2. Answer these questions:
What is coded for in DNA? How is it coded?
What is the primary structure of a protein?
Proteins
The sequence of A, T, G, C
Sequence of amino acids
What are proteins used for?
Structure
Controlling the biochemistry of an organism
Enzymes, antibodies
3. From DNA to Protein
DNA cannot leave the nucleus
Protein is made at the ribosomes in the cytoplasm and
attached to the rough endoplasmic reticulum
Therefore, a message must be sent from the DNA to the
ribosome
4. From DNA to Protein
The messenger is RNA (mRNA)
DNA Protein: occurs in 2 steps
Transcription
Making the coded message (mRNA)
Translation
Reading the coded message
5. How is RNA different from DNA?
RNA
DNA
Single-stranded
Double-stranded
Sugar = ribose
Sugar = deoxyribose
A, U, G, C
A, T, G C
6.
7. 3 types of Ribonucleic Acid (RNA)
mRNA
rRNA
Messenger RNA
Brings instructions from DNA in the nucleus to the cytoplasm
(where ribosomes are found)
Ribosomal RNA
Part of the ribosome that binds to the mRNA and uses the
instructions to assemble the amino acids in the correct order
tRNA
Transfer RNA
Delivers the amino acids to the ribosome to be assembled
into a protein
8. Transcription: DNA to mRNA
DNA is unzipped
mRNA is formed, complementary to one of the
strands of DNA
1.
2.
RNA polymerase (enzyme) joins the nucleotides of
RNA together
9. Transcription
The mRNA is processed
3.
Not all nucleotides in DNA code for making protein
Introns – noncoding sequences
Exons– coding sequences
Introns are removed and exonsare spliced together
For protection from enzymes in the cytoplasm, the ends
of the RNA strand are ‘covered’
5’ GTP cap
3’ poly-A tail
10. Translation: mRNA to Protein
~20 amino acids and 4 nitrogenous bases
(A, U, G, C)
How can 4 bases form a code for all possible proteins?
A group of 3 bases code for 1 amino acid
Each group is called a codon
64 combinations are possible when a sequence of 3
bases is used, therefore there are 64 different mRNA
codons
Not all codons code for proteins.
UAA = stop
AUG = start
More than one codon can code for the same amino
acid, but for any one codon, there can only be one amino
acid
14. Mutations
Answer this question:
How does DNA encode the characteristics of an
organism?
Each codon in DNA codes for an amino acid (or start/stop) used
to build protein which shapes an organism's characteristics
DNA mRNA Protein Characteristics
A mutation is any change in the genetic code
(nucleotide sequence)
Mutations are random
15. The Causes of Mutations
DNA fails to copy accurately
External influences can create mutations
Chemicals or radiation break down DNA
When the cell repairs the DNA, it might not do a perfect
job of the repair
16. Types of Mutations
Substitution
One base is exchanged for another
This will change the codon which could…
Code for a different amino acid and change the protein
Code for the same amino acid and do nothing (silent mutation)
Change the code to ‘stop’ and make an incomplete protein that
will probably not function
Insertion
Extra base pairs are inserted into a new place in the DNA
17. Types of Mutations
Deletion
A section of DNA is lost, or deleted
Frameshift
Since protein-coding DNA is divided into codons three
bases long, insertions and deletions can ‘shift’ the code
18. The Effects of Mutations
All cells contain DNA = lots of places for a mutation
to occur
Somatic mutations occur in non-reproductive cells
and won't be passed onto offspring
19. The Effects of Mutations
Germ line mutations occur in reproductive cells like
sperm and eggs and can be passed to offspring and
has large scale effects on evolution
The mutation could do nothing
The mutation could do something small…
The mutation could have large consequences…
http://evolution.berkeley.edu/evolibrary/article/0_0_0/mutations_
06
