Question

please help! im confused

Background info: There are four grain phenotypes in this ear of corn: Purple & Smooth (A), Purple & Shrunken (B),Yellow&Smooth (C) and Yellow & Shrunken (D). These four grain phenotypes are produced by the following two pairs of heterozygous genes (P&p and S & s) located on two pairs of homologous chromosomes (each gene on a separate chromosome), where purple (P) is dominant over yellow (p), and smooth (S) is dominant over shrunken (s). Experimental data: An ear of corn has a total of 381 kernels, including 216 Purple& Smooth, 79 Purple & Shrunken, 65 Yellow & Smooth, and 21 Yellow&Shrunken. 1. What is the null hypothesis? 2. What are the degrees of freedom? 3. What is z2 What is the p value (approximate range)? 4. What is your conclusion? 5.

Answer 1

a) Null hypothesis parent plant is heterozygous for both traits

PpSs*PpSs

	PS	Ps	pS	ps
PS	PPSS (smooth, purple)	PPSs (smooth, purple)	PpSS (smooth, purple)	PpSs (smooth, purple)
Ps	PPSs (smooth, purple)	PPss ( purple, shrunken )	PpSs (smooth, purple)	Ppss ( purple, shrunken )
pS	PpSS (smooth, purple)	PpSs (smooth, purple)	ppSS (yellow, smooth)	ppSs (yellow, smooth)
ps	PpSs (smooth, purple)	Ppss ( purple, shrunken )	ppSs (yellow, smooth)	ppss ( yellow, shrunken)

b)  smooth, purple: purple, shrunken: yellow, smooth: yellow, shrunken=9:3:3:1

So there are 4 phenotypes degrees of freedom= number of phenotypes-1

= 4-1

=3

c) chi-square value

Expected ratio is

Purple smooth: yellow smooth: purple, shrunken: Yellow, smooth=216:79:65:21

Purple smooth: yellow smooth: purple, shrunken: Yellow, smooth= 10.28:3.76: 3.09:1

phenotypes	Observed (O)	Expected (E)	(O-E)^2/E
Purple, smooth	9	10.28	0.182
yellow, smooth	3	3.76	0.19253
Purple, shrunken	3	3.09	0.0027
yellow shrunken	1	1	0

Chi-square value= 0.182+0.19253+0.0027+0

= 0.37723

d) P value we take is P<0.05

e) here chi-square value which we got from the table is 0.37723 which is less than 7.815, 7.815 is the value which we got from the table and the chi-square value is 0.37723 which is less than 7.815 so we accept the null hypothesis

so the parent plant is heterozygous for both traits.

Answer 2

1. If purple fur (P) is completely dominant over yellow fur (p), and two homozygous individuals PP and pp are crossed, what will be the phenotypic ratios of the offspring? Use a Punnett square to show your work.

2.