These seven original questions follow the four lessons in inheritance evidence rather than family assumptions. The families and organisms are fictional.
Try each question before opening the answer, and write the possibilities when the evidence does not settle a genotype.
Questions
Q1. Fictional pedigree: two unaffected parents have an affected daughter. Is the trait dominant or recessive, and what are the parents’ genotypes?
Answer
Recessive, since two unaffected parents had an affected child. Both parents are Aa, and the daughter is aa.
Q2. Why can a pedigree question not tell you about a real family’s genetic health?
Answer
It is a fictional method exercise with no medical or family detail about real people. A real family’s questions belong with a doctor or a genetic counsellor.
Q3. Cross Tt × Tt. A student says four offspring must give exactly one short plant. Correct the statement.
Answer
Each offspring has a 1 in 4 chance of being short. The expected count is one in four on average, but any number from none to four is possible.
Q4. In the same cross, what is the chance that two offspring are both short?
Answer
1/4 × 1/4 = 1/16, or 6.25%, because the offspring are independent.
Q5. A red-flowered plant (R dominant) is crossed with a white-flowered plant, and the offspring are half red and half white. State the red parent’s genotype and explain.
Answer
Rr. The white parent is rr and gives only r. A half-white result means the red parent also gave r, so it is heterozygous.
Q6. A tall plant (T dominant) is described only as tall. State its genotype.
Answer
TT or Tt. The phenotype does not separate them. A test cross with a short plant would decide.
Q7. Fictional family: two carrier parents (Aa × Aa) have an unaffected child. What is the chance the child is a carrier?
Answer
2 in 3. The outcomes are AA, Aa, Aa, aa, and the aa outcome is ruled out because the child is unaffected. Two of the remaining three are Aa.
If you got these wrong
Q1 and Q2 point to reading a fictional pedigree. Q3 and Q4 need probability for one offspring versus a family count.
Q5 and Q6 link to two genotypes, one phenotype. Q7 belongs to spotting missing information.
The claim, evidence and explanation revision desk and the mistake log help you repeat and track errors. For teacher support, see online one-to-one Biology tuition.