NUCLEIC ACIDS & PROTEINS HL BIOLOGY Van Roekel 11/6/14

BILL Draw and label a simplified structure of DNA.

Enzyme Lab Lab Report Due – Friday, November 14. If data is not completed, schedule time with me to complete it. Be sure to graph processed data and figure our averages and standard deviations. Print copy off, no google docs!

Nucleic Acids Nucleic Acids are organic compounds that code for protein sequences. REMEMBER: DNA  RNA Protein

DNA Structure Two antiparallel strands in the shape of a double helix. Each strand is a chain of nucleotides bonded together Nucleotides are composed of phosphate group, deoxyribose sugar, and one of four nitrogenous bases.

Nucleotide O O=P-O N CH2 O C1 C4 C3 C2 Phosphate Group 5 Nitrogenous base (A, G, C, or T) CH2 O C1 C4 C3 C2 5 Sugar (deoxyribose)

DNA Structure-Nucleotide For HL (IB BIO II) you need to be familiar with the numbering of carbon atom in sugar

DNA Structure- Backbone DNA backbone is composed of alternating deoxyribose sugar and phosphate groups Held together by covalent bonds called a phosphodiester bond. Phosphate—oxygen—carbon

DNA Structure-Backbone Condensation reactions occur between the phosphate group of the 5’ carbon and the hydroxyl group on the 3’ carbon. Nucleotides are always added to the 3’ side of chain. DNA strands always have a free 5’ carbon end with a phosphate group and a free 3’ carbon end with a hydroxyl group attached

Nucleotides are bonded together by condensation reactions

DNA Structure-Base Pairing Nitrogenous bases are held together by hydrogen bonds Purines always pair with Pyrimidines Adenine pairs with Thymine via two hydrogen bonds Guanine pairs with Cytosine via three hydrogen bonds

DNA Structure-Base Pairing Purines Pyrimidines Double ring structures Single ring structures

2 minute convo Summarize how nucleic acids are formed.

DNA vs RNA DNA 1- Deoxyribose sugar 2- Bases: Adenine, Thymine, Cytosine, Guanine 3- Double-stranded helix arrangement RNA 1- Ribose sugar 2- Bases: Adenine, Uracil, Cytosine, Guanine 3- Single stranded

BILL - Compare DNA and RNA Deoxyribose Sugar Thymine as a base Double stranded Ribose Sugar Uracil as a base Single Stranded

DNA Packaging DNA is paired with a type of protein called a histone to form a nucleosome Nucleosome: the basic unit of DNA packaging DNA wrapped around two protein molecules, each of which has 4 different histones Negatively charged DNA is attracted to Positively charged histones

DNA packaging-Nucleosome http://www.youtube.com/watch?v=gbSIBhFwQ4s

DNA Packaging-Nucleosome When DNA is wrapped around histones, it is inaccessible to transcription enzymes Packaging thus controls transcription process, only allowing certain areas to be involved in protein synthesis Nucleosomes are essential to the “supercoiling” of DNA molecules to form chromosomes-tightly packs all genetic material into condensed chromosomes.

DNA Sequencing Protein-Coding Sequences Single copy genes with coding functions. Provide base sequences essential to produce proteins at cell ribosomes. 2% of human genome codes for proteins Determined by Human Genome Project: began in 1970s, completed in 2001

DNA Sequencing Protein-Coding Sequences Genes are made of numerous fragments of protein encoding information, and non-encoding fragments. Protein encoding fragments are exons Non-protein encoding fragments are introns

DNA Sequencing Highly repetitive sequences 5-45% of human genome Composed of 5-300 base pairs per repetition Up to 100,000 replications ….GTTACGTTACGTTACGTTACGTTACGTTAC…. Satellite DNA: clusters of repetitive DNA in discrete areas Repetitive DNA does not code for proteins

DNA Sequencing-Structural Structural DNA is highly coiled DNA that does not have a coding function. Generally located around centromere and on ends of chromosomes. A.K.A “Pseudogenes” which have no function

Review Questions Draw the two strands of a DNA molecule representing their antiparallel relationship and complementary base pairing. Explain how nucleosomes would contribute to transcription control. Would exons or would introns be more likely to contain highly repetitive sequences? Why?