Class Notes (1,100,000)
CA (620,000)
McMaster (50,000)
BIOLOGY (2,000)
Lecture 4

BIOLOGY 1A03 Lecture Notes - Lecture 4: Protein Subunit, Centromere, Missense Mutation


Department
Biology
Course Code
BIOLOGY 1A03
Professor
Rosa Da Silva
Lecture
4

This preview shows pages 1-3. to view the full 11 pages of the document.
Module 4 DNA Mutations
UNIT I: HOW COMMON ARE MISTAKES?
VARYING MUTATION RATES
Mutations are the source of genetic variation
If errors at the nucleotide level are not corrected, the incorrect nucleotide bases can
be used as a template in the next replication round, resulting in mutation
propagation
Most animals have a low probability of acquiring a new mutation at a nucleotide pair
during replication
Viruses have a higher mutation rate, with RNA/retro viruses having the highest due to
delicate RNA backbone/no proofreading
SOMATIC VS. GERMLINE MUTATIONS
SOMATIC CELL
Cell will be the progenitor of a population of identical daughter cells following cell
division
The earlier in the developmental cascade in which a mutation occurs, the larger the
spread
If a mutation arises in a cell that is no longer dividing/in the G0 cycle, the effect is
largely negligible
Mutations are never passed onto progeny
GERMLINE CELL
Mutations are passed onto progeny- every cell in the developing embryo will carry the
mutation
find more resources at oneclass.com
find more resources at oneclass.com

Only pages 1-3 are available for preview. Some parts have been intentionally blurred.

JOSHUA & ESTHER LEDERBERG (1952)
Showed that mutations (i.e. antibiotic resistance) are random and not directed
Allowed bacterial growth into colonies in a petri dish with non-selective
supplemented nutrients/agar (agar plate I)
Following colony growth, the Lederbergs stamped the original plate I onto a cloth
They then stamped this cloth onto a new selective plate containing penicillin in the
agar, which only allows growth of penicillin-resistant bacteria
STAMPING/REPLICA PLATING: preserves relative arrangement of colonies on the new
plate relative to the first agar plate
Only a few colonies that were stamped from plate I survived the exposure to the
penicillin on plat II
Most other bacterial colonies were killed
The surviving colonies must carry a mutation that makes them penicillin-resistant
find more resources at oneclass.com
find more resources at oneclass.com

Only pages 1-3 are available for preview. Some parts have been intentionally blurred.

The process of replica plating means the original colony that grew on penicillin agar
could be isolated from original, non-selective agar and used to test the
hypothesis
Colonies on plate I would have never originally been exposed to penicillin
It can be concluded that the mutation existed in the population prior to penicillin
exposure
Evidence that mutations create random genetic variation
UNIT II: DNA REPAIR
DNA DAMAGE: CAUSES & CONSEQUENCES
Spontaneous/induced mutations occur frequently
Left uncorrected, mutations will lead to cell death, cancer, again, and disease
DNA can acquire mutations due to DNA replication errors, or mutagens/agents that
increase probability of mutations at specific regions along the strand
Most damage can be repaired by specialized enzymes such as DNA ligase which fix
breaks in the backbone
find more resources at oneclass.com
find more resources at oneclass.com
You're Reading a Preview

Unlock to view full version