Alleles

[Deathby]

Ok this is going to sound like a really basic question, but what is an allele?

 

I know the dictionary definition is "the different types of a gene" eg. A,B,O for blood types, but is it also the two halves of a gene?

 

If it isn't, what do you call those two halves? (aka complete this sentence everyone has two ___ for each gene, you get one ___ from your mother and one ___ from your father.

[Skye]

If you have a certain gene, one copy of it may differ a little from another in terms of the nucleotide sequence. The different variations are called alleles.

 

There might be a specific name I haven't heard of or don't remember, but I would say the two copies of a gene you get from each parent are called homologs. More precisely they are homologs that are at the same locus (position) on each homologous chromosome. They may be the same allele, in which case the organism is homozygous for that gene, or they may be different alleles, in which case it is heterozygous.

[Dr_666]

Ok this is going to sound like a really basic question, but what is an allele?

 

Hey,

 

You can think of the genome as a big dictionary made up of many words. Each of these words (the genes!) contains information required for performing a biological function. For instance, many genes are actually instructions on how to build proteins, which are molecules that play many different roles in the cells.

 

What you need to know is that the cells of some organisms (like humans, for example) are given TWO copies of the dictionary. These dictionaries are weird because they might not be exactly identical, and some of the words in each copy might have slightly different definitions. Each of these versions of a gene (or "word") is called an allele.

 

The advantage of having two copies of each gene (two "alleles") is obvious if you consider that the "dictionaries" that you inherit (one from your mother and the other one from your father) have some pages or words damaged or missing.

 

Let me know if you need more information,

 

Dr_666

[jowrose]

very good analogy dr 666. simply put alleles are just the different options of a certain gene. Say Black or Brown hair. brown would be the dominant allele and would be denoted H (capital H for hair) and black would be recessive and denoted h (lower case h for hair). The main use of this concept is in Punnett squares where the probabilities of displaying either the dominant or recessive alleles are determined.