ADA 2007 Bio # 28

[Jordwin]

"Which statement concerning alleles is true for diploid organisms?"

1. At most only two alleles occur at a given locus in an organisms genome.
2. Alleles occupy an identical locus in homologous chromosomes.
3. Alleles of a given gene usually occur on non-homologous chromosomes.
4. A single chromosome usually carries two alleles of each gene.

A. 4
B. 1 and 2
C. 3
D. 1, 2 and 4
E. 3 and 4

I don't understand this answer. I looked on Bootcamp's explanations of the 2007 test and I didn't understand it much through their reasoning either. Anyone know how 4 isn't part of the answer, but 1 is? Is locus not equal to a spot on a chromosome?

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[vgupt]

Yes the locus is the location of an allele on a chromosome. E is incorrect because a single chromosome doesn't carry two alleles of a gene. A pair of homologous chromosomes do. A person inherits 2 copies of each chromosome, one from their mom and one from their dad. This means that as stated in answer A, A diploid person can have a maximum of two different alleles at that specific locus. Sorry about the wordy answer. Hope this helps.

 

[Jordwin]

Yes the locus is the location of an allele on a chromosome. E is incorrect because a single chromosome doesn't carry two alleles of a gene. A pair of homologous chromosomes do. A person inherits 2 copies of each chromosome, one from their mom and one from their dad. This means that as stated in answer A, A diploid person can have a maximum of two different alleles at that specific locus. Sorry about the wordy answer. Hope this helps.

Yep this helps, thanks!

 

[ikulu]

I didn't do the ada practice test yet, but is the answer B?

 

[Jordwin]

I didn't do the ada practice test yet, but is the answer B?

Yeah