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.

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

haemophilia is X-linked recessive (allele h). A carrier mother, X^HX^h, has children with an unaffected father, X^HY. The mother's gametes run down the side. Click the cell for an affected son.

♀ X^HX^h♂ X^HY

1X^h × Y
2X^h × X^H
3X^H × Y
4X^H × X^H

2.GeneticsHard

In a population of 10000 in Hardy–Weinberg equilibrium, 9% show a recessive trait. How many individuals N are expected to be homozygous dominant?

N = 10000q² = 0.09

N =

3.Cell biologyMedium

What directly drives ATP synthase to make ATP in mitochondria?

AElectrons from NADH flowing directly through ATP synthase
BOxygen diffusing into the matrix
CProtons flowing back into the matrix down their gradient
DGlucose binding to ATP synthase

4.Cell biologyHard

Avery, MacLeod and McCarty treated the transforming extract with different enzymes. Which result showed that DNA was the transforming principle?

ANone of the enzymes had any effect
BOnly protease destroyed the transforming activity
COnly RNase destroyed the transforming activity
DOnly DNase destroyed the transforming activity

3Solutions

1.Genetics

Answer: X^h × 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

X^hY, X^hX^H, X^HY, X^HX^H

Find the cell

X^h × Y = X^hY

Answer

Cell X^h × Y → X^hY

2.Genetics

Answer: N = 4900

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 = √0.09 = 0.3

p = 0.7

Homozygous dominant

p² = 0.49

N = 10000·0.49 = 4900

Answer

N = 4900

3.Cell biology

Answer: C · Protons flowing back into the matrix down their gradient

Why this is the answer

The electron transport chain pumps protons into the intermembrane space. Their flow back through ATP synthase turns it and powers ATP synthesis.

Answer

C · Protons flowing back into the matrix down their gradient

4.Cell biology

Answer: D · Only DNase destroyed the transforming activity

Why this is the answer

Transformation still happened after proteases and RNase, but not after DNase. This showed that DNA, not protein or RNA, carried the hereditary information.

Answer

D · Only DNase destroyed the transforming activity

ExamProblems · examproblems.com/courses/biology