Biology Chapter on DNA Structure and Function

Rosalind Franklin's Contribution

• Rosalind Franklin used X-ray photography to study the structure of DNA.

What is DNA?

• DNA is the blueprint of life.
• DNA is responsible for making cell structures and enzymes.

Monomers of DNA

• The DNA molecule is built from monomers called nucleotides.

Components of DNA Nucleotides

• Each DNA Nucleotide is composed of:
  • deoxyribose
  • a phosphate group
  • a nitrogenous base

Nitrogenous Bases in DNA

• The four nitrogenous bases in DNA are:
  • Adenine (A)
  • Thymine (T)
  • Cytosine (C)
  • Guanine (G)

DNA Replication

• During DNA replication, if one strand of DNA has the bases C-T-A-G-G-T, the complementary strand will have the bases G-A-T-C-C-A.

What is mRNA?

• mRNA carries a message from the nucleus to the ribosome.

Nitrogenous Bases in mRNA

• The four nitrogenous bases in mRNA are:
  • Adenine (A)
  • Uracil (U)
  • Cytosine (C)
  • Guanine (G)

What is Transcription?

• Transcription is the process of making mRNA from the DNA template
• The process of making proteins from the mRNA code is called translation

Where does Transcription Take Place?

• Transcription takes place in the nucleus.

mRNA after Transcription

• If the DNA sequence is A-A-C-C-T, the mRNA sequence after transcription will be U-U-G-G-A.
• mRNA is a single-stranded helix.

What are Genetic Mutations?

• A Genetic Mutation is a change in the DNA sequence.

Types of Genetic Mutations

• Point Mutation - When a single base pair is changed.
  • Substitution - A base pair is swapped with another base pair.
  • Insertion - An addition of a base pair.
  • Deletion - A removal of a base pair.

What Causes Mutations?

• Mutagens can cause mutations in DNA
• Mutagens are factors that cause DNA mutations.
• Mutagens can include:
  • radiation
  • chemicals

Levels of Classification

• There are eight levels of classification:
  • Domain
  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species

DNA and Evolution

• DNA is used to determine what organisms are most closely related.

The Shape of DNA

• DNA is shaped like a double helix.

Types of Chromosomes

• There are two types of chromosomes:
  • Autosomes - Chromosomes that carry the genes that determine a person's traits
  • Sex Chromosomes - Chromosomes that determine a person's sex

The Role of DNA in Genetic Diagrams

• Genetic diagrams, like those studied in class, are based on differences in DNA.

The Genetic Code

• The genetic code uses mRNA codons to determine which amino acid gets incorporated into a protein.
• The four nitrogenous bases in mRNA are:
  • Adenine (A)
  • Uracil (U)
  • Cytosine (C)
  • Guanine (G)

The Importance of DNA

• DNA is vital for life
• It carries the instructions for building and maintaining an organism.

The Function of DNA Primase

• DNA Primase unzips a DNA molecule and separates the base pairs during replication.

Impact of DNA Mutations

• DNA mutations can lead to:
  • Genetic disorders
  • Cancer
  • Variations in traits

How is DNA Replicated?

• DNA Replication is the process of making a copy of a DNA molecule.
• The process goes through the following steps:
  • Unwinding: The double helix is unwound, the two strands are separated.
  • Base Pairing: Each strand serves as a template for the creation of a new complimentary strand.
  • Joining: The new strands join with their complementary strands forming two new DNA molecules.

What is the process called of making proteins from DNA?

• The process of making proteins from DNA is called protein synthesis.

What are the two main steps of protein synthesis?

• Transcription - The process of copying the genetic code from DNA into a messenger RNA (mRNA) molecule.
• Translation - The process by which the mRNA molecule is used to construct a protein.

What is tRNA?

• tRNA is a type of RNA that transfers the correct amino acid to the ribosome during translation.