Post on 22-Dec-2015
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 RNAProtein
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
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OO=P-O O
Phosphate Group
NNitrogenous base (A, G, C, or T)
CH2
O
C1C4
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
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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• Double ring structures
Pyrimidines• Single ring structures
2 minute convo• Summarize how nucleic acids are formed.
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DNA vs RNA
• DNA1- Deoxyribose sugar2- Bases: Adenine, Thymine, Cytosine, Guanine3- Double-stranded helix arrangement
• RNA1- Ribose sugar2- Bases: Adenine, Uracil, Cytosine, Guanine3- Single stranded
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BILL - Compare DNA and RNA
DNA• Deoxyribose Sugar• Thymine as a base• Double stranded
RNA• 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?