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GENE
EXPRESSION Individuality & Mutations
I. Are all genes turned on in all cells?
The answer is NO!
Every body cell contains your DNA (genetic
make-up)
Cells “use” only genes specific for function
EX. Red blood cells use only genes that
make it carry oxygen
Can you list more examples of
proteins made? Enzymes, insulin, cell membrane, hair, muscles
**THEREFORE, NOT ALL DNA IS
EXPRESSED (MADE INTO PROTEIN) IN EVERY CELL!**
This video segment investigates why one
species of fruit fly has wing spots while
another genetically similar one does not.
As the video explains, although two
organisms may both possess the same
gene linked to a particular trait, this trait
may not be expressed unless the gene is
turned on
4
Turning genes on video (5 min):
http://www.teachersdomain.org/reso
urce/novat10.sci.life.evo.fruitfly/
II. Review: Determining Sex Human Chromosomes
46 in a normal human cell!
Two types: a) Normal chromosomes: 44 in each BODY CELL; 22 in each
GAMETE (sex cell) b) Sex chromosomes: 2 in each BODY CELL; 1 in each
GAMETE (sex cell) MALE: X and Y FEMALE: X and X
Is this a
male or a
female??
Karyotype
Chances for having a boy or girl? 50% OF
COURSE…LET’S SEE!
X Y
X X
XX
XX XY
XY
http://www.brainpop.com/science/cellularlifeandgenetics/geneticmutatio (2:33)ns
DNA fails to copy accurately
III. Mutations: What happens when DNA goes wrong
A change in the genetic material which effect genetic information and traits
Not all mutations are bad, some are beneficial
Ultimate source of genetic variation (depends on environment)
MUTATIONS MUST OCCUR IN SEX CELLS IN ORDER FOR THEM TO BE PASSED ON TO NEXT GENERATION!!!!!!!!!!
When do mutations occur?
During replication (meiosis / mitosis) and protein synthesis
Mutations caused by Mutagenic Agents:
1. Radiation
x- rays, UV, radioactive substances
2. Chemicals
formaldehyde, benzene, asbestos fibers, nicotine
A. Chromosomal Mutations Change in number of chromosomes or structure
Ex: normal human body cell = 46 Human Karyotype Arrangement of a male
Types of Chromosomal Mutations 1. Deletion
A portion of a chromosome is taken
away form a chromosome
2. Duplication
A portion of one chromosome
breaks off and is attached to its
homologous chromosome giving it
an extra copy
3. Inversion
A portion of a chromosome breaks
off and then becomes reattached to
the same chromosome in an
inverted (upside down) fashion
4. Translocation
transfer of one section of a
chromosome
Genetic Disorders Relating to
chromosomal mutations
Down Syndrome
Due to nondisjunction
failure of homologous
chromosomes to
separate during
meiosis
An extra
chromosome 21
Klinefelter Syndrome
• XXY abnormal sexual development and infertility
B. Gene Mutations
A random change in DNA sequence
**Review** What does DNA ultimately code for?
Proteins!!!
Is construction of protein based on original DNA strand?
Yes! (b/c it is what codes for mRNA)
What would happen to the protein if DNA sequence
was changed?
Wrong protein made
Wrong shape of protein
This would make protein unusable
DNA MUTATION VIDEO
http://www.bing.com/videos/search?q=mutation+videos&FORM=VIRE6#v
iew=detail&mid=0F73B8E85CE1098084470F73B8E85CE109808447
A. POINT MUTATION: affects 1 nucelotide (base)
Example: CTC on DNA makes mRNA = GAG codes for
GLUTAMINE If T changed to A, would have GUG which codes for VALINE
Wrong AMINO ACID is coded for which means, wrong
PROTEIN is made
Types of Gene Mutations
B. FRAME-SHIFT: A base is deleted or added
Example: TCA-TTT on DNA;
mRNA = AGU-AAA on codes for Serine + Lysine
If the T is deleted in the DNA, the mRNA would now
read GUA-AA
rRNA will CODE “GUA” first which is for Valine
1. Similar if a base is added
2. Wrong AMINO ACID is coded for = wrong PROTEIN is
made OR Translation will abruptly STOP
Disorders from Gene Mutations
Sickle cell anemia – Sickle shaped
cells get caught in capillaries (can’t
transport oxygen sufficiently)
Cystic Fibrosis- affects recessive allele
mutating the CFTR gene
Normal red
blood cells (top)
and sickle cells
(bottom)
IV. Environmental Expression
Some genes are “turned on” under certain environmental conditions.
EX. Himalayan Rabbit: Fur changes color due to TEMPERATURE change WARM = White fur (no pigment
produced)
COLD = Black fur
Why does this make sense? Because black absorbs the heat,
helping little bunny rabbit to stay warm
• How do we know that traits and diseases are genetically related?
• THE HUMAN GENOME PROJECT
• What is it? Project to identify the location of 30,000 genes
• Why do it? To identify the locations of genetic diseases and possibly control and/or eliminate them
• How far along are we? The map was completed in 2004
V. The Human Genome
Class and/or Homework:
Topic 3 RB pages 50-52
Read these pages and answer questions 23-31 on loose leaf paper
Topic 3 RB pgs 50-52
23) 4
24)a gene mutation is a change in the instructions of the gene. The nitrogenous bases forms the code instructions, so changing this sequence would alter the amino acid/protein
25) 3
26) 2
27) 4
28) 1
29) 1
30) 4
31) 1