View
118
Download
2
Category
Tags:
Preview:
Citation preview
DNA, RNA, and Protein Synthesis
Chapter 10
DISCOVERY OF DNASection 1
Griffith’s Experiments
• Fredrick Griffith studied bacteria that cause pneumonia– Some strains, or types, were harmful and
caused pneumonia in mammals (smooth)– Other strains were harmless and did not
cause pneumonia (rough)
Griffith’s Experiments
• Used the two strains of bacteria in four experiments
• Discovered that genetic material can be transferred from one cell to another and change those cells
• He called this transformation
Griffith’s Experiments
Avery’s Experiments
• Oswald Avery wanted to find out what factor caused the transformation in Griffith’s experiments
• Discovered that the factor was DNA
Hershey-Chase Experiment
• Experimented with bacteriophages – viruses that infect bacteria
• Confirmed that DNA is the hereditary molecule
Hershey-Chase Experiment
DNA STRUCTURESection 2
DNA Double Helix
• Structure of DNA discovered in 1953 by James Watson and Francis Crick
• Used Maurice Wilkins and Rosalind Franklin’s x-ray picture of DNA to help
DNA Nucleotides
• Made of two long strands of nucleotides– Each nucleotide contains three parts
• Five-carbon sugar (deoxyribose)• Phosphate group• Nitrogenous base
DNA Nucleotides
Bonds Hold DNA Together
• Structure is similar to a spiral staircase– Alternating sugar and
phosphate molecules = side handrails of the staircase
– Base pairs = steps of the staircase
Nitrogenous Bases
• Four kinds of bases– Adenine– Guanine– Thymine – Cytosine
Complementary Bases
• Base-pairing rules: • cytosine always pairs with guanine• adenine always pairs with thymine
Complementary Bases
• What is the complementary sequence of bases for the following strand of DNA?
• ACCTGTGAGAC• TGGACACTCTG
DNA REPLICATIONSection 3
DNA Replication
• DNA replication is the process by which DNA is copied in a cell before a cell divides
Steps of DNA Replication
1. Enzymes called helicases separate the DNA strands
Steps of DNA Replication
2. Enzymes called DNA polymerases add complementary nucleotides to each of the original strands
Steps of DNA Replication
3. DNA polymerases finish replicating the DNA and fall off– Result is two separate
and identical DNA molecules
DNA Errors in Replication
• DNA replication is usually very accurate– Only about one error occurs for every billion
nucleotides• When mistakes occur, a change in the
nucleotide sequence results in a mutation
PROTEIN SYNTHESISSection 4
Flow of Genetic Information
• DNA RNA protein
RNA Structure and Function
• RNA is very similar to DNA – long strand of nucleotides
RNA Structure and Function
• RNA is different from DNA in the following ways:– Contains the sugar ribose instead of
deoxyribose– Contains uracil instead of thymine– Single-stranded– Much shorter than DNA
Types of RNA
• There are three major types of RNA that each play a different role in protein synthesis
Types of RNA
• Ribosomal RNA (rRNA) – makes up part of the ribosome
Types of RNA
• Messenger RNA (mRNA) – carries the message from DNA in the nucleus to the ribosomes in the cytoplasm
Types of RNA
• Transfer RNA (tRNA) – transfers amino acids to the ribosome to make a protein
The Genetic Code
• The genetic code is the rules for how a sequence of bases codes for a particular amino acid
• Each group of three nucleotides is called a codon and codes for an amino acid
The Genetic Code
Transcription
• Instructions for a gene coded in DNA are rewritten into an RNA molecule
Translation
• Translation = the making of a protein
Steps of Translation
1. mRNA is fed through a ribosome three bases at a time
Steps of Translation
2. Molecules of tRNA translate the mRNA code by picking up a specific amino acid from the cytoplasm
Steps of Translation
3. In the ribosome, bases on the tRNA match with bases on the mRNA like pieces of a puzzle
Steps of Translation
4. tRNA releases their amino acids and they become linked in a chain
Recommended