RNA/DNA

[KhymiSi]

Is the percentage composition of elements (C,H,O,N,P,S) in RNA and DNA the same? Could you argue that they are?

Thanks!

[pi]

Have you seen the difference between uracil and thymine?

Also, does the question specify a length for each and a specific sequence for each?

[KhymiSi]

Have you seen the difference between uracil and thymine?

Also, does the question specify a length for each and a specific sequence for each?

The question gives a table in which the assumed nucleic acid is: Carbon 30 Hydrogen 38 Oxygen 16 Nitrogen 14 Phosphorus 2 and Sulphur 0.

It says that one student claimed that it was a single stranded molecule whereas another said it was a double-stranded molecule. Then it asks if they could be both correct and explain why.

[Stick]

I think you just use an even/odd principle. If you're dealing with a DNA molecule, the number of nucleotides would be even (since there are two strands) whereas the amount could also be odd for a RNA molecule since it only contains one strand.

[palladium]

We did that question in class just yesterday - our teacher said that both students could be correct, as it was the only biomacromolecule out of the 4 in the table which could be a nucleic acid.

For the explanation, you can write that a nucleic acid can be both single-stranded (RNA) or double-stranded (DNA), therefore it is difficult to tell which student is correct without further information (which was given in the next question, in the test that we did, anyway).

Hope I helped!

[Snorlax]

The question gives a table in which the assumed nucleic acid is: Carbon 30 Hydrogen 38 Oxygen 16 Nitrogen 14 Phosphorus 2 and Sulphur 0.

It says that one student claimed that it was a single stranded molecule whereas another said it was a double-stranded molecule. Then it asks if they could be both correct and explain why.

I did this exact question early today. Nelson biology investigate and inquire?
I wrote something along the lines of that there is not enough infomation given such as if it has an additional oxygen (ribose sugar) or what N-base's were present.

[Yacoubb]

Personally, I feel this is an ambiguous question if you are not given additional information (e.g. relative length of molecule, the sugar part of the nucleotide).

[KhymiSi]

We did that question in class just yesterday - our teacher said that both students could be correct, as it was the only biomacromolecule out of the 4 in the table which could be a nucleic acid.

For the explanation, you can write that a nucleic acid can be both single-stranded (RNA) or double-stranded (DNA), therefore it is difficult to tell which student is correct without further information (which was given in the next question, in the test that we did, anyway).

Hope I helped!

Thank-you that helped a lot. I was thinking it was along the lines of that but had no idea how to word it. 

[palladium]

Personally, I feel this is an ambiguous question if you are not given additional information (e.g. relative length of molecule, the sugar part of the nucleotide).

Just out of curiosity, RNA molecules would be shorter than DNA, right? I mean, logically, they would be, but seeing as I don't really trust my brain, can anyone confirm? Thanks

Also, you're welcome KhymiSi

[Snorlax]

Just out of curiosity, RNA molecules would be shorter than DNA, right? I mean, logically, they would be, but seeing as I don't really trust my brain, can anyone confirm? Thanks

Also, you're welcome KhymiSi

Length wise? I wouldn't think so...

[alondouek]

Just out of curiosity, RNA molecules would be shorter than DNA, right? I mean, logically, they would be, but seeing as I don't really trust my brain, can anyone confirm? Thanks

Well, it really depends on:

• The sequence length of the DNA strand - understandably it can vary greatly
• If the RNA strand is mRNA.

If the second point holds true, we can arrive at two different conclusions based on the stage of mRNA synthesis. In Unit 4, you will learn that during the synthesis of the mRNA strands used in protein synthesis, there are two main forms of mRNA.

The mRNA strand that is transcribed (via transcription) from the DNA template strand is termed pre-mRNA. It is a complete complementary copy of the DNA template sequence - and it contains both introns and exons. Exons are coding sequences (i.e. they will code for something), while introns are non-coding (thought to be regulatory) sequences.

A process occurs called 'RNA splicing', which results in the removal of all intron sequences from the pre-mRNA. The remaining mRNA strand, which is capped by a 'poly-A' tail (as in, AAA... repeating), is termed 'mRNA' and is what is used in translation.

As such, we can say that pre-mRNA is the same length as the DNA template strand, but the final, spliced mRNA is shorter.

N.B. You don't need to know this for unit 3, but it always helps to have as broad a knowledge base as possible in biology.

[palladium]

Well, it really depends on:

• The sequence length of the DNA strand - understandably it can vary greatly
• If the RNA strand is mRNA.

If the second point holds true, we can arrive at two different conclusions based on the stage of mRNA synthesis. In Unit 4, you will learn that during the synthesis of the mRNA strands used in protein synthesis, there are two main forms of mRNA.

The mRNA strand that is transcribed (via transcription) from the DNA template strand is termed pre-mRNA. It is a complete complementary copy of the DNA template sequence - and it contains both introns and exons. Exons are coding sequences (i.e. they will code for something), while introns are non-coding (thought to be regulatory) sequences.

A process occurs called 'RNA splicing', which results in the removal of all intron sequences from the pre-mRNA. The remaining mRNA strand, which is capped by a 'poly-A' tail (as in, AAA... repeating), is termed 'mRNA' and is what is used in translation.

As such, we can say that pre-mRNA is the same length as the DNA template strand, but the final, spliced mRNA is shorter.

N.B. You don't need to know this for unit 3, but it always helps to have as broad a knowledge base as possible in biology.

Thanks! Actually, our teacher taught us about protein synthesis last week :/ it was completely unexpected, but hey :O Admittedly, I'm still not too familiar with it so I'll read up on it, thanks for your explanation!