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.

New problemsBack to the course

In the print window, choose “Save as PDF” to keep a copy on your device.

1Formulas and methods

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

2Practice problems

1.GeneticsMedium
♂♀YXB​XB​Xb​

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 an unaffected son.

♀ XBXb♂ XBY
  1. 1XB × Y
  2. 2XB × XB
  3. 3Xb × Y
  4. 4Xb × XB
2.GeneticsHard
AAAa?Aa?aap (A)q (a)p (A)q (a)q² = 0.16f = ?

A recessive condition affects 16% of a population in Hardy–Weinberg equilibrium. What fraction f of the population are carriers (heterozygous)?

q² = 0.16
f =
3.Cell biologyMedium

The Golgi apparatus mainly:

  1. AProduces ATP
  2. BBreaks down old organelles and engulfed bacteria with enzymes
  3. CReplicates DNA
  4. DModifies, sorts and packages proteins for transport
4.Cell biologyHard

A double-stranded DNA sample contains 30% adenine. What percentage is guanine?

  1. A30%
  2. B70%
  3. C40%
  4. D20%

3Solutions

1.Genetics

Answer: XB × 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

XBY, XBXB, XbY, XbXB

Find the cell

XB × Y = XBY

Answer

Cell XB × Y → XBY
2.Genetics

Answer: f = 0.48

Hardy–Weinberg: in a large, randomly mating population with no selection, the allele frequencies p (dominant) and q (recessive), p + q = 1, give genotype frequencies p², 2pq and q².

Allele frequencies

q = √0.16 = 0.4
p = 1 − 0.4 = 0.6

Carriers

2pq = 2·0.6·0.4 = 0.48

Answer

f = 0.48
3.Cell biology

Answer: D · Modifies, sorts and packages proteins for transport

Why this is the answer

The Golgi modifies proteins (e.g. glycosylation) and sorts them into vesicles for secretion, membranes or lysosomes.

Answer

D · Modifies, sorts and packages proteins for transport
4.Cell biology

Answer: D · 20%

Why this is the answer

A = T = 30%, so A + T = 60%. The remaining 40% is split equally between G and C, so G = 20%.

Answer

D · 20%

ExamProblems · examproblems.com/courses/biology