Download DNA

LABs
5-Structure of DNA and RNA
6-DNA Transcription (Gene Expression)
7- DNATranslation
8-Mutation
In the last lab
The DNA
 Deoxyribonucleic Acid (DNA); the genetic material
of all cellular organisms and most viruses.
 DNA responsible for preserving, copying and
transmitting information within cells and from
generation to generation.
General Structure of Nucleic Acid
DNA and RNA are
long chain polymers of
small chemical
compound called
nucleotides.
Nucleotides
Nucleotides; ring shaped structures composed of:
 Nitrogenous base; these bases are classified based on
their chemical structures into two groups:
 Purine; double ringed structure (Adenine and Guanine).
 Pyrimidine; single ring structures (cytosine and thymine).
 Sugar
 Phosphate group
Nucleotides
• DNA: Four different types of nucleotides differ in
nitrogenous base:

A is for adenine;

G is for guanine;

C is for cytosine and

T is for thymine.
 RNA: thymine base replaced by uracil base.
The RNA
 Three major classes of RNA:
o messenger (mRNA),
o transfer (tRNA) and
o ribosomal (rRNA).
 RNA is a single stranded; the pyrimidine base uracil
(U) replaces thymine and ribose sugar replaces
deoxyribose.
(Gene Expression)
Transcription
RNA polymerase makes a copy of information
in the gene (complementary RNA)
complementary
to one strands of DNA
(Gene Expression)
Translation
a messenger RNA (mRNA) molecule,
leaves the cell nucleus and enters the
cytoplasm, where it directs translating
to a sequence of amino acids during
protein synthesis.
FROM DNA
TO
PROTEIN
GENE STRUCTURE
 Most
of the genes consist of; short coding
sequences or exons are interrupted by a longer
intervening noncoding sequence or introns .
To get an mRNA molecule that yields a
working protein, the cell needs to trim out the
intron sections and then stitch only the exon
pieces together (see drawing). This process is
called RNA splicing.
The codon AGC codes for the amino acid
serine, and the codon ACC codes for the
amino acid threonine.
How Codons Work?
Methionine
16 Pu
17
9
A
17:1
13 12 Py 10
1
2
3
4
5
6
U* 7
A
C
C
73
72
71
70
69
68
67
Py 59A*
66
65 64 63 62 C
49 50 51 52 G T C
y
Py
G*
22 23 Pu 25
G
26
2020:120:2A
27
1
28
29
30
31
Py*
Anticodon
Pu
47:16
47:15
43 44
42 45
41 46
47
40
47:1
39
38
Pu*
U
34
U 35
C
A 36
TRANSLATION - INITIATION
fMet
Large
subunit
5’
E
P
A
UAC
GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA
3’
mRNA
Small
subunit
TRANSLATION - ELONGATION
Polypeptide
Arg
Met
Phe
Leu
Ser
Aminoacyl tRNA
Gly
Ribosome
5’
E
P
A
CCA
GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA
3’
mRNA
TRANSLATION - ELONGATION
Polypeptide
Met
Phe
Leu
Ser
Gly
Arg
Aminoacyl tRNA
Ribosome
5’
E
P
A
CCA UCU
GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA
3’
mRNA
TRANSLATION - ELONGATION
Polypeptide
Met
Phe
Leu
Ser
Gly
Arg
Ribosome
5’
E
P
A
CCA UCU
GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA
3’
mRNA
TRANSLATION - ELONGATION
Polypeptide
Met
Phe
Leu
Ala
Ser
Gly
Aminoacyl tRNA
Arg
Ribosome
E
CCA
5’
P
A
UCU
GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA
3’
mRNA
TRANSLATION - ELONGATION
Polypeptide
Met
Phe
Leu
Ser
Gly
Arg
Ribosome
5’
E
Ala
P
A
UCU CGA
GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA
3’
mRNA
What is a mutation?
change in the nucleotide sequence or
arrangement in DNA.
Mutations may be beneficial,
neutral(Eye color) or harmful(Sickle Cell
Anemia).
Mutations are changes in the genotype
which may or may not affect the
phenotype.
Types of mutation
1-Genomic Mutation
-change in chromosome number.
-error in separation in mitosis or meiosis.
e.g. Turner’s syndrome - 45, X.
Kleinfelter’s syndrome – 47, XXY.
2-Chromosome Mutations
- change in chromosome structure.
 -part of chromosome is:
* duplicated (may be beneficial ).
* deleted.
* inverted .
translocated (moved to another spot on the same
chromosome or another chromosome)
may cause transformation of cell to a cancer cell.
3-Gene Mutations
- change in an individual gene due to an error
in replication or failure of repair mechanism.
mutation may occur in a somatic cell or in a
‘germ cell’
2-Induced mutations
Chemical agents
-
alkylating agents .
Physical agents
- Ionizing radiation.
- UV radiation
Thank
you