1. • Exam II Tuesday 5/10 – Bring a scantron with you!
Announcements
● Tutoring Center
SCI I, 407
M 12-3, 5:30-6:30; W 8-9, 5:30-6:30,
Th 8-12, 6-7; F 8-9
● MasteringBiology Assignment due Tuesday 5/10
• Exam II Tuesday 5/10 – Bring a scantron with you! 1

2. Nucleic Acids ● Include DNA and RNA Information storage molecules
They provide the directions for building proteins
Gene
DNA
RNA
Protein
Amino acid
Nucleic acids 2

3. Nucleic Acids ●Nucleic acids are polymers of nucleotides
Nitrogenous base
(A,G,C, or T)
Phosphate
group
Thymine (T)
Sugar
(deoxyribose)
Base
DNA, deoxyribonucleic acid
RNA, ribonucleic acid
Nitrogenous base
A, G, C, or U
Uracil U
Phosphate
group
Sugar ribose 3

4. Nucleic Acids ●Each DNA nucleotide has one of the following bases:
Adenine (A)
Guanine (G)
Cytosine (C)
Thymine (T)
Adenine A
Guanine G
● Each RNA nucleotide has one of the following bases:
Adenine (A) Guanine (G) Cytosine (C) Uracil (U)
Thymine T
Cytosine C 4

5. Nucleic Acids ●Nucleic Acid Structure Sugar-phosphate backbone Bases
pair
Nucleotide
Hydrogen
bond
Bases
a DNA strand
polynucleotide
b Double helix
two polynucleotide strands 5

6. DNA Structure Phosphate group Nitrogenous base Nitrogenous base
(can be A, G, C, or T)
Sugar
Nucleotide
Thymine (T)
DNA
double helix
Phosphate
group
Sugar
(deoxyribose)
DNA nucleotide
Polynucleotide
Sugar-phosphate
backbone

7. DNA Structure
*Early 1950’s Rosalind Franklin
*1953 Watson and Crick

8. DNA Structure

9. Flow of Genetic Information
DNA functions as the inherited directions for a cell or organism.
How are these directions carried out?
Gene
DNA
RNA
Protein
Amino acid
Nucleic acids

10. Flow of Genetic Information
An organism’s genotype is its genetic makeup, the sequence of nucleotide bases in DNA.
The phenotype is the organism’s physical traits, which arise from the actions of a wide variety of proteins.
Gene
DNA
RNA
Protein
Amino acid
Nucleic acids

11. Flow of Genetic Information
DNA strand
TRANSCRIPTION
RNA
TRANSLATION
Codon
Polypeptide
Amino acid

12. Second base of RNA codon
Phenylalanine
(Phe)
Tyrosine
(Tyr)
Cysteine
(Cys)
Serine
(Ser)
Stop
Stop
Leucine
(Leu)
Stop
Tryptophan (Trp)
Histidine
(His)
Leucine
(Leu)
Proline
(Pro)
Arginine
(Arg)
Glutamine
(Gln)
First base of RNA codon
Third base of RNA codon
Asparagine
(Asn)
Serine
(Ser)
Isoleucine
(Ile)
Threonine
(Thr)
Lysine
(Lys)
Arginine
(Arg)
Figure The dictionary of the genetic code, listed by RNA codons.
Met or start
Aspartic
acid (Asp)
Valine
(Val)
Alanine
(Ala)
Glycine
(Gly)
Glutamic
acid (Glu)
Figure 10.11

13. Transcription (a) A close-up view of transcription
RNA polymerase
DNA of gene
Promoter
DNA
Initiation
Terminator DNA
RNA
Area shown in
part (a) at left
Elongation
RNA nucleotides
RNA polymerase
Termination
Growing RNA
Figure Transcription
Newly
made
RNA
Completed RNA
Direction of
transcription
Template
strand of DNA
RNA
polymerase
(a) A close-up view of transcription
(b) Transcription of a gene
Figure 10.13

14. Translation Translation requires: mRNA ATP Enzymes Ribosomes
Cap
Start of genetic
message
Translation requires:
mRNA
ATP
Enzymes
Ribosomes
Transfer RNA (tRNA)
End
Tail

15. Translation Transfer RNA (tRNA): Acts as a molecular interpreter
Amino acid
attachment site
Transfer RNA (tRNA):
Acts as a molecular interpreter
Carries amino acids
Matches amino acids with codons in mRNA using anticodons
Hydrogen
bond
RNA
polynucleotide
chain
Anticodon
tRNA
(simplified
representation)
tRNA polynucleotide
(ribbon model)

16. Translation Ribosomes are organelles that:
Coordinate the functions of mRNA and tRNA
Are made of two protein subunits
Contain ribosomal RNA (rRNA)
Next amino acid
to be added to
polypeptide
tRNA binding sites
Growing
polypeptide
P site
A site
Ribosome
tRNA
Large
subunit
mRNA
binding
site
mRNA
Small
subunit
Codons
(a) A simplified diagram
of a ribosome
(b) The “players” of translation

17. Initiation of Translation
Met
Large
ribosomal
subunit
Initiator
tRNA
P site
A site
mRNA
Start
codon
Small ribosomal
subunit

18. Peptide bond formation
Amino acid
Polypeptide
P site
mRNA
Anticodon A
site
Codons
Codon recognition
ELONGATION
Stop
codon
Peptide bond formation
New
peptide
bond
Figure The elongation of a polypeptide. (Step 4)
mRNA
movement
Translocation

19. Transcription Polypeptide Nucleus Stop codon Intron RNA processing Cap
RNA polymerase
Transcription
Polypeptide
Nucleus
DNA
mRNA
Stop
codon
Intron
RNA processing
Cap
Termination
Tail
mRNA
Intron
Anticodon
Amino acid
Ribosomal
subunits
Codon
tRNA
Figure A summary of transcription and translation. (Step 6)
Enzyme
Elongation
ATP
Initiation
of translation
Amino acid
attachment

20. Mutations A mutation is any change in the nucleotide sequence of DNA.
Mutations can change the amino acids in a protein.
Mutations can involve:
Large regions of a chromosome
Just a single nucleotide pair
Normal hemoglobin DNA
mRNA
Normal hemoglobin
Mutant hemoglobin DNA
Sickle-cell hemoglobin

21. Mutations

22. Human Disorders