomeres protect the DNA from degradation o They need a primer and need telomerase (enzyme that adds repetitive nucleotide sequences) Genetic Mutation any alteration to DNA sequence of organism’s DNA Causes of genetic mutations o Environmental, chemical, but most often spontaneously o Physical mutagens Ionizing radiation (Xray) Photochemical damage (UV light) Reactive chemicals can directly interact with DNA or interact with processing agents of the cell Mutagen any compound that cause mutagens Biological agents incorrect base pair, viruses, and transposons Types of mutations Point mutation a single base pair substitution either transition (pyrimidine by another pyrimidine), transversion (purine by pyrimidine); 3 types: o Missense mutation cause of 1 amino acid to be replaced by another amino acid, may be harmless if they amino acids have similar properties o Nonsense mutation a stop codon is formed, causes premature shortening o Silent mutation a single nucleotide change that makes a new codon that codes for the same amino acid, no change to protein sequence Insertions the addition or removal of a single nucleotide, which cases a frameshift Deletions a serious mutation Inversions a segment of the chromosome undergoes breakage and rearrangement within itself Amplifications a segment of the chromosome is duplicated Translocations is a result of recombination of nonhomologous chromosomes o Transposons may cause recombination depends on directionality Loss of heterozygosity is when a diploid organism has one allele that is lost ( may be due to deletion or recombination), loss of the normal allele Effects of mutation This may have lossoffunction (have little to no function) Haploinsufficiency has only a single functional copy of a gene o Must express enough for gene to maintain good health Good vs. Bad o Some mutations maybe beneficial (sickle cell vs. malaria) o Others may be disease causing (cancer and metabolism)