DNA and Genetics

The Structure of DNA

Chromosomes are made of DNA. Each chromosome contains thousands of genes. The sequence of bases in a gene forms a code that tells the cell what protein to produce.

A Complex Molecule• The shape of the molecule is like a twisted

zipper. It is called a double helix.• The scientist that discovered DNA and its

shape realized that smaller molecules of DNA bond together and form this double helix shape.

The Genetic Code

• Genes and DNA: A gene is a section of DNA molecule that contains the information to code for one specific protein.

• Order of the Bases: The order of the nitrogen bases along a gene forms a genetic code that specifies what type of protein will be produced.

Adenine (A) Cytosine (C) Thymine (T) Guanine (G)

How Cells Make ProteinsReplication: the process of copying a DNA

molecule to make another DNA molecule which produces identical strands of DNA.

• The Role of RNA: The genetic messenger, RNA, must first carry the genetic code from the DNA inside the nucleus into the cytoplasm. It is also made of nucleotides.

• Types of RNA: Messenger RNA, Transfer RNA, and ribosomal RNA. The process of making protein from RNA is called translation.

Translating the Code

• To make proteins, messenger RNA copies information from DNA in the nucleus. Messenger RNA and Transfer RNA then use this information to produce proteins.

Mutations

• A mutation is any change in a gene or chromosome. It can cause a cell to produce an incorrect protein during translation. As a result, the organism’s trait, or phenotype, may be different from what it normally would have been.

• The word comes from a Latin word that means “change.”

Types of MutationsDuring DNA Replication:-A cell can end up with too many or too few

chromosomes-A cell can also end up with extra segments of

chromosomes.

Effects of Mutations

• Good : can be a source of genetic variety.» Antibiotic resistance in bacteria

• Harmful: if it reduces its chance for survival and reproduction.

Odd fur coloring that makes it stand out in its environment

Homework

• Read and add to notes pages 174-180.• Test is on Friday, May 8.• We will go over your notes in class tomorrow.

Study!!!