Explain how dna results in the expression of a gene using the following words: dna, mrna, trna, gene, transcription, and translation

1st step: the transcription of the genes of the DNA into pmRNA ( pre-messenger RNA) takes place in the nucleus.

For each gene, only one strand of the DNA is transcribed but this strand varies according to the genes.

RNA synthesis is catalyzed by RNA polymerase, an oligomeric enzyme. There are 3 types in eukaryotes.

Transcription occurs from the 5 'end to the 3' end of the genes.

2nd step: the processing of the pmRNA takes place in the nucleus

at. a cap of 7-methylguanosine triphosphate is added to the 5 'end of the pmRNA

b. a poly-A tail (50 to 250 nucleotides of adenine) is added to the 3 'end of the pmRNA

These modifications protect messenger RNA from too rapid degradation in the cytoplasm.

c. excision of introns (the parts of the gene that do not encode a polypeptide) of the pmRNA

d. splicing of the exons (the coding strands) of the pre-messenger RNA.

The pre-messenger RNA thus mature becomes messenger RNA (mRNA).

The mRNA is then exported to the cytoplasm via nuclear pores.

3rd step: the translation of the mRNA into protein takes place in the cytoplasm at the level of ribosomes and requires the presence of transfer RNA (tRNA) loaded with the corresponding amino acids and energy in the form of GTP.

tRNAs are synthesized in the nucleus.

The synthesis proceeds from the N-terminus of the protein to the C-terminus.

4th step (depending on the proteins): co-translational or post-translational modifications such as glycosylation (covalent binding of oses to proteins) which takes place in the endoplasmic reticulum and is then finished in the Golgi apparatus.

In prokaryotes, transcription, and translation take place in the cytoplasm and can be simultaneous.

answer: the blood-brain barrier is a layer of specialized membranes and cell processes designed to keep undesirable substances from passing from the bloodstream into the precious tissues of the brain. while the blood-brain barrier does keep most bad things out of the central nervous system, it is not impermeable.

explanation: