Do Now 1. What is RNA? 2. What are proteins used for in our bodies?
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Transcript of Do Now 1. What is RNA? 2. What are proteins used for in our bodies?
Do Now 1. What is RNA?
2. What are proteins used for in our bodies?
DNA Transcription
and TranslationSections 12.3 and 12.4
Gene Segment of DNA that codes for
a protein The Central Dogma of
Biology: DNA codes for RNA and RNA
makes protein (the synthesis of)
Beadle and Tatum Experiment Experiments on mold, Neurospora, were
the first to demonstrate the relationship between genes and enzymes.
Studied mold spores that were mutated by exposure to X-rays and grown on a complete medium Minimal Medium- no amino acids
provided Complete Medium- all amino acids
provided. (normally Neurospora can grow on both)
Beadle and Tatum Continued Grew spores exposed to X-rays on minimal
medium. When there was no growth, the mutant was tested to see what amino acid it lacked.
When the mutant grew on the minimal medium with arginine (amino acid), the mutant was missing the enzyme needed to make arginine.
One Gene-One Enzyme Beadle and Tatum’s Hypothesis:
One Gene- One Enzyme.
One gene codes for one polypeptide. polypeptide - a chain of covalently bonded
amino acids.
(proteins are made of one or more polypeptide)
Let’s make some observations about RNA’s structure
RNA
RNA stands for:Ribonucleic acid
RNA is found:Nucleus and Cytoplasm
RNA Structure
Like DNA, RNA is made up of subunits called _____________, which are made of three parts: Sugar (ribose) Phosphate Nitrogen Base
RNA’s Nitrogen Bases Adenine (A) Cytosine (C) Guanine (G) Uracil (U)
There are 3 types of RNA:
1. Messenger RNA (mRNA) – long strands of RNA nucleotides that are formed complementary to one strand of DNA.
1. Carries genetic information from DNA in the nucleus to Ribosome in the cytoplasm.
Types of RNA:
2. Ribosomal RNA (rRNA) – associates with protein to form the ribosome.
Types of RNA:
3. Transfer RNA (tRNA) – smaller segments of RNA nucleotides that transport amino acids to the ribosomes.
All RNA is … Single stranded
Many different shapes
“Cheap copy” of DNA
Fill in chart below:
DNA RNA
Structure
Sugar
Base
Example strand: Complimentary:
TACGA
Do NowFill in the Venn Diagram below:
What are the three types of RNA? What is the purpose of each?
DNA RNABoth
Transcription
First step in making proteins Process of taking one gene (DNA) and
converting into a mRNA strand
Location: Nucleus of the cell
Steps to Transcription 1. An enzyme (RNA polymerase)
attaches to the promoter (start signal region) of a gene and unwinds the DNA
Steps to Transcription (Cont.) 2. One strand acts as a template.
Steps to Transcription (Cont.) 3. A mRNA copy is made from the
DNA template strand by RNA polymerase
4. mRNA is made until it reaches the termination (stop signal) sequence
5. mRNA is released, and the two strands of DNA rejoin.
Template vs. Non Template Strand
Transcription animation
https://www.youtube.com/watch?v=ztPkv7wc3yU
Transcribe this DNA to mRNA
Do Now Label the Transcription diagram
mRNA Processing
Pre-mRNA – the original sequence of RNA created during transcription
mRNA reaches the ribosomes
RNA ProcessingIn Eukaryotes only
Introns- non-coded sections (a.k.a “Junk” DNA)
Exons- codes for a protein
Before RNA leaves the nucleus, introns are removed and exons are spliced together
A 5’cap and poly A tail are added to ends of the sequence
mRNA leaves the nucleus through the nuclear pores
Why is it necessary to add the poly A tail and 5’ cap?
Keeps mRNA from degradation, and helps mRNA bind to ribosome.
RNA Processing
Let’s try this example…
Original DNA Sequence (DNA): 5’ GTACTACATGCTATGCAT 3’ Translate it (RNA): 3’ CAUGAUGUACGAUACGUA 5’
Add the 5’ cap:
3’ CAUGAUGUACGAUACGUA 5’ cap
Finish the job!
Remove the introns “UGUA” and “AUAC”:
3’ CAUGAUGUACGAUACGUA 5’ cap
3’ CAUGACGGUA 5’ cap
Add a poly A tail onto the 3’ end
3’ CAUGACGGUA 5’ capPoly A tail
Think, Pair, Share Take a minute think on your own, then pair with your
partner, and share your ideas!
Evolutionary, why do you think there are introns?
Where did they come from?
Remember there is NO wrong answer!
Do Now Perform transcription on this DNA
segment: GCTTCATACGA
Do RNA processing and remove the introns: GAA and UGC
Proteins are made up of amino acids!!!
Proteins are polymers of amino acids
Only 20 different amino acids
BUT there are hundreds of thousands of different proteins
How can this be?
Let’s compare to it to the English languageHow many letters are in the alphabet?A,b,c,d,…26
How many words are there?Miss, P, is, smart, .. Almost infinite!
Each word has a unique structure of letters.
Similar to proteins and amino acids
Proteins- (PCFNa)
-made of 20 different Amino Acids
- Amino Acids bond to form polypeptide chains
How do amino acids form these peptide chains?
Peptide Bonds – Link each amino acids together to form proteins created by dehydration synthesis!
How many water molecules are formed from 2 amino acids?
How many water molecules are formed from 100 amino acids?
Pg. 339
Pg. 339
Protein
Structure
http://www3.interscience.wiley.com:8100/legacy/college/boyer/0471661791/structure/HbMb/hbmb.htm
Translation Production of proteins from mRNA
mRNA goes to the ribosomes in the cytoplasm or the RoughER and produces proteins
Three main stages: Initation Elongation Termination
Ribosome
Two subunits to the ribosome Large subunit, and small subunit
3 sites (grooves) on the ribosome (A, P, E ) A: tRNA binding site
P: polypeptite bonding site
E: exit site
Steps to TranslationInitiation:1. mRNA leaves the nucleus and binds to a ribosome
2. The two ribosomal subunits come together at the 5’ end of the mRNA.
3. Ribosome will find the start Codon (AUG) and the first tRNA molecule will attach This is the only tRNA that will attach to the P site
(and skip the A site)
The first amino acid is always methionine.
Codon: group of 3 nucleotides on the messenger RNA that specifies one amino acid (64 different codons)
tRNA tRNA has an anticodon that
matches the codon on the mRNA strand
Anticodon: Group of 3 unpaired nucleotides on a tRNA strand. (binds to mRNA codon)
Steps to Translation (Cont.)Elongation:
4. Amino acids attached to a tRNA molecules are brought over to the mRNA, and load in at the A site of the ribosome.
5. A polypeptide bond is formed between the amino acids in the P and A sites of ribosome.
6. Ribosome shifts over, opening up the A site for a new tRNA molecule.
7. tRNA in the E site leaves, leaving behind the amino acid.
Steps to Translation (Cont.) Termination:
8.Translation is terminated when a stop codon is reached. There are three different stop codons UGA, UAA, UAG.
9. The release factor recognizes the stop codon, attaches to the mRNA strand in the A site of ribosome, and releases the polypeptide strand. All the factors break apart and can be reused again.
Translation Animations
http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/translation.swf
https://www.youtube.com/watch?v=JTc18Yh7bSU
Think-Pair-Share The mRNA sequence reads the following
codons: What amino acids do they stand for? AUG
GGA
GAG
CAA
** What amino acid does the anticodon CGU stand for?***
Think – Pair - Share
Find the amino acid sequence for the following mRNA sequence (translation)
AUGCGACGAAUUUAA
Do Now Do transcription on this DNA
sequence:
TTTTATACTGAGGGTTAACTCGT
Do Translation- Remember to start the right place!
1. 2. 3.
4. 5. 6.
Do Now
Take the following amino acid sequence, do reverse transcription and translation (find RNA and DNA).
Methionine, Arginine, Alanine, Serine, Tryptophan, Tyrosine, Leucine, Valine, stop
What do you notice about your DNA sequences?
Do Now Template strand of DNA: 5’ TTACGGCTAGGAGTAGCCGAATTCTG 3’
Remove the introns: CUCAUC
Determine protein sequence
How do cells know what protein to make when? Gene Regulation: ability of an organism to
control which genes are transcribed.
Controlling Transcription Transcription factors ensure that a gene is used
at the right time and that protein are made in the right amounts
The complex structure of eukaryotic DNA also regulate transcription.
Everyone develops from a zygote
Zygote undergoes mitosis
Cell differentiation: cells become specialized
Certain gene sequences determine cell differentiation ……But how does that happen?
HOX Genes
Homeobox Genes (Hox Genes) are sequences of DNA that are responsible for the general body pattern of most animals.
Are transcribed at specific times, and located in specific places on the genome.
Control what body part will develop in a given location.
Telephone
We are going to play the game telephone.
Every time a DNA makes a copy (spreading of a message), mutations can happen (mistakes in a message)
Mistakes in DNA Cell make mistakes in replication, and
transcription
Most often these mistakes are fixed
When these mistakes aren’t fixed, it causes a mutation.
A permanent change that occurs in a cell’s DNA is called a mutation.
Point Mutation Substitution: A change in just one base pair
Missense Mutation: amino acid is change
Nonsense Mutation: amino acid is changed to a stop codon
Cause translation to terminate early.
Usually leads to proteins that can’t function normally.
Silent Mutation: change codes for same amino acid and cause no change in protein produced.
Frameshift Mutations Causes the reading frame to shift to the left or the right
Insertion: Addition of a nucleotide
Deletion: Removal of a nucleotide
ACGAAATACAGACAT Decide what type of mutation occurred:
ACGAAATAGAGACAT
ACAAATACAGACAT
ACGAAATACAGGACAT
Causes of Mutations Mutations can happen spontaneously
Mutagens: Certain chemicals or radiation that can cause DNA damage
Causes bases to mispair and bond with the wrong base
High-energy forms of radiation, such as X rays and gamma rays, are highly mutagenic.
Sex Cell vs. Somatic Cell Mutations
Somatic cell mutations are not passed on to the next generation.
Mutations that occur in sex cells (gamete cells) are passed on to the organism’s offspring and will be present in every cell of the offspring
Chromosomal MutationsInversion: Piece of chromosome can be
broken off, duplicated, or moved to another chromosome
Fragile X Syndrome Repeat of CGG about 30 times
Causes mental and behavior impairments
Protein Folding and Stability Substitutions also can lead to genetic
disorders.
Ex. Sickle Cell Anemia (caused by a substitution mutation)
Can change both the folding and stability of the protein
Sickle Cell Anemia