Transcription and Genetic Code
Transcription unit, RNA processing in eukaryotes, codons, and features of the genetic code. (Biology › Molecular Basis of Inheritance, NEET UG syllabus.)
What is Transcription and Genetic Code?
The process of synthesizing RNA from a DNA template.
Key points
- Describe the process of transcription in both prokaryotes and eukaryotes.
- Identify and explain the function of each component of a transcription unit.
- Detail the post-transcriptional modifications (capping, tailing, splicing) in eukaryotes.
- Define the genetic code and list its salient features.
Common exam trap
Confusing the coding strand with the template strand during transcription.
Definitions
- Term
Transcription
- Meaning
The process of synthesizing RNA from a DNA template.
- Term
Transcription Unit
- Meaning
A segment of DNA that contains a promoter, a structural gene, and a terminator, and is transcribed into an RNA molecule.
- Term
Promoter
- Meaning
A DNA sequence where RNA polymerase binds to initiate transcription.
- Term
Terminator
- Meaning
A DNA sequence that signals the end of transcription.
- Term
hnRNA (heterogeneous nuclear RNA)
- Meaning
The primary transcript in eukaryotes, which undergoes processing to become mature mRNA.
- Term
Capping
- Meaning
Addition of methyl guanosine triphosphate to the 5' end of hnRNA in eukaryotes.
- Term
Tailing
- Meaning
Addition of adenylate residues (poly-A tail) to the 3' end of hnRNA in eukaryotes.
- Term
Splicing
- Meaning
The process of removing introns (non-coding sequences) and joining exons (coding sequences) in eukaryotic hnRNA.
- Term
Genetic Code
- Meaning
The set of rules by which information encoded in genetic material (DNA or mRNA sequences) is translated into proteins.
- Term
Codon
- Meaning
A sequence of three nucleotides that together form a unit of genetic code in a DNA or RNA molecule.
- Term
Degeneracy of Genetic Code
- Meaning
The property that most amino acids are specified by more than one codon.
- Term
Unambiguous Genetic Code
- Meaning
The property that one codon codes for only one specific amino acid.
- Term
Universal Genetic Code
- Meaning
The property that the genetic code is largely the same for all organisms.
Learning objectives
Describe the process of transcription in both prokaryotes and eukaryotes.
Identify and explain the function of each component of a transcription unit.
Detail the post-transcriptional modifications (capping, tailing, splicing) in eukaryotes.
Define the genetic code and list its salient features.
Identify the start and stop codons and their significance.
Relate specific codons to their corresponding amino acids.
Prerequisites
Basic structure of DNA and RNA.
Understanding of the Central Dogma of Molecular Biology.
Knowledge of different types of RNA (mRNA, tRNA, rRNA).
Basic concept of a gene.
Common mistakes
Confusing the coding strand with the template strand during transcription.
Forgetting the 5' to 3' directionality of RNA synthesis.
Mixing up the steps or order of eukaryotic RNA processing.
Not remembering all three stop codons or the specific amino acid for the start codon.
Misunderstanding the features of the genetic code, e.g., thinking it is overlapping.
Keywords
Transcription
RNA Polymerase
Promoter
Terminator
hnRNA
Capping
Tailing
Splicing
Intron
Exon
Genetic Code
Codon
Degeneracy
Universality
Start Codon
Stop Codon
mRNA
tRNA
rRNA
Practice preview
Which of the following sequences in a transcription unit defines the binding site for RNA polymerase?…
easy
What is the primary function of capping in eukaryotic hnRNA processing?…
easy
If the sequence of the coding strand in a transcription unit is 5'-ATGCATGC-3', what would be the sequence of the mRNA transcribed from it?…
medium