no mRNA trascription = no translation = no protein synthesis = death
The enzyme helicase unwinds and “cuts” open the DNA molecule for replication. Single-stranded binding proteins keep the DNA strands separated. Primase attaches an RNA primer codon. DNA polymerase then adds new nucleotides on the leading strand.
Codons signal start and stop points on the DNA strand Lagging strand uses Okasaki fragments to build complimentary DNA strands.
Scribes copying biblical text - just packaged differently (new binding/cover) = transcription
Like trying to walk out of the library with every book on the shelves.
Translation involves changing languages (no longer DNA to RNA - both nucleic acids, but Nucleic Acid to Protein)
peptide bonds hold amino acids together, forming polypeptide chains,
20 different amino acids (some coded for by more than one anticodon).
Introduction to DNA & RNA Replication Transcription Translation
Why Did Caesar Die?The Roman emperor Claudius Caesar (10 B.C.– A.D. 54) had an appetite for the delicate taste of mushrooms. Historians believe that Caesar’s wife, Agrippina, wanted to poison him. She mixed into Caesar’s favorite dish of mushrooms a few of the poisonous species Amanita caesarea. These poisonous mushrooms contain a substance that blocks the activity of an enzyme required for the cells to transcribe messenger RNA from DNA.For the first 10 hours after Caesar ate the mushrooms, all seemed well as the mushroom poisons entered the blood stream and were absorbed by the liver and kidneys. About 15 hours after eating the mushrooms, Caesar’s liver cells stopped functioning. Nausea, diarrhea, and delirium affected him as his liver and kidneys could no longer filter and detoxify wastes and other harmful substances from the blood. He died two days later from liver failure.
DNA (Deoxyribonucleic Acid) DNA holds the instructions for all cell functions and all production of proteins Chromosomes are just tightly wound and packaged strands (molecules) of DNA DNA is made up of repeating segments called nucleotides
DNA Nucleotide Nitrogenous bases: Adenine Guanine Thymine Cytosine Every living thing on earth shares these same 4 nucleotides
Nucleotide Sequence An elk, elm and eel all have the same four nucleotides that make up their DNA Like the letters in their names, the order (or sequence) of their nucleotides determine different traits that result in very different organisms being produced
DNA Base-pairing•DNA is made from 2 rows of side-by-sidenucleotides arranged in a specific order• DNA has specific pairing between the bases: Guanine must pair with Cytosin Adenine must pair with Thymine
DNA Double Helix Nitrogenous bases form the “rungs” of the DNA “ladder” 1. Adenine (A) 2. Guanine (G) 3. Thymine (T) 4. Cytosine (C)
DNA Replication In order for cells to reproduce (make more of themselves), DNA must be copied Each of the 46 strands of the original DNA serve as a template for new copies A single strand of human DNA, stretched out, would be about 6 feet long, containing over 80 million base pairs That’s about 46,000 books worth of information in 1 cell! With incredible accuracy, all of a cell’s DNA can be replicated in about one hour
Replication First, DNA strands are unwound and enzymes “unzip” the molecule Next, new nucleotides are added according to base pairing rules This occurs simultaneously at many different places along a single strand of DNA Parental DNA New DNA Templates
REPLICATION: DNA is copied A codon is a 3-nuceotide segment which signals something • Start and stop codons signal where replication can begin and end.
Think of it this way… Replication • Making exact copies • DNA DNA • Like a copy machine
DNA Replication Quiz1. Why is replication necessary? So both new cells will have the correct DNA2. When does replication occur? During Interphase (S phase). A---? T3. Describe how replication works. G---? C Enzymes unzip DNA and complementary C---? G nucleotides join each original strand. T---? A4. What happens to the original DNA? A---? T It serves as a template and half is incorporated G---? C into each of the two new strands. A---? T5. Use the base pairing rule to T---? A create the complementary strand:
Transcription - portable copies During Interphase G1 or G0 (normal cell function), DNA supplies the “codes” for proteins to be built DNA first must be transcribed into smaller mRNA segments, serving as portable copies Why? • Smaller segments are easier to move around • Sending strands 80 million nucleotides long would be inefficient (might be too long to find the “start”) • It’s safer to send a copy than the original
RNA vs. DNA Ribose instead of deoxyribose Uracil instead of Thymine Shorter strands Single-stranded
TRANSCRIPTION: DNA to mRNA mRNA = “messenger” RNA DNA partially “unzips” mRNA nucleotides line up on one side to form a matching mRNA strand RNA retains DNA sequences • Uracil replaces Thymine when matching with Adenine mRNA takes the code to ribosomes in the cytoplasm
Think of it this way… Transcription • Same information, portable packaging • DNA RNA • Like Bible-time scribes
Transcription Quiz1. Why is transcription necessary? Shorter mRNA strands are copied from DNA to carry codes to ribosomes outside the nucleus. A-- U2. Describe transcription. C-- G DNA strands separate, then one side is used as a template to assemble mRNA nucleotides. C-- G3. What are the main differences between G-- C DNA and RNA. T-- A RNA has ribose instead of deoxyribose; DNA has C-- G 2 strands while RNA has one; RNA has uracil instead of thymine and RNA has shorter strands. A-- U4. Use base pairing rules to create an C-- G mRNA strand from this DNA template: G-- C
TRANSLATION: mRNA to Protein Messenger RNA carries the pieces of copied genetic code out of the nucleus to a ribosome mRNA is “fed” into the ribosome Ribosome helps tRNA "read” the code and assemble a protein
Transfer RNA - tRNA tRNA = “transfer” RNA One tRNA molecule is composed of ~ 80 nucleotides, three exposed nitrogen bases (the anticodon) and one amino acid tRNA anticodons match up with tRNA mRNA codons inside a ribosome molecule As each tRNA molecule binds to an mRNA codon, its amino acid is Amino dropped off and linked together acids These assembled amino acid chains (polypeptides) fold into specific shapes to become new proteins anticodon The order of amino acids determines what kind of protein is made codon mRNA
mRNA Amino Acid “codes” U C A G UUU Phenylalanine UCU UAU Tyrosine UGU Cysteine U UUC (Phe) UCC UAC (Tyr) UGC (Cys) C SerineU UUA UCA (Ser) UAA Stop UGA Stop A UUG UCG UAG Stop UGG Tryptophan (Trp) G CUU Leucine CCU CAU Histidine CGU U CUC (Leu) CCC CAC (His) CGC C Proline ArginineC CUA CCA (Pro) CAA CGA (Arg) A Glutamine CUG CCG CAG (Gln) CGG G AUU ACU AAU Asparagine AGU Serine U Isoleucine (Asn) (Ser) AUC ACC Threonine AAC AGC CA (Ile) AUA ACA (Thr) AAA AGA A Lysine Arginine AUG Methionine (Met) ACG AAG (Lys) AGG (Arg) G GUU GCU GAU Aspartic Acid GGU U GUC GCC GAC (Asp) GGC C Valine Alanine GlycineG GUA (Val) GCA (Ala) GAA GGA (Gly) A Glutamic Acid GUG GCG GAG (Glu) GGG G
How Cells make Proteins mRNA copies small segments of DNA and carries the code out of the nucleus to the ribosomes mRNA is fed through ribosomes in cytoplasm tRNA match up with mRNA codons (inside ribosomes) and drop off amino acids Ribosomes bond amino acids together to form proteins
Translation Quiz1. Why is translation necessary? It makes sure the right amino acids are joined together to form the correct protein.2. Describe translation. Information from mRNA is used to produce proteins during normal cell functions.3. What are codons? mRNA segments containing 3 nucleotides that code for a specific amino acid.4. Using a chart, identify the amino acids coded for by this mRNA strand: UGG - tryptophan CAG - glutamine UGGCAGUGC UGC - cysteine
Think of it this way… Translation • Information changes forms • RNA Protein • Like translating English to French or translating blueprints into a building
A helpful way to remember… Replication • Making exact copies • DNA DNA • Like a copy machine Transcription • Same information, new packaging • DNA RNA • Like sticky notes Translation • Genetic info interpreted • RNA Protein • Like translating English to French or translating blueprints into a building