DNA

[TsukiMarx]

What is the relationship between DNA, chromosomes, genes and alleles?
this is a little difficult to piece together...

[plasmodesmata11]

dna makes up chromosomes, chromosomes contain genes, and alleles are varieties of genes

[akki313]

Here's the order arrangement:
DNA combines to give genes.. which further combines to give alleles.. thousands of alleles constitute a chromosome ..
DNA - >genes - > alleles -> chromosomes..

[JackBean]

genes.. which further combines to give alleles..

not at all!!! Alleles are versions of genes!

[ark]

A chromosome consists of,except in RNA viruses, a DNA. Such a DNA contains multiple genes coding specific products ( polypeptides, RNA).Alleles are different forms (variants) of a gene.

[jwalin]

hmm the following will help
chromosome is made of 2 chromatin each of which is made by one single DNA
DNA has many genes on it
genes are made up off nucleotides

now alleles hmm its just the alternative form of genes
for example: lets say a plant has TT or Tt if its tall and tt if its short.
now in this the gene is the alphabet "t" while the allele is the capital or the small "t"

[simina]

Can you help me understand what exactly is nucleosome periodicity? We are studying it by adding micrococcal nuclease within the nucleus and studying it by SDS-PAGE.The results we had, showed several bands around 6 (nucleosomes that were cut by the nuclease). I do not really know how to interpret the results caz I do not understand what they mean by periodicity (this is supposed to analise it from the SDS-PAGE photo). Any ideas?

[jonmoulton]

I think this is a case where winding the DNA onto histones protects it from the nuclease, so the DNA is cut only in regions between the histones. If the same length of DNA is wound around each histone and every DNA segment between histones gets cut, the fragments after inter-histone degradation would be roughly the same size. Perhaps the nuclease doesn't cut between every histone; then you would see some double-length fragments, triple-length fragments etc. If you run the fragments out on a gel you would see a ladder and analysis of the masses of the ladder rungs would reveal that they are integer multiples of the mass of the smallest rung -- that is, the masses are periodic.

I've not done this. Anyone have experience with nucleosome periodicity?

[simina]

That is more clear for me thank you. Some bands are indeed a bit bigger than others, although it is not very clear!