Transcript Slide 1 - Port Fest Baltimore 2015

Mutations in Human Genes
Independent Research!
You will conduct your own independent research in order to
explain how mutations can cause genetic disorders in humans.
Write to explain the following:
• Explain the “steps” of how a mutation goes from DNA to
protein.
• What is a mutation?
• What is sickle cell anemia? What PROTEIN is affected by this
disorder? (2)
• What is hemophilia? Why does hemophilia affect men more
often? (2) ** You will learn more about this today!
Are you COLORblind?
Are you COLORblind?
Take the test!
Write down the numbers that you see. You only
have 3 seconds for each number.
How did you do!?
Do you see a picture below?
What number do you see?
2?
An individual with Red/Green color blindness
will see a 2 revealed in the dots.
5?
An individual with normal color vision will
see a 5 revealed in the dots.
COLORblindness
• About 1 in 10 males in the U.S. is colorblind
• Only 1 in 100 females is colorblind
• Why is this such a big difference?
COLORblindness
• About 1 in 10 males in the U.S. is colorblind
• Only 1 in 100 females is colorblind
• Why is this such a big difference?
The gene for being colorblind is on the X chromosome.
If a man's one X chromosome is color defective he will
be colorblind; a woman must inherit two color defective
X chromosomes to be colorblind (1 from each parent).
Sex-Linked
Genes
Chromosomes
What are sex chromosomes?
• Sex chromosomes = X or Y (Male XY,Female XX)
What are autosomes?
• Autosomes = chromosomes that are not sex
chromosomes
What are
Sex-Linked Traits?
• Certain disorders are sex-linked, passed from
mother  son by a defective gene on the X
chromosome.
• In females, sex chromosomes = XX
• In males = XY
•
What are examples Sex-Linked
Genes?
1.
Red-green color blindness (very common in males)
– Cannot distinguish red from green
2.
Hemophilia (affects more males)
– blood does not clot properly; can literally bleed to
death
3.
Muscular dystrophy (carried by females)
– gradual deterioration of muscle cells, short life
spans
Sex-Linked Genes in Fruit Flies
Drosophila melanogaster
Why are these diseases so
prevalent in males?
Answer:
– Genes are located on
X chromosome and
are recessive
– Women have two X
chromosomes (XX),
so the normal one will
be dominant.
– Men only have one X
chromosome, so if it
carries the gene, then
they will express it.
XB = normal vision Xb = colorblind
Punnett Practice
Rachel’s dad is colorblind but her mom isn’t. However,
she is colorblind. How is this possible? Draw a Punnett
Square to show your answer.
What is Rachel’s genotype?
What are the chances that Rachel’s parents produce
more colorblind children?
Sex-Linked Genes Quiz
• 1. Sex-linked genetically inherited traits: a) can appear in both
males and females b) are only found in males c) are only found in
females d) result from premarital sexual intercourse
• 2. Y-linked traits are inherited: a) only by females b) only by
males c) by both males and females
• 3. Harmful X-linked traits are: a) inherited only from mothers
b) more numerous than Y-linked ones c) most likely to show up in
the phenotype of daughters
• 4. Red-green color blindness is: a) an X-linked trait b) a Y-linked
trait c) both X and Y linked
• 5. Men with red-green color blindness inherited the genes for it
from: a) their mothers b) their fathers c) either their mothers or
fathers
Exit Quiz: Punnett Practice
Travis has muscular dystrophy but his older brothers do
not. His mother and father are both normal. Draw a
Punnett Square to show his parents’ genotypes.
Can his brothers (who are normal) carry the gene for
muscular dystrophy?