Theme 1A Flashcards
Genetics
study of heredity and variation in cells, individuals, & populations
study of genes
Gene
functional unit of heredity and variation
DNA sequence involved in making RNA & protein
found on chromosomes & part of the genome that encodes for RNA & protein
Molecular Genetics
study of structure and function of genes at the molecular level
Allele
variant forms of a gene caused by differences in DNA sequence
Genotype
gene(s) inherited by an organism
Phenotype
visible traits
Genome
entire DNA sequence (ACGT) of an organism
Gene Expression
“turning on” a gene to produce RNA & protein (coding gene)
RNA can be _________ & __________
coding & noncoding
coding = mRNA - only one that makes protein
non-coding = tRNA & rRNA
Gene Expression Diagram
slide 7
Protein Expression
the type & abundance of proteins in the cell
The protein ultimately determines the phenotype of the cell because…
they control every reaction in the cell
Enzymes
proteins catalyzing the synthesis and transformation of all biomolecules
Avery, MacLeod, & McCarthy (Classical Experiment)
What was the hypothesis, experimental approach, and conclusion?
Hypothesis: transforming principle could be protein, DNA, or RNA
Experimental Approach: eliminate each type of molecule in S cells and see whether transformation of R cells into S virulent form still occurs
Conclusion: if type of molecule is absent, and transformation is gone, then this molecule is the transforming principle
Structure Proteins
maintenance of cell shape
Signaling Proteins
hormones and receptors
Why is genetics important?
human health
forensics
agriculture
environment
evolutionary biology
Griffith - Classical Experiment
found a substance that could genetically transform Streptococcus pneumoniae (pneumonia causing bacteria in mammals)
Conclusion: some molecules (Transforming principle) released when S cells were killed could transform R cells genetically to the virulent S form; transformation was permanent and heritable
What are two things responsible for phenotypic variation
Different alleles (variation in gene sequence results in changes in aa sequence of proteins) and differential regulation of gene and protein expression (how much gene is being turned on/off)
What are 3 classical experiments that led to estabilishing DNA as a hereditary molecule?
- Griffith
- Avery, MacLeod & McCarthy
- Hershey and Chase
Streptococcus pneumoniae
Smooth Strain (S):
Rough Strain (R):
(Griffith) bacterial pathogen causing pneumonia in mammals
S: bacterium surrounded by a polysaccharide capsule - filmy sugary layer; protected by capsule from immune system, which allows for infection, therefore virulent
R: lacks polysaccharide capsule, cannot evade immune system, therefore non-virulent
Avery, MacLeod, & McCarthy (Classical Experiment)
What was the experiment?
Enzymes that destroyed RNA (rnase), proteins (protease), and DNA (dnase) were added to cell extract/cytoplasm of heat-killed S cells. If the R cells did not transform into the S virulent form when a molecule was removed, then that molecule was the transforming principle.
- No transformation occurred when DNA was destroyed, making DNA the transforming principle
Life Cycle of a Virus (Lytic Cycle)
- massive reproduction of virus resulting in host cell lysis (virulent - harmful to host)
- viral DNA replicated seperately from bacterial chromosome
Life Cycle of a Virus (Lysogenic Cycle)
- replication of viral genome (latent)
- viral DNA is integrated into the bacterial chromosome
- life long infection that can only be controlled
- asymptomatic
When can lysogeny switch to lytic cycle?
If viral DNA is excised from bacterial chromosome
Hershey and Chase (Classical Experiment)
determining if bacteriophage injects DNA or protein into E.coli
- label bacteriophage DNA & proteins with radioactive isotope 32P and 35S, respectively
- allow infection of E.coli with bacteriphage
- separate attached bacteriophage and E.coli with a blender
- assay presence of 32P (DNA) and 35S (protein) in detached bacteriophage, E. coli cells, and progeny bacteriophage (done in lytic phase - not shown)
Results:
- no 35S in E.coli cells & progeny bacteriphage; found in detached bacteriophage; not HERITABLE
- 32P found in E.coli cells and progeny bacteriophage; none in detached bacteriophage; HERITABLE
Hershey & Chase
What would you expect to see if it was done in lysogeny?
not sure
