Traits and Probability

Question

anonymous · Answer

Check my answers, please?

anonymous · Answer

1.  	A Punnett square has letters at to the top and left sides of the grid. What cellular process is represented by these letters?
 	
	monohybrid
	fertilization
	mitosis
	meiosis <<<

anonymous · Answer

2. 	A cross involving a single trait with two contrasting forms, or alleles, is known as a _____________________.
 	
	monohybrid cross
	testcross
	dihybrid cross <<<<
	heterozygous cross

anonymous · Answer

3. 	Abyssinian guinea pigs have a rosette (long and bushy) coat that is controlled by a dominant gene. A short and smooth coat is recessive to the rosette allele. A breeder conducts a testcross to see if his Abyssinian guinea pig is homozygous or heterozygous. If the pig is homozygous, what is the phenotypic ratio in the offspring?
 	
	100% smooth coats
	50% rosette coats 50% smooth coats <<<<
	100% rosette coats
	75% rosette coats 25% smooth coats

anonymous · Answer

4. 	Genotypes cannot always be determined by phenotypes.
 	
	True 
	False <<<<

cmorris2004 · Answer

are these test questions

anonymous · Answer

No.  Just homework.

cathyangs · Answer

I think you have the wrong answers for 2, 3, and 4. 

2) A cross for one trait with 2 alleles would be a 2x2 Punnett. A dihybrid cross involves 2 separate traits, with 2 alleles of each trait, for a 4x4 square. I think the answer is A.

3) A test cross is where parent 1 with the dominant phenotype is bred with parent 2 who expresses the recessive phenotype (and therefore is aa, for A being dominant and a being recessive, parent 2 is homozygous recessive). 
Therefore, if "A breeder conducts a testcross to see if his Abyssinian guinea pig is homozygous or heterozygous. If the pig is homozygous, what is the phenotypic ratio in the offspring?" The pig in question is parent 1 in my explanation. Parent 1 can only be AA or Aa, homozygous or heterozygous - so parent 1 is AA if the pig is homozygous. If you cross AA with the aa parent 2, then the offspring would all be Aa. Thus, the phenotypic ratio in the offspring would be 100% dominant (A), or 100% rosette in this case. The answer is A.

4) "Genotypes cannot always be determined by phenotypes" is a true statement. As in the example above (question 3) a pig could have the dominant phenotype for a trait (showing A), but that would not be enough to tell if its genotype were AA or Aa, which are different. The answer is True.

anonymous · Answer

Thank you!

cathyangs · Answer

No problem! Hopefully you understand the reasoning now.