PCAT PCAT Genetics 1 — Questions and Answers
Question 1: What is the probability of two heterozygous parents (Aa × Aa) producing a homozygous recessive offspring?
- 25% (Correct answer)
- 50%
- 75%
- 100%
Correct answer: 25%
In a monohybrid cross of Aa × Aa, the offspring ratio is 1 AA : 2 Aa : 1 aa, giving a 25% chance of the aa genotype.
Question 2: Which type of mutation involves the insertion or deletion of a nucleotide that causes a shift in the reading frame?
- Frameshift mutation (Correct answer)
- Point mutation
- Silent mutation
- Missense mutation
Correct answer: Frameshift mutation
Frameshift mutations result from insertions or deletions that shift the codon reading frame, altering all downstream amino acids.
Question 3: In incomplete dominance, what is the phenotype of a heterozygous individual?
- An intermediate phenotype (Correct answer)
- The dominant phenotype
- The recessive phenotype
- An unpredictable variable phenotype
Correct answer: An intermediate phenotype
Incomplete dominance produces a blended intermediate phenotype in heterozygotes, such as pink flowers from red and white parents.
Question 4: What term describes genes located on the same chromosome that tend to be inherited together?
- Linked genes (Correct answer)
- Alleles
- Homologous genes
- Codominant genes
Correct answer: Linked genes
Linked genes are physically located on the same chromosome and are transmitted together unless separated by crossing over.
Question 5: Which RNA molecule carries genetic information from the nucleus to the ribosomes?
- mRNA (Correct answer)
- tRNA
- rRNA
- snRNA
Correct answer: mRNA
Messenger RNA (mRNA) is transcribed from DNA in the nucleus and carries the coding sequence to ribosomes for translation.
Question 6: What is the process by which mRNA is used to synthesize a protein at the ribosome?
- Translation (Correct answer)
- Transcription
- Replication
- Transduction
Correct answer: Translation
Translation is the ribosomal process of reading mRNA codons and assembling the corresponding chain of amino acids into a protein.
PCAT PCAT Genetics 1
What is the probability of two heterozygous parents (Aa × Aa) producing a homozygous recessive offspring?