Download Mendelian Genetics, cont. Thursday, October 30, 2008 SI Leader

Mendelian Genetics, cont.
Thursday, October 30, 2008
SI Leader: Jenny F.
Review Question: What is the difference between genotype/phenotype?
Terms/Concepts: The Rule of Multiplication and the Rule of Addition- How do these relate to
Punnet squares?, Mendel’s Hypotheses, What do we know now about Mendel’s original
hypotheses?, How do you determine if something is true breeding?, Testcross,
monohybrid/dihybrid/trihybrid/multihybrid crosses, the Rule of Independent Assortment,
Incomplete Dominance, Alleles, Blood type allele example, Polygenic Inheritance, Human
Height Example/Human Eye Color Example/Human Skin Color Example, Chromosome Theory
of Inheritance
1. How do the Rule of Multiplication and the Rule of Addition differ?
-Rule of multiplication: the probability of obtaining a particular pair of gametes is equal to the
product of each individual gamete’s probability.
-Rule of addition: the probability of a particular combination of alleles is equal to the sum of all the
separate ways that combination can arise
2. Use the concepts in question 1 and a Punnet Square to determine the following question: A
female fruit fly with ebony body color (ee) and white eyes (ww) is mated with a male fruit fly
with normal body color (EE) and normal eye color (WW). What phenotypes exist? And at
what frequency?
3. The scientist conducting the experiment in question 2 accidentally crosses a fruit fly with
normal body color (Ee) and normal eye color (WW) with a fly with ebony body color (ee) and
white eyes (ww). What results should we expect? How do they differ from the “correct”
experiment in question 2?
4. What do we now know with certainty about Mendel’s original hypotheses?
Mendel hypothesized: Inheritance is “particulate”, Segregation of “particles” during
gamete production. One “particle”from each parent. Dominant and recessive forms.
What we now know for sure: These “particles”are genes – the basic units of inheritance,
Obtain genes from each parent, Dominant and recessive alleles exist, Diploid genome is
divided in half during gamete formation (i.e., during meiosis I)
5. What is a test cross? Give an example of two genotypes you would cross during a test
cross. A test cross is the method used to find out if something is true-breeding. You
cross an uknown with a known homozygous recessive. If you get all dominant
phenotypes- then true breeding. If you get a recessive genotype- then it means that
the organism in question was heterozygous.
6. What is the Rule of Independent Assortment (in YOUR own words)? Alleles for different
genes segregate independently during gamete production.
7. What is incomplete dominance? Give an example that we discussed in class. Dominance
is shared, no recessiveness. Red and white flower = pink
8. What possible GENOTYPES for A, B, AB, and O blood exist? (hint: you can draw out the
Punnet square if needed -> O A B along the top and O A B along the side). What
PHENOTYPES do each genotype display?
9. What is polygenic inheritance? Give three examples of this concept discussed in class.
A trait is governed by one or more gene (Is not like the “either/or” traits that Mendel
experimented with). They typically are expressed as continuous variation such as in:
eye color, skin color, and human height.
10. What is the Chromosome Theory of Inheritance?
•Chromosomes and genes both present in pairs in diploid organisms
•Homologous chromosomes and alleles segregate during meiosis
•Fertilization restores diploid condition