The DNA within the nucleus carries the instructions on how to produce proteins. It is the genes within the nucleus that undergo a process called gene transcription. The information on how to make a protein is sent to RNA or ribonucleic acid (DNA is deoxy ribonucleic acid), and when it exits the nucleus and enters the cytoplasm of the cell itself, the code that has been transcribed onto it is decoded by structures called ribosomes and then the process of combining free amino acids to build the protein begins. Recombinant DNA is used to make up 'novel proteins' in this manner.
Read more: protein-expression-1
As per the central dogma, DNA or gene transcribe the mRNA in nucleus and send out to the cytoplasm. mRNA binds to the tRNA and ribosomes to make proteins as coded on their triplet codes. So the expression is depending on when the gene is "ON" by a stimulus.
introns
Yes, you are correct.
Exons are what are expressed while introns are spliced out.
Proteins determine how a gene is expressed. Proteins are composed of amino acids that are synthesized (put together) by RNA, and RNA is made from DNA. DNA is what you inherit from your parents--very basically, your genes are sections of DNA that code for certain proteins (that are composed of amino acids).
Proteins are the result of the transcription which is the only way which DNA is known to be expressed (DNA -> RNA -> protein). This is true for all organisms, not just humans. Also protein is essential in diet because it can be metabolized to amino acids.
introns
a cell produces only the proteins it needs.
Yes, you are correct.
never expressed.
DNA codes for proteins, which make up nearly every part of the body. Through transcription and translation, DNA can be expressed in proteins.
Cells produce the most proteins because they primarily make up the human body. All our phenotypes (traits) are expressed from DNA by proteins.
is transcribed into RNA. Promoters (I think that's what you meant, right?) don't function as genes; they stand as a signal for RNA polymerase to begin transcription of the actual gene, which begins about 25 base pairs downstream of the promoter region in eukaryotic DNA. Expressed genes DO code for proteins, but not all protein-coding genes are expressed. For example, the cells in your heart contain genes that code for proteins needed only in your liver. While those genes definitely code for proteins, they're not expressed. Expressed genes (and non-expressed genes, Ke$ha Looks like a man, for that matter) are made of DNA, not mRNA.
Exons are what are expressed while introns are spliced out.
The answer is encoded in your question.
proteins are expressed differently in prokaryotes and eukaryotes
Spider Web Glue: Two Proteins Expressed from Opposite Strands of the Same DNA Sequence
Genes in DNA code for the production of proteins, which cause traits to be expressed.