Question

A sequence of DNA reads: 5’ TCT GGC AAT CGC TAT 3’

1.What is the sequence of nucleotides on the complementary strand of DNA?

2.Which strand of DNA serves as the template strand – 5’ to 3’ or 3’ to 5’?

3.List the sequence of codons that result from the transcription of this DNA

4.What is the sequence of amino acids encoded by this DNA (Refer to the chart on the next page)?

5.How would the sequence of amino acids change if the first triplet of DNA read 5’ ACT 3’ instead of ‘5 TCT 3’?

Answer 1

1.

Nucleotide sequence on the complementary DNA strand is given below-

3'-AGA CCG TTA GCG ATA-5'

2.

DNA is composed of two complementary strands but only one strand acts as a template strand that is transcribed by RNA polymerase during RNA synthesis. This strand runs in 3' to 5' direction and is also known as non-coding strand while the other strand is known as coding strand (5' to 3' direction- resembles RNA except uracil is present instead of thymine).

3.

Once the above DNA sequence is transcribed, newly synthesized RNA strand would have following sequence of codons that run in 5' to 3' direction -

4.

After transcription and translation, the sequence of amino acid formed is shown below-

5.

When ACT codon replaces TCT in DNA, the amino acid sequence would have threonine instead of serine and the rest of the amino acid sequence would be same as earlier.