21 - 1CH110 – Nucleic Acids Nucleic acids Nucleic acids Nucleic acids: –Maintain genetic...

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Transcript of 21 - 1CH110 – Nucleic Acids Nucleic acids Nucleic acids Nucleic acids: –Maintain genetic...

The nucleic acidsTemplate for RNA
RNA = ribonucleic acid
Each nucleotide has 3 parts:
A phosphate unit
phosphate
sugar
base
S
S
S
S
S
S
B
B
B
B
B
B
P
P
P
P
P
P
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CH110 – Nucleic Acids
THE SUGAR PART
The major difference between RNA and DNA is the different form of sugar used.
Ribose C5H10O5
in RNA
DeoxyRibose C5H10O4
in DNA
O
HOCH2
H
H
H
H
OH
OH
OH
O
HOCH2
H
H
H
H
OH
H
OH
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Purines & Pyrimidines
Sugar-phosphate backbone
Causes each DNA chain to coil around the outside of the attached bases like a spiral stair case.
Base Pairing
Hydrogen bonding occurs between purines and pyrimidines. This causes two DNA strands to bond together.
adenine - thymine guanine - cytosine
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guanine
cytosine
thymine
adenine
N
N
O
DNA - Secondary Structure
hydrogen bonds.
bases will form pairs.
Sugar-phosphate backbone
DNA coils around outside of attached bases like a spiral stair case.
Results in a double helix structure.
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The combination of the stairstep sugar-phosphate backbone and the bonding
between pairs results
The actual chain is like a coiled spring.
It is something similar to what happens when protein chains form an alpha helix.
It is the sequence (order) of the amines coming off of the backbone that give us all our genetic information
Just like the sequence of words in a sentence give it meaning.
Of the like in words meaning just sentence a give sequence it. (Get my meaning ? )
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Strands are connected by H-bonds between the amines.
Like steps of a spiral staircase
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around protein - histomes. The acidic DNA’s are
attracted to the basic histones.
21 - *
CH110 – Nucleic Acids
It also was clear in the 1960s that the chromosomes of cells
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The normal number of chromosome pairs varies among the species.
Animal Pairs Plant Pairs
Man 23 Onion 8
Cat 30 Rice 14
Mouse 20 Rye 7
Rabbit 22 Tomato 12
Honeybee, White pine 12
female 16 tounge fern
CH110 – Nucleic Acids
DNA: Self - Replication
When a cell nucleus divides, the bridging hydrogen bonds break (with the aid of enzymes) and the intertwined strands unwind from each other.
The amines left sticking out from each strand are now free to pick up new partners from the plentiful supply present in the cell.
19.unknown
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in opposite directions.
The initial
CH110 – Nucleic Acids
The messenger RNA (mRNA) move outside the nucleus to the cytoplasm where Ribosomes are anxiously awaiting their arrival.
rRNA
rRNA
CH110 – Nucleic Acids
The messenger RNA (mRNA) move outside the nucleus to the cytoplasm where Ribosomes are anxiously awaiting their arrival.
rRNA
rRNA
CH110 – Nucleic Acids
The messenger RNA (mRNA) move outside the nucleus to the cytoplasm where Ribosomes are anxiously awaiting their arrival.
rRNA
rRNA
CH110 – Nucleic Acids
The messenger RNA (mRNA) move outside the nucleus to the cytoplasm where Ribosomes are anxiously awaiting their arrival.
rRNA
rRNA
rRNA
Ribosomal RNA – rRNA: Platform for protein synthesis. Holds mRNA in place and helps assemble proteins.
rRNA
The mRNA is the train slowly moving through the station.
rRNA
Codons
mRNA
AUG
GCU
AUG
UUG
5’
3’
transports amino acids to site of protein synthesis.
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Initiation AUG
A total of 64 condons are used for all amino
acids and for starting and stopping. All protein
synthesis starts with methionine. After the poly-
peptide has been made, an enzyme removes this
amino acid.
Each AA is activated by reacting with an ATP
The activated AA is then attached to particular tRNA... (with the correct anticodon)
C
G
A
fMET
anticodon
Termination
After the last translocation (the last codon is a STOP), no more AA are added.
“Releasing factors” cleave the last AA from the tRNA
The polypeptide is complete
E.Coli plasmid bodies
Result is a “sticky end”
Addition of a gene from a second organism
Spliced DNA is replaced and organism synthesizes the new protein
83
83
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What is the sequence of bases in mRNA produced
from a section of the template strand of DNA that has
the sequence of bases: 3’–C–T–A–A–G–G–5’?
1. 5’–G–A–T–T–C–C–3’
2. 5’–G–A–U–U–C–C–3’
3. 5’–C–T–A–A–G–G–3’
*
What is the sequence of bases in mRNA produced
from a section of the template strand of DNA that has
the sequence of bases: 3’–C–T–A–A–G–G–5’?
3’–C–T–A–A–G–G–5’?
2. 5’–G–A–U–U–C–C–5’
*
*
The following section of DNA is used to build a mRNA
for a protein.
A. What is the corresponding mRNA sequence?
B. What are the anticodons on the tRNAs?
C. What is the amino acid order in the peptide?
Learning Check
A. What is the corresponding mRNA sequence?
5’—CUU—GGG—AAA—3’ mRNA
B. What are the anticodons for the tRNAs?
mRNA codons CUU GGG AAA
tRNA anticodons GAA CCC UUU
C. What is the amino acid order in the peptide?
mRNA 5’—CUU—GGG—AAA—3’
Leu — Gly — Lys