Download DNA History, Mutations Gene Regulation

DNA
History, Mutations
Gene Regulation
BSC 1005 Concepts of Biology
Professor Tcherina Duncombe
Palm Beach State College
Frederick Griffith (1928) : How do certain types of
bacteria produce pneumonia in humans?
Griffith Experiment: transformation
Oswald Avery (1944): Which molecule was
most important in transformation?
• Extract/juice from heatkilled bacteria
• Treated with enzymes: p,
l, c, RNA
• Transformation occurred
• Treated with same
mixture: DNA
• No transformation
• DNA = transforming
factor
Alfred Hershey-Margaret Chase (1952): Viruses
Bacteriophage: bacteria eater
Radioactive markers = phosphorus ( DNA ), sulfur ( Protein )
Radioactivity in bacteria = phosphorus
Hershey-Chase
Experiment
Figure 12.4 The DNA double helix
Rosalind Franklin: DNA Double Helix
• X – ray diffraction
• Pictures of DNA
• X = Strands twisted
around each
other:Coils
• Angle= 2 strands
• Other clues= nitrogen
bases near center
Double Helix: Nobel Prize 1962
James Watson
Francis Crick
Barbara McClintock
(1903 – 1992)
• Transposons = transposable
sequences = jumping genes
• DNA sequences scattered
randomly about on the
chromosomes
• Unusual: are repeated
thousands of times/can move
around from one
chromosome to
another/Maize
• Began Dec. 7, 1941
• Nobel Prize: Physiology and
Medicine 1983
What is DNA?
• Deoxyribonucleic Acid
• Contains genetic
information for all
living things
• Determines an
organism’s traits
• Controls by dictating
which proteins are
made
DNA: genetic information
Components of DNA
• Nucleotides
• 5-carbon sugar =
deoxyribose
• PO4 group
• Nitrogenous base
Structure of DNA
• Nucleotides: 3 parts
• simple sugar:
deoxyribose
• phosphate group
• nitrogen base:
adenine
thymine
cytosine
guanine
Nucleotide Structure
ATP
4-15
Nitrogenous
Bases
4-16
DNA: Base Pairs
• Cytosine (C) pairs
with Guanine (G)
• Adenine (A) pairs with
Thymine (T)
• Hydrogen Bonds
connect the base
pairs
Chargaff’s Rules: Base Pairing
Nucleotide
ALLELES
Within a species, individuals sometimes have alternate versions of a
gene for a given protein. These instructions can result in a different
version of the same trait.
ALLELE
Alternate versions
of a gene that code
for the same trait
ALLELE 1
ALLELE 2
ALLELE 3
Protein production Protein production Protein production
The protein, influenced by the environment and in some
cases other genes, then produces the trait.
Cell Cycle
Chromosomes: DNA and proteins
• Visible during cell
division
• Replicates: copied
• Sister Chromatids
• Centromeres
Replication of DNA
• DNA molecule unzips
• Free nucleotides bond to each strand by base
pairing
• Continues until 2 new strands are made
DNA Replication 1
4-24
From DNA to Protein
RNA: Ribonucleic Acid
•
•
•
•
Single strand
Uracil instead of thymine
Ribose instead of deoxyribose
3 major types:
mRNA
tRNA
rRNA
Transcription
tRNA
Translation: mRNA to protein
Translation
HOW GENES WORK: AN OVERVIEW
Inside nucleus
DNA
TRANSCRIPTION
The sequence for a
gene is copied from
DNA to a middleman
molecule called
mRNA.
Cytoplasm
mRNA
TRANSLATION
The sequence for a
gene, now encoded
in mRNA, is used to
direct the production
of a protein.
Genes
Protein molecule
Nuclear
pore
Grandmother’s
cookbook
Copying cookie
recipe to index card
Index card
with recipe
Combining and
baking ingredient
Chocolate
chip cookies
Genetic Code
• Translation: occurs at the ribosome
• Results: sequence of amino acids
• DNA → mRNA → tRNA anticodon →
tRNA codon
• Codon = 3 base triplett
• Start = AUG
• Stop = UAA, UAG, UGA
DNA:
A T C G T G A G T
__ __ __ __ __ __ __ __ __
mRNA:__ __ __ __ __ __ __ __ __
tRNA: __ __ __ __ __ __ __ __ __
tRNA: __ __ __ __ __ __ __ __ __
AA:
_______ ________ ________
Point Mutations: change in one or a few
nucleotides
Substitution
Insertion
Frameshift
Deletion
CTGGAG
TCTGGAG
Effect of Mutations
Chromosomal Mutations
Causes of Mutations
• Changes in the genetic material (DNA)
• Gene mutations
• Chromosomal mutations
Two types of mutations
Effects of Mutations
Gene
Regulation
• Operon
• Repressors
• lac operon: bacteria
• Lactose= glucose +
galactose