II. Assessing Real Results of Mendelian Crosses To test whether Mendel\'s patter
ID: 281379 • Letter: I
Question
II. Assessing Real Results of Mendelian Crosses To test whether Mendel's patterns hold true in real examples of these crosses, we will be using specially bred corn (Zea mays). Corn is an ideal test species for genetic crosses because every ear of corn contains hundreds of seeds (kernels), each the offspring of the planned cross, allowing a very large sample size to be produced quickly and with minimal resources needed compared to lab animals. A. Monohybrid Crosses A monohybrid cross is another term for a one-trait cross. In this species of corn, purple kernels (R) are dominant over yellow kernels (r). Obtain an ear of corn that resulted from a monohybrid cross of two heterozygous individuals. Choose 5 adjacent rows of kernels and count how many are each color. Log these numbers in the table provided. Repeat this same count, but this time use an ear of corn that results from a cross of a heterozygous individual and a homozygous recessive individual.Explanation / Answer
8. Purple kernels (R) is the dominant trait and yellow kernels (r) is the recessive trait.
The genotype of a heterozygous individual is Rr
To calculate the expected %
Ratio expected during a monohybrid cross is dominant: recessive= 3:1
Calculating percentage
Expected % for purple(dominant) = ¾*100= 75
Expected % for yellow(recessive)=1/4*100= 25
Phenotype
Observed Number
Observed %
Expected %
Purple
60
75
75
Yellow
20
25
25
9. For monohybrid cross, observed results fit the expected patterns
10. To calculate the expected %
Ratio expected during a dihybrid cross is
Purple,full : Purple,wrinkled: Yellow,full:yellow,wrinkled= 9:3:3:1
Calculating percentage
Expected % for Purple,full = 9/16*100= 56.25%
Expected % Purple,wrinkled =3/16*100= 18.75%
Expected % for Yellow,full =3/16*100= 18.75%
Expected % for yellow,wrinkled = 1/16*100=6.5%
Phenotype
Observed Number
Observed %
Expected %
Purple,full
45
56.25
56.25
Purple, wrinkled
15
18.75
18.75
Yellow, full
15
18.75
18.75
Yellow, wrinkled
5
6.25
6.25
Phenotype
Observed Number
Observed %
Expected %
Purple
60
75
75
Yellow
20
25
25