Ap biology frq review answers answers: (2010)

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AP Biology FRQ Review ANSWERS

1. (2010)

Certain human genetic conditions, such as sickle cell anemia, result from single base-pair mutations in DNA.

(a) Explain how a single base-pair mutation in DNA can alter the structure and, in some cases, the function of a protein. (4 points maximum)

DNA (3 points maximum)

• Define mutation; change in bases: A, C, G or T.

• Describe type of mutation: duplication, frameshift, nonsense, deletion, substitution (point mutation).

• Describe central dogma: DNA  RNA  protein.

• Describe process of central dogma: transcription  translation.

• Translation of codons: 3 nucleotides  1 amino acid.

• Redundancy in genetic code: 64 combinations: 20 amino acids (or can result in “stop” codon).

Protein (3 points maximum)

• Describe altered protein structure: primary, secondary, tertiary, quaternary.

• Describe protein function change: active site conformation, oxygen binding.

• Describe structural change: hydrophobic/hydrophilic interactions, disulfide bonds, R-group interactions, hydrogen bonds.

(b) Explain, using a specific example, the potential consequences of the production of a mutant protein to the structure and function of the cells of an organism. (4 points maximum)

• Type of change: dominant, recessive.

• Changed protein  changed trait/character/function (gain or loss of function).

• Description of example (any trait).

• Description of protein structure or example after change.

• Description of function after change.

• Elaboration with sickle: mutation/effect in organism, Glu  Val, etc.

• Heterozygotic advantage (resistance to malaria).

(c) Describe how the frequency of an allele coding for a mutant protein may increase in a population over

time. (4 points maximum)

Hardy-Weinberg equation, with description (p2 + 2pq + q2 = 1; p + q = 1).

• Natural selection/adaptation, with description or example.

• Additional point for elaboration of natural selection.

o More born than will survive, variations in individuals, variations in gene pool, sexual

selection, adaptations to environment  differential reproductive success.

Small population, with description or example (genetic drift).

• Sexual selection or inbreeding, with description or example.

• Immigration/emigration/migration, wit

2. (2009)

(a) Describe the structure of the ATP or the GTP molecule. (1 point each; 2 points maximum)

• Adenosine + 3 phosphates or guanosine + 3 phosphates.

• Elaborating on the phosphate bonds, e.g., unstable, negatively charged.

Mentioning without explaining “high-energy bonds” is insufficient.

• Adenosine or guanosine described as adenine or guanine bound to ribose.

Note: adenine + ribose + 3 phosphates earns 2 points.

(b) Explain how chemiosmosis produces ATP. (1 point each; 3 points maximum)

• Electron transport, e.g., linked to proton pumps, coenzymes, NADH.

• H+ pumped to one side of the membrane, photosynthesis—inside thylakoid, respiration—outside cristae.

• Proton gradient established, has potential energy or capacity to do work.

• ATP synthases or channel proteins generate ATP.

(c) Describe TWO specific cell processes that require ATP and explain how ATP is used in each process.

(4 points maximum)

(d) An energy pyramid for a marine ecosystem is shown below. Label each trophic level of the pyramid and provide an example of a marine organism found at each level of this pyramid. Explain why the energy available at the top layer of the pyramid is a small percentage of the energy present at the bottom of the pyramid. (3 points maximum)

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