Transcript Regulation of Gene Expression – Part III

Regulation of Gene Expression – Part III
Spring 2013 - Althoff Reference: Mader & Windelspecht Ch. 13)
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Lec
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Gene
Mutations
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Gene Mutations
A gene mutations is __________ change in the
_____________________ in DNA
The “change” can result in
a) no effect on protein activity to
b) complete inactivity
A ____________________ is one that occurs in
_______________ and can be passed to
subsequent generations.
A ____________________ is one that occurs in
___________—and therefore may only affect a
small number of cells in a tissue
Somatic mutations _________ passed on to
future generations
Causes – 2 basic types
• ________________ mutations = happen for no
apparent reason…a result of abnormalities in normal
biological processes
• ___________ mutations = induced by ____________
______________. They may result from exposure to
a) toxic chemicals
b) radiation
c) other?
These “exposures” “induce/cause” changes in
base sequences of DNA
Spontaneous Mutations
• Again, associated with “normal” biological processes
• Example: moveable piece of DNA, termed a
___________, may “jump” from location to another,
disrupting one or more genes…leading to an
abnormal product
Interrupted
DNA sequence
Spontaneous Mutations…con’t
• Again, associated with “normal” biological processes
• Example: On rare occasions, a base in DNA can
undergo a _________________ that leads to a
mispairing during replication…a subsequent base
pair change may be carried forth in future
generations
• This ↑example is a rare occurrence because….
_______________—the enzyme that carries out
replication—__________ the new strand against
the old strand and ________ mismatched
nucleotides…and _______ it with the correct one
• Estimates: only ___ mistake in every ___________
nucleotide pair replications
Induced Mutations
• Are known as _____________
• Those mutagens known to cause cancer are also
known as _______________
• Sources for chemical mutagens include:
a) food we eat
i) AF-2 once used in Japan – now banned
ii) Safrole flavoring agent once used in
root beer – now banned
iii) Acrylamide—a natural product found in
French fries—suspected mutage
b) industrial chemicals & tobacco smoke
i) tobacco changes several known organic
chemicals known as carcinogens
Induced Mutations…con’t
• Forms of radiation known to cause mutations:
X-rays
gamma rays
Ultraviolet (UV) radiation
• UV - absorbed by pyrimidines in DNA
• UV - if 2 thymine molecules next to one another, UV
radiation may cause them to bind together…forming
_______________. Result: kink in the DNA. They can
sometimes be repaired/removed by ____________
enzymes
Mutations effect on Protein Activity
• ____________________– change in a ________ DNA
nucleotide, and, therefore, possible change in a
specific amino acid
ex. What results in the cell
sickled red blood cell
• ____________________– occur most often when 1 or
more nucleotides are either a) inserted or b) deleted
from DNA. Result: a completely new sequence of
codons and nonfunctional protein.
Ex. THE CAT ATE THE RAT. If “C” is deleted, the
framework shifts resulting in…
THC ATA TET HER AT
Mutations Can Cause Cancer
• Current estimate: ________ people will develop
cancer at some time in their lives
--of the affected: 1/3 of the women will die
1/4 of the males will die
• 3 deadliest forms of cancer:
a) lung
b) colon and rectal
c) breast
• Cancer results from a series of accumulated mutations
as noted earlier this semester (see Lab 9 & text
Chapter 9)
Cancer…con’t
1• __________________ genes ordinarily act as brakes
on cell division…especially if abnormalities detected.
2• _______________ stimulate cell division but are
turned off in fully differentiated , non-dividing cells.
3• When proto-oncogenes mutate, they become
_______________ that are ______________________.
4• The result of 2 and 3: cell division occurs
_____________ because a ______________ pathway
that reaches from the plasma membrane to the
nucleus is non-functional.
Cell Signaling Pathway that Stimulates a
_______________ TUMOR SUPPRESSOR GENE
Cell Signaling Pathway that Stimulates an
_______________________
Cancer…con’t
• Recall ____________________from last lecture (#19)…
• One of the 5 ways to control
gene expression
• Transcription factors are
fundamental to
a) DNA replication &
repair
b) cell growth & division
c) __________________
d) __________________