PCAT PCAT Genetics 3

Question 1

What is the central dogma of molecular biology?

Accepted Answer

DNA → RNA → Protein

Answer

The central dogma states that genetic information flows from DNA to RNA via transcription, then from RNA to protein via translation.

Question 2

Which enzyme synthesizes new DNA strands by adding complementary nucleotides during replication?

Accepted Answer

DNA polymerase

Answer

DNA polymerase adds complementary deoxyribonucleotides to the growing strand, always synthesizing in the 5' to 3' direction.

Question 3

A test cross involves mating an organism of unknown genotype with which type of individual?

Accepted Answer

Homozygous recessive

Answer

Crossing with a homozygous recessive individual reveals the unknown genotype because offspring phenotype ratios reflect the hidden alleles.

Question 4

Which inheritance pattern occurs when both alleles are simultaneously and fully expressed in a heterozygote?

Accepted Answer

Codominance

Answer

Codominance occurs when both alleles produce their distinct phenotypes simultaneously, as seen in AB blood type expressing both A and B antigens.

Question 5

Which type of point mutation creates a premature stop codon, causing early termination of protein synthesis?

Accepted Answer

Nonsense mutation

Answer

A nonsense mutation substitutes an amino acid codon with a stop codon, producing a truncated and usually nonfunctional protein.

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