BLOCK 3: MBG: EXAM 3 REVIEW SLIDES FROM STEDING

Deamination

• Removal of an amine group from an amino acid or other organic molecule.
• Consequence: Could result in a point mutation, changing the genetic code.

Colinear vs Split

• Describes the relationship between a gene and its protein product.
• Colinear: DNA sequence directly translates into a protein sequence.
• Split: DNA sequence does not directly translate, due to introns.

Polyadenylation

• The addition of a poly(A) tail to a messenger RNA (mRNA) transcript.
• Function: Protection, transport out of the nucleus, and increased translation.

Methyltransferase

• An enzyme that adds a methyl group to a molecule.
• Function: Influences gene expression, DNA replication, and repair.
• Specific case: Methyltransferases are important for mRNA capping.

Exon

• A segment of a gene that is transcribed into mRNA and translated into protein.

Intron

• A segment of a gene that is transcribed into mRNA but not translated into protein.
• Function: Can regulate gene expression and contribute to the creation of different protein isoforms.

Lariat

• A loop-shaped structure formed during intron splicing.
• Function: Facilitates the removal of introns from pre-mRNA.

snRNA

• Small nuclear RNA.
• Function: Essential components of the spliceosome, involved in mRNA processing.

snRNP

• Small nuclear ribonucleoprotein.
• Function: A complex of snRNA and proteins that performs splicing of pre-mRNA.

Spliceosome

• A complex of snRNPs that removes introns from pre-mRNA.

Upstream Elements

• DNA sequences located before a gene.
• Function: Often regulate gene expression by interacting with transcription factors.

Downstream Elements

• DNA sequences located after a gene.
• Function: Can influence mRNA stability and translation.

Regulatory Elements

• DNA sequences that control gene expression by influencing the recruitment or accessibility of RNA polymerase.
• Function: Include promoters, enhancers, and silencers.

RNA Modification / RNA Editing

• Changes to RNA molecules after transcription.
• Function: Can modify the sequence, structure, or stability of RNA.
• Consequence: Can generate unique protein products by altering the genetic code or creating alternative splicing patterns.

RNA Processing in Prokaryotes vs Eukaryotes

• Prokaryotes: RNA processing is simpler, with fewer steps and fewer factors involved.
• Eukaryotes: RNA processing is more complex, involving capping, splicing, and polyadenylation.

Basic Structure of RNA Molecules (Emphasis on Eukaryotic mRNA)

• Structure: Single-stranded linear molecule.
• Eukaryotic mRNA:
  • 5' cap (methylguanosine cap)
  • 5' untranslated region (UTR)
  • Protein-coding region
  • 3' UTR
  • poly(A) tail

The Role of mRNA Processing in Eukaryotes

• Function: Prepares mRNA for translation.
• Stages:
  • Capping
  • Splicing
  • Polyadenylation

Importance of mRNA Capping

• Functions:
  • Protects mRNA from degradation.
  • Enhances translation efficiency.
  • Facilitates nuclear export.
  • Regulates translation initiation.

snRNA vs mRNA

• snRNA:
  • Small nuclear RNA.
  • Involved in splicing.
  • Location: Nucleus.
  • Short, non-coding sequences.
  • Contains elements for transcription.
• mRNA:
  • Messenger RNA.
  • Encodes proteins.
  • Location: Nucleus and cytoplasm.
  • Long, coding sequences.
  • Contains elements for transcription and translation.

Spliceosome & snRNPs

• Spliceosome: The protein/RNA complex that performs splicing.
• snRNPs: The core components of the spliceosome.

Roles of Each snRNP:

• U1: Recognizes the 5' splice site.
• U2: Recognizes the branch point and interacts with the 3' splice site.
• U4: Associates with U6 and brings it to the splicing complex.
• U5: Binds to both exons and helps to align them for splicing.
• U6: Catalyzes the splicing reaction and promotes the release of the lariat intron.

Stages of Spliceosome Assembly and Splicing

• Stage 1: Recognition of the splice sites (U1 and U2 binding).
• Stage 2: Assembly of the complete spliceosome.
• Stage 3: Intron removal.
• Stage 4: Exon ligation.
• Stage 5: Disassembly of the spliceosome.

Alternative Splicing

• Definition: A process that allows different protein isoforms to be produced from the same gene.
• Regulation: Influenced by various factors like transcription factors, splicing factors, and environmental cues.
• Role: Increases the functional diversity of biological systems.
• It can create:
  • Different protein domains or lengths
  • Alter protein activity
  • Changes in protein localization