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Lab Make-Ups If you missed the strawberry lab or the candy dye lab you need to Borden ASAP to sign-up. The Candy dye lab kit will be returning to Fred Hutch Thurs., March 1 and will not be available after that.
Warm-up DNA Review 2/22/07 Write the DNA strand and complimentary base pairs that match: #1 AGC AGG CTT AGT ACT CGA #2 GCT AGT ACC CAT CTG GAT
AGENDA • Warm-up • Stamp Obj. 12.3 • Go over dye lab results • Notes: Transcription/Translation • In class activity transcription/translation • Discuss lab on for Monday • No homework
What we already know… • DNA encodes the information to make proteins • DNA cannot leave the nucleus • Protein synthesis occurs outside of the nucleus, on a ribosome
How does it happen? DNA encodes the information to make RNA.........and RNA molecules function together to make protein
Structure of RNA • Single stranded • Built of nucleotide • 5-Carbon Sugar = ribose sugar • Phosphate Group • Nitrogenous base: • Adenine, Uracil, Guanine, and Cytosine
3 Types of RNA • Messenger RNA (mRNA) • carries information to ribosomes for protein production • Transfer RNA (tRNA) • brings specified amino acids from the cytoplasm to the ribosomes where the protein chain is made • Ribosomal RNA (rRNA) • the ribosome and protein
Transcription DNA mRNA
Transcription • molecule of DNA is copied into a complementary strand of mRNA • Occurs in the nucleus
How does it happen? • DNA unzips and exposes one gene as a template • A complementary strand of RNA is formed • A – U • G – C • mRNA strand exits nucleus & moves into cytoplasm • The two strands of DNA re-attach and recoil
Try it yourself … • Transcribe Strand 1 of the DNA molecules below • 1 - T T A G G A C T G C A A T T G 2 - A A T C C T G A C G T T A A C • 1 - C A G T C C G A A C G T T T A 2 - G T C A G G C T T G C A A A T
Answers • A A U C C U G A C G U U A A C • G U C A G G C U U G C A A A U
Translation mRNA protein
Translation • mRNA is “read” & a protein is created from amino acids • Occurs at ribosome
Steps of Translation 1. mRNA moves to ribosomes 2. rRNA on the ribosome binds to the mRNA and starts “reading” codons. • Codons – 3 letter code that specifies a particular amino acid. • start codon = AUG • stop codon = UAA, UAG, or UGA 3. AUG binds to the first anticodon of tRNA
4. tRNA transfer amino acids until the rRNA reaches a stop codon on the mRNA 5. ribosome releases protein and mRNA • protein to be used by the cell • mRNA to synthesize more protein molecules
Try it yourself! • DNA template strand DNA: TACGATCGAACGTAT • mRNA codon: • tRNA anticodon: • Amino Acids :
Transcription/Translation video http://www.youtube.com/watch?v=1GWI7qcQWbA • Transcription/Translation Activity • Tape your work into lab notebook, do not take home the main worksheet
mRNA Activity • Here is a strand of mRNA. Arrange your tRNA molecules to determine the sequence of Amino Acids that this mRNA codes for. • AUG CUA UCA UCA UAU GGA GUA ACU AGU UUU CGC AUU CCG CAU ACA CGG GUU CUC CCU CAC AGG UGG GGG UGU CUA ACC UUA CCC GCA UCG UAA
Mutations • Mutations lead to mistakes in the proteins being made. • Mutations can happen during DNA replication and change the “blueprint of the cell” Or During transcription or translation so a wrong protein or no protein is made
Types of mutation • Point mutation- one nucleotide changes • Frameshift mutation- an insertion or deletion of a nucleotide that changes all codons after that point • Chromosomal mutation- all of the genes on a certain chromosome can be affected. Or change the location of genes on the chromosome.
Transcription • The information in the DNA not only contains amino acid (aa) sequences, it also has “junk” DNA. • Exon: RNA that codes for a.a. • Intron: junk RNA/DNA • Enzymes in the nucleus snip out the exon and the RNA molecule is protected and sent outside of the cell.