Biology 103, week 4 notes
Biology 103, week 4 notes 103
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This 4 page Class Notes was uploaded by Kierra Thompson on Sunday September 18, 2016. The Class Notes belongs to 103 at University of Southern Mississippi taught by Emily Clark in Fall 2016. Since its upload, it has received 8 views. For similar materials see Biology & Society in Science at University of Southern Mississippi.
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Date Created: 09/18/16
Week 4 Biology notes DNA: structure, replication, and protein synthesis DNA o Hereditary molecule that is common in all life forms o Passed from parent to offspring o Instruction manual which dictates how we’re assembled o Found in the nucleus o Molecules are super long, need to be organized Organized by chromosomes Chromosome o Single long dna molecules wrapped around proteins o Humans have 23 pair For each pair, one from mom, one from dad o Last pair is the sex chromosome o XX female o XY male Dna is composed of nucleotides o Nucleotides have 3 parts Sugar Phosphate Base o Nucleotides have 1 of 4 bases 1) Adenine (A) 2) Thymine (T) 3) Guanine (G) 4) Cytosine (C) Double Helix o Two strands of nucleotides pair up and twist around each other to form a spiral shape The phosphate of one nucleotide binds to the sugar of another forms the backbone Bases are hydrogen bound to each other and form the rungs of the ladder. This holds the two strands together! A binds to T G binds to C Dna is used as the foundation for a number of activities o The most basic is replication Natural process which cells make an identical copy of a DNA molecule Body needs to undergo mitosis (division of cells) Takes place in the nucleus Complimentary base-pairing rules o Unwind DNA strand dna helicase o Dna polymerase, an enzyme reads the old sequence and add complementary nucleotides o Now 2 copies of the original molecule exist o Each molecule consists of one of the strands of the original DNA molecule and a new strand. Dna replication is semi conservative o Each molecule consists of one of the strands of the original DNA DNA is an instruction manual that tells your body how to make proteins o Instructions are found in your genes Gene is a sequence of DNA that contains the instruction to make at least one protein Humans have about 20,000 genes Where do you find Genes? Found on chromosomes Each chromosome carries a unique set of genes Synthesis of a protein from a gene is called gene expression What is Gene expression process of converting genetic information into protein two main steps: o transcription and translation o Transcription occurs in the nucleus of the eukaryotic cells and cytoplasm of prokaryotic cells o Transaction occurs in ribosomes in cytoplasm Transcription o molecules of messenger RNA (mRNA) are synthesized from the instructions encoded in genes o RNa polymerase binds to the regulatory sequence of the gene to be transcribed. DNA strands unwind, exposing the coding sequence of the gene Gene has 2 very important components o Coding sequence – part of the gene that determines the amino acid sequence of a protein o Regulatory sequence - part of the gene that determines when, where, and how much protein a gene makes. Transcription cont.…. o Rna polymerase copies strand of DNA into a complementary strand of mRNA o Complementary mRNA forms from a DNA template according to the rules of base pairing, except that in RNA, “A” pairs with “U” (uracil) o mRNA is formed, detaches from DNA sequence and DNA reforms its double helix Gene expression: transcription o Completed mRNA leaves the nucleus o DNA does not leave the nucleus Ready to be transcribed again…replicated...whatever is needed All systems go for Translation One in the cytoplasm, mRNA molecules are decoded so that the correct protein can be assembled. Step 1 attach to the protein maker o mRNA associates with a ribosome Step 2 decode the mRNA o Ribosomes moves along the mRNA reading it in groups of 3 nucleotides (codons) o A codon specifies a particular amino acid Genetic code o Set of rules relating particular mRNA codons to particular amino acids o Two important features Its redundant multiple codons for one amino acid Its universal in every living organism, the code is read the same way Step 3 Bring the anti-codon o Once the mRNA codon has been read, transfer RNA (tRNA) bring the corresponding amino acids o tRNA knows where to drop off the amino acid because they have an anti-codon which is complimentary to the codon o once tRNA has deposited the correct amino acid, the ribosome moves to the next codon o happens until the ribosomes hit the stop codon Step 4 Completed amino acid chain detaches from the ribosome and folds into its 3-D shape Becoming a grown up protein Amino acid chain is initially linear How it folds and shapes depends on the order of amino acid Form = function If wrong AA gets inserted during translation o How the protein fold could change o The function could be completely off
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