AP Biology Grid-In Practice Questions

 
You will see six grid-in questions on the AP Biology test. They appear in the second part of the multiple choice section and require you to perform mathematical and scientific calculations to find the answer. While they appear in the multiple choice section, no answer choices are given to you. You must rely solely on your abilities to solve the question. You will have 90 minutes to answer all 63 multiple choice questions and 6 grid-in questions.
 

Practice Question 1


In a particular species of guppy, tails can either be long or short and either feathered or straight. A mating between a short feather-tailed female and a short straight-tailed male produces 30 short straight-tailed guppies, 42 short feather-tailed guppies, 10 long straight- tailed guppies, and 14 long feather-tailed guppies. Calculate the chi-squared value for the null hypothesis that the short feather-tailed guppy was heterozygous for the feather-tailed gene. Give your answer to the nearest hundredth.




2.66

The expected progeny would have phenotypes according to the following frequencies: three short straight-tailed, three short feather- tailed, one long straight-tailed, and one long feather-tailed. There are a total of 96 progeny as a result of this cross, so the null hypothesis would be that we would expect to see 36 short straight-tailed, 36 short feather-tailed, 12 long straight-tailed, and 12 long feather-tailed. We construct the chi-squared analysis as follows:

Practice Question 2

What is the probability that the genotype rrss will be produced by a cross in which the genotypes of the parents are both RrSs?


1/16 or 0.06

We have to create a Punnett square for the following cross: RrSs × RrSs.

RS

Rs

rS

rs

RS

RRSS

RRSs

RrSS

RrSs

Rs

RRSs

RRss

RrSs

Rrss

rS

RrSS

RrSs

rrSS

rrSs

rs

RrSs

Rrss

rrSs

rrss

According to the Punnett square, only 1 out of every 16 of the offspring will have the rrss genotype. Therefore, the probability of the rrss genotype is 1/16, or approximately 0.06.