DNA and genes?!?

1. Non-coding regions are distinguished by whether or not they match the anti-codons.

2. Excision reduces the number of genes, reduction in the "required" genes would be the fact that codons can code for several different genes.

1. Non-coding regions of DNA are usually in loops of repeating DNA patterns. Genes can be distinguished, as they are the places where the DNA is unzipped to allow transcription to occur, producing mRNA. This is then used in protein sysnthesis.

You might want to google it - just to check.

Get in a study group.  Post a note or something.  These are good thought questions and if you aren't getting it from your professor you need something better than yahoo answers as a long term solution...
1. for example: coding regions have long sequences of open reading frames.  that is, they are not interrupted by the STOP codon.
2. for example: genes can be alternatively spliced after the production of mrna so that one gene can code for multiple proteins.
other decent answers to both questions exist.

Also alot of gene duplication and "pseudogenes".
Several organisms love pack-ratting DNA and genes while some seem to want to keep a tiddy house.
The extra "junk" doesn't appear to do significant harm, tho yes a waste of resources.  Many scientists have proposed that some of the extra non-coding DNA may have a structural role.

Here are some possible answers to your Qs:
1.  
Non-coding regions are usually more A/T rich.
While coding regions have 50-70% G/C so to be in tune with translation of the codons to amino acids.  
The deduced aa sequence (in perfect uninterupted frame) of a gene, that someone isolates can be entered into a database.  There is a chance the gene or a similar has been cloned from human or other organism.

True genes at some point are transcribed into mRNA which is single stranded.
The higher G/C can also contribute to added secondary structure of the mRNA, thus making it more stable, less susciptible to degradation.

Coding DNA sequences are usually more conserved, stabile over time (point, deletion, additions) can be lethal thus selected out of the population.
Numerous mutations can occur in non-coding non-regulatory regions without negative consequences.  

True genes also have sequences that act as promoters and regulatory elements just upstream of the coding region.
A good molecular biologist can often spot these sequences from a printout with his/her eye without the aid of DNA sequence analysis software.

True genes with the correct introns spliced out should not have premature stop codons in them.
Otherwise synthesis of the protein will drop off sooner than the true stop site.  The lack of a stop codon means it will run until it randomly hits one.  Both events usually result in a nonfunctional protein that needs to be degraded.

2.
Usually people wonder why there are more genes than needed in a particular organism.  Due to redundancy etc.
Mutation/deletion events can inactivate an extra or nonessential gene.
If multiple alike genes are closely linked on the same chromosome (at the same locus), uneven recombination can remove parts of the chromosome thus eliminating some of the extra genes.
The same process can make additional genes as well.

There is also gene silencing, but I think you have enough info to regurgitate to your Prof.