Biology: Genetics and Cell Biology: practice problems and exam questions

Mendelian genetics, crosses and probabilities, and the structure and processes of the cell.

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Cram pack (PDF)Formula sheets, method steps and practice problems with full solutions, ready to print.

Topics in this course

  1. Geneticsmonohybrid crosses · dihybrid crosses · Hardy–Weinbergcalculations
  2. Cell biologykey terms and facts · applying the concepts · cases and analysismultiple choice

Exam tips for Biology: Genetics and Cell Biology

  • Write out the Punnett square, even for a simple cross.
  • Keep genotype and phenotype ratios apart.
  • Link every organelle to its function.

Worked examples

GeneticsEasy
Aa ♀aa ♂Aaaa????

In pea plants, purple flowers (A) are dominant over white (a). A plant with genotype Aa is crossed with a plant with genotype aa. What is the probability P that an offspring has purple flowers?

Aa × aa

Find P

Show hints
  1. Write the gametes of each parent and fill in the Punnett square.
  2. Each of the four boxes is equally likely.
  3. Purple shows with at least one A: AA or Aa.
Show the answer and the step-by-step solution

Mendelian genetics: each parent passes on one allele of each gene, chosen at random. A Punnett square lists every combination of gametes, each equally likely. A dominant allele (capital letter) shows whenever it is present; a recessive one only in the homozygous form. Genes on different chromosomes are inherited independently, so their probabilities multiply.

Punnett square

Aa, Aa, aa, aa

Count

P = 2/4 = 0.5

Answer

P = 0.5
Cell biologyMedium

How do steroid hormones such as cortisol mainly act on their target cells?

  1. AThey are taken up by phagocytosis and digested
  2. BThey bind a membrane receptor and open ion channels, changing the cell's membrane potential
  3. CThey activate adenylyl cyclase from outside the cell
  4. DThey cross the membrane and bind intracellular receptors that change gene transcription
Show hints
  1. Steroids are lipid-soluble.
  2. Two wrong answers are now crossed out. One of the remaining two is right.
Show the answer and explanation

Why this is the answer

Steroids diffuse through the membrane and bind receptors in the cytoplasm or nucleus. The hormone–receptor complex acts as a transcription factor.

Answer

D · They cross the membrane and bind intracellular receptors that change gene transcription

How practising works

  • “Practise this course” mixes problems from all its topics, like a real exam.
  • Every problem has new values, so you learn the method instead of an answer.
  • Stuck? Open a small hint first, and the full explanation only when you need it.
  • Mock exams are timed and have no hints, and you get your score and a full review at the end.

Calculators for this course

Punnett square calculator

Related courses

General Chemistry
Practise this course for freePractise this courseTake a mock exam5 free problems every day. No card needed.