Week 2: Genetic Coding Flashcards
What is the genetic code?
The genetic code is the set of rules by which information encoded in mRNA sequences is translated into amino acids.
Each group of 3 nucleotides in RNA is called a ‘codon’.
How is mRNA formed from DNA?
DNA code is transcribed into mRNA, and pre-mRNA is adapted into mature mRNA.
This process involves splicing and other modifications.
What role do tRNAs play in translation?
tRNAs carry amino acids and act as adapters during protein synthesis.
They match codons in mRNA to the appropriate amino acids.
What is a codon?
A codon is a sequence of three nucleotides in mRNA that specifies a particular amino acid.
There are 64 possible codons for the 20 amino acids.
What is the significance of the AUG codon?
The AUG codon acts as a start codon and specifies the amino acid Methionine (Met).
What are stop codons?
Stop codons signal the end of the translation process.
The three stop codons are UAA, UAG, and UGA.
What is an Open Reading Frame (ORF)?
An Open Reading Frame (ORF) is the part of a gene that is translated into a protein.
It is defined by the presence of a start codon and a stop codon.
How many reading frames are there per strand of DNA?
There are three reading frames per strand of DNA.
This means that a single strand can be read in three different ways.
What is degeneracy in the genetic code?
Degeneracy refers to the phenomenon where multiple codons can code for the same amino acid.
This allows for more than one codon to specify a single amino acid.
What are aminoacyl-tRNA synthetases?
Aminoacyl-tRNA synthetases are enzymes that couple each amino acid to its corresponding tRNA.
Each amino acid has a specific synthetase.
What is the role of ribosomes in protein synthesis?
Ribosomes facilitate the binding of tRNAs to mRNA and catalyze the formation of peptide bonds between amino acids.
What is the process of polypeptide chain elongation?
Polypeptide chain elongation involves the binding of incoming aminoacyl-tRNA, the formation of peptide bonds, and the shifting of tRNAs through the ribosome.
Fill in the blank: The _______ is the reading frame that produces the correct protein sequence.
Open Reading Frame (ORF)
How fast does protein synthesis occur?
The rate of protein synthesis is about 2 amino acids per second.
What are polyribosomes?
Polyribosomes are clusters of ribosomes translating a single mRNA molecule simultaneously.
This increases the efficiency of protein synthesis.
What modifications might new polypeptide chains undergo to become functional?
New polypeptide chains may undergo folding, binding of cofactors, and post-translational modifications such as glycosylation or phosphorylation.
True or False: Humans have approximately the same number of genes as proteins.
False
Humans have around 20,000 genes but potentially more than 6,000,000 proteins due to splicing and other factors.
How many genes do humans have?
Around 20,000
Estimates for the number of proteins range from 20,000 to over 6,000,000.
What process allows the number of proteins to exceed the number of genes?
Splicing
What is the purpose of splicing?
Allows creation of different proteins from the same gene, saving resources and energy
What is exon skipping?
A splicing mechanism that can lead to the evolution of new useful proteins
What percentage of the genome is coding?
Surprisingly low
What are some components of non-coding DNA?
- Introns
- Transcription promoters
- Transcription enhancers/silencers
- tRNAs
- rRNAs
- Heterochromatin
Which fields study DNA, RNA, and proteins respectively?
- DNA: Genomics
- RNA: Transcriptomics
- Proteins: Proteomics
