c.17

Garrod hypothesized that "inborn errors of metabolism" such as alkaptonuria occur because

• metabolic enzymes require vitamin cofactors, and affected individuals have significant nutritional deficiencies.

• enzymes are made of DNA, and affected individuals lack DNA polymerase

• certain metabolic reactions are carried out by ribozymes, and affected individuals lack key splicing factors.

• genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes

A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is

• 3' UCA 5'

• 3' UGA 5'

• 5' TCA 3'

• 3' ACU 5'

The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following?

• A gene from an organism can theoretically be expressed by any other organism

• DNA was the first genetic material

• The same codons in different organisms translate into different amino acids

• Different organisms have different types of amino acids

The figure above shows a simple metabolic pathway. According to Beadle and Tatum's hypothesis, how many genes are necessary for this pathway?

• 1

• 2

• 3

• It cannot be determined from the pathway

Refer to the metabolic pathway illustrated above. If A, B, and C are all required for growth, a strain that is mutant for the gene-encoding enzyme A would be able to grow on medium supplemented with

• nutrient A only

• nutrient B only

• nutrient C only

• nutrients A and C only

efer to the metabolic pathway illustrated above. If A, B, and C are all required for growth, a strain that is mutant for the gene-encoding enzyme B would be able to grow on medium supplemented with

• nutrient A only

• nutrient B only

• nutrient C only

• nutrients A and C only

Rank the following one-base point mutations (from most likely to least likely) with respects to their likelihood of affecting the structure of the corresponding polypeptide.

1> insertion mutation deep within an intron

2> substitution mutation at the third position of an exonic codon

3> substitution mutation at the second position of an exonic codon

4> deletion mutation within the first exon of the gene

• 1, 2, 3, 4

• 4, 3, 2, 1

• 2, 1, 4, 3

• 3, 1, 4 ,2

A possible sequence of nucleotides in the template strand of DNA that would code for the polypeptide sequence phe-leu-ile-val would be

• 5' TTG-CTA-CAG-TAG 3'

• 5' AUG-CTG-CAG-TAT 3'

• 3' AAA-AAT-ATA-ACA 5'

• 3' AAA-GAA-TAA-CAA 5'

What amino acid sequence will be generated, based on the following mRNA codon sequence?

5' AUG-UCU-UCG-UUA-UUC-UUG 3'

• met-arg-glu-arg-glu-arg

• met-glu-arg-arg-glu-leu

• met-ser-leu-ser-leu-ser

• met-ser-ser-leu-ser-leu

Refer to the figure above. What would the anticodon be for a tRNA that transports phenylalanine to a ribosome?

• UUU

• AAA

• TTT

• CCC