Studied by 16 people
What is the Biological Function
Gregor Mendel (1822-1884) revealed that….
heredity is the result of discrete units of inheritance.
Traits are not blended - can either have mom or Dad traits can be pasted down generation from generation
Wilhelm Ludvig Johannsen coined the term gene to refer the …
not or particle of inheritance
Phenotype - Trait expressed by gene
Genotype - collection of genes that code for phenotype
Archibald Garred
Identifies alkaptonuria as a heritable geneticc disease that follows Mendel’s law
Alkaptonuria
black urine - inborn error of metabolism used of pedigree
What is the Biochemical basis of hereditary?
Majority of death resulted from secondary infections of…
Streptococcus pneumoniae
What are the two strains of streptococcus pneumoniae
Rough Colony (R)
Smooth Colony (S)
What is the R strain
benign (lacks a protective capsule, recognized and destroyed by host’s immune system)
S-strain
Is virulent (polysaccharide capsule prevents detection by host’ immune system)
Fredirck Griffith (1928) discovered that the ..
dead virulent strain of S. pneumonia (S-strain) could transform the harmless form (R-strain) into the virulent form.
Avery, and McCarty and Mcleod discovered that…
R-strains could be transformed with DNA extracts from dead S-strains
Conclusion
the molecule that carries the heritable information is DNA
Bacteriophage are?
They consist of two component
Class of Viruses that infect bacteria
Requires bacterial host for replication
DNA Genome
Protein Capsid
Bacteriophage life cycle
The genetic information required for viral replication must be contained in either the DNA or the proteins
Hershey and chase (1952)
Labeled Bacteriophage with radioactive elements
Phosphorous of DNA
The sulfur of Amino Acids - Cysteine and methionine
Traced the transfer of those elements to the infected bacteria
Hershey and Chase confirmed What?
Experiment DNA and Protein/sulfur put in viruses that allowed to infect E.coil- blender shear off viral heads off bacter- infected bacteria contained 35P not S35
Nucleotides
A nucleotide consist of a nitrogen-containing base, a five-carbon sugar, and one or more phosphate groups
Carbons of the deoxyribonucleotide (monomer unit of DNA)
1’
Base attached
2’
Deoxygenated in DNA
3’
OH - forms phosphodiester bond
5’
Phosphate group attached
What are the Nucleotide bases
What are Pyrimidine and Purine bases
DNA Polymerization
Hydrolysis of Phosphor anhydride bond provide energy
Creates favorable reaction - high energy → Low energy
Erwin Chargaff do?
Nucleotide occur in predictable ratios in living things
What is Chargaff's Rule?
A = T
G = C
Discovery of the structure of DNA - Watson, Crick, Wilkins, and Franklin
Discovery of structure of DNA - Watson, Crick, Franklin, and Wilkins
Double helix with Bases pointing inward
Complementary base-pairing between purine and pyrimidine explain Chargaff’s rule
Complementary base-pairing of DNA makes it possible to faithfully replicate of genetic material
Each strand serves as a template to make a new double helix - semi-conservative replication.
Part 2 - DNA and Chromatin Structure
DNA Structure backbone is assembled via condensation reactions forming…
Phosphodiester bonds
Nucleotides are connected 5’ to 3’ and strands are..
one strand and the other…
antiparallel
One strand runs 5’ to 3’
Other runs 3’ to 5’
DNA Structure is held together by…
Hydrogen bonds between bases
G to C bonds are… than A to T
Stronger
Increasing the GC content increases the … of DNA
Stability
The DNA Helix has two grooves
Major groove - 22 A wide - primary site of sequence specific binding of protein
Minor groove - 12 A wide - primary non-specific binding of proteins
Major DNA sequence features (2)
Genome
Gene
Genome?
The complete DNA sequence of an organism
Gene
Portion of the genome transcribed to RNA and usually translated into a protein
Genes are read (transcribed) …..from either strand of the double helix
5’ to 3’
Replication Origin
Special sequence where the replication of DNA begins
Centromere
A special sequence that attaches to mitotic spindle and allows chromosome separation in mitosis
Telomere
Repetitive sequences at the ends of Chromosomes that protect from degradation and/or fusion with other chromosomes
The Problem with DNA is that it’s Thin and Extremely long molecule.
Each cell in your body has 2 meters of DNA
How does DNA fit in the cell?
DNA is packed with proteins into a complex called chromatin
Histone proteins are major elements of…
chromatin
Histone protein come together in an …. complex which DNA wraps around.
Octomer
Nucleosome?
The histone + DNA Complex
Histones proteins are…. charged and attract the …. charged DNA
Positively charged
Negatively charged
Decondense Chromatin appears like …..
DNA wraps around nucleosome ….times …bp
Beads on a string
1.7 times (147 basepairs)
Another histone protein…. can …
H1 can link histones together and help condense the chromatin fibers
Chromatin fibers are … into loops by …
Folded
CTFC proteins
What do CTFC do?
Pull loop through until it reaches a specific sequence
Matches Specific DNA Sequences
Chromosome loop-forming clamp proteins
What is the Result of this?
Each DNA molecule has been packaged into a Mitotic chromosome that is 10,000-fold shorter than its fully extended length
Fully condense at Meta-phase of cell cycle
DNA in Eukaryote cells is organized into ..
Chromosomes
What is a chromosome
Complex of DNA (One continuous helix) and many proteins
In human chromosomes are paired …
Homologous chromosomes, one from each parent
Chromosomes take on different conformations through the cell cycle
Interphase, meta phase, interphase
In interphase, when cell is not dividing,..
different chromosomes reside in distinct territories within the nucleus.
Nucleus chromatin is found in two forms
Heterochromatin
Euchromatin
Heterochromatin
That is condensed and not transcriptionally active by telomere and centromere.
Euchromatin
That is loose and transcriptionally active
Chromatin conformation and composition is dynamic and modified for specific biological function
Chromatin remodeling complex (3)
Positions nucleosomes
Condenses and decondense
Requires ATP
The Histone proteins have….terminal tails that are…
N-terminal tails that are modified to mark regions of genome for transcriptional activation or silencing
What are the 5 Levels of DNA
Double helix
Beads on a string - DNA wraps around Histone 1.7 times 147bp creating nucleosome
Chromatin fibers are made with Histone HI
Chromatin fiber loops with CTFC - pull loop through until it reaches a specific sequence
Folded loops are fully condensed at meta-phase of cell cycle
