DNA Replication &
Protein Synthesis
Designed by Mr. Gaccione
DNA is located in the nucleus in the form of chromosomes.
If the DNA of one cell is stretched out, it makes a 7 ft. long string.
There are 5 trillion cells in the human body.
If you connected all the DNA together, it would be long enough that it would take light over 10 hours10 hours to travel its length.
• Chromosomes contain a single, long piece of DNA
• A chromosome is about 0.004 mm long • The DNA is about 4 cm long
• This is 10,000x longer than the chromosome • Thus DNA must be wrapped tightly to fit into cells
• Imagine fitting 900 yards (300m) of rope into a backpack.
• The DNA molecule looks like a ladder that has been twisted.
• The DNA molecule is • made from two strands, • twisted together in a • double helix.
• Watson & Crick – • created the double • helix model for DNA.
The Structure of DNADNA is a long molecule made up of repeating units called nucleotides.
Each nucleotide is made up of three parts:
1. phosphate group2. carbon sugar (deoxyribose)3. nitrogen base
Repeating Nucleotides
• The sides of the DNA ladder(backbone) is formed by phosphate and sugar groups.
• The nitrogenous bases are • the rungs of the DNA ladder.
• DNA is 250 million nitrogen bases long.
• RNA is 3000 nitrogen bases long.
• There are four kinds of nitrogenous bases.
• They are divided into two classes:
purines and pyrmidines
•Purines (bigger) – Adenine and Guanine
•Pyrmidines (smaller) – Cytosine and Thymine
Nitrogenous Bases
Chargaff’s Rules• Chargaff discovered how the
nitrogenous bases bond together.
•Adenine always bonds with Thymine Cytosine always bonds with Guanine
DNA
Hydrogen bonding
•The particular order of the nitrogen bases is called the DNA sequence.
•This sequence makes each individual unique.
•An elm tree, eel & an elephant has the same DNA, but what makes them different is the order of the bases.
DNA Sequence
• Each chromosome carries 2,000 genes.
• 23 chromosomes = 30,000 to 40,000 genes
This is known as “The Human Genome”
• Genes are locations on chromosomes that give us our traits.
• Many of these are common to all human beings.
• So, 99.9% of your DNA is identical to everyone else's.
DNA & Genes
• The remaining 0.01% influences the differences between us.– height, hair color and – susceptibility to a particular disease
• Environmental factors, such as lifestyle (smoking and nutrition) also influence the way we look and our susceptibility to disease.
DNA & Genes
• Mutations are caused by mutatgens.Examples of mutagens:
UV rays, smoking & radiation
• Mutations are mistakes in the nitrogen bases or in the DNA sequence.
Mutations
Point Mutation
C
Thymine mutation
• Caused by exposure to UV light.
• 2 adjacent thymine residues become covalently linked.
Mutations• RNA polymerase adds ribonucleotides not
deoxynucleotides
• RNA polymerase does not have the ability to proofread what they transcribe
• RNA will have an error 1 in every 10,000 nucleotides
• DNA will have an error 1 in ten million nucleotides)
DNA Replication DNA replication makes an exact copy of the strand,
complete with 1 old and 1 new strand.
Step 1 DNA unwinds & unzips with the help of DNA polymerase Step 2 Each strand of the parent DNA is used as a
template to make the new daughter strand. Step 3 Free floating nucleotides are added by DNA polymerase.
DNA Replication
C T A C C G G
G A T G G C C T A T
• ・ DNA acts as a “manager” in the process of making proteins.
• ・ DNA is the template or starting sequence that is copied into RNA that is then used to make a protein.
DNA to mRNA to Protein
RNA differs from DNA
1. Ribose is the sugar rather than deoxyribose.
2. Uracil instead of ThymineAdenine, Guanine Cytosine stay the same.
3. Single stranded
Three Different RNAs1. messenger RNA (mRNA) – takes a message
or 3 letter code(codon) from DNA
GUA---UUC---GUU---AGU---UGA
2. ribosomal RNA (rRNA) – meeting place for three RNAs
3. transfer RNA (tRNA) – brings anti-codon & amino acid
Ribosome
Protein Synthesis -2 StepsTranscription & translation
Transcription:First step in protein synthesis
mRNA transcribes a message (code) from DNA
Occurs in the nucleus
Protein Synthesis Transcription
DNA
Cytoplasm
Nucleus
RNA
Transcription
ExportG AAAAAA
Protein Synthesis -Transcription
Step 1 DNA unwinds & unzips with the help of RNA
polymerase
Step 2 Only one strand of the parent DNA is used as a
template to make mRNA.
Step 3Free floating nucleotides are added by RNA
polymerase, making mRNA.
Protein Synthesis-Transcription
Protein Synthesis Transcription
Protein Synthesis -Transcription
aking mR from D template
C U A C C G G A U A
Protein Synthesis -Translation
Translation Goal: to make a protein
Second step in protein synthesis
All three RNAs meet(mRNA, rRNA & tRNA)
Occurs in the cytoplasm
Amino acid
UAC--UUC--GUU--AUG--
--AUG--Amino acid
Anti-codon
tRNA brings anti-codon & amino acid
Protein Synthesis - Translation
Draw and label the boxes, tRNA, mRNA & rRNA
tRNA
mRNA
rRNA
Ribosome
- AUG--UUC--GUU--AGU--UGA 5’
Amino Acid?
Amino Acid?
Amino Acid?
Amino Acid?
Amino Acid?
rRNA & mRNA are in the cytoplasm. Where is tRNA???
Translation
Met Phe Val Ser Stop!
ANTI-CODON?UAC ANTI-
CODON?
ANTI-CODON?
ANTI-CODON?
ANTI-CODON?
AAG CAA UCA ACU
Protein Synthesis -Translation Review
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?
??
? ?
?
?
? ?
rRNA
mRNA
rRNA
rRNA
tRNAmRNA
mRNA
mRNA
tRNA
tRNA
Amino acid
Protein Synthesis -Translation Review
• Translation is the meeting of all three RNAs (mRNA, rRNA & tRNA).
• It takes place in the cytoplasm. • • The goal is to string together amino acids to
form a protein.
• Proteins make up our skin, blood, muscles, heart, enzymes, stomach lining & intestinal linings.
Protein Synthesis - Key Words
TranscriptionDNA
Double Helix3’-5’ strand 5’-3’ strand
Phosphate GroupDeoxyribose
SugarsRibose sugars
Hydrogen Bonds
RNA polymeraseNucleus
Nuclear poreER
Complementary base pairs
rRNAmRNAtRNA
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