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Subunit of DNA consisting of a sugar, phosphate group, and nitrogenous base (A,C, G, T) : Sugar/phosphate group = backbone : Nitrogenous bases = ribs
- (DeoxyriboNucleic Acid)
- 1. Sugar: Deoxyribose
- 2. Nitrogenous bases: A, C, G, T
- 3. Strands: Double - stranded
- (RiboNucleic Acid)
- 1. Sugar: Ribose
- 2. Nitrogenous bases: A, C, G, U
- 3. Strands: Single - stranded
Watson & Crick
- 1.Discovered molecular structure of DNA
- a. Sugar-phosphate backbone
- b. Nitrogenous base ribs
- c. Complementary base-pairs
Complementary Base Pairing
- 1. Adenine pairs with Thymine or Uracil
- a. A-T (DNA) or A-U (RNA)
- 2. Cytosine pairs with Guanine
- a. C-G (always)
- 2 strands of parental DNA separate, each becoming a template for the assembly of two complementary daughter strands
- Each new DNA molecule = 1 new strand + 1 old strand (maintaining DNA integrity)
Sequence of nucleotide bases in an organism’s DNA.
Physical expression of nucleotide sequences in an organism.
Transfer of genetic information from DNA to RNA.
Assembly of proteins using the information transferred to RNA.
Carries genetic code from DNA into cytoplasm (messenger).
Recognizes genetic code, matching amino acids to it in the correct order (transfer).
With proteins, forms the ribosome, assembling amino acids into proteins (ribosomal).
- 3 nucleotide sequence that specifies a particular amino acid; basic unit of genetic code (“word”); on mRNA.
- Each codon code for one of 20 amino acids.
- 3 nucleotide sequence that is complementary to a codon on mRNA; on tRNA.
- Carries with it one of 20 amino acids.
Internal, non-coding regions of RNA (nonsense).
Internal, coding regions of RNA (expressed).
Introns are removed and exons are joined together forming a mRNA strand with a continuous coding sequence.
- Any change in the nucleotide sequence of DNA.
- Good mutations: evolution
- Bad mutations: inherited diseases, cancer
Results from errors during DNA replication, recombination.
Agents that cause errors during DNA replication. *Chemical, *Radioactive, *Viral.
Types of Mutations
- 1) Base substitution: Replacement of one base or nucleotide by another in a DNA sequence.
- 2) Insertions/Deletions: Addition/subtraction of a base or nucleotide in a DNA sequence.
- Replacement of one base or nucleotide by another in a DNA sequence
- Silent mutation – different base sequence, but same amino acid (no effect)
- Missense mutation – different base sequence with different amino acid (minor to major effect)
- Non-sense mutation – different base sequence, amino acid becomes a stop codon (premature, non-functioning amino acid)
- Addition/subtraction of a base or nucleotide in a DNA sequence
- All nucleotides downstream from the mutation will be regrouped into different codons
- Effects are usually disastrous!
Obligate Intracellular Parasites
Infectious particles that function only when existing inside a living cell.
DNA or RNA surrounded by a protein coat.
Natural History of Viruses
- 1. First discovered in 19th century, origin unknown.
- 2. Not classified in any kingdom (not living).
- 3. Occur in multiple shapes & sizes.
- 4. Capable of mutating.
Viruses that infect bacteria.
- 1. Generally viruses are species specific; some-times even cell specific.
- 2. Viruses seek out cells with receptor sites to which they can attach: ie) Measles – skin cells, Mumps – salivary gland cells, Hepatitis – liver cells, Herpes – nerve cells.
- 3. A virus enters a cell or simply injects its own DNA into the cell. Ie) Viral DNA consists of 3 – 500 genes (eukaryotic DNA consists of 10,000 genes)
- 4. A virus takes over the host’s metabolic path-ways, utilizing host ATP and enzymes. Ie) A single virus can generate 1,000’s of new virus particles.
- A virus that is in one species and mutates in order to infect a different species.
- ie) Bird flu transmitting through the bird species and infecting the human species.