Genetic Code and Protein Synthesis

Protein Composition and Synthesis

• Proteins are composed of amino acids.
• There are 20 different amino acids.
• The order of amino acids determines a protein's shape and function.

RNA Bases

• The four bases in RNA are adenine (A), uracil (U), cytosine (C), and guanine (G).

Genetic Code

• The genetic code is a set of rules that translates DNA or RNA sequences into proteins.

Codons

• A codon is a set of three RNA bases that codes for one amino acid.
• There are 64 possible codons (4³).
• Multiple codons can code for the same amino acid.

Amino Acid Codons

• UAU codes for tyrosine.
• CGA codes for arginine.
• GCA codes for alanine.
• AGC codes for serine.

AUG Codon

• AUG codes for methionine.
• It also functions as a start codon.

Stop Codons

• UAA, UAG, and UGA are stop codons.

Ribosome Role

• Ribosomes read mRNA and assemble amino acids into proteins.

Translation

• Translation is the process of synthesizing proteins from mRNA.

Steps in Translation (Figure 14.6)

• Initiation: The ribosome binds to mRNA and locates the start codon (AUG).
• Elongation: tRNA molecules deliver amino acids to the ribosome, which links them together.
• Termination: The ribosome encounters a stop codon, releasing the newly formed protein.
• Folding: The protein folds into its functional shape.

Molecular Roles

• mRNA: Carries the genetic code from DNA to ribosomes (recipe).
• tRNA: Delivers amino acids to the ribosome (delivery service).
• rRNA: Forms part of ribosomes, helping assemble proteins (protein-building machine).

Protein Purpose

• Proteins build tissues, catalyze reactions, and regulate processes.

DNA as a Universal Code

• DNA's genetic code is universal, used by all living organisms.

DNA vs. RNA Differences

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

RNA Function

• mRNA: Carries genetic instructions from DNA to ribosomes.
• tRNA: Matches amino acids to codons.
• rRNA: Forms part of ribosomes, facilitating protein synthesis.

Transcription

• Transcription is the process of creating an RNA copy of a gene from DNA.

Transcription Location (Eukaryotes)

• Transcription occurs in the nucleus.

RNA Polymerase Roles

• Unzips DNA: Allows DNA to be copied.
• Builds RNA strand: Matches RNA bases to the DNA template.

Mutation Definition

• A mutation is a change in the DNA sequence.

Mutation Causes

• Errors in DNA replication during cell division.

Point Mutation Definition

• A point mutation affects one or a few nucleotides.

Point Mutation Types (Figure 14-16)

• Substitution: One nucleotide is replaced by another.
• Insertion: A nucleotide is added.
• Deletion: A nucleotide is removed.

Frameshift Mutation Definition

• Frameshift mutations change the reading frame of the genetic code.

Frameshift Mutation Types

• Insertions and deletions alter the grouping of codons.

Chromosomal Mutation Types (Figure 14-17)

• Deletion: Loss of a chromosome segment.
• Duplication: A chromosome segment is copied.
• Inversion: A chromosome segment flips and reinserts.
• Translocation: A chromosome segment moves to another chromosome.

Mutagen Definition

• A mutagen is an agent increasing the chance of DNA mutations.

Mutation Effects

• Mutations can be neutral, beneficial, harmful, or lethal.

This quiz explores the intricate details of protein composition, synthesis, and the genetic code. You'll learn about amino acids, codons, and the translation process, highlighting the role of RNA in protein assembly. Test your knowledge of how genetic information is translated into functional proteins.