Chapter 39: The Genetic Code Flashcards
The pathway to protein synthesis is ____
Translation
The language of _____ sequence is translated to the language of an _____ sequence.
Nucleotide
Amino Acid
Process of translation requires a ____
Genetic Code
The __ letter word of DNA (RNA) is translated to the ___ letter alphabet of proteins
4
20
Nucleotides resemble ____
Letters
Codons resemble _____.
Words
Genes resemble _____.
Sentences
Genome resembles _____.
Book
Each codon is a _____ of nucleotides.
Triplet
The genetic code is a collection of…
Codons
For 20 AAs, there should be…
20 codons
Each codon should have __ nucleotides to impact specificity to each amino acid for a specific codon
3 nucleotides
1 nuc used = 4 combinations
2 nuc = 16 combinations
3 nuc = 64 combinations
What are the 4 characteristics of the Genetic Code?
Specificity, Universal, Redundant, Non-overlapping
What does it mean for the genetic code to be specific?
A specific codon always codes for the same amino acid
e.g. UUU codes for Phenylalanine, it can never code for another AA
What does it mean for the genetic code to be universal?
All living organisms have the same genetic code
There is an exception to the universal rule in _____ codons. AUA codes for methionine instead of isoleucine and UGA codes for tryptophan instead of termination codon
Mitochondrial
____ & ____ code for arginine in the cytoplasm but in the mitochondria they are termination codons
AGA & AGG
Most organisms use the same genetic code because its important for production of
Recombinant proteins
Some organisms have slight modifications - in ciliated protozoa, codons that are ___ signals in most organisms, encode ____.
Stop
Amino Acids
______ also use variations of the genetic code
Mitochondria
What does it mean for the genetic code to be redundant?
(degenerate) Although each codon corresponds to a single AA, a single AA can have multiple codons
(e. g. Tryptophan and Methionine have multiple codons)
What does it mean for the genetic code to be non-overlapping?
All codons are independent sets of 3 nucleotides. There is no overlapping. Codon is read from fixed starting point as a continuous sequence of nucleotides, 3 at a time
The starting point it extremely important and is known as the
Reading Frame
Translation of the correct message requires selection of the correct reading frame
The sequence of bases is read sequentially from a fixed starting point until termination in a ___ to ___ direction
5’ to 3’
What are the two types of codons?
Non Sense and Initiator
What are non sense codons?
Codons that do not code for any AA. They are known as termination or stop codons as well
What are the 3 non sense codons out of the 64 codons?
UAA
UAG
UGA
What happens when a non sense codon is inserted into the growing polypeptide chain?
The ribosome pauses and falls off the mRNA
What is the initiator codon in majority of proteins?
AUG
In a few cases, GUG may be used as the initiator code
____ is the only AA specified by just one codon
Methionine
Mutations can be explained using the
Genetic Code
What are the two main types of mutations?
Point mutations & Frame Shift mutations
What are the three types of point mutations?
Silent, Nonsense, and Missense
Trichophalangeal syndrome type 1 (TRPS1) is due to
Frameshift mutation
Clinical manifestations due to TRPS1
Hair loss, finger and toe malformation and facial deformities
