DNA STRUCTURE
A DNA nucleotide contains three parts. Name all three
Deoxyribose sugar, phosphate group, and nitrogen base.
What molecule carries a copy of the genetic instructions from DNA to the ribosome?
mRNA
Where does translation occur?
At the ribosome in the cytoplasm.
A mutation changes one DNA base, but the amino acid and protein remain unchanged. What type of mutation is this?
Silent mutation.
A DNA strand contains:
A T G C C A
Write the complementary DNA strand.
T A C G G T
DNA template:
TAC GGA CTT
Write the mRNA sequence produced during transcription.
AUG CCU GAA
What is the relationship between a codon and an amino acid?
Each codon helps specify which amino acid should be added to the growing protein.
What is the difference between a substitution and a deletion?
Substitution replaces one base with another. Deletion removes a base.
A student says, “DNA and RNA are basically the same because they both contain genetic information.” Give two structural differences between DNA and RNA that prove this statement is incorrect.
DNA is double-stranded; RNA is usually single-stranded. DNA has deoxyribose and thymine; RNA has ribose and uracil.
Put these events in the correct order:
DNA opens → RNA polymerase attaches → mRNA is produced → mRNA leaves the nucleus.
An mRNA codon is:
CAG
What is the complementary tRNA anticodon?
GUC
Why can a deletion be more disruptive to a protein than a substitution?
A deletion can cause a frameshift, changing how the remaining codons are read.
A mutation changes one DNA base from C to T. Explain why changing one base can potentially affect a protein.
The DNA change can alter the mRNA codon, which can change the amino acid added during translation and potentially change the protein.
A student says, “Translation happens in the nucleus because that is where DNA is.” Explain why the student is incorrect.
Transcription occurs in the nucleus, but translation occurs at the ribosome in the cytoplasm. mRNA carries the instructions from the nucleus to the ribosome.
A tRNA arrives at the ribosome with an anticodon that matches the mRNA codon. What happens next?
The correct amino acid is added to the growing polypeptide chain.
Original:
ACT TTG CGA
Mutated:
ACT TTC GA
What type of mutation occurred, and why can it affect the amino acid sequence?
Deletion; removing a nucleotide shifts the reading frame and changes the way codons are read.
Explain why the sequence of bases in DNA is important for determining the final protein produced by a cell.
The DNA base sequence determines the mRNA sequence, which determines codons and therefore the amino acid sequence of the protein.
Explain transcription using all four terms:
DNA • RNA polymerase • mRNA • nucleus
RNA polymerase uses DNA in the nucleus as a template to build a complementary mRNA strand.
Explain translation using at least 6 of these terms:
ribosome • mRNA • codon • tRNA • anticodon • amino acid • stop codon • protein
mRNA attaches to the ribosome → codons are read → tRNA anticodons match codons → amino acids are brought in → amino acids are joined to form a polypeptide → stop codon ends translation.
The original strand of DNA is ACT TTG CGA The mutated strand of DNA is ACT TTC GA This is a _______________ mutation that causes a _________ of amino acids.
What is a deletion? What is a frameshift?