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
Duchenne muscular dystrophy is X-linked recessive (allele d). A carrier mother, XDXd, has children with an unaffected father, XDY. The mother's gametes run down the side. Click the cell for a carrier daughter.
♀ XDXd♂ XDY
- 1XD × XD
- 2XD × Y
- 3Xd × XD
- 4Xd × Y
2.GeneticsHard
Two AaBb parents are crossed. Gene A gives tall plants (dominant) or short plants; gene B gives yellow seeds (dominant) or green seeds. Click the one cell for an offspring that is homozygous for tall plants and shows green 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
Which tag added in the Golgi sends enzymes to the lysosomes?
- AA nuclear localisation signal
- BUbiquitin
- CMannose-6-phosphate
- DA KDEL sequence
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?
- ACytolysis
- BHaemolysis
- CPlasmolysis
- DTurgor
3Solutions
1.Genetics
Answer: Xd × XD
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
XDXD, XDY, XdXD, XdY
Find the cell
Xd × XD = XdXD
Answer
Cell Xd × XD → XdXD
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: C · Mannose-6-phosphate
Why this is the answer
In the Golgi, lysosomal enzymes receive mannose-6-phosphate. Receptors that bind this tag package them into vesicles bound for lysosomes.
Answer
C · Mannose-6-phosphate
4.Cell biology
Answer: C · 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
C · Plasmolysis
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