Transcript SBI3C - Genetics 2

Heredity
We know that traits are
inherited, but how?
• What characteristics do you have in
common with your parents? Your
grandparents?
• If you have siblings, what characteristics
do you have in common with them?
Take a look at yourself…
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Dominant or Recessive?
Cheek Dimples
• cheek dimples are
dominant
Brown/black eyes?
• brown/black eyes
are dominant over
blue/green eyes
Attached Earlobes?
• attached earlobes
are recessive
Widow’s Peak?
• pointed hairline is
dominant over
straight hairline
Hitchhiker’s thumb?
• a straight thumb is
dominant over a
bent thumb
Tongue roller?
• the ability to roll your
tongue is dominant
Left thumb on top?
• when you fold your
hands, the left
thumb on top is
dominant over the
right thumb on top
6 fingers?
• polydactyly is
dominant
How are these traits inherited?
Monks are known for many
things…
Gregor Mendel (1822-1884)
• Austrian monk
• did experiments with
garden peas that laid
the foundation for
modern genetics
• “the father of modern
genetics”
•
http://science.discovery.com/tvshows/greatestdiscoveries/videos/100greatest-discoveries-shortsgenetics.htm
Mendel’s conclusions
• inherited characteristics are controlled
by factors that occur in pairs
• one factor masks the effect of another
(the principle of dominance)
• a pair of factors separate during the
formation of sex cells
• each sex cell contains only one factor
for each characteristic
Punnett square
• chart that organizes the possible
combination of “factors” in offspring
• See this website for a simple animation
on creating a Punnett square:
• http://www.ctahr.hawaii.edu/dnatoday/g
enepool/genepool%20think.html
Questions
• Read 4.2 (p.134-137) and answer the
following questions: #1,3 (p. 137-138)