DNA Lifes Instruction Manual or What Genes are

DNA Life’s Instruction Manual or What Genes are Made Of

What can DNA do? • 1. Can replicate before cell division. Remember MEIOSIS and MITOSIS, chromosomes need to replicate before they divide • 2. Can direct protein synthesis. It tells the RIBOSOME to make a protein.

Why is the DNA the genetic material • DNA doubles prior to cell division (mitosis) • DNA divides equally between daughter cells • A body cell has 2 X the amount of DNA as a gamete(egg or sperm)

Discovery of DNA • 1952 Rosalind Franklin-studies DNA molecule using x-ray diffraction • 1953 Watson and Crick- develop double helix model

The Shape of the DNA Molecule • DNA is a complex organic molecule with a double helix shape. (a twisted ladder) • It consists of 2 phosphate-sugar backbones connected by a series of nucleotide bases. (colored letters)

DNA Nucleotide Bases • • • Adenine A Thymine T Guanine G Cytosine C These bases are joined together in a specific way… • A with T G with C • We call this base pairing.

DNA Structure

DNA Replication • The bonds between the base pairs are weak hydrogen bonds and can be broken easily. This means that the molecule can unwind and unzip itself. • Each side of the DNA molecule has all the information necessary to make a complementary (second) side. • Each piece of “old” DNA will act as a template for a “new” piece of DNA.

DNA Copies Itself!! • Because of base pairing, each strand of DNA can replicate itself making two new strands of DNA. • It uses extra nucleotide bases (in cell) to create this copy. • All of the work of DNA replication is done by enzymes!! • The main enzyme is called DNA polymerase

Semi-Conservative Replication • The result is that each new copy of DNA produced by this process is made up of ½ original DNA molecule and ½ new DNA molecule. This makes the process semi-conservative.

RNA • RNA is a nucleic acid like DNA • RNA is single stranded. • RNA does not contain thymine but instead has the base called uricil which bonds with adenine. • RNA has many functions in the cell, most importantly it is critical in the process of protein synthesis

Mutations • What happens when a mistake is made in replication of DNA? • Most mutations are NOT helpful!! But every so often, a beneficial mutation occurs (black moths)

Types of Mutations Point Mutations – the change in one single nucleotide base. substitution – one letter replaces another in the sequence. (ex. A->G) insertion – one letter is added to the sequence. (ex. a new T is added) deletion – one letter is removed from the sequence. (ex. a G is removed)

• Make a substitution in the following DNA ATTGCGTGTG ATTACGTGTG Make an insertion in the original sequence ATTGCGATGTG Make a deletion in the original sequence ATGCGTGTG

Larger Mutations • Inversions – when 2 or more bases (letters) are switched into reverse order. • Duplications – when bases are repeated in the original order more than one time. • Translocations – when bases are moved from one area of the sequence to another.

Make an 3 base inversion mutation in the following DNA sequence… ATTGCGTGTG ATCGTGTGTG Make a duplication of the inversion here ATCGTCGTGTGTG Make a translocation of 3 bases from another DNA sequence of T G C C A A to the original DNA ATTGCCCAAGTGTG

Protein Synthesis The Central Dogma • DNA holds the _______ to make Proteins • ____ transfers the CODE to the Ribosome • _______ are strings of amino acids coded for by DNA • Proteins are the “______” of the cell Structure, enzymes, communication, etc.

Transcription • The DNA message is _____ into an m. RNA message by complementary ______ pairing

Translation • The m. RNA then goes into the _____ to give the code for a protein to the ribosome. ______ (transfer) molecules will bring the correct _______ to the ribosome.

DNA

Mutations • Sometimes mistakes can be made in the copying process of DNA. Any change in the original sequence of base pairs is called a mutation.

Protein Synthesis The Central Dogma • DNA holds the CODE to make Proteins • RNA transfers the CODE to the Ribosome • Proteins are strings of amino acids coded for by DNA • Proteins are the “workhorses” of the cell Structure, enzymes, communication, etc.

Transcription • The DNA message is transcribed into an m. RNA message by complementary base pairing

Translation • The m. RNA then goes into the cytoplasm to give the code for a protein to the ribosome. t. RNA molecules will bring the correct amino acid to the ribosome.

DNA

Mutations • Sometimes mistakes can be made in the copying process of DNA. Any change in the original sequence of base pairs is called a mutation.