1. DNA, RNA and Protein

2. A. The Structure of DNA (Deoxyribonucleic Acid)
DNA is double stranded and in the shape of a double helix.

3. 2. The monomers of DNA are called nucleotides: made of a sugar (deoxyribose),
a phosphate group
and a nitrogen base
Phosphate group
Nitrogen Base
Deoxyribose Sugar

4. 3. There are four types of DNA bases and they pair specifically:
Adenine
Thymine
with
Guanine
Cytosine
with

5. DNA Looks Like a Ladder The alternating sugar and
phosphates form the sides
of a ladder and the nitrogen
bases form the rungs. The
Two sides of the ladder are
held together with hydrogen
bonds

6. A T C G G C T A T C G A T A G C C G A T A G C T
4. If the sequence of one strand is known, the other strand is known
A T C G G C T A T C G A T A G C C G A T A G C T

7. DNA Works as a Code
Codon- a three nucleotide sequence that codes for a single amino acid
With 4 different types of nucleotides in triplet codes, 64 combinations are possible
61 of the codons code for 20 amino acids
3 codons signal a stop- Identifies the end of a protein
The genetic code is exact. If a sequence of DNA is known, the resulting amino acid chain (protein) is known

8. DNA codons Amino Acid Isoleucine ATT, ATC, ATA Leucine
CTT, CTC, CTA, CTG, TTA, TTG
Valine
GTT, GTC, GTA, GTG
Phenylalanine  
TTT, TTC
Methionine
ATG
Cysteine 
TGT, TGC
Alanine      
GCT, GCC, GCA, GCG
Glycine  
GGT, GGC, GGA, GGG
Proline      
CCT, CCC, CCA, CCG
Threonine  
ACT, ACC, ACA, ACG
Serine       
TCT, TCC, TCA, TCG, AGT, AGC
Tyrosine  
TAT, TAC
Tryptophan  
TGG
Glutamine  
CAA, CAG
Asparagine  
AAT, AAC
Histidine 
CAT, CAC
Glutamic acid  
GAA, GAG
Aspartic acid 
GAT, GAC
Lysine       
AAA, AAG
Arginine  
CGT, CGC, CGA, CGG, AGA, AGG
Stop codons
TAA, TAG, TGA

9. DNA Replication

10. C. DNA Replication The structure of DNA explains how it replicates
DNA “unzips” down the middle
b) Free floating nucleotides pair up with both sides of the DNA molecule
ATCGA
TAGCT
ATCGA
TAGCT
ATCGA
TAGCT
ATCGA
TAGCT
Original
Exactly Copied DNA Strands

11. DNA Replication
This process produces two exact DNA molecules (Chromosomes) that are the same
DNA never leaves the nucleus

12. If DNA never leaves the nucleus, how can the DNA message get to the site of protein production, the ribosome?

13. Answer: The DNA message is copied to RNA during the process of Transcription

14. How do RNA and DNA differ?

15. D. The Structure of RNA RNA is single stranded
The sugar in RNA is Ribose, not deoxyribose as in DNA
The DNA nucleotide thymine is replaced by the RNA nucleotide Uracil

16. E. RNA’s Functions: Two Types, Two Jobs
m-RNA (messenger RNA) delivers the copied DNA from the nucleus to the Ribosome- the site of protein synthesis
t-RNA (transfer RNA) picks up specific amino acids in the cytoplasm and delivers them to the ribosome

17. Ribosome

18. F. Steps in Protein Synthesis
DNA molecule unzip where the desired gene is located
Free floating RNA nucleotides pair with the DNA strand forming m-RNA (Transcription)
The m-RNA leaves the nucleus and goes to a ribosome
A specific t-RNA delivers a specific amino acid to the ribosome (Translation)
The m-RNA codon matches with the t-RNA anticodon bringing the amino acid into its proper place
When the next amino acid is in place, the two are joined in a condensation reaction
The process is repeated until a stop code is read and a complete protein is formed

19. G. Mutation- change in the genetic code
1. Gene Mutation or Point Mutation- a nucleotide base is added, subtracted or changed to produce a change in the amino acid sequence of a protein

20. Genetic Code with RNA Codons

21. Proline Glutamic Acid Glutamic Acid
A change in a single base in the DNA strand will result in a change in the m-RNA strand and the resulting protein
Normal Hemoglobin
Amino Acids
DNA
RNA
GGA CTC CTC
CCU GAG GAG
Proline Glutamic Acid Glutamic Acid
Sickle Cell Hemoglobin
Proline Valine Glutamic Acid
GGA CAC CTC
CCU GUG GAG

27. 2. Chromosome Mutation- involves a change in many genes
a) Deletion- part of a chromosome is lost
b) Inversion- part of a chromosome is flipped around
c) Translocation- part of a chromosome is added to another chromosome

28. 3. Somatic & Germ Mutations
a) Somatic mutations: change that occurs in body cells. Affects only the individual. Ie. cancer
b) Germ Mutations- changed in the genetic code of gametes that will affect the individuals offspring
4. Mutagens- substances capable of causing damage to DNA
5. Most mutations are harmful

29. 6. Frame Shift Mutations
An insertion or deletion that results in the reading frame being shifted.
All codons following the mutation will be changed.
Example:
THE RED DOG ATE THE CAT
HER EDD OGA TET HEC AT