Differences and similarities between DNA and RNA. Synthesis of proteins

1. * C,H,O,N,S Amino acids
• Meat, fish, chicken, egg
white,milk, cheese, pork,
peas, beans and cereals
• Soluble in WATER
• Needed for CELLS,ANTIBODIES,
ENZYMES; used for ENERGY if all
the stores have run out (17kj/g)
• We eat food to make us! by re
assembling it

3. Ok! But what happens to the
Amino Acids that are needed?
It’s like cooking pizza! !
DNA MrNA
Amino
Acids
Ribosomes
Proteins

4. • We go from
to torNA Proteins
nucleus cytoplasm
Transcription Translation

5. information flows in one direction
when genes are expressed
The Central Dogma of
molecular biology:

6. • Nucleic acids made up of
chains of nucleotides
• Nucleotides consist of:
– A nitrogenous base
– A sugar (ribose)
– A phosphate
• Two types of nucleic acids
in cells:
– Deoxyribonucleic acid (DNA)
– Ribonucleic acid (RNA)

7. Nucleic acids have
primary and secondary
structures
– DNA
• Double-
stranded helix
• Carries genetic
information
• Transmitted
from parents
to children in
the sexual
gamets
– RNA
• 3 kinds (mRNA,
tRNA, rRNA)
• All single
strands

8. • The different bases in
the nucleotides which
make up DNA and RNA
are:
– Adenine
– Guanine
– Cytosine
– Thymine (DNA only)
– Uracil (RNA only)
• Chemical structure only
allows bases to bind with
specific other bases due
to chemical structure
DNA RNA
Adenine Uracil**
Thymine* Adenine
Guanine Cytosine
Cytosine Guanine

9. - Located in 23 pairs
of chromosomes in
nucleus of cell
– Genetic code
universal in all
organisms
– Mitochondrial
DNA slightly
different
– DNA has two
functions:
• Replication -
reproduces itself
when cell divides
• Information
transmission
– via protein
synthesis

10. Each parent strand serves as a template for a new strand and
the two new DNA strands each have one old and one new strand
Parent strands
New / daughter
strand
: combination of DNA &
histones

11. • To start, an enzyme breaks the hydrogen bonds that hold base-
pairs together.
• This process “unzips” the DNA molecule.
• Other enzymes find and correctly match free- floating
nucleotides to the two sides of the now open DNA molecule.
• This process continues until the entire molecule has been
replicated.
Growth
Growth
Replication
fork
DNA
polymerase
New strand
Original
strand
DNA
polymerase
Nitrogenous
bases
Replication
fork
Original
strand
New strand

12. :
carries genetic
information from DNA in nucleus
to cytoplasm where proteins
synthesize
carries amino acids from amino
acid pool to mRNA
joins with ribosomal proteins in
ribosome where amino acids joined
to form protein primary
structure.

13. making mRNA
from DNA
base sequence in
mRNA is translated
into an amino acid
sequence in a protein
Transcription
Translation
RNA
polymerase
catalyses
synthesis
of RNA

14. formed on a single strand of DNA by the
process of transcription in the nucleus
Transcription requires an enzyme known
as RNA polymerase

15. Base sequence of mRNA is
complementary to that of DNA
CODON: is a set of three adjacent nucleotides, also
called triplet, in DNA or mRNA that designates a
specific amino acid to be incorporated into a
polypeptide
Each polypeptide contains a combination of any or all of
the 20 different amino acids
The properties of proteins are determined by the order in
which different amino acids are joined together

16. Promoters serve as punctuation
marks, telling the RNA
polymerase:
where to start
which strand of
DNA to read
the direction to
take from the start
1
2
3

17. Function: carry
amino acids present
in the cytoplasm to
the ribosome

18. Occur in
the
nucleus
1. modification of
both ends of
pre-mRNA
2. removal of
introns

20. ribosome

21. Besides the cytoplasm, name TWO other
regions inside the eukaryotic cell that
contain ribosomes.
Chloroplast Mitochondrion
Some ribosomes in chloroplast & mitochondria
are even smaller than those of prokaryotes.

22. • Mitochondria contain their
own DNA and protein
synthesizing machinery
• Mitochondrial genetic code
slightly different
– Codon-anticodon interactions
simplified
• Synthesise only small
number of proteins
– Most mitochondrial proteins
coded for in nucleus and
transported into mitochondria

24. • Information in mRNA translated into
primary sequence of a protein in 4
steps:
– ACTIVATION
– INITIATION
– ELONGATION
– TERMINATION

25. A U G G G C U U AAA G C A G U G C A C G U U
This is a molecule of messenger RNA.
It was made in the nucleus by
transcription from a DNA molecule.
mRNA molecule
codon

26. A U G G G C U U AAA G C A G U G C A C G U U
A ribosome on the rough
endoplasmic reticulum attaches to
the mRNA molecule.
ribosome

27. A U G G G C U U AAA G C A G U G C A C G U U
It brings an amino acid to
the first three bases (codon)
on the mRNA.
Amino acid
tRNA molecule
anticodon
U A C
A transfer RNA molecule
arrives.
The three unpaired bases (anticodon)
on the tRNA link up with the
codon.
Start codon is AUG; first amino acid is always
methionine, which may be removed after
translation.

28. A U G G G C U U AAA G C A G U G C A C G U U
Another tRNA molecule comes into
place, bringing a second amino acid.
U A C
Its anticodon links up with the
second codon on the mRNA.

29. A U G G G C U U AAA G C A G U G C A C G U U
A peptide bond forms between the
two amino acids.
Peptide bond

30. A U G G G C U U AAA G C A G U G C A C G U U
The first tRNA molecule releases its
amino acid and moves off into the
cytoplasm.

31. A U G G G C U U AAA G C A G U G C A C G U U
The ribosome moves along the mRNA
to the next codon.

32. A U G G G C U U AAA G C A G U G C A C G U U
Another tRNA molecule
brings the next amino acid
into place.

33. A U G G G C U U AAA G C A G U G C A C G U U
A peptide bond joins the second
and third amino acids to form a
polypeptide chain.

34. A U G G G C U U AAA G C A G U G C A C G U U
The polypeptide chain gets longer.
The process continues.
This continues until a termination
(stop) codon is reached.
The polypeptide is then
complete.

35. Termination: translation ends
when a stop codon [ UAA, UAG,
UGA] enters the A site.

36. Enzymes
degrade mRNA
The ribosome
subunits
dissociate.

37. A ribosome can combine with any mRNA and
all tRNAs. What is the significance of
this?

38. • The end product of protein
synthesis is a primary structure
of a protein.
• A sequence of amino acid bonded
together by peptide bonds.
aa1
aa2
aa3
aa4
aa5
aa200
aa199

39. methionine glycine serine isoleucine glycine alanine stop
codon
protein
A U G G G C U C C A U C G G C G C A U A AmRNA
start
codon
Primary structure of a protein
aa1 aa2 aa3 aa4 aa5 aa6
peptide bonds
codon 2 codon 3 codon 4 codon 5 codon 6 codon 7codon 1

40. A protein may be moved to an
organelle or out of the cell

41. List four materials
(shown here) that are
required for translation to
occur:
1. Amino acids
2. mRNA
3. tRNA
4. ribosome

42. What happens if a mutation occurs at
a GENE?
Protein produced may fail to function
= genetic disease
e.g. Sickle-Cell Anaemia:
Mutation at a SINGLE base

43. Haemoglobin – has
more than 300
amino acids
A single base
change in the gene
for haemoglobin
results in a lethal
condition

44. Wrong sequence of amino acids =
Wrong folding =
NON FUNCTIONAL PROTEIN

45. Transcription
• Information transcribed from DNA
into RNA
– mRNA carries information for
protein structure, but other RNA
molecules formed in same way
• RNA polymerase binds to
promoter nucleotide sequence at
point near gene to be expressed
• DNA helix unwinds
• RNA nucleotides assemble along
one DNA strand (sense strand) in
complementary sequence to order
of bases on DNA beginning at start
codon (AUG - methionine)
• Transcription of DNA sense strand
ends at terminator nucleotide
sequence
• mRNA moves to ribosome
• DNA helix rewinds
From: Tortora, GJ & Grabowski SR (2000) Principles of Anatomy and
Physiology (9th Ed). New York: John Wiley & Sons. P88.

46. • DNA structure by Hank Green
https://www.youtube.com/watch?v=8kK2zwjRV0M (you
can add subtittles!!)
• Protein Synthesis by Hank Green
https://www.youtube.com/watch?v=itsb2SqR-R0 (you can
add subtittles too!!)
Funny videos: AMEBA SISTERS
. Differences between DNA and RNA:
https://www.youtube.com/watch?v=0Elo-zX1k8M
• Protein Synthesis:
https://www.youtube.com/watch?v=h5mJbP23Buo