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DNA and RNA Structure
DNA and RNA are nucleic acids. They consist of chemical units called nucleotides. The nucleotides are joined by a sugar-phosphate backbone
DNA Bases and Shape Adenine (A) pairs with thymine (T) Cytosine (C) pairs with guanine (G) Shape:double helix
RNA bases Uracil (U) Cytosine (C) Adenine (A) Guanine (G)
DNA Replication DNA strands separate
Each strand becomes a template for the assembly of a complimentary strand from a ready supply of free nucleotides.
Nucleotides line up one at a time along the template strand – following the base pairing rules
Enzymes catalyze the entire process…
Origin of replication
  • Site of start point for replication
Bidirectional replication
  • Replication proceeds outward in opposite directions
Replication Bubble & Forks Origin of replication provides an opening called a replication bubble that forms two replication forks DNA replication occurs near the fork
Primer & Okazaki Fragments Synthesis begins with a primer Lagging strand made as Okazaki fragments that have to be connected later
Direction of DNA rep Proceeds 5’ to 3’ direction
DNA is... very fast, accurate, proofread and repairs self during rep
DNA polymerases: Are enzymes Make the covalent bonds between the nucleotides of a new DNA strand Are involved in repairing damaged DNA
Transcription VS Translation Transcription, the transfer of genetic information from DNA into an RNA molecule (switch T to U) Translation, the transfer of information from RNA into a protein (AA) - every 3 bases -> AA
possible 3 base sequences 64 =genetic code (different comb = AA)
codon 3 base triplet, start and stop codons tell enzymes where to begin/end synthesis
As it is made, a polypeptide: Coils and folds
Assumes a three-dimensional shape, its tertiary structure
Several polypeptides may come together, forming a protein with quaternary structure
mutagens & mutation Physical or chemical agents that cause mutationsA mutation is any change in the nucleotide sequence of DNA - Although mutations are often harmful, they are the source of genetic diversity, which is necessary for evolution by natural selection.
Types of Mutations
Base substitution, the replacement of one base by another Nucleotide deletion, the loss of a nucleotide Nucleotide insertion, the addition of a nucleotide
virus Possess genetic material in the form of nucleic acids Are not cellular and cannot reproduce on their own.
Bacteriophages, or phages viruses that attack bacteria.
plant virus Viruses that infect plants can: Stunt growth Diminish plant yields Spread throughout the entire plant Viral plant diseases: Have no cure Are best prevented by producing plants that resist viral infection
Animal Viruses
Viruses that infect animals are:
Common causes of disease
May have RNA or DNA genomes
Some animal viruses steal a bit of host cell membrane as a protective envelope.
HIV HIV is a retrovirus, an RNA virus that reproduces by means of a DNA molecule. Retroviruses use the enzyme reverse transcriptase to synthesize DNA on an RNA template. HIV steals a bit of host cell membrane as a protective envelope.
AIDS AIDS (acquired immune deficiency syndrome) is: Caused by HIV infection and Treated with drugs that interfere with the reproduction of the virus
Viroids Viroids are small circular RNA molecules that do not encode proteins
Prions Prions are misfolded proteins that somehow convert normal proteins to the misfolded prion version Prions are responsible for neurodegenerative diseases including: Mad cow disease Scrapie in sheep and goats Chronic wasting disease in deer and elk Creutzfeldt-Jakob disease in humans
DNA vs RNA DNA: T, double stranded, deoxyribose sugar RNA: U, single stranded, ribose sugar