Download Lab Biology - Chapter 10

Lab Biology - Chapter 10 Nucleic Acids & Protein Synthesis
I. DNA (Deoxyribonucleic Acid)
A. Function
1. DNA stores info that tells cells which proteins to make.
B. Structure
1. Each DNA molecule is 2 long chains of nucleotides.
a. Deoxyribose - sugar
b. Phosphate Group
c. Nitrogen Bases: (1) adenine - ‘A’ (3) cytosine - ‘C’
(2) guanine - ‘G’ (4) thymine - ‘T’
2. Double Helix
a. 1953 Watson & Crick proposed DNA is 2 nucleotide
chains that twist into shape of spiral staircase.
b. DNA ‘Ladder’
(1) Phosphate & Sugar form “backbone” of DNA ladder.
(2) Nitrogen Bases form “rungs” of ladder and are
complimentary base pairs: A&T always pair
G&C always pair
C. Replication
1. DNA makes exact copies of itself.
a. the 2 nucleotide chains separate between base pairs.
b. DNA polymerases ( enzymes ) move along separated
chains and cause new chains of DNA to assemble and
bond to existing nucleotides.
c. Sequences remain exact.
Ex: if original chain is:
A T T C C G
then new chain will be:
T A A G G C
2. Accuracy & Repair
a. enzymes “proofread” & repair errors in replication
b. mutation - change in nucleotide sequence
 replication error
 chemicals
 UV radiation
II. RNA ( Ribonucleic Acid)
A. Function
1. RNA is responsible for movement of genetic information
from the DNA in nucleus to site of protein synthesis in
cytoplasm. (ribosomes)
B. Structure
1. Chain of nucleotides; similar to DNA except:
a. Ribose - sugar
b. Uracil ( U ) pairs with A ( instead of T )
C. Types of RNA
1. messenger RNA ( mRNA )
 carries genetic info from DNA to cytoplasm
2. Transfer RNA ( tRNA )
 binds to amino acids
3. Ribosomal RNA ( rRNA )
 make up ribosomes where protein is made
D. Transcription
1. Transcription is process by which genetic info is copied
from DNA to RNA
2. RNA polymerase ( enzyme ) synthesizes RNA copies of
DNA sequences
3. Promoter - region of DNA that marks beginning of the
DNA chain to be copied
4. When RNA polymerase binds to promoter, that region
separates & 1 chain is transcribed
5. Termination Signal - sequence of genes that mark end
III. Protein Synthesis
A. Function
1. Production of Proteins
2. Proteins determine the structure & function of each cell.
B. Structure
1. Proteins are made up of amino acids ( 20 kinds )
C. Genetic Code
1. Codon - a combination of 3 mRNA nucleotides
2. Each codon codes for a specific amino acid
D. Translation
1. Translation - the process of assembling polypeptides
(amino acids) from info in mRNA
a. tRNA transports amino acids to ribosomes
b. anticodon - sequence of 3 tRNA nucleotides
c. tRNA anticodons pair w/complimentary mRNA codons
d. amino acids are joined to form a polypeptide
e. polypeptides make up a protein