Objectives Compare the structure of DNA and RNA Summarize the process of transcription Outline the major steps of translation
SCS:B-4.4
Traits are determined by proteins that are built according to the instructions found on DNA
Proteins are not built directly from DNA but from RNA (ribonucleic acid) Copy of the DNA that is decoded
Single stranded string of nucleotides Different bases
Has uracil instead of thymine Different sugar – ribose
A gene’s instructions for making a protein are coded in the sequence of nucleotides in the gene
Instructions are transferred from DNA to RNA in a process called transcription
The instructions are then decoded to make a protein in a process called translation
1. RNA polymerase binds to the DNA molecule at the specific sequence that needs to be translated
2. RNA polymerase unwinds and separates strands
3. RNA polymerase adds nucleotides and links complimentary base until it reaches a “stop” signal.
4. RNA detaches then it leaves the nucleus to be translated.
3 types of RNA are made during transcription Messenger RNA (mRNA) – copy of the DNA Transfer RNA (tRNA) – carries nucleotides
to the ribosome Ribosomal RNA (rRNA) – part of the
ribosome
RNA instructions are written as a series of 3 nucleotide sequences of mRNA called codons
Each codon codes for an amino acid or a start or stop signal
the sequence can be decoded using the a genetic code Specifies the amino acid, so it tells you
what protein is being made Nearly universal
Takes place in the cytoplasm mRNA, tRNA, and rRNA are involved Ribosomes are the site of protein
synthesis Translation can take place at multiple
places on the mRNA
1. mRNA leaves the nucleus; ribosome attaches at the start codon (AUG)
2. tRNA brings the complimentary anticodon with a amino acid attached
3. A peptide bond forms after another tRNA brings a second amino acid
4. The ribosome continues the above process until a stop message is reached in the mRNA.
5. The newly made protein detaches and the ribosome break apart.
Objectives Summarize how protein synthesis is
regulated Describe the types of mutations that
can occur during translation
SCS:B-4.4
Protein synthesis is controlled by “on” and “off” switches This switch is called an operator
Controls the access of RNA polymerase to the sequence of DNA
A protein (repressor) binds to the DNA to keep RNA polymerase from binding to the promoter site (the group of genes that codes for a specific protein)
Most of your DNA does not code for anything useful Introns – non coding region
Are “cut” out during translation Exons – regions that actually code for
proteins