Does DNA encode for tRNA?

[maccha]

My textbook says that DNA encodes for tRNA. Doesn't it just encode for proteins?

[biohazard]

DNA is transcribed into RNA, so DNA is not even directly involved in protein production - proteins are translated from RNA. This RNA is called the messenger RNA. In similar manner, DNA has genes for transfer RNA, i.e. DNA encodes for tRNA. There are also other types of RNA, which are likewise produced by genes within DNA.

Your textbook is correct.

[jwalin]

how is that so
i am in the 12 th so please do explain.
i thought only protiens were made from DNA.
how can DNA help make RNA???
does it follow the same pathway as that of a protien

[JackBean]

Sure it does.
First there is transcription, the process, where is DNA transcripted to RNA (of any kind, e.g. tRNA, rRNA or pre-mRNA)
Second there is translation, where is mature mRNA translated into protein with help of rRNA (the formation of ribozyme and the reaction) and tRNA (brings amino acids able to couple to form the peptide).
But EVERY RNA molecule is transcripted from DNA!

[jwalin]

okay.
i know m rna is transcribed. but will r RNA and t RNA also be??
although you made it clear. just to make sure.

[JackBean]

sure, every type of RNA (there are plenty) must be first transcribed

[biohazard]

Maybe think it this way: DNA is transcribed into RNA from a gene. If it is to become an mRNA, it will be further processed and then translated into a protein product. In a similar manner, also rRNA and tRNA are transcribed from DNA - they just aren't then translated into anything; they function in their RNA form, although rRNA is "attached" to proteins so as to make a functional ribosome and tRNA is often further processed and must fold into its functional form in order to carry out its task of transporting amino acids to the ribosome.

It is also worth noting that in eukaryotes, some subunits of ribosomal RNA and types of transfer RNA are produced by mitochondrial DNA, not nuclear DNA that contains all but few genes within the eukaryotic cell (although nuclear DNA also contains rRNA and tRNA genes).

[JackBean]

It is also worth noting that in eukaryotes, some subunits of ribosomal RNA and types of transfer RNA are produced by mitochondrial DNA, not nuclear DNA that contains all but few genes within the eukaryotic cell (although nuclear DNA also contains rRNA and tRNA genes).

But you means these used in mitochondria, don't you?

[biohazard]

At least the mitochondrial DNA-produced rRNA and tRNA are used within the mitochondrion. Mitochondrial DNA already encodes for some 22 types of tRNA, so there's probably no need for external tRNA. Similarly, mitochondrial DNA encodes for 2 subunits needed for ribosomes.

Many mitochondrial proteins are produced by the nuclear DNA, but as far as I know, mitochondrial RNAs are coded for by the mitochondrial DNA. After all, cytoplasmic and mitochondrial ribosomes differ in structure, and I think this is due to the different origins of their components.

[JackBean]

OK, it just dod sound, like some cytosolic or nuclear RNAs are coded by mitochondrial DNA.

I think, that one subunit of ribosome is actually also coded by nuclear DNA. I will try to look for it afterwards

[kolean]

What also is exciting is the field of miRNA (microRNA).

This single strand of RNA that is transcribed from DNA, binds up into a hairpin structure upon being transcribed.
These structures are then processed into an approximately 75 nucleotide long structure by the Drosha protein complex in the nucleus. Using the channel transporter protein Exportin, the RNA structure icrosses the nuclear membrane into the cytoplasm, where the remaining structure is then further processed by the Dicer protein complex in the cytoplasm to make the final miRNA structure.

This structure is a short interferring-like RNA that is only 21-23 nucleotides long. It can then bind to its target which is usually a mature mRNA (encoding for a protein). This binding can be by exact complementary base pairing as observed in the plant model, or several base pairs off as seen in the animal model. The miRNA then regulates the mRNA by its binding to the 3'UTR region of the target mRNA, and can then "interfere" with the translation of the mRNA or even have the mRNA degraded!

[JackBean]

And how is this related to the topic?