Transcript SBI3U - Mendelian Genetics 5.1

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
• experiments with
garden peas
• “the father of
modern genetics”
• http://science.discovery.com/
tv-shows/greatestdiscoveries/videos/100greatest-discoveries-shortsgenetics.htm
Mendel’s Pea Plants Terms
• true-breeding
• hybrid
Mendel’s Experiments Terms
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P generation
F1 generation
monohybrids
monohybrid cross
F2 generation
Mendel’s conclusions
• organisms carry 2 “factors” for each
trait, one from each parent
• factors can be dominant or recessive
• law of segregation explains how only
one copy of each gene is in gametes
More terms…
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gene, allele
phenotype, genotype
homozygous, heterozygous
dominant allele, recessive allele
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
Test Cross
• An individual has the dominant
phenotype for a trait.
• How can you determine if the individual
is homozygous or heterozygous?
• Do a test cross…
Practice Questions
• Let’s look at the Practice questions you
did for homework (on pages 190 &
191)…