Biology Forums - Study Force

 Why does the cell need to make an RNA molecule?


Explain the purpose/function of the promoter sequence?

 3) What could happen if a gene does not have a promoter sequence?

 4) How did you determine the start codon?

 5) Why does the cell need to make an RNA molecule?

 6) Define "codon" and explain the relationship between the linear sequence of codons on mRNA and the linear sequence of amino acids in a polypeptide.
 7) Translate the following mRNA sequences and indicate the type and consequences of mutations. Original sequence: CUCUCAUAUCCGCUGGCU

Mutated sequence1: GUGAGCUAUCCCUUGACU        Mutation(s) _____________-
Mutated sequence 2: CUCUCAUAACCGCUGACU        Mutation(s){_____________
 Mutated sequence 3: GUCUCAUAUCCCUGACU         Mutation(s)__________________

Both of these questions are the same. Now, you haven't specified with RNA molecule you want discussed, so I found a topic that discusses the purpose behind all three.

Link: https://biology-forums.com/index.php?topic=1568329.0

The promoter ensures that the initiation of every RNA occurs at the same site. Otherwise, the ensuing polypeptide might be missing amino acids, or it might contain extra amino acids.

For more information, review this topic: https://biology-forums.com/index.php?topic=16066.msg50285#msg50285

Answer the rest as you read :)

Read my previous post ^^ Some valuable information there pertaining to this ...

A gene without a promoter is like building a car without an ignition switch. You have something that could work, but doesn't.

The promoter always exists upstream the start of the gene. So likely you knew the promoter sequence, then several nucleotides laters, you noticed the sequence TAC. TAC is the RNA complement to AUG, which codes for the amino acid methionine. This codon is also called the "start" codon because it denotes the site where translation is initiated for nearly all eukaryotes.

By the way, are these questions based on a lab/simulation you did?

Codons are RNA nucleotide triplet in that codes for a specific amino acid. Along the mRNA molecule exists nucleotides that are grouped in triplets starting from the start codon, AUG (as discussed above). That said, if you know the sequence of amino acids making up a polypeptide, each amino acids has 3 to 4 known codes that transcribe to that amino acids. Interestly, codons are read by the ribosomes, which enable to polypeptide to form.

CUCUCAUAUCCGCUGGCU > LSYPLA (original)

GUGAGCUAUCCCUUGACU > VSYPLT

Nearly everything is wrong here, holy smokes! Also, at the end, ACU is found in place of GCU. ACU is a stop codon, rendering this polypeptide unusable. Hence it's a nonsense mutation too.

CUCUCAUAACCGCUGACU > LS.PLT

Looks like two missense mutations. Also, at the end, ACU is found in place of GCU. ACU is a stop codon, rendering this polypeptide unusable. Hence it's a nonsense mutation too.

GUCUCAUAUCCCUGACU > VSYP.

This is missing a nucleotide at the very end, hence there's a deletion. Also at the beginning, C is replaced with G. This is called a missense mutation. Only what's in green actually is the same. At the end, ACU is found in place of GCU. ACU is a stop codon, rendering this polypeptide unusable. Hence it's a nonsense mutation too.