replication, transcription and translation
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Replication, Transcription and Translation. Honors Biology Powerpoint #2 – Chapter 12. Warm Up: Base Pairing. 1. A C C T G A. 2. G C T A. G A G. What is the DNA ‘backbone’ made of?. Phosphate and Sugar. Nucleotide. Hydrogen bonds. - PowerPoint PPT PresentationTRANSCRIPT
Replication, Transcription and Translation
Honors BiologyPowerpoint #2 – Chapter 12
Warm Up: Base Pairing1.
2.
A C C T G A
G C T AG A G
What is the DNA ‘backbone’ made of?
Phosphate
and Sugar
DNA Replication
Hydrogen bonds
Nucleotide
Sugar-phosphate backbone
KeyAdenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
What is DNA replication?Making a copy of DNA
Why is DNA replication important for cells and
multicellular organisms? Replication allows cells to divide
Forming cells that are genetically identical to the original
When does DNA Replication occur? After the cell grows big enough to divide, during interphase, the “S” phase
DNA Replication
Growth
Growth
Replication fork
DNA polymerase
New strand
Original strand DNA
polymerase
Nitrogenous bases
Replication fork
Original strand
New strand
Important Enzyme #1
HelicaseUnwinds DNA at the replication fork.
Important Enzyme #2
DNA PolymerasePrincipal enzyme in DNA replication; adds nucleotides to growing strand of DNA and proofreads new strand of DNA
Steps in DNA Replication1. Helicase enzyme breaks the hydrogen bonds between base pairs. This unzips the double helix at a position called the replication fork.
2. There is an abundant supply of nucleotides in the nucleus for the formation of the new polynucleotides.
3. Nucleotides base pair to the bases in the original strands with hydrogen bonds.
4. DNA polymerase joins together the nucleotides together with strong covalent bonds to form a new complementary polynucleotide strand.
5. The double strand reforms a double helix.
6. Two copies of the DNA molecule form behind the replication fork. These are the new daughter chromosomes.
Drawings of the steps in DNA Replication
DNA Polymerase
Helicase
Some Important DNA Facts A strand of DNA
has 2 ends, the 5’ (5-prime) and 3’ (3-prime) ends.
DNA is ALWAYS copied from 5’ to 3’
Some Important DNA Facts There are multiple ‘bubbles’ of DNA
replicated at the same time
What is ‘semi-conservative’ replication?
In the new DNA created, one strand is from the original, and one is a new one.
Semi = part ofConserve = save
Why is ‘semi-conservative’ important?
The DNA is copied EXACTLY generation to generation
RNAWhere is DNA stored? ______________________
What organelle makes proteins? ______________________
Where are proteins made? ______________________
Nucleus
Ribosomes
Cytoplasm
What problem might this pose?
DNA can not take directions for making proteins to the ribosomes.
How does RNA solve this problem?RNA is a disposable copy of DNA that can leave the nucleus
B. RNA’s structure is very similar to the structure of DNA except for 3 major differences:
1. RNA has ribose sugar instead of deoxyribose
Nitrogen Base
2. RNA is single-stranded
3. RNA has uracil (U) instead of thymine (T)
DNA: AGTCCTTTAGTRNA: AGUCCUUUAGU
There are three main types of RNA:
1. Ribosomal RNA (rRNA)
rRNA is found in ribosomes, and
creates the active site for protein
formation
2. Transfer RNA (tRNA)
tRNA contains the anticodon, and
brings amino acids to create proteins
3. Messenger RNA (mRNA)
mRNA provides the template for making proteins
III. Transcription
A. Transcription: Producing RNA by copying part of the DNA’s nucleotide sequence
RNADNA
RNApolymerase
Adenine (DNA and RNA)Cystosine (DNA and RNA)Guanine(DNA and RNA)Thymine (DNA only)Uracil (RNA only)
B. Describe the process of transcription using drawings.
1. RNA Polymerase rips open the DNA double helix
2. RNA polymerase grabs bases and lines them up with the original DNA strand
3. Half of the DNA is copied into a strand of mRNA, then the DNA strand closes, hydrogen bonds reform
Transcription
C. How does RNA polymerase know where
to start?
Starts when it finds a
“promoter” (specific base
sequence)Found near the
beginning of a gene
sequence
D. Describe the process of RNA editing
RNA editing is a process that occurs in the nucleus.
It removes introns “intervening sequences” and leaves mRNA with only the exons “expressed sequences.”
After editing a cap and tail are attached and the mRNA is ready to enter into the cytoplasm.
IV. TranslationA. Proteins are long chains of amino acids. B. Codon: 3 consecutive
nucleotides that “code” for a specific amino acid.
What is the universal “start” codon:
AUG What are the three “stop” codons?
UGA, UAA, UAG
The Genetic Code
The Genetic Code
C. Use the genetic code below to translate the following mRNA sequences:
1. mRNA: A U G U A U C G G G C A U U U U A A
2. mRNA:U C C A U G G A A G U G A U U C C A U A A
3. mRNA:C C A U G U G U C C C C A A U G A A A A
C. Use the genetic code below to translate the following mRNA sequences:
1. mRNA: A U G U A U C G G G C A U U U U A A
2. mRNA:U C C A U G G A A G U G A U U C C A U A
A
3. mRNA:C C A U G U G U C C C C A A U G A A A A
Methionine (START), Tyrosine, Arginine, Alanine, Phenylaline, STOP.
Serine, Methionine, Glutamic Acid, Valine, Isoleucine, Proline, STOP
Methionine, Cysteine, Proline, Glutamine, STOP, Lysine
D. Translation:The decoding of RNA into a polypeptide chain (protein)
E. The Central Dogma of Biology is:
DNA RNA protein
Where does the first
step take place? Nucleus
Where does the second step take place? Cytoplasm
F. What is the job of tRNA during translation? Bringing amino acids to the ribosomes and match them up with the correct base on mRNA.
What is an anticodon? The three bases on a tRNA that match with the mRNA codons.
G. What is the role of the ribosome during translation? It is the site of protein assembly
H. 1) mRNA is transcribed in the nucleus then travels to the cytoplasm
Cytoplasm
Nucleus
mRNA
2) Ribosome grabs mRNA. tRNA brings amino acids to the ribosome
Cytoplasm
mRNA Start codon
Ribosome
Methionine
PhenylalaninetRNA
Lysine (amino acid)
3) tRNA matches with complimentary mRNA.
Ribosome makes peptide bond between amino acids, and breaks the bond between tRNA and amino acid.
mRNA RibosomeTranslation direction
LysinetRNA
Peptide bond
4) Peptide chain continues to grow until ribosome reaches a stop codon
Protein is complete.
tRNARibosome
Growing polypeptide chain
mRNA Stop codon