Biology: Genetics: Transcription and Translation Worksheet

Question 1

State the central dogma of molecular biology and explain what information is transferred at each step.

Accepted Answer

The central dogma is DNA to RNA to protein. During transcription, information in DNA is copied into RNA. During translation, the information in mRNA is used to build a protein from amino acids.

Question 2

Transcribe this DNA template strand into mRNA: TAC GGA CTT AAG ACT.

Accepted Answer

The mRNA sequence is AUG CCU GAA UUC UGA. RNA uses A, U, C, and G, and it pairs U with A instead of using T.

Question 3

A DNA coding strand has the sequence ATG TTT CCG TAA. Write the mRNA sequence that would be produced from this gene segment.

Accepted Answer

The mRNA sequence is AUG UUU CCG UAA. The mRNA matches the coding strand except that uracil replaces thymine.

Question 4

Translate this mRNA sequence into an amino acid chain using the codon information given: AUG = methionine, GCU = alanine, UUU = phenylalanine, GGA = glycine, UAA = stop. Sequence: AUG GCU UUU GGA UAA.

Accepted Answer

The amino acid chain is methionine, alanine, phenylalanine, and glycine. Translation stops at UAA because it is a stop codon and does not code for an amino acid.

Question 5

Identify the start codon and the stop codon in this mRNA sequence: CCA AUG AAC UGC UGA GGU.

Accepted Answer

The start codon is AUG, and the stop codon is UGA. Translation begins at AUG and ends when the ribosome reaches UGA.

Question 6

Explain the role of RNA polymerase during transcription.

Accepted Answer

RNA polymerase binds to a promoter region of DNA, separates the DNA strands, and builds a complementary RNA strand using one DNA strand as the template.

Question 7

Describe what happens to pre-mRNA in a eukaryotic cell before it leaves the nucleus.

Accepted Answer

Pre-mRNA is processed before leaving the nucleus. Introns are removed, exons are joined together, a 5 prime cap is added, and a poly-A tail is added to help protect and export the mRNA.

Question 8

For the mRNA codon GCU, write the complementary tRNA anticodon.

Accepted Answer

The complementary tRNA anticodon is CGA. The bases pair G with C, C with G, and U with A.

Question 9

A DNA template strand changes from TAC AAA CCG ATT to TAC AAG CCG ATT. Transcribe both versions into mRNA and determine whether the amino acid changes. Use this codon information: AUG = methionine, UUU = phenylalanine, UUC = phenylalanine, GGC = glycine, UAA = stop.

Accepted Answer

The original mRNA is AUG UUU GGC UAA, which codes for methionine, phenylalanine, and glycine. The changed mRNA is AUG UUC GGC UAA, which codes for methionine, phenylalanine, and glycine. The amino acid sequence does not change, so this is a silent mutation.

Question 10

A DNA template strand is TAC GGA CTT ACT. A single base is inserted after the first three bases, making it TAC AGG ACT TAC T. Explain why an insertion mutation can have a large effect on the protein.

Accepted Answer

An insertion mutation can shift the reading frame, which changes how the mRNA is divided into codons. This frameshift can change many amino acids after the insertion and may create an early stop codon.

Question 11

Compare where transcription and translation occur in a eukaryotic cell.

Accepted Answer

In a eukaryotic cell, transcription occurs in the nucleus where the DNA is located. Translation occurs at ribosomes in the cytoplasm or on the rough endoplasmic reticulum.

Question 12

Explain the functions of the ribosome's A site, P site, and E site during translation.

Accepted Answer

The A site holds the incoming tRNA carrying the next amino acid. The P site holds the tRNA attached to the growing polypeptide chain. The E site is where the empty tRNA exits the ribosome.

Question 13

A coding DNA sequence changes from GAG to GTG. The mRNA codon changes from GAG to GUG. Use this codon information: GAG = glutamic acid and GUG = valine. Identify the type of mutation and explain its effect.

Accepted Answer

This is a substitution mutation because one DNA base is replaced by another. It is a missense mutation because the codon changes from coding for glutamic acid to coding for valine.

Question 14

A gene segment has the DNA template strand TAC CGT TTA ATC. Transcribe it into mRNA, then identify the codons.

Accepted Answer

The mRNA sequence is AUG GCA AAU UAG. The codons are AUG, GCA, AAU, and UAG.

Question 15

Explain why the sequence of bases in mRNA determines the sequence of amino acids in a protein.

Accepted Answer

The mRNA sequence is read in codons, and each codon specifies an amino acid or a stop signal. Because ribosomes read codons in order, the order of mRNA bases determines the order of amino acids in the protein.

Biology: Genetics: Transcription and Translation

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