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
haemophilia is X-linked recessive (allele h). A carrier mother, XHXh, has children with an unaffected father, XHY. The mother's gametes run down the side. Click the cell for an affected son.
♀ XHXh♂ XHY
- 1XH × XH
- 2XH × Y
- 3Xh × XH
- 4Xh × Y
2.GeneticsHard
Two AaBb parents are crossed. Gene A gives purple flowers (dominant) or white flowers; gene B gives round seeds (dominant) or wrinkled seeds. Click the one cell for an offspring that is shows both white flowers and wrinkled seeds.
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
Gut epithelial cells take up glucose against its gradient with a sodium–glucose cotransporter. What kind of transport is this?
- AFacilitated diffusion
- BSecondary active transport
- CPrimary active transport
- DSimple diffusion
4.Cell biologyHard
A plant cell placed in a concentrated salt solution loses water and its membrane pulls away from the cell wall. What is this called?
- AHaemolysis
- BTurgor
- CCytolysis
- DPlasmolysis
3Solutions
1.Genetics
Answer: Xh × Y
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
XHXH, XHY, XhXH, XhY
Find the cell
Xh × Y = XhY
Answer
Cell Xh × Y → XhY
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: B · Secondary active transport
Why this is the answer
The Na⁺/K⁺ pump uses ATP to make a sodium gradient. SGLT1 uses the energy of sodium flowing in to drag glucose in against its gradient.
Answer
B · Secondary active transport
4.Cell biology
Answer: D · Plasmolysis
Why this is the answer
In a hypertonic solution water leaves the vacuole by osmosis. The protoplast shrinks away from the rigid wall, which is plasmolysis.
Answer
D · Plasmolysis
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