Genetics
- Monohybrid cross (Aa × Aa)
- genotypes 1 : 2 : 1, phenotypes 3 : 1
- Dihybrid cross
- phenotypes 9 : 3 : 3 : 1
- Hardy–Weinberg
- p + q = 1, p² + 2pq + q² = 1
- Independent genes
- multiply the probabilities
Biology: Genetics and Cell Biology: cram pack
Formula sheets, the key method steps for every topic and 4 practice problems, with full solutions at the back.
1Formulas and methods
2Practice problems
1.GeneticsMedium
red-green colour blindness is X-linked recessive (allele b). A carrier mother, XBXb, has children with an unaffected father, XBY. The mother's gametes run down the side. Click the cell for a carrier daughter.
♀ XBXb♂ XBY
- 1XB × Y
- 2XB × XB
- 3Xb × Y
- 4Xb × XB
2.GeneticsHard
Two AaBb parents are crossed. Gene A gives round seeds (dominant) or wrinkled seeds; gene B gives black fur (dominant) or white fur. Click the one cell for an offspring that is homozygous for round seeds and shows white fur.
AaBb × AaBb
- 1Ab × aB
- 2Ab × AB
- 3Ab × ab
- 4Ab × Ab
- 5aB × aB
- 6aB × AB
- 7aB × ab
- 8aB × Ab
- 9ab × aB
- 10ab × AB
- 11ab × ab
- 12ab × Ab
- 13AB × aB
- 14AB × AB
- 15AB × ab
- 16AB × Ab
3.Cell biologyMedium
During which phase of mitosis do sister chromatids separate?
- AAnaphase
- BMetaphase
- CTelophase
- DProphase
4.Cell biologyHard
Cyanide is rapidly lethal because it inhibits which component of the cell?
- AHexokinase in glycolysis
- BThe Na⁺/K⁺ pump directly
- CATP synthase's rotor
- DCytochrome c oxidase (complex IV)
3Solutions
1.Genetics
Answer: Xb × XB
Punnett square: one parent's gametes run along the top, the other's down the side. Each cell joins the gamete above it with the gamete beside it, and every cell is equally likely. A recessive trait only shows when both alleles are recessive; for an X-linked trait, sons get their only X from the mother.
Fill the square
XBY, XBXB, XbY, XbXB
Find the cell
Xb × XB = XbXB
Answer
Cell Xb × XB → XbXB
2.Genetics
Answer: Ab × Ab
Punnett square: one parent's gametes run along the top, the other's down the side. Each cell joins the gamete above it with the gamete beside it, and every cell is equally likely. A recessive trait only shows when both alleles are recessive; for an X-linked trait, sons get their only X from the mother.
Genotype asked for
AAbb
Gametes
A homozygous genotype needs the same gamete from both parents, so only one cell in the 16 fits.
Ab × Ab = AAbb
Answer
Cell Ab × Ab → AAbb
3.Cell biology
Answer: A · Anaphase
Why this is the answer
In anaphase cohesin is cleaved and chromatids are pulled to opposite poles by spindle microtubules.
Answer
A · Anaphase
4.Cell biology
Answer: D · Cytochrome c oxidase (complex IV)
Why this is the answer
Cyanide binds cytochrome c oxidase and stops electron transfer to oxygen. The proton gradient collapses and aerobic ATP production stops.
Answer
D · Cytochrome c oxidase (complex IV)
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