Class Notes (836,128)
Canada (509,645)
Biology (1,284)
BIOL 205 (111)
Lecture

Lecture7.pdf

6 Pages
74 Views
Unlock Document

Department
Biology
Course
BIOL 205
Professor
Ian D Chin- Sang
Semester
Fall

Description
The Green Revolution in agriculture (1960-2000) - doubling of population also occurred - to keep up with demand food production also had to keep up w/ demand What made the green revolution possible? • identifying mutations in plants that would increase yield or nutritional value • examples: • sd1: an allele for a recessive trait that results in short stature. Makes plants more resistant to toppling over in wind and rain, also increase seed yield. • why? Increase seed yield b/c putting less resources in growing taller • bph2: an allele for a recessive trait that confers resistance to brown plant hoppers (insect) • Can we make the double sd1;bph2 mutant? ◦ Yes we can: if on different chromosomes can be easy ◦ but if on same chromosome → more challenging Mendel’s Law of Independent Assortment A/a ; B/b GeneAand gene B are on different chromosomes AB/ab GeneAand gene B are on the same chromosome or Ab/aB A/a · B/b Unknown position for geneAand gene B heterozygote for a single gene:A/a = monohybrid double heterozygote such as A/a; B/b = dihybrid. Round and wrinkled phenotypes * progenydoesn't look like parents at all • let’s just look at seed shape: ◦ round: (315 +108)= 423 ◦ wrinkled: (101 +32)= 133 3:1 round:wrinkled • Let’s just look at seed color: ◦ yellow: (315 +101)= 416 3:1 yellow:green ◦ green: (108 +32)= 140 • so the two 3:1 ratios are hidden in the 9:3:3:1 • Note he did this with combinations of all seven traits and always got the 9:3:3:1 To visualize the random combination of these two ratios we can use a branch diagram What could the combination of the two 3:1 ratios mean biologically? • Mendel's Second Law: Different gene pairs assort independently in gamete formation*. • For two heterozygous gene pairs A/a and B/b, the b allele is just as likely to end up in a gamete with an a allele as with an Aallele, and likewise for the B allele. * We now know that this only applies to genes on different chromosomes We have explained the 9:3:3:1 phenotypic ratio as two randomly combined 3:1 phenotypic ratios. But can we also arrive at the 9:3:3:1 ratio from a consideration of the frequency of gametes, the actual meiotic products? How do we calculate the frequency of meiotic products from the F1 dihybrid R/r;Y/y Punnett square illustrating the genotypes underlying a 9 : 3 : 3 : 1 ratio Mendel went on to test his principle of independent assortment: ← hypothesis Working with independent assortment Predicting Progeny ratios. Geneticists can work in two di
More Less

Related notes for BIOL 205

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit