Question

Organisms that have two identical alleles for a particular trait are said to be

Answer 1

Hi @luiarena !
Such organisms are called as DIPLOID organisms

Answer 2

@lularena @Abhisar This question has no answer. Diploid refers to the copy number of chromosomes and is independent of the alleles. We are diploid and have lots of alleles that are identical and lots that are not.

Another issue is that it says "Organisms that have two identical alleles for a particular rait are said to be[?]" Well, in Fungi and many Angiosperms cells can be triploid, pentaploid, 8n, and even 32n. Many Fungi also have more than one nucleus per cell and these nuclei can have different ploidy. This means you can have two identical copies on one nucleus and a different allele copy on the other nucleus. So it should state clearly that there is only two alleles.

So, my point is, You never call an organism a name because of its allele identities because unlike the ploidy number, which is nearly constant in all cells except for gametes, there is a huge variation in all the alleles of all the genes in an organism. When discussing alleles you don't say, "The organism is X"; you say, "The organisms is X for gene Y."

This X should be heterozygous (different alleles) or homozygous (same alleles).

Answer 3

But alleles are on homologous chromosomes ?

Answer 4

@Abhisar I'm not sure what you mean. The ploidy of a cell only refers to the number of homologous chromosomes. The number of alleles is, in some way, dependent on that but not completely. There are some genes that have only one copy in the entire genome and other genes that have thirty or forty copies of the exact gene on a single chromosome. The different versions of those genes are the alleles.

Answer 5

I just wanted to know that if it is certain for an organism to have two homologus chromosomes if it has a pair of allele ?
@mrdoldum

Answer 6

@Abhisar No, but it would be unusual for a organism with two homologous chromosomes to not have a pair of alleles at a particular loci. This is because allele doesn't mean different. We say WW and Ww and treat both as two alleles b/c they are on different chromosomes (physically different not different chromosome number). In rare events a gene can be deleted or damaged in other way on one homolog but not the other. This is why I say no, but it would be rare and unusual.

Answer 7

Then sir cant we say that Organisms that have two identical alleles are generally diploid ?
@mrdoldum

Answer 8

@Abhisar Yes, but we cannot call them that based only on the alleles of a particular gene b/c that is not how diploid is defined.

Answer 9

@Abhisar Actually, an organism that has two alleles it is almost always diploid. If we ignore some of the really weird things, things like fungi, than it is essentially always diploid. Doesn't matter if the alleles are identical or not.

Answer 10

yes sir ... since an organism that has two alleles is almost always diploid...that's why i thought DIPLOID will be the answer

Answer 11

@Abhisar Ah, I see. I think the best answer is that the organism is homozygous for that particular gene.

Answer 12

oh yes u r correct.......i just didn't thought bou that !

Answer 13

OMG...yes it will be homozygous...silly me !