Science AHSGE

Standard IV-2 DNA, RNA and Proteins

Deoxyribonucleic Acid (DNA)

Double Helix Double stranded; twisted

ladder Found in the form of

chromosomes Genes- Relatively small

segment of DNA that codes for the synthesis of a specific protein. 

Model developed by Watson and Crick

Nucleotide- Base, sugar and phosphate group

DNA

Long strands (sides) of DNA molecule- alternating sugars and phosphates; phosphodiester bonds

Deoxyribose- sugar of DNA Rungs of the ladder made of nitrogen-

base pairs Held together by a hydrogen

bonds Four bases:

Adenine-Thymine (2 H bonds) Guanine-Cytosine (3 H

bonds) Purines: A and G Pyrimidines: T and C Order makes up the code for

specific characteristics in the body

DNA Replication

Duplication (copying) of DNA strands DNA Helicase splits DNA molecule in half/2 templates or parental

strands Single stranded binding proteins (SSBs) keep from joining back Replication fork- Point of DNA separation

RNA Primase brings in starter nucleotides DNA Polymerase binds complimentary strands of DNA to the

Primase starter Leading strand continuously grows Lagging strand grows in sections (Okazaki fragments) in the

opposite direction Ligase fills in gaps

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DNA Replication

Ribonucleic Acid (RNA) Single-stranded Ribose- sugar of

RNA Four bases:

Adenine-Uracil Cytosine-Guanine Notice, Thymine is

replaced with Uracil

Transcription- Making Messenger RNA (mRNA) from DNA (Occurs in nucleolus) DNA unzips and

complementary RNA nucleotides are paired up with DNA nucleotides

Promoter- Signals where transcription begins (TATA box)

Transcription

Protein Synthesis1. mRNA travels out of the nucleus to the ribosome 2. 3 mRNA bases (codon) will pair with a complimentary tRNA

base triplet (anticodon)- AUG- start codon begins on the P site of the ribosome

3. Transfer RNA (tRNA) anticodons specify certain amino acids- New tRNA molecules bring in a.a. to the A site

4. Amino acids from the P and A sites are linked by peptide bonds on the ribosomes- Used tRNA molecules exit from the P site, the A site tRNA

moves over and a new tRNA comes in 5. Linked amino acids become proteins on the ribosomes6. Proteins- Build cell structures and function as enzymes to

speed up/regulate cell processes

Protein Synthesis

TranscriptionTranslation

DNA to RNA to Proteins

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