Chapter 1 - Major Biological Functions of DNA Flashcards
Genetics
Study of genes and variation in cells, individuals and populations.
How does heredity happen?
Where does variation come from?
Gene
functional unit of heredity and variation.
DNA sequence involved in making RNA and protein.
Molecular Genetics
The study of structure and function of genes at the molecular level.
Alleles
variant forms of a gene caused by differences in DNA sequences.
(variation in eye color/height)
Genotype
genes inherited by an organism
Phenotype
Visible traits
Body plan, behavior, illnesses/diseases
Genome
entire DNA sequence (ACGT) of an organism.
Gene Expression
“turning on” a gene to produce RNA and protein (coding gene).
Coding RNA
makes protein (mRNA)
Non-coding RNA
does not make protein (tRNA, ribosome RNA)
Protein expression
the type and abundance of proteins in the cell.
What determines the phenotype of the cell?
Proteins because they control every reaction in the cell.
Even though DNA is the information molecule that directs protein expression/
Enzymes
catalyzes the synthesis and transformation of all biomolecules.
Structural proteins
maintains the cell shape.
Signalling proteins
hormones and receptors.
How do alleles contribute to phenotypic variation?
Alleles of a gene have differences in DNA sequence that result in variation in protein expression and therefore, phenotype.
Why sequence genomes?
To understand the types and abundance of RNA and protein result in a phenotype of an organism, we need to identify all the genes in the genome.
More complex = larger genome size but number of genes does not speak about complexity.
Why is studying molecular genetics important?
Human health, Forensics (DNA Fingerprinting), Agriculture, Environment, Evolutionary biology
Who established DNA as the hereditary molecule in 3 classical experiments? (Who studied how the transfer of genetic information happens?)
- Griffith
- Avery, MacLeod & McCarthy
- Hershey & Chase
Griffith Experiment
Transforming principle.
Streptococcus pneumonia was transformed from non-virulent to virulent.
Transformation was permanent and heritable.
- Smooth Strain: virulent. Has a polysaccharide (sugar-based) coat that protected it from the immune system.
- Rough Strain: non-virulent. (doesn’t cause sickness)
Avery, Macleod & McCarthy
Identified what is the transforming principle: DNA, RNA or protein.
They separated cells by component. If the molecule is absent and transformation is gone, that is the transformation molecule.
Hershey & Chase
Found evidence from bacteriophage.
Two radioactive isotopes were injected into the phages.
a) Sulfur: affects proteins.
b) Phosphorus: affects DNA.
- One batch of phage was labeled with S, the other labeled with P.
- Phages infected bacteria.
- Cultures were centrifuged to separate bacteria from phages.
- Radioactivity was measured.
- Heavier material (bacteria) moved to bottom forming a lump called a pellet & Lighter materials (phage) remained near the top forming a layer called supernatant. - P was found in the pellet (inside bacteria) and S was found in the supernatant (outside bacteria).
Found the final evidence establishing DNA as the hereditary molecule even though proteins were more complex.
Bacteriophage Reproduction
- Lytic Cycle: virus hijacks cell to make viral proteins, the cell splits and releases the viral proteins.
- Lysogeny: bacteriophage inserts itself into the bacteria chromosome.
Lytic Cycle Steps
microphage docks onto bacteria, injects viral DNA, microphage is replicated, cell breaks open and mature phage released.
