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Unit 8: Genetics- Study Guide
8a. Meiotic Errors and Karyotypes
1. Vocabulary
a. Nondisjunction-
b. Monosomy-
c. Trisomy-
d. Karyotype-
2. How does nondisjunction occur?
3. What chromosomes are affected by each of these conditions? How are they affected?
a. Downs Syndrome-
b. Edwards Syndrome-
c. XXX Syndrome-
d. Turner Syndrome-
4. What sorts of information can a karyotype provide?
a.
b.
c.
5. Be able to identify a monosomy or trisomy from a karyotype and determine an individuals sex.
8b. Mendelian Genetics and Punnett Squares
1. Vocabulary
a. Trait-
b. Cross-
c. Gene-
d. Locus-
e. Genotype-
f. Phenotype-
g. Dominant allele-
h. Recessive allele-
i. Homozygous-
j. Heterozygous-
2. Who was the father of genetics?
a. What organism did he study?
b. What were his three laws of inheritance?
i.ii.
iii.
3. Given a written scenario, be able to determine that it is describing this type of inheritance.
4. Know how to use a Punnett Square. (See word problems later in document for practice)
a. Given information you must be able to draw a Punnett square and use it to answer the
following questions
i. Genotypes present (both parental and offspring)
ii. Phenotypes present (both parental and offspring)
iii. Probability of genotypes
iv. Probability of phenotypes
8c. Sex-Linked Inheritance
1. Given a written scenario, be able to determine that it is describing this type of inheritance.
2. What is the normal sex genotype that produces a:
a. Male?
b. Female?
3. What is different about the X and Y chromosomes?
a. X chromosome-
b. Y chromosome-
4. Who (if anyone) is more likely to inherit a recessive X-linked trait? Why?
5. Who (if anyone) is more likely to inherit a dominant X-linked trait? Why?
6. Be able to do a Punnett square describing the phenotype and genotype of the offspring and/or
parents. (See word problems later in document for practice)
a. Make sure to include X and Y chromosomes!
8d. Pedigrees
1. How are each of the following represented on a pedigree?
a. Male-
b. Female-
c. Person with trait-
d. Person without trait-
e. Carrier-
2. If a trait is dominant there can be no ______________________ in the pedigree.
3. If a trait is sex-linked recessive no males can be a ______________________.
4. Be able to identify information about individuals on a pedigree given their number location on
the diagram. (See problem later on in document for practice)Genetic Word Problems
8b. Mendelian Genetics
> 1.
Let's say that in seals, the gene for the length of the whiskers has two alleles. The dominant
allele (W) codes long whiskers & the recessive allele (w) codes for short whiskers. There are
only two phenotypes for this trait.
a. What percentage of offspring would be expected to have short whiskers from the cross
of two long-whiskered seals, one that is homozygous dominant and one that is
heterozygous?
> b.
If one parent seal is pure long-whiskered and the other is short-whiskered, what
percent of offspring would have short whiskers?
2. In purple people eaters, one-horn is dominant and no horn is recessive. Draw a Punnett Square
showing the cross of a purple people eater that is heterozygous for horns with a purple people
eater that does not have horns. What genotypes and phenotypes are possible for offspring?
What is the probability of each?
# 3. Woodrats are medium sized rodents with lots of interesting behaviors. You may know of them
as packrats. Let's assume that the trait of bringing home shiny objects (H) is controlled by a
single locus gene and is dominant to the trait of carrying home only dull objects (h). Suppose
two heterozygous individuals are crossed. If 100 offspring were observed, how many of each
genotype would be expected? How many of each phenotype?4. The ability to curl your tongue up on the sides (T, tongue rolling) is dominant to not being able
to roll your tongue. A woman who can roll her tongue marries a man who cannot. Their first
child has his father's phenotype. What are the genotypes of the mother, father, and child?
a. What is the probability that their second child won't be a tongue roller?
8c. Sex-Linked Traits
1. Red-green color-blindness is a sex-linked trait, recessive trait associated with the X
chromosome and is designated as c. Normal vision is dominant and is designated as C. If a
colorblind woman married a man with normal vision, what are the genotypic and phenotypic
ratios of their offspring? Could any of their daughters be colorblind?
2. If a father and his son are both colorblind, is it possible that he inherited this trait from his
father? Why or why not?
3. Bent is a dominant sex-linked trait, B, and causes short, crooked tails in mice. If a normal
tailed female, b, is mated to a bent tailed male, what are the genotypic and phenotypic ratios of
their F1 offspring?4. Hemophilia is a sex-linked recessive trait designated with h. The normal blood clotting
mechanism is dominant and designated with H. A non-hemophiliac man marries a
non-hemophiliac woman whose father was a hemophiliac. What are the genotypes and
phenotypes of the couple and their future offspring?
8d. Pedigrees
1. This trait is mostly likely _________________________________ because there are no carriers.
2. Identify the sex and phenotype for individual III-3. _________________________________
3. Identify the sex and phenotype for individual II-6. _________________________________
4. If there was a carrier how would this be represented in one of the shapes?
5. This trait is likely on a _________________________________ chromosome because men and women are
equally affected.