Genetic Mutations Overview

Mutation Definitions

• Mutation: A change in the DNA sequence of a cell.
• Point Mutation: A mutation affecting one or a few nucleotides in a gene.
• Frameshift Mutation: Genetic alterations from insertions or deletions of nucleotides (not in multiples of three) that disrupt the reading frame of the genetic code. Common types include insertions and deletions.

Point Mutation Types

• Substitution: One nucleotide base is replaced by another.
• Insertion: A nucleotide is added to the DNA sequence. A frameshift mutation may result if the insertion is not a multiple of three.
• Deletion: A nucleotide is removed from the DNA sequence. A frameshift mutation may result if the deletion is not a multiple of three.

Chromosomal Mutation Types

• Deletion: A segment of a chromosome is lost. Example: Cri-du-chat syndrome (chromosome 5 deletion).
• Duplication: A segment of a chromosome is copied and appears more than once. Example: Charcot-Marie-Tooth disease (chromosome 17 duplication).
• Inversion: A segment of a chromosome breaks off, flips, and reinserts in reverse order. Example: Inversion on chromosome 9 (often harmless, potentially linked to infertility).
• Translocation: A segment of one chromosome breaks off and attaches to a different, non-homologous chromosome. Example: Chronic myelogenous leukemia (CML) where chromosomes 9 and 22 translocate.

Mutagens and Mutation Effects

• Mutagens: Physical, chemical, or biological agents that increase the likelihood of mutations in DNA.
• Mutation Effects: Diverse, including:
  • Neutral: Silent mutations or mutations in non-coding regions.
  • Beneficial: Mutations that provide advantages (e.g., antibiotic resistance).
  • Harmful: Mutations that cause diseases or disorders (e.g., cancer, genetic conditions).
  • Lethal: Severe mutations disrupting essential genes.

DNA vs. RNA Differences

• Sugar: DNA has deoxyribose, RNA has ribose.
• Strands: DNA has two strands, RNA has one.
• Bases: DNA uses thymine (T), RNA uses uracil (U).

Types of RNA and Their Functions

• mRNA (messenger RNA): Carries instructions from DNA to ribosomes for protein synthesis.
• tRNA (transfer RNA): Delivers correct amino acids to the ribosome based on mRNA instructions.
• rRNA (ribosomal RNA): Forms part of the ribosome; aids in linking amino acids during protein synthesis.

Transcription

• Transcription: A cell makes a copy of a gene in the form of RNA.
• Location (Eukaryotes): Occurs in the nucleus.

RNA Polymerase Roles

• Unzipping DNA: RNA polymerase separates the DNA strands for copying.
• Building the RNA strand: RNA polymerase matches RNA bases to the DNA template.

Protein Composition

• Proteins: Made of amino acids.
• Amino Acids: 20 different types.

Protein Structure and Function

• Amino Acid Order: Determines the shape and function of a protein.

RNA Bases

• Four RNA bases: Adenine (A), Uracil (U), Cytosine (C), Guanine (G).

Genetic Code and Codons

• Genetic Code: The set of rules transforming DNA or RNA into proteins.
• Codon: A set of three RNA bases that code for one amino acid.
• Codons: 64 possible codons (4³).
• Amino Acids: 20 different amino acids.
• Multiple Codons: Multiple codons can code for the same amino acid.

Codon-Specific Amino Acids

• UAU: Tyrosine
• CGA: Arginine
• GCA: Alanine
• AGC: Serine
• AUG: Methionine (start codon)

Stop Codons

• Stop Codons: UAA, UAG, UGA.

Ribosome Role (Protein Synthesis)

• Ribosome Role: Reads mRNA and assembles amino acids into proteins.

Translation

• Translation: The process of synthesizing a protein using mRNA.

Translation Steps (referring to Figure and text description)

• Initiation: Ribosome binds to mRNA, finds the start codon (AUG).
• Elongation: tRNA brings amino acids; they are joined (peptide bond).
• Termination: Ribosome reaches a stop codon; the protein chain is released.
• Folding: The protein folds into its functional shape.

Molecules in Protein Synthesis and Their Roles

• mRNA (messenger RNA): Carries the genetic code from DNA.
• tRNA (transfer RNA): Carries amino acids to the ribosome.
• rRNA (ribosomal RNA): Component of the ribosome, aids in protein synthesis.

Protein Purpose

• Protein Purpose: Build tissues, catalyze reactions, regulate processes.

DNA as Universal Code

• DNA Universal Code: Identical genetic coding system for all living organisms.