Chap 14:
Mendel and the Gene
Supplemental Instruction
Iowa State University
Leader: Julie
Course: Biology 211
Instructor: Dr. Holscher
Date:
1. Many recessive ____-linked traits cause human diseases and disorders
2. Fathers pass sex-linked alleles to all of their ___ _____, but to none of their ______.
Ex: You’re researching color blindness in a family. You already know the parents phenotypes:
The husband is color blind but the wife is not. Of their eight children, half are boys and half are
girls. You know that there are 2 boys with color blindness and 2 girls with color blindness. How
is this possible if only their father has colorblindness?
Ex: You realize that studying x-linked recessive traits is so much fun and decided to do more!
You come across another family. The father is colorblind and the mother is not. One of their sons
is colorblind also, except he is pissed about it! He hardly speaks to his father because he blames
him for making him colorblind. With all your genetic knowledge how might you council this boy
to help his relationship with his father?
1.
a.
b.
c.
Simple Mendelian patterns may deviate when:
A single gene produces multiple _________.
When _________ are not completely dominant or recessive.
When a particular _______has more than two alleles.
2. Most genes have multiple phenotypic effects. This is called?
3. Describe the difference between Complete and Incomplete dominance.
4. True or False: Dominant alleles are always more common in population than recessive
alleles.
5. Traits that are “either or” traits are referred to as what?
6. Traits that vary in a population along a continuum creating a bell shaped curve are
called what?
7. Who was the first scientist to associate a specific gene with a specific chromosome?
8. A normal character phenotype is referred to as what? Alternative traits are called?
Supplemental Instruction
1060 Hixson-Lied Student Success Center  294-6624  www.si.iastate.edu
9. Morgan’s three proposed ideas:
i. Genes are said to be _ ______ and are inherited together as a unit
called a _________ _________.
ii. Due to ______ __ ______ during meiosis, __________ chromosomes
can exchange pieces of chromosomes and create new combinations of
________.
iii. The likely hood of a crossover occurring in the region between two
genes depends on the ________ between the two genes.
10. Explain what a genetic map is? What is it based on (what makes it)?
11. Recombination frequency
12. True or False: The farther apart two genes are, the higher the probability that a cross over
will occur?
The Challenger Question!
In a particular animal species, a long tail (T) is dominant to a short tail (t), and a blonde hair (B)
is dominant to grey hair (b). When a TtBb female is mated with a ttbb male, the observed
distribution of offspring is as follows 411 offspring with a long tail and blonde hair, 101
offspring with a long tail and grey hair, 312 offspring with a short tail and blonde hair, and 386
offspring with a short tail and grey hair. Based on these offspring, what is the approximate
recombination frequency?