NAME _____________________________
Protein Synthesis and Mutations
Review Sheet
PROTEIN SYNTHESIS
Transcription
Structure of RNA and DNA
RNA- ribose, single stranded, uracil not thymine
Enzyme involved in transcription
RNA polymerase
Steps involved in transcription
RNA polymerase identifies the promoter region of a single gene. It
unzips the DNA and copies one side (the “template strand”) of DNA until
it reaches a termination sequence and then stops. The molecule being
built is mRNA.
Purpose of transcription
To copy a single gene to make mRNA (intermediary molecule)
Location where transcription takes place
Nucleus
mRNA processing
What is mRNA splicing?
mRNA needs to be “edited” before leaving the nucleus. Here, the introns
are removed and exons are ligated together.
Where does splicing take place? Nucleus
Intron vs. Exon
Introns are non-coding regions of mRNA and are removed before
translation; Exons are coding regions of mRNA and are ligated together
before translation.
Translation
What are the steps in translation? Initiation, elongation, and termination
What are the important molecules involved? Messenger RNA, transfer
RNA, and ribosomal RNA
What are the three major types of RNA (mRNA, tRNA and rRNA) and their
functions
mRNA- copies a gene from DNA and carries the message over to the
ribosome to be translated. Codons.
tRNA- carries the amino acid on one side and an anti-codon on the
other. If the anti-codon of tRNA complements the mRNA codon, the
amino acid will be added to the chain.
rRNA- com ponent of the ribosome, like the “workbench” for translation
How does the appropriate amino acid get added?
The tRNA anticodon must match/complement the mRNA codon.
What is an anti-codon, codon?
Anti-codon is a triplet of tRNA nucleotides and the codon is a triplet of
mRNA nucleotides
Where are they located and how are they related? See above
What is the significance of translation?
It is how mRNA gets interpreted into a chain of amino acids
Be able to use the Genetic Code Chart
Mutations
Chromosomal mutations (for examples see notes)
Duplication
Deletion
Inversion
Translocation
Types of sequence (nucleotide) mutations and there possible outcomes
Substitution: 1 base pair changes, like GCC  GCA
Deletion: 1 base pair is removed, causing the reading frame to move
down one base, changing the amino acids
Insertion: an additional base pair is added, this will move the reading
frame over by 1, changing the amino acids
What causes these mutations?
Frame shifts (insertions and deletions), point mutations (any
change in a single nucleotide of DNA sequence)
When would mutations affect offspring of the parent? Only if the mutations
occur in the REPRODUCTIVE cells (aka “germ line”). Fertilization takes
place, and now every cell in the new baby will contain the mutation.
When would mutations not affect the offspring? When they occur in the
body cells (aka “somatic cells”) of the individual. For example, skin
cancer caused by sun exposure over a person’s lifetime can NOT be
passed on to their offspring.
Examples of each type of mutation (substitution, insertion, deletion)
Be able to make an example of these, like the work sheet on mutations
we did in class
Substitutions can have a no effect on a protein—how is that possible?
If the substitution changes one codon to a different codon for the SAME
AMINO ACID
Mutagens
Agents that cause changes in DNA/mutations Ex: Benzene, dioxins,
formaldehyde, UV light exposure, radiation
You should be able to write the complementary strands of DNA and RNA
Be able to use the genetic code table to determine an amino acid sequence
Remember you are to use this as a GUIDE to the main topics
that may be included on the test. You should also review
your notes, the textbook, activities, websites and videos that
have been done during this topic for more specific details.