Download Review Packet

Review Packet
Genetics
Complete this review packet to help you prepare for the test. I t will be collected on test
day.
Vocabulary
Group 1: Genes
1. Gene
2. DNA
Group 3: Dihybrid Cross
3. Codon
1. Law of dominance/recessiveness
4. Amino Acid
2. Law of segregation
5. Protein
3. Law of independent assortment
6. Traits
7. Acquired
Group 4: Sex-linked
8. Inherited
1. Sex-linked
2. Autosomes
Group 2: Basic genetic rules
3. Sex chromosomes
1. Genotype
2. Phenotype
Group 5: Multiple alleles, polygenic
3. Allele
1. Multiple alleles
4. Homozygous dominant, recessive
2. Polygenic traits
5. Heterozygous
6. Complete dominance
Group 6: Pedigrees
7. Incomplete dominance
1. Pedigree
8. Co-dominance
2. Carrier
9. Test cross
Basic Genetic Rules



Be able to explain the difference between genotype and phenotype.
Be able to describe the different between complete dominance, incomplete dominance
and co-dominance.
Be able to solve basic punnet squares and give the phenotypic and genotypic ratios.
1. Rolling your tongue is a dominant trait. A male who can roll his tongue has a kid with a female that cannot roll
her tongue. The male is heterozygous for the tongue-rolling trait. What are the chances that the child can roll
his or her tongue? What are the chances that the child cannot roll his or her tongue?
2. A rooster with gray feathers is mated with a hen of the same phenotype. Among their offspring, 15 chicks
are gray, 6 are black and 8 are white. What is the simplest explanation for the inheritance of these colors
in chickens? What offspring would you predict from the mating of a gray rooster and a black hen?
3. Describe the difference between incomplete dominance and co-dominance.
Write in the color for each genotype below:
B = black
b = white
BB
Bb
bb
Complete dominance
Incomplete dominance
Co-dominance
4. A man has six fingers on each hand, and six toes on each foot. His wife and their daughter have
the normal number of digits. Extra digits is a dominant trait. What fraction of this couple’s
children would be expected to have extra digits?
Dihybrid


Be able to explain each of Mendel’s three rules.
Be able to do a dihybrid cross and determine the phenotypic and genotypic ratios
1. Summer squash:
Color: White fruit (Y) is dominant over yellow (y)
Shape: disc shape (D) dominant over spherical (d)
What would be the genotypic and phenotypic ratios in a cross between YyDd x Yydd?
What is the probability of getting a white, spherical squash?
2. Please give the phenotypic ratio of the offspring from the following cross:
AaBb x AaBb
3.
What is the probability that this pair of parents will produce the indicated offspring? AaBbCc x AaBbCc =
AabbCC. HINT: Multiply probabilities together!!
4. In some plants, a true breeding (homozygous), red-flowered strain gives all pink flowers when crossed with
a white flowered strain (RR(red) x rr(white) = Rr(pink)). If flower position (axial (aa) or terminal (A)) is
inherited as it is in peas, what will be the ratios of genotypes and phenotypes of the generation resulting
from the following cross: axial red (true-breeding) x terminal white (true-breeding)?
Sex-linked



Be able to assign X and Y chromosomes to males and females.
Understand where males and female get their X and Y chromosomes from.
Be able to do a sex-linked punnett square using X’s and Y’s.
1, If a female fruit fly heterozygous for red eyes (XRXr) is crossed with a white-eyed male (XrY), what percent of
their male offspring would have white eyes? Use a punnett square to prove your answer.
a. 0 %
b. 25 %
c. 50 %
d. 75 %
e. 100 %
2. One pair of genes for coat color in cats is sex-linked. The gene B produces yellow coat, b produces black
coat, and the heterozygous Bb produces tortoise-shell coat. What kind of offspring will result from the
mating of a black male and a tortoise-shell female?
3. A girl is a hemophiliac (a sex-linked, recessive disease).
a. What are the possible genotypes and phenotypes of her parents?
b. Assuming that her mother is normal, what were this girl’s chances of being born with the disease?
c. Our girl gets married to a boy who is normal. What is the probability that their first child with be a boy
with hemophilia?
d. Their first child is a girl – what is the probability that she will be a hemophiliac?
5.
A disorder, such as red-green color-blindness, which occurs more often in males than females is
best described as being:
a. sex linked
b. homozygous recessive
c. heterozygous
d. homozygous dominant
Multiple Alleles & Polygenic Traits



Be able to explain what multiple alleles and polygenic traits are.
For blood typing, be able to explain which alleles are dominant and recessive.
Be able to do a punnett square for blood types.
1. Imagine that a newly discovered, recessively inherited disease is expressed only in individuals
with type O blood, although the disease and blood group are independently inherited. A normal
man with type A blood and a normal woman with type B blood have already had one child with
the disease. The woman is now pregnant for a second time. What is the probability that the
second child will also have the disease? Also, please give the genotypic ratio for the possible
outcomes.
2. A man with type A blood marries a woman with type B blood. Their child has type O blood. What are the
genotypes of these individuals? What other genotypes, and in what ratio, would you expect in offspring
from this marriage?
3. Color pattern in a species of duck is determined by one gene with three alleles. Alleles H and I are
codominant, and allele k is recessive to both. How many phenotypes are possible in a flock of ducks that
contains all the possible combinations of these three alleles?
4. A particular characteristic is classified as polygenic when:
a. the alleles of the gene controlling the characteristic are heterozygous
b. the alleles of the gene controlling the characteristic are homozygous
c. the characteristic results from the influence of a number of different genes
d. the gene locus for the characteristic is frequently involved in the crossing over process
Pedigrees & Random

Be able to interpret pedigrees and assign genotypes to individuals.
1. Karen and Steve each have a sibling with sickle-cell disease. Neither Karen, Steve, nor any of
their parents has the disease, and none of them have been tested to reveal sickle cell trait. Based on
this incomplete information, calculate the probability that if this couple has a child, the child will have
sickle-cell disease. Sickle-cell is an autosomal, recessive disease.
2. Imagine you are a genetic counselor, and a couple planning to start a family came to you for
information. Charles was married once before, and he and his first wife had a child who has
cystic fibrosis (cystic fibrosis is an autosomal, recessive disorder). The brother of his current wife
Elaine died of cystic fibrosis. Please create a pedigree with this information, and then determine
the probability that Charles and Elaine will have a baby with cystic fibrosis (Neither Charles, nor
Elaine, nor their parents have cystic fibrosis).
3. Using a basic cross between a red (RR) and a white (rr) flower, please describe the following:
The offspring phenotypic ratio resulting from complete dominance
The offspring phenotypic ratio resulting from incomplete dominance
The offspring phenotypic ratio resulting from co-dominance
How could you expand this cross to be a dihybrid cross?
4. How many possible phenotypes would you expect from the following crosses
Complete Dominance
Incomplete Dominance
Co-dominance
Multiple alleles
Polygenic traits