The questions below all refer to the provided pedigree. In humans, the locus (M/m) is associated with
the regulation of dopamine synthesis in the brain. The mutation of this allele results in abnormal
dopamine signaling, which is connected to neurobehavioral disorders. Individuals with a mutated M
allele may experience cognitive impairments, motor dysfunction, and conditions such as Parkinson’s
disease and Attention Deficit Hyperactivity Disorder (ADHD). Research indicates that variations in the
M allele’s function can have a considerable influence on an individual’s risk for these neurobehavioral
disorders.
In the pedigree presented, black circles/squares indicate individuals affected by the disorder. White
circles/squares represent unaffected individuals. Carriers are not explicitly identified for you (you must
infer based on the information provided). It is assumed that if a trait is rare in a population (like this
one), we presume individuals marrying into the family are NOT carriers. Hint: Pay attention to the
symbols.
Reminder: Copying answers from a previous semester assignment’s is a violation of academic
integrity and will result in a zero for the assignment.
BIO 340 Spring 2024 — Recitation 3 Short Answer
Finding all the genotypes for everyone within the pedigree is extremely helpful but not graded.
1). Circle/Highlight the correct mode of transmission for this disorder (1point):
X-linked Recessive Autosomal Recessive
Y-linked X-linked Dominant
Autosomal Dominant Epistatic
3). What is the probability that II-5 is a carrier of this disorder? Show your work with a Punnett
Square in addition to stating the probability. (1 points total, 0.5 point for work and 0.5 point for
correct answer). Hint: We know the sex of II-5 and we know II-5 has an affected sibling.
2). Circle/Highlight ALL the potential genotype(s) of the based on the pedigree for the
following individuals (1 point):
XM = X-linked Dominant
XmX = X-linked Recessive Carrier
XmXm = X-linked Recessive Affected
I-1: MM / Mm / mm / XMX/ XmX / XmXm / XX / XMY / XmY / XY
II-2: MM / Mm / mm / XMX / XmX / XmXm / XX / XMY / XmY / XY
III-3: MM / Mm / mm / XMX / XmX / XmXm / XX / XMY / XmY / XY
IV-4: MM / Mm / mm / XMX / XmX / XmXm / XX / XMY / XmY / XY
4). If III-2 and III-3 have another child, what is the probability that they have a male child that
will have the disorder? Show your work with a Punnett Square, in addition to stating the probability.
(2 points total, 1 point for work and 1 point for correct answer)
Hint: Remember to factor in the probability of having a male child if the mode of transmission is
sex-linked.
5) IV-3 goes on an exotic vacation and meets the love of their life, Wendy. It is determined that
20% of the XX population where Wendy lives is a carrier for this disorder. If we assume Wendy
has the same risk of being a carrier as everyone else in their population (20%), what is the
probability that IV-3 and Wendy will have a male with the disorder? Show your work (via math
and/or Punnett squares, 1 point) in addition to stating the final probability (1 point). (2 points
total)
Hint: You will need to determine all the following information in order to calculate the final answer.
The probability that Wendy is a Carrier:
The probability that Wendy passes on a recessive allele:
The probability that an XX individual and an XY individual will have a XY child:
Final Probability that IV-3 and Wendy would have an affected male child: