Challenge Your DNA Genetics Knowledge Quiz

1. He genetic code is essentially the same for all organisms. What can be inferred from this?

Genes cannot move between species

Different organisms cannot express foreign genes

All organisms share identical traits

A gene from one organism can be expressed in another

Because the genetic code is universal, the same codons specify the same amino acids in all organisms. This allows genes transferred between species to be expressed correctly, which is the basis of genetic engineering. For example, bacterial cells can express human genes such as insulin because they interpret the genetic code in the same way.

Explanation

Because the genetic code is universal, the same codons specify the same amino acids in all organisms. This allows genes transferred between species to be expressed correctly, which is the basis of genetic engineering. For example, bacterial cells can express human genes such as insulin because they interpret the genetic code in the same way.

2. Adenine is found in all members of which group?

Cytosine, ribose, thymine

Lipids, amino acids, carbohydrates

ATP, RNA, and DNA

Chlorophyll, starch, collagen

Adenine is a nitrogenous base found in nucleic acids and energy-carrying molecules. It is present in DNA, RNA, and ATP. These molecules are central to genetic information storage and cellular energy transfer, making adenine essential across biological systems.

Explanation

Adenine is a nitrogenous base found in nucleic acids and energy-carrying molecules. It is present in DNA, RNA, and ATP. These molecules are central to genetic information storage and cellular energy transfer, making adenine essential across biological systems.

3. Garrod proposed that inborn errors of metabolism occur because

Environmental factors affect enzymes

Psychological food aversion

Genes control enzyme production

Mutations only in noncoding DNA

Garrod proposed that genes control enzyme production. Inborn errors of metabolism occur when mutations prevent proper enzyme formation, disrupting metabolic pathways. This idea laid the foundation for understanding genetic diseases as biochemical defects rather than environmental or behavioral issues.

Explanation

Garrod proposed that genes control enzyme production. Inborn errors of metabolism occur when mutations prevent proper enzyme formation, disrupting metabolic pathways. This idea laid the foundation for understanding genetic diseases as biochemical defects rather than environmental or behavioral issues.

4. Which best represents a true codon?

Any random nucleotide triplet

Three nucleotides in the correct reading frame

A triplet containing a stop signal

A triplet in a different reading frame

A codon is a sequence of three nucleotides read during translation. For it to function correctly, it must be in the proper reading frame. Triplets outside the reading frame do not correspond to correct amino acids and therefore are not functional codons.

Explanation

A codon is a sequence of three nucleotides read during translation. For it to function correctly, it must be in the proper reading frame. Triplets outside the reading frame do not correspond to correct amino acids and therefore are not functional codons.

5. If enzyme A in a pathway A → B → C is defective, what occurs?

Increased B and C

No change in B and C

Accumulation of A, no B or C

Decreased A, increased B and C

When enzyme A is defective, the conversion of A to B cannot occur. As a result, substrate A accumulates while products B and C are not produced. This is a classic example of how enzyme defects disrupt metabolic pathways.

Explanation

When enzyme A is defective, the conversion of A to B cannot occur. As a result, substrate A accumulates while products B and C are not produced. This is a classic example of how enzyme defects disrupt metabolic pathways.

6. If A, B, and C are required for growth, a mutant lacking enzyme A grows on

Minimal medium only

Minimal medium + A

Minimal medium + B

Minimal medium + C

A mutant lacking enzyme A cannot convert A into B. Supplying B bypasses the defective step, allowing the organism to still produce C and grow. Supplementing A alone would not help because the conversion step is blocked.

Explanation

A mutant lacking enzyme A cannot convert A into B. Supplying B bypasses the defective step, allowing the organism to still produce C and grow. Supplementing A alone would not help because the conversion step is blocked.

7. If A, B, and C are required for growth, a mutant lacking enzyme B grows on

Minimal medium + A

Minimal medium + B

Minimal medium + C

Minimal medium only

If enzyme B is defective, the organism cannot convert B into C. Supplying C directly bypasses the blocked step, allowing growth. Providing A or B does not resolve the defect because conversion to C still cannot occur.

Explanation

If enzyme B is defective, the organism cannot convert B into C. Supplying C directly bypasses the blocked step, allowing growth. Providing A or B does not resolve the defect because conversion to C still cannot occur.

8. What amino acid sequence results from 5' AUG-UCU-UCG-UUA-UCC-UUG 3'?

Phe-glu-lys-leu-arg-lys

Met-ser-ser-leu-ser-leu

Thr-gly-arg-ile-ser-pro

Ala-arg-leu-tyr-ala-lys

Translation begins at AUG, which codes for methionine. The subsequent codons translate to serine, serine, leucine, serine, and leucine. Using the genetic code table confirms the sequence met-ser-ser-leu-ser-leu.

Explanation

Translation begins at AUG, which codes for methionine. The subsequent codons translate to serine, serine, leucine, serine, and leucine. Using the genetic code table confirms the sequence met-ser-ser-leu-ser-leu.

9. Which supports the idea that RNA evolved before DNA?

RNA is single-stranded

DNA lacks hydroxyl groups

DNA polymerase requires RNA primers

DNA uses thymine

DNA polymerase cannot begin replication without a primer, which is made of RNA. This dependence suggests RNA existed before DNA, supporting the RNA-world hypothesis where RNA served as both genetic material and catalyst.

Explanation

DNA polymerase cannot begin replication without a primer, which is made of RNA. This dependence suggests RNA existed before DNA, supporting the RNA-world hypothesis where RNA served as both genetic material and catalyst.

10. What is the role of tRNA during translation?

Carries DNA to ribosome

Builds ribosomes

Delivers amino acids to ribosome

Synthesizes mRNA

tRNA molecules carry specific amino acids to the ribosome. Each tRNA has an anticodon that pairs with a codon on mRNA, ensuring amino acids are added in the correct order during protein synthesis.

Explanation

tRNA molecules carry specific amino acids to the ribosome. Each tRNA has an anticodon that pairs with a codon on mRNA, ensuring amino acids are added in the correct order during protein synthesis.