1. From DNA to Proteins

2. Remember…Characteristics of Living Things
made up of units called cells
reproduce
based on a universal genetic code (DNA)
grow and develop
obtain and use materials and energy (metabolism)
respond to their environment (adapt)
maintain a stable internal environment (homeostasis)
taken as a group, organisms evolve

3. DNA Function Structure stores genetic information to make proteins
double sided chain of nucleotides that form a double helix

4. Parts of a DNA Nucleotide
Sugar: deoxyribose
Phosphate group
Nitrogen base
Adenine (A)
Guanine (G)
Cytosine (C)
Thymine (T)

5. The Nitrogenous Bases Purine: double ring Adenine Guanine Pyrimidine:
one ring
Thymine
Cytosine

6. Watson and crick
DNA is a double helix/spiral staircase or two nucleotide chains wrapped around each other in spiral.
Shape discovered by James Watson and Francis Crick; young scientists at Cambridge University
Backbone is alternating sugars and phosphates.
Nitrogen bases attach the two strands in the center.

7. Number of A = T
Number of G = C
Chargaff’s Observations
Adenine (A) & Thymine (T) bind
Guanine (G) & Cytosine (C) bind
Double ring (A, G) to a single ring (T, C)
The bases are connected to each other in the double helix by weak hydrogen bonds.
Therefore, it was determined…

8. Complementary base pairs
Pairing Between Bases
A purine on one strand is always paired with a pyrimidine on the opposite strand
Complementary base pairs
The sequence of bases on one strand of DNA determines the sequence of bases on the other strand
TCGAACT
AGCTTGA

9. DNA Organization
DNA is very long. The nucleus of each human cell contains more than 1 meter of DNA.
So how does it all fit?
DNA is wrapped around proteins to make chromatin which is tightly wrapped and coiled into chromosomes.
REMEMBER: DNA makes up genes and genes make up chromosomes.

10. DNA replication
Watson & Crick: “It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material”

11. DNA REPLICATION Process of copying DNA
Cells use enzymes to unwind the DNA and copy it using complementary base pairing rules.
Makes EXACT copies of DNA.

12. DNA Replication
DNA has 2 complementary strands that follow base pairing rules (A-T and C-G).
DNA strands separate or unzip.
a) DNA helicases: enzymes that open the double helix by breaking hydrogen bonds between the two strands
b) Replication forks: the areas of the double helix separates
Step 1
Original strands serve as templates. Enzyme (DNA polymerase) binds new nucleotides to the template strands following base pairing rules.
Step 2
Result is 2 exact copies of DNA, each having one original strand and one new strand.
Step 3

13. Copying DNA Build daughter DNA strand
use original parent strand as “template”
synthesis enzyme = DNA polymerase
add new matching bases
DNA
Polymerase

14. Replication = fast & accurate
In humans, 50 nucleotides/second are added to a DNA strand
There are hundreds of origins of replication…replicating DNA takes just a few hours!
Proofreading: DNA POLYMERASE
Errors sometimes occur!
The wrong nucleotide may be added to a new strand
Can only add nucleotides to the growing strand if the previous nucleotide was correctly paired
Can backtrack and remove the incorrect nucleotide
Reduces errors in DNA to 1/1 billion nucleotides
Video Wrap-Up

15. Rna carries DNA’s instructions

16. Protein Synthesis: Part 1
So… How does the cell get the instructions
from the nucleus to the ribosomes?
CELL
CYTOPLASM
NUCLEUS
RIBOSOMES – where proteins are made
DNA – stores info to make proteins
mRNA
Where are the instructions to make proteins?
Where are proteins made?
It makes a copy to send called – messenger RNA

17. Protein synthesis Proteins are made on the ribosomes in the cytoplasm.
DNA (instructions to make proteins) must stay in the nucleus.
How does the cell get the directions from the nucleus to the ribosomes?
IT MAKES A COPY!
Messenger RNA (mRNA) is a disposable copy of DNA that can leave the nucleus.

18. Decoding Information in DNA
Traits, such as eye color, are determined by proteins that are built according to instructions coded in DNA
Proteins are not built directly from DNA
RNA (ribonucleic acid) is involved

19. DNA: Deoxyribonucleic Acid
RNA:
Ribonucleic Acid
Structure:
Single Strand of Nucleotides
Sugar Ribose
Nitrogenous Bases
Adenine (A)
Guanine (G)
Cytosine (C)
Uracil (U)
DNA: Deoxyribonucleic Acid
Double Strand of Nucleotides
Sugar Deoxyribose
Thymine (T)

20. three types of RNA Messenger RNA (mRNA) Transfer RNA (tRNA)
carries DNA code out of nucleus / “disposable copy”
Transfer RNA (tRNA)
build proteins following instructions from mRNA
Ribosomal RNA (rRNA)
makes up ribosomes

21. Transcription
REMEMBER: DNA cannot leave the nucleus so mRNA is used as a copy of DNA that can leave the nucleus.
Transcription
the process which makes mRNA by copying part of the DNA
Cells use enzymes to unwind the DNA and make mRNA using the complementary base pairing rules.
(Happens much like DNA replication.)

22. Transcription Steps A – T C – G G – C A – T C – G T – A
DNA has 2 complementary strands that follow base pairing rules (A-T and C-G).
1. DNA strands separate or unzip
2. One of the original strands serves as a template. Enzyme (RNA polymerase) binds new RNA nucleotides to the template strand following base pairing rules. (A-U, C-G)
3. mRNA leaves the nucleus and carries the instructions to the ribosomes. The DNA “re-zips”
A – T C – G G – C A – T C – G T – A
A T C G G C A T C G T A
A - U T C - G G G - C C A - U T C - G G T - A A
A – T U C – G G G – C C A – T U C – G G T – A A 1 2 3
Transcription Animation

23. Protein synthesis: part 2
mRNA carries the instructions for making proteins which are made of amino acids.
BUT ….
RNA language – A, U, C, G
Protein language – 20 different amino acids (examples: arginine, valine, serine, etc.)
How would you follow directions that were written in a different language? TRANSLATION

24. translation
Process of assembling proteins (chains of amino acids) from the information in mRNA
mRNA has to be translated into a protein’s amino acid sequence.
Occurs on the ribosomes and uses all 3 types of RNA
tRNA has an amino acid attached at one end and 3 nucleotides at the other end called an anti-codon.
mRNA is read in groups of 3 nucleotides called codons.

25. Special codons
Start: AUG: codes for the amino acid methionine – helps a ribosome bind on and starts the translation
Stop: UAA, UAG, UGA: tells the ribosome to stop translating and release the finished protein

26. mRNA to protein = Translation
mRNA  instructions
ribosome  instruction reader
tRNA  builders
ribosome
mRNA
Protein Complete!

27. TRANSLATION STEPS
5. Process continues until the ribosome reads a stop codon, at which time it releases the finished amino acid chain (AKA: protein)
4. Another tRNA with the complementary anti-codon binds to the mRNA codon. The amino acid from the tRNA binds to methionine.
3. Ribosome shifts down the mRNA to the next codon.
2. tRNA with the complementary anti-codon (UAC) binds to the mRNA codon bringing the amino acid methionine with it.
1. Ribosome attaches to the mRNA at the start codon (AUG)

30. Recap of Protein Synthesis
mRNA is made in the nucleus using DNA as a template. (TRANSCRIPTION)
mRNA leaves nucleus and travels to ribosomes.
Proteins are made by tRNA at the ribosomes using mRNA as instructions. (TRANSLATION)

31. The Genetic Code
Chart shows which amino acid that each mRNA codon represents.
Read by starting at the center and working outwards.

32. The mRNA code For ALL life! Code is redundant Start codon Stop codons
strongest support for a common origin for all life
Code is redundant
several codons for each amino acid
mutation insurance!
Strong evidence for a single origin in evolutionary theory.
Start codon
AUG
methionine
Stop codons
UGA, UAA, UAG

33. Transcription & Translation Practice
DNA: G T T A C A C G C A G T A C T
C A A U G U G C G U C A U G A
glut – cyst – alan – serin – stop
transcription
RNA:
translation
Protein:

34. SO…
How will gene mutations affect the mRNA that is copied from the DNA? How will gene mutations affect the protein coded for by the mRNA? How will gene mutations affect the organism that contains these proteins?

35. Gene Mutations Gene mutations: changes in a single gene
Point Mutation: substitution of a single nucleotide
Example:
Correct DNA: TAC CAT ATG TGG CAT
Substitution: TAC CAT ATC TGG CAT
Effect: Only one codon is affected so only one amino acid in the protein is affected.

36. Only one amino acid affected

37. Point mutation leads to Sickle cell anemia
What kind of mutation?

38. Frameshift mutations Deletion Insertion THERATANDTHECATATETHEREDBAT
THERTANDTHECATATETHEREDBAT
THERTANDTHECATATETHEREDBAT
Insertion
THERAATANDTHECATATETHEREDBAT
THERAATANDTHECATATETHEREDBAT

39. 2. Frameshift Mutation: deletion or insertion of nucleotides Example:
Normal DNA : TAC CAT ATG TGG CAT
Insertion: TAC CAT AAT GTG GCA T
Deletion: TAC CAA TGT GGC AT
Effect: Reading frame is shifted so all of the codons from that point on are different making all of the amino acids in the protein different too.

40. All or most amino acids affected
Insertion
Cysteine
Arginine
All or most amino acids affected

41. All or most amino acids affected
Deletion
Stop
Leucine
Arginine
All or most amino acids affected

42. Cystic fibrosis Primarily whites of European descent
strikes 1 in 2500 births
1 in 25 whites is a carrier (Aa)
normal allele codes for a membrane protein that moves Cl- across cell membrane
mutant channel limit movement of Cl- (& H2O) across cell membrane
thicker & stickier mucus coats cells
mucus build-up in the pancreas, lungs, digestive tract & causes bacterial infections
without treatment children die before 5; with treatment can live past their late 20s
Cystic fibrosis is an inherited disease that is relatively common in the U.S. Cystic fibrosis affects multiple parts of the body including the pancreas, the sweat glands, and the lungs. When someone has cystic fibrosis, they often have lots of lung problems. The cause of their lung problems is directly related to basic problems with diffusion and osmosis in the large airways of the lungs.
People without cystic fibrosis have a small layer of salt water in the large airways of their lungs. This layer of salt water is under the mucus layer which lines the airways. The mucus layer in the airways helps to clear dust and other inhaled particles from the lungs.

44. Identifying Mutations
Normal DNA: ATACGATGCTAGCGATCG
Mutated DNA: ATAGGATGCTAGCGATCG
Point Mutation: G substituted for C
Mutated DNA: ATACGATTGCTAGCGATCG
Frameshift Mutation: Insertion of T
Mutated DNA: ATACGTGCTAGCGATCG
Frameshift Mutation: Deletion of A

45. From gene to protein protein DNA mRNA trait tRNA transcriptionaa
transcription
translation
DNA
mRNA
protein
ribosome
tRNA aa U C A G
trait
nucleus
cytoplasm

46. DNA transcription mRNA Can you tell the story? ribosome tRNA
amino acids
mRNA
Can you tell the story?
protein
ribosome
tRNA
translation

47. Gene Expression = protein synthesis
DNA
TACGCACATTTACGTACGCGG
mRNA
AUGCGUGUAAAUGCAUGCGCC aa
protein
trait

48. Remember…Characteristics of Living Things
made up of units called cells
reproduce
based on a universal genetic code (DNA)
grow and develop
obtain and use materials and energy (metabolism)
respond to their environment (adapt)
maintain a stable internal environment (homeostasis)
taken as a group, organisms evolve