Transcript SBI3U - 5.1 Mendelian Genetics

5.1 Mendelian Inheritance
Monks are known for many
things…
Gregor Mendel (1822-1884)
• Austrian monk
• “the father of
modern genetics”
• https://www.youtube
.com/watch?v=0vAA
f4g5iF8
Pea Plant Experiments
• Mendel crossed true-breeding plants
(the P generation) to form hybrids (the
F1 generation)
• F1 generation were monohybrids
because they differed only in 1
characteristic
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
Take a look at yourself…
Which characteristics do you
think are 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?
Back to Mendel…
More terms…
• alleles are specific forms of genes;
some alleles are dominant, some
recessive
• phenotype is the outward appearance
of the genotype, which is the set of
alleles an individual has
• genotypes can be homozygous or
heterozygous
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’s genotype is homozygous or
heterozygous?
• Do a test cross…