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 affected father, XbY. The mother's gametes run down the side. Click the cell for a carrier daughter.
♀ XBXb♂ XbY
- 1Xb × Xb
- 2Xb × Y
- 3XB × Xb
- 4XB × Y
2.GeneticsHard
Two AaBb parents are crossed. Gene A gives yellow seeds (dominant) or green seeds; gene B gives purple flowers (dominant) or white flowers. Click the one cell for an offspring that is homozygous for yellow seeds and shows white flowers.
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
What is the net ATP yield of glycolysis per molecule of glucose?
- A2 ATP
- B36 ATP
- C1 ATP
- D4 ATP
4.Cell biologyHard
In the intrinsic (mitochondrial) pathway of apoptosis, which event leads to caspase activation?
- AFusion of lysosomes with the nucleus
- BBinding of a death ligand to the Fas receptor on the cell surface
- CEntry of glucose into the mitochondria
- DRelease of cytochrome c from mitochondria into the cytosol
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
XbXb, XbY, XBXb, XBY
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 · 2 ATP
Why this is the answer
Glycolysis uses 2 ATP and produces 4, a net gain of 2 ATP, plus 2 NADH and 2 pyruvate per glucose.
Answer
A · 2 ATP
4.Cell biology
Answer: D · Release of cytochrome c from mitochondria into the cytosol
Why this is the answer
Cell stress lets pro-apoptotic Bcl-2 family proteins release cytochrome c. With Apaf-1 it forms the apoptosome, which activates caspase-9. Fas binding starts the extrinsic pathway.
Answer
D · Release of cytochrome c from mitochondria into the cytosol
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