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DefinitionsMonohybridCross
DihybridCross
Codominance, IncompleteDominance
Pedigrees,Sex-Linkage
The region of a chromosome that codes for one protein is called a
_____. A particular version of it is called an _____ and is usually
represented by one or more letters.
With respect to the gene for antler length in moose (letter G), suppose that the dominant phenotype is long antlers, and the recessive phenotype
is short stunted antlers.With respect to the gene for coat pattern (letter P), the recessive
phenotype is a white chest spot, and the dominant phenotype is no spot.A moose with the genotype Ggpp
will have this phenotype.
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Match Law with Illustrative Example:A. Law of DominanceB. Law of Segregation
C. Law of Independent Assortment
1. Because the genes for chin dimples and hitchhiker’s thumb are on different chromosomes,
these traits are not inherited together.2. A parent with the genotype YY will only produce
children with a dominant phenotype.3. A parent with the genotype UuTt produces
gametes with only one U/u allele and only one T/t allele.
One cat carries heterozygous, long-haired traits (Ss), and its
mate carries homozygous short-haired traits (ss). This is the
probability of an offspring with short hair.
One flower is heterozygous red (Rr) and it is crossed with a
homozygous white (rr) plant. This is the probability of red-
colored offspring.
In dogs, there is an hereditary deafness caused by a recessive gene, “d.” A kennel owner has a
male dog that she wants to use for breeding purposes if possible. The dog can hear, so he
must be either DD or Dd. If the dog’s genotype is Dd, the owner doesn’t to use him as a long-
term breeder. To find out, she breeds him with a deaf female (dd). They have 10 puppies.
If the male was heterozygous, this many puppies will be deaf. If he was homozygous, this many
puppies will be deaf.
Two plants with a dominant phenotype are crossed. 25% of their offspring have a recessive
phenotype.Therefore, these must have been their genotypes. (Homozygous
dominant, homozygous recessive, or heterozygous)
This is a cross showing a heterozygous male mated with a homozygous female.
A (1) aa Aa (3) aaa (2) Aa aa
The numbered boxes 1, 2, and 3 represent these three real-world cells
respectively.
What is the probability that the offspring of a cross of iikk x iiKK would have a dominant phenotype
for both genes?
A heterozygous platypus with twisted claws and pink foot pads
mates with another platypus who is homozygous recessive for both
traits.What are their odds of having
twisted-clawed, pink-foot-padded baby platypii?
Two black-eyed, orange-gilled fish are both heterozygous (BbGg).
What are their odds of having pale-eyed, pink-gilled offspring?
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A farmer has a female goat that is homozygous recessive for both a thin
coat and stunted hooves (tthh).He wants offspring with thick coats and
normal hooves. He has his choice of males that are TThh, TtHh, or TtHH. Which male is most likely to produce
thick-coated, normal-hooved offspring, and what chance does he have?
A frog with striped feet mates with a frog with spotted feet, producing
babies whose feet have both stripes and spots. It’s an example of this
kind of inheritance pattern.
Suppose koalas exhibit incomplete dominance with respect to nostril
color, and the letter N/n is used for the gene. If a black-nostrilled koala mates with a white-nostrilled koala,
what will be the phenotype and genotype of the offspring?
If color is incompletely dominant, what are the odds that a red flower and an orange flower could have
yellow offspring?
Recall that for blood type, A and B are codominant alleles while O is recessive to
both.In Mamma Mia, Sophie wants to know who her father is, but she could’ve saved herself
all that trouble. She has Type B blood, while her mother has Type A. Of her three possible fathers, Sam was Type O, Bill was type A, and Harry was type AB. Could any
of them be the right guy?
Recall that for blood type, A and B are codominant alleles while O is recessive to both. And when it
comes to Rh factor, + is dominant to -.
What are the odds that an AB+- mother and an AO-- father would
have a child with B- blood?
A woman who is XAXA has two children with a man who is XaY.
One is a daughter and the other is a son. What are the odds that at least one of the children has the recessive
phenotype?
Suppose a gene is carried on the Y-chromosome. A woman marries a
man who has the dominant phenotype for this gene. What are
the odds that a daughter would have the dominant phenotype, and what
are the odds that a son would?
If two blue-footed boobies with shiny feathers have five children, and one of them has dull feathers, are shiny feathers the dominant or recessive phenotype? (Making a
pedigree is recommended)
Hemophilia is recessive and X-linked in humans. What are the odds that a hemophiliac father and carrier mother would have a hemophiliac
son?
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Complete genotypes for this pedigree, and give probability that person 1 is heterozygous. Remember
shaded = recessive phenotype. Use the letter R/r.
1