Genetics ratios?

Question

I was working on problems in Genetics.One question says that 2 black guinea pigs were mated and after many years they had 28 black and 9 white offsprings.What is the parental genotype?If I take the parental genotypes as heterozygotes(Bb),I end up with 3:1 ratio which would mean 27:9..what is the right way to do this?
Similarly-when 3 yellow round pea seeds are grown and then crossed with green wrinkled pea seeds,the offspring were 24Yellow round,26 yellow wrinkled,25 green round and 25 green wrinkled.When I used YyRr as the parental genotype,I got 25 of each kind as the answer..I can't figure how to get the 24 and 26..can someone please help?

Answer 1

Your problem is, you're expecting reality to conform exactly to statistics, and your teacher is trying to get across to you that it doesn't. A 50% chance of being round doesn't mean that EXACTLY 50% of the peas will be round--just that approximately half of them will be. A ratio of 24:26 is certainly acceptable. As for the guinea pigs, what do you want? There are 37 offspring, and you seem to expect EXACTLY 1/4 of them to be white. 37 isn't even divisible by 4! When you're dealing with statistics, you have to allow a little slack.

Answer 2

The guinea pigs parents are, as you said, BbXBb.
The Punnett square only tells you what the EXPECTED
ratio should be in the offspring. 28:9 is real close to the expected 27:9, so that checks and is OK.
With the peas, do this Punnett square : YyRr X yyrr.
You will get close to the 1:1:1:1 ratio that you show in your question.

Answer 3

The ratio is 9:6:a million, on account which you're dazzling, a dihybrid bypass IS 9:3:3:a million, yet 3 are Rss and 3 are rrS. on account that they're the two sandy, there are 6 sandy. and confident, a monohybrid bypass is 3:a million

Answer 4

Remember, biology hardly ever works out exactly perfectly. A kid here or there in this situation isn't that big of a deal.


As one of my professors loved to say:
"This stuff isn't rocket science, it's much harder."