Lecture 8 RNA processing and Genetic Code; Translation

Non-Coding RNA

RNA molecules that are not translated into proteins but play crucial roles in regulating gene expression

Gene

Unit of DNA transcribed into RNA.

Genes will be translated into protein, function of that made protein is function of a gene, these genes are protein-coding genes

snRNA

Small nuclear RNAs

• Non-coding RNA

splicing pr-mRNA), regulating gene expression and other RNA processing events

Spliceosome

Large assembly of proteins and snRNA

Removes introns from pre-messenger RNA to create mature mRNA

Intron/Extron

Exon- Portion of primary transcript retained in mature mRNA (Coding regions and UTRs)

Intron- Portion of primary transcript removed from mature mRNA (DONT contain coding sequences)

Coding Region

Part of gene that codes for proteins

5’/3’ UTR

region of mRNA that regulate gene expression after transcription

Alternative Splicing

Allows single gene to produce multiple proteins with different functions

5’ cap and 3’ poly A tail

protect the mRNA from degradation and facilitate its translation by helping ribosomes bind to the 5' end, while the poly-A tail also aids in nuclear export and stability of the mRNA molecule. 

RNA binding protein

proteins that specifically recognize and bind to RNA molecules.

miRNA

non-coding RNA molecules that regulate gene expression by binding to messenger RNA (mRNA). This process controls the amount and type of proteins produced by

RISC

RNA, Induced, Silencing, Complex

Regulate gene expression by silencing target RNAs. RISCs are involved in aspects of eukaryotic biology

Ribosome

Synthesize protein in cells

Codon

a sequence of three nucleotides found in DNA or RNA that codes for a specific amino acid.

Reading Frame

the specific way a sequence of nucleotides in DNA or mRNA is divided into groups of three, called codons, which are then translated into amino acids during protein synthesis; essentially, it defines the "correct" order of codons to read to produce a functional protein

Mutation

A DNA sequence change can occur due to replication errors, damaging agents, or environmental factors, resulting in beneficial, harmful, or neutral effects.

Do all Genes encode proteins ?

Not all genes encode proteins; some encode functional RNA molecules, such as transfer RNA (tRNA) and ribosomal RNA (rRNA).

Why does alternative splicing increase the number of proteins encoded by a specific genome?

This process can generate different mRNA transcripts from the same pre-mRNA, leading to the production of diverse proteins from a single gene.

How do miRNAs find their target mRNAs?

by base-pairing with complementary sequences, mainly in the 3' UTR, leading to mRNA degradation or translation inhibition.

How is mRNA stability controlled and what is the purpose?

mRNA stability is regulated by protein and miRNA binding, mRNA modifications, and ribosome interactions to control gene expression and protein production timing.

What role do miRNAs play in gene expression control?

by binding to target mRNAs and either degrading them or preventing their translation.

What is a start codon and a stop codon?

A start codon is a specific sequence of nucleotides (AUG in most cases).

A stop codon is a sequence (UAA, UAG, or UGA) that signals the end of protein synthesis.

Why is a triplet code used to encode amino acids?

(4^3 = 64 possible codons) provides enough unique combinations to encode all amino acids, including redundancy for error minimization

What is a ribosome

A ribosome is a molecular machine found in all living cells that synthesizes proteins. It reads the mRNA sequence and translates it into a polypeptide chain by linking together the appropriate amino acids.

How many different ways can a given RNA be translated?

alternative splicing, translational regulation, internal ribosome entry sites, and ribosomal frameshifting.

What sets the reading frame?

The reading frame is set by the start codon (usually AUG) during the initiation of translation. This start codon determines the correct grouping of nucleotides into codons.

What is the impact of a mutation on amino acid sequence?

• Silent mutation: No change in the amino acid sequence.

• Missense mutation: One amino acid is replaced by another.

• Nonsense mutation: A stop codon is introduced prematurely, truncating the protein.

• Frameshift mutation: Insertion or deletion of nucleotides that shift the reading frame, altering the entire downstream amino acid sequence.