DNA Structure and Protein Synthesis Review

DNA Structure and Composition

• DNA Molecule Composition:

  • DNA is made up of nucleotides, which are the monomers of DNA.

• Nitrogenous Bases:

  • The four nitrogenous bases of DNA are Adenine (A), Thymine (T), Cytosine (C), and Guanine (G).

  • Complementary Base Pairing:

  • For every adenine in a DNA strand, there is an equal amount of thymine, and for every cytosine, there is an equal amount of guanine.

• Shape of DNA:

  • DNA is commonly described as a double helix.

Genes and Protein Synthesis

• Genes:

  • Genes are used to make proteins, which are composed of amino acids (the monomers of proteins).

• Goal of DNA Replication:

  • The goal of DNA replication is to produce two identical copies of a DNA molecule.

  • Semi-conservative Replication:

  • Each new DNA molecule consists of one old strand and one new strand.

mRNA Information

• What is mRNA?:

  • Messenger RNA (mRNA) is a type of RNA that carries genetic information from DNA to the ribosome.

• Differences Between mRNA and DNA:

  • 1. mRNA is single-stranded, whereas DNA is double-stranded.

  • 2. mRNA contains uracil (U) instead of thymine (T).

  • 3. The sugar in mRNA is ribose, while in DNA it is deoxyribose.

• mRNA Production:

  • mRNA is produced during transcription from a DNA template.

Codons and Translation

• Codons:

  • Codons are sequences of three nucleotides in mRNA that specify an amino acid.

• Anti-Codons:

  • Anti-codons are complementary sequences in tRNA that match codons in mRNA.

• Function of Codons:

  • Each codon provides the necessary information to specify a particular amino acid.

• tRNA and rRNA:

  • tRNA (transfer RNA) brings amino acids to ribosomes during protein synthesis.

  • rRNA (ribosomal RNA) is a component of the ribosome and helps facilitate the process of translation.

• Translation:

  • Translation is the process of synthesizing proteins from mRNA.

  • This process occurs in the ribosomes in the cytoplasm.

Mutations in DNA

• Definition of a Mutation:

  • A mutation is a change in the DNA sequence that can affect the formation of proteins.

• Types of Mutations:

  • Mutations can be classified into gene mutations (affecting single genes) and chromosomal mutations (affecting larger sections of DNA).

• Effects of Mutation:

  • A mutation alters the DNA code, which can change the structure and function of proteins produced during protein synthesis.

• Health Implications:

  • Incorrectly made proteins can lead to health problems, such as Cystic Fibrosis (CF) or Sickle Cell Anemia due to their dysfunctional characteristics.

• Potential for Benefit:

  • Mutations can theoretically be beneficial, providing genetic diversity and potential advantages in certain environments.

Types of Mutations (Honors Only)

• Silent Mutation:

  • No change in the amino acid sequence.

• Frameshift Mutation:

  • Caused by insertions or deletions that shift the reading frame of the genetic code.

• Substitution Mutation:

  • One base is replaced by another, potentially altering the amino acid sequence.

• Deletion Mutation:

  • A segment of DNA is lost, which can have significant effects on protein function.

• Duplication Mutation:

  • A segment of DNA is duplicated, potentially leading to an excess of a certain protein.

• Inversion Mutation:

  • A segment of DNA is reversed within the chromosome, which may disrupt gene function.