2. I. DNA, RNA, and protein synthesis
A. Central dogma of molecular biology
1. DNA → RNA → Protein
3. I. DNA, RNA, and protein synthesis
B. DNA
1. Is the genetic material in your cells
2. It was passed on to you from your parents and
determines your characteristics
4. I. DNA, RNA, and protein synthesis
3. DNA forms a double helix
a. DNA is double stranded
b. And bonds to the opposite
strand
c. This creates strength and
prevents the DNA from being
easily broken
d. There are four bases of DNA
adenine, cytosine, guanine, and
Thymine
5. I. DNA, RNA, and protein synthesis
C. RNA
1. Is another nucleic acid like DNA but differs in
several ways
a. Is a single stranded molecule
b. It can leave the nucleus
c. Contains the nitrogen base uracil (U) instead of
thymine
6. I. DNA, RNA, and protein synthesis
2. Three types of RNA
a. Messenger RNA (mRNA) copies the genetic
instructions from DNA in the nucleus, and carries
them to the cytoplasm.
b. Ribosomal RNA (rRNA) helps form ribosomes, where
proteins are assembled.
c. Transfer RNA (tRNA) brings amino acids to
ribosomes, where they are joined together to form
proteins.
7. I. DNA, RNA, and protein synthesis
D. Protein synthesis
1. process in which cells make protein consists of
two processes: transcription and translation
8. I. DNA, RNA, and protein synthesis
2. Transcription
a. DNA → RNA
b. It occurs in the nucleus
c. During transcription, a copy of mRNA is made that is
complementary to a strand of DNA
9. I. DNA, RNA, and protein synthesis
3. Translation
a. RNA → protein
b. It occurs at a ribosome
c. During translation, a protein is synthesized using the
codons in mRNA as a guide
d. All three types of RNA play a role in translation.
10. I. DNA, RNA, and protein synthesis
E. Genetic code
1. The genetic code consists of the sequence of
bases in DNA or RNA.
a. Groups of three bases form codons, and each codon
stands for one amino acid (or start or stop).
b. The codons are read in sequence following the start
codon until a stop codon is reached.
c. The genetic code is universal, unambiguous, and
redundant.
12. II. Mutations
A. Causes of mutations
1. Spontaneously
2. Environmental factors (mutagen)
a. Radiation
b. Chemicals
c. Infectious Agents
13. II. Mutations
B. Types of mutations
1. Germline mutations
a. occur in gametes
b. significant because they can be transmitted to offspring
2. Somatic mutations
a. occur in other cells of the body
b. may have little effect on the organism because they are
confined to just one cell and its daughter cells
c. Cannot be passed on to offspring
14. II. Mutations
C. Chromosomal alterations
1. are mutations that change chromosome
structure
2. they occur when a section of a chromosome
breaks off and rejoins incorrectly or does not
rejoin at all
17. II. Mutations
D. Point mutations
1. change in a single nucleotide in DNA
Ex) UUU changed to UCU
Type Description Example Effect
Silent
mutated codon
codes for the same
amino acid
CAA (glutamine) →
CAG (glutamine)
none
Missense
mutated codon
codes for a
different amino
acid
CAA (glutamine) →
CCA (proline)
variable
Nonsense
mutated codon is a
premature stop
codon
CAA (glutamine) →
UAA (stop) usually
serious
18. II. Mutations
E. Frameshift
1. deletion or insertion of one or more nucleotides
that changes the reading frame of the base
sequence
2. frameshift mutation can dramatically change
how the codons in mRNA are read
3. this can have a drastic effect on the protein
product
19. II. Mutations
F. Effects of mutations
1. The majority of mutations have no effect or are
neutral mutations
2. Mutations that have a positive effect are
beneficial mutations
20. II. Mutations
3. Mutations that have a negative effect are
harmful mutations
a. Genetic disorder is a disease caused by a mutation in
one or a few genes
b. Cancer is a disease in which cells grow out of control
and form abnormal masses of cells
i. It is generally caused by mutations in genes that regulate
the cell cycle
