Transcription and Translation: Protein synthesis
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Transcript of Transcription and Translation: Protein synthesis
Transcription and Translation: Protein
synthesis
What we already know…
DNA encodes the information to make proteins
DNA cannot leave the nucleusProtein synthesis occurs outside
of the nucleus, on a ribosome
DNA encodes the information to make RNA.........and RNA molecules function together to make protein
How does it happen?
Structure of RNA
Single stranded Built of nucleotide
5-Carbon Sugar = ribose sugar
Phosphate Group Nitrogenous base:
Adenine, Uracil, Guanine, and Cytosine
NO THYMINE IN RNA
3 Types of RNA
Messenger RNA (mRNA) DNA cannot leave the nucleus so 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
3 Types of RNA
Transcription
DNA mRNA
Transcription Process by which a molecule of DNA is
copied into a complementary strand of mRNA
Occurs in the nucleus
How does it happen?
1. DNA unzips and exposes one gene as a template
2. A complementary strand of RNA is formedo A – Uo G – C
3. mRNA strand exits the nucleus and moves into the cytoplasm
4. The two strands of DNA re-attach and recoil
Transcription movie http://learn.genetics.utah.edu/units/basics/transcribe/
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
Process by which the mRNA is “read” and a protein is created from amino acids
Occurs at the ribosome
Steps of Translation
1. mRNA moves to the ribosomes
2. the 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. the ribosome releases the protein and the mRNA protein to be used by the cell mRNA to synthesize more protein molecules
Movie of Translation
http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter15/animations.html#
mRNA-amino acid chart
Try it yourself!
DNA template strand
DNA: TACGATCGAACGTAT mRNA codon: tRNA anticodon: Amino Acids :
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.
mRNA splicing
http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter15/animations.html