1. History
• Frederick Griffith (1928) – experimented with
pneumonia – ability to cause disease was
inherited by the transformed bacteria’s offspring,
the transforming factor might be a gene
• Oswald Avery (et al.) (1944) – nucleic acid DNA
stores and transmits the genetic information
from one generation of an organism to the next
(genes are composed of DNA)

2. Cont.
• Hershey-Chase (1952) – genetic material
of the bacteriophage was DNA, not protein
• Watson-Crick – develop the double-helix
model of the structure of DNA
• Gilbert-Maxam-Sanger (1977)-develop
methods to read the DNA sequence
• Human Genome Project (2000) –
sequence all human DNA

3. Function of DNA
• 1. genes have to carry information from
one generation to the next
• 2. put information to work by determining
the heritable characteristic of organisms
• 3. genes have to be easily copied

4. Components
• DNA – long molecule made up of units
celled nucleotides
• Nucleotides:
– 5-carbon sugar
– Phosphate group
– Nitrogenous base

5. Cont.
• Purines:
• Adenine and guanine
• Pyrimidines:
• Cytosine and thymine
• Form chains in A=T and G=C (Chargaff’s
rules)
• Base pairing – hydrogen bonds form
between certain bases

6. Cont.
• Chromatin – DNA and a protein (histones)
called nucleosomes
• Nucleosomes can fold DNA into tiny space

7. Replication
• Each strand of DNA in the double helix
has the exact information needed to copy
itself
• Produces two new complementary strands
following the rules of base pairing
• Each strand of the double helix of DNA
serves as a template for the new strand

9. Cont.
• Replication – duplicates its DNA
(replication forks)
• Enzymes “unzip” by breaking the
hydrogen bond
• DNA polymerase is the enzyme used in
replication and “proofreads” the DNA to
maximize the perfect copy of DNA

10. RNA and Protein Synthesis
• RNA –long chain of nucleotides of sugar,
phosphate and base
• Differences:
– Ribose (sugar)
– Generally single-stranded
– Contains uracil in place of thymine

11. Cont.
• Three main types of RNA: mRNA, rRNA,
and tRNA
• mRNA: carry copies of instructions for
assembling amino acids into proteins;
serve as a “messenger” for DNA to rest of
the cell
• rRNA: proteins are assembled on
ribosomes

12. Cont.
• tRNA: transfers each amino acid to the
ribosome as it is specified by coded
messages in mRNA
• Transcription: RNA polymerase binds to
DNA and separates the DNA strand, RNA
polymerase then uses one strand of DNA
as a template from which nucleotides are
assembled into a strand of RNA

13. Cont.
• RNA polymerase enzyme will only bind to
DNA regions where promoters are
present, which have specific base
sequences
• Introns are not involved in coding proteins,
exons are the DNA sequences that code
for proteins and are “expressed” in the
synthesis of proteins

14. Cont.
• Introns are removed from the final RNA
molecule and the exons are spliced
together to from the mRNA
• Proteins form from long chains of amino
acids called polypeptides – containing and
or all of the 20 different amino acids
• mRNA’s “language” of instructions is
called the genetic code

15. Cont.
• Bases on RNA – A, U, C, G read 3 letters
at a time, each coded “word” is called a
codon and will represent a specific amino
acid or stop codons
• Translation - decoding or reading of
codons takes place in ribosomes, and
uses information from mRNA to produce
proteins

16. Steps in RNA
• 1. mRNA transcribes from DNA in
nucleus and released into cytoplasm
• 2. mRNA in cytoplasm attaches to
ribosome and each codon of mRNA
moves through the ribosome and specific
amino acid is transferred to polypeptide
chain ---tRNA has 3 unpaired bases called
anticodon

17. Mutations
• Mutations – mistakes (harmful/beneficial)
• Changes in genetic material
• Point mutation happens at a single point in
a base and includes: substitution, deletion,
and insertion and are called frame shift
mutations
• Causes can be dramatic as code has
“shifted” from that point on

18. Cont
• Chromosomal mutations
• Deletion – loss of all or part of
chromosome
• Duplication – extra copy is produced
• Inversion – reverses the direction of parts
of chromosomes
• Translocation – chromosome breaks off
and attached to another

19. Cont.
• Harmful – cause many genetic diseases
(Down Syndrome, Turner’s syndrome,
Fragile X syndrome and cancers)
• Beneficial – large crops, allows for
variations in species

20. Progeria

22. 22q11 deletions

23. Wolf-Hirschhorn

24. Neurofibromatosis

25. Proetus Syndrome

26. Regulation
• Operon – group of genes that operate
together
• Eukaryotic genes are controlled
individually and have regulatory
sequences that are complex
• Differentiation – specialized structure and
function
• Hox genes – control cells and tissues