Download Chapter 10 - Nucleic Acids and Protein Synthesis

Chapter 10 - Nucleic Acids and Protein Synthesis
I. DNA (Deoxyribonucleic acid)
A. Structure of DNA
1. polymer made of nucleotides (Monomer)
a. deoxyribose sugar
b. phosphate group
c. nitrogen-containing base
(makes one nucleotide different from another)
2. Bases
a. purines (2 carbon rings)
1) adenine (A) and guanine (G)
b. pyrimidines (1carbon ring)
1) cytosine (C) and thymine (T)- only in DNA; Uracil
(U)- ONLY in RNA
3. complementary base pairing
a. C-G and A-T
b. connected by hydrogen bonds (weak bonds)
1) C and G have 3
2) A and T have 2
4. double helix (proposed by Watson and Crick model- 1953)
a. 2 nucleotide chains that wrap around each other (like a
spiral staircase)
* inspired by x-ray photograph of DNA crystals by
Rosalind Franklin
* sugar on outside
* 2 strands
DNA and Base Couples
b. ladder model
1) sides - alternating deoxy. sugar and phosphate
2) rungs - nitrogen bases attached to deoxy. sugar
a) purine always attached to a pyrimidine
3) hydrogen bonds hold two half ladders together
(between H and an O or an N atom)
c. nucleotide sequence of one half is exact complement of
other half
http://www.youtube.com/watch?v=qy8dk5iS1f0&feature=related
B. Replication of DNA (occurs in the Nucleus)
1. process of copying DNA in a cell
2. enzymes called helicases break H bonds and 2 sides
separate
3. DNA polymerase enzyme assembles new DNA half using
nucleotides found in nucleus
4. each half serves as a template (pattern) to make a new half
5. two exact copies of original DNA produced (due to
complementary nature of nucleotides)
1) each has one old and one new half
http://www.youtube.com/watch?v=4jtmOZaIvS0
6. mutation - a change in the nucleotide sequence
II. RNA (Ribonucleic acid)
A. Structure of RNA
1. ribose sugar
2. uracil replaces thymine
3. single strand
4. Types of RNA
a. messenger RNA (mRNA) - carries genetic info. from
DNA to cytoplasm (ribosome)
b. transfer RNA (tRNA)(cloverleaf) - binds to specific
amino acids
c. ribosomal RNA (rRNA) - makes up ribosomes
III. Protein Synthesis (production of proteins)
A. Transcription
1. process where genetic info. is copied from DNA to RNA
a. DNA is blueprint for all proteins
b. proteins made at ribosomes
c. DNA can’t leave nucleus
2. RNA polymerase (transcription enzyme) binds to promoter
(beginning of a single gene) (Gene- small section of a
chromosome that determines a specific trait)
3. DNA section (gene) separates
4. RNA polymerase attaches to DNA nucleotide and adds
complementary RNA nucleotide
5. continues till RNA poly. reaches termination signal (marks
end of gene)
6. mRNA leaves nucleus
B. Proteins
1. polymers made of polypeptides (made of amino acids)
2. 20 amino acids
C. The Genetic Code
1. sequence of mRNA nucleotides translated into sequence of
amino acids
2. codon - sequence of 3 mRNA bases that code for a specific
amino acid
a. start codon (AUG)(methionine) - starts translation
b.stop codon - (UAA, UAG, UGA) cause translation to stop
D. Translation
1. assembling amino acids from mRNA code
2. tRNA transports amino acids to ribosome (region that binds
to specific amino acid)3. (opposite amino acid attachment site) - sequence of 3 bases
complementary to a specific codon (ANTICODON)
a. insures that amino acids added in order prescribed by
mRNA
4. ribosomes (free and attached) have one binding site for
mRNA and two for tRNA
5. ribosome attaches to start codon and moves along to each
codon until stop codon reached
a. matching of anticodon and codon causes amino acids to
join previous one and form peptide bond
b. several ribosomes may translate same mRNA
http://www.wisc-online.com/objects/index_tj.asp?objID=AP1302
http://www.youtube.com/watch?v=KvYEqGb7XN8&feature=related
http://www.youtube.com/watch?v=NJxobgkPEAo
Human Genome Project:
 Has discovered 20,000 genes