Simple Question from ada sample test. Is it right?

[Parson]

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This is really basic, but question 28 from the free ada sample test says these statements are true?
Diploid organism:
1: at most only two alleles occur at a given locus in an organisms genome.(true b/c diploid)
2: Alleles occupy an identical locus in homologous chromosomes.(true)
4: A single chromosome usually carries two alleles of each gene. (huh?)

Is # 4 really true and I'm haveing a brain fart? B/C it Seems it can only be true if you account for the fact that DNA is double stranded

 

[teefie]

This is really basic, but question 28 from the free ada sample test says these statements are true?
Diploid organism:
1: at most only two alleles occur at a given locus in an organisms genome.(true b/c diploid)
2: Alleles occupy an identical locus in homologous chromosomes.(true)
4: A single chromosome usually carries two alleles of each gene. (huh?)

Is # 4 really true and I'm haveing a brain fart? B/C it Seems it can only be true if you account for the fact that DNA is double stranded

Yeah. alleles are just different or alternative forms of the same gene. i.e. dominant and recessive or recessive recessive. You have two alleles per each gene. Think Mendelian gentics and those stupid pea plants. YyGg

 

[Parson]

yes, but would one allele be on one of the homologous(from one parent) chromosomes and the other alleles be on the other homologous(from other parent) chomosome.

so only one allele/gene per chromosome and not two?

 

[Hannamsm]

You need to remember that the word chromosome can be considered either single or paired. It is used interchangeably.

 

[Parson]

Ok I kinda see it. I guess it just threw me when it said "single chromosome".

So I was thinking of "one" of the chromosomes from the homologous pair, since humans have 46 chromosomes comprised of 23 homologous pairs.

 

[Hannamsm]

Ok I kinda see it. I guess it just threw me when it said "single chromosome".

So I was thinking of "one" of the chromosomes from the homologous pair, since humans have 46 chromosomes comprised of 23 homologous pairs.

Yea got it 👍

 

[dat_student]

This is really basic, but question 28 from the free ada sample test says these statements are true?
Diploid organism:
1: at most only two alleles occur at a given locus in an organisms genome.(true b/c diploid)
2: Alleles occupy an identical locus in homologous chromosomes.(true)
4: A single chromosome usually carries two alleles of each gene. (huh?)

Is # 4 really true and I'm haveing a brain fart? B/C it Seems it can only be true if you account for the fact that DNA is double stranded

Hint: sister chromatids 🙂

 

[aevea]

I've got to agree with parson on this one--the question wording is ambiguous at best. While a single chromosome carries 2 copies of the same allele after S-phase, that doesn't mean 2 alleles (see #1). The word "usually" is also problematic--sure karyotypes are always done with replicated chromosomes but most somatic cells are locked in G1-phase which is before replication.

I also had a problem with #38 on the math:

38. Jill has six different books. How many ways can Jill select two different books?

A. 36
B. 30
C. 18
D. 15
E. 12


Credited response:





B

 

[dat_student]

..
38. Jill has six different books. How many ways can Jill select two different books?

A. 36
B. 30
C. 18
D. 15
E. 12
...

6 * 5 = 30

 

[aevea]

That's definitely what they're thinking. But the wording of the question sounds more like a combination than a permutation. If the books are ABCDEF, then selecting AB is the same result as selecting BA so we need to divide out the redundancy: 6!/2!(6-2)! or 6(5)/2.

I guess their logic is based on the word "ways"; even though AB and BA are the same result, selecting A then B is a different "way to select two different books" from selecting B then A.

 

[dat_student]

... selecting A then B is a different "way to select two different books" from selecting B then A.

yes, "A then B" is one way; "B then A" is a different way of selecting the same two books. 🙂

 

[bevzi]

Where did you get the sample ADA tests. Please let me know.

This is really basic, but question 28 from the free ada sample test says these statements are true?
Diploid organism:
1: at most only two alleles occur at a given locus in an organisms genome.(true b/c diploid)
2: Alleles occupy an identical locus in homologous chromosomes.(true)
4: A single chromosome usually carries two alleles of each gene. (huh?)

Is # 4 really true and I'm haveing a brain fart? B/C it Seems it can only be true if you account for the fact that DNA is double stranded

 

[teefie]

on the ada website under DAT.

 

[bevzi]

Thanks. I will look for them too.

on the ada website under DAT.