Law of Independent Assortment
|
|
- Melinda Bryant
- 5 years ago
- Views:
Transcription
1 Dihybrid Crosses
2 Dihybrid Crosses Dihybrid Cross ~ genetic cross considering 2 gene traits at the same time, each consisting of nonidentical alleles. i.e. Mendel crossed numerous traits repeatedly in dihybrid crosses and found he always obtained the same ratio 9:3:3:1 ~ and thus develops Law of Independent Assortment
3 Law of Independent Assortment During gamete formation, the two alleles for one gene segregate or assort independently of the alleles for other genes.
4 Law of Independent Assortment Diploid Gamete
5 Law of Independent Assortment Diploid Gamete
6 Law of Independent Assortment Diploid Gamete
7 Law of Independent Assortment Diploid Or... Gamete
8 Law of Independent Assortment Diploid Or... Gamete
9 Law of Independent Assortment Diploid Or... Or... Gamete
10 Law of Independent Assortment Diploid Or... Or... etc... Gamete
11 Law of Independent Assortment Diploid Dad So... Gamete
12 Law of Independent Assortment Diploid Dad Mom Gamete
13 Sample Problem #1 In humans, free earlobes are controlled by the dominant allele E and attached earlobes by the recessive allele e. The widow s peak hairline is regulated by the dominant allele H, while the straight hairline by the recessive allele h. What would be the genotype and phenotype ratio of the F1 generation if a man heterozygous for both free earlobes and widow s peak has children with a woman also heterozygous for both free earlobes and widow s peak?
14 1. Let E be dominant free earlobes let e be recessive attached earlobes let H be dominant widow s peak let h recessive straight hair line 2. Parents P1 cross: EeHh x EeHh 3. Alleles: EH, Eh, eh, eh & EH, Eh, eh, How did eh you do that?
15 Step 3: EeHh x EeHh
16 Step 3: EeHh x EeHh EH
17 Step 3: EeHh x EeHh EH Eh
18 Step 3: EeHh x EeHh EH Eh eh
19 Step 3: EeHh x EeHh EH Eh eh eh
20 Step 3: EeHh x EeHh EH Eh eh eh EH
21 Step 3: EeHh x EeHh EH Eh eh eh EH Eh
22 Step 3: EeHh x EeHh EH Eh eh eh EH Eh eh
23 Step 3: EeHh x EeHh EH Eh eh eh EH Eh eh eh
24 P1 Cross: Step 3: EeHh x EeHh This is how you do step #3! Alleles for Punnet Square: EHEheHeh x EHEheHeh
25 EH Eh eh eh EH eh Eh EEHH EEHh EeHH EeHh The Alleles of each parent is EeHH placed on EeHh the outside eehhof your eehh 4x4 punnet square EEHh EEhh EeHh Eehh eh EeHh Eehh eehh eehh
26 EEHH ~ 1 eehh ~ 2 EEHh ~ 2 EEhh ~ 1 EeHH ~ 2 Eehh ~ 2 EeHh ~ 4 eehh ~ 1 eehh ~ 1 Therefore the genotype ratio is 1:2:2:4:1:2:1:2:1 for above order
27 Free earlobes & widow s peak = = 9 Attached earlobes & widow s peak = 1+2 =3 Free earlobes and straight hairline = 1+2= 3 Attached earlobes and straight hairline = 1 thus, the ratio of phenotypes is 9:3:3:1
28 Practice Crosses 1. State The phenotypes and genotype probability for a cross between a pure plant with round yellow seed and pure plant with wrinkled green seed. Round is dominant over wrinkled and yellow is dominant over green.
29 Let R be dominant round trait let r be recessive wrinkled trait let C be dominant yellow trait let c be recessive green trait Cross P1: RRCC x rrcc Alleles: RC, RC, RC, RC x rc, rc, rc, rc
30 RC RC RC RC rc RrCc RrCc RrCc RrCc rc RrCc RrCc RrCc RrCc rc RrCc RrCc RrCc RrCc rc RrCc RrCc RrCc RrCc
31 RrCc - 16 Therefore, 100% of P1 are RrCc and will be round and yellow.
32 Pedigree Charts Pedigree Chart ~ a graphic presentation of a family tree that permits patterns of inheritance to be followed for a single gene. chart contains a number of symbols that identify gender, relationships between individuals and whether an individual expresses a trait or carries the
33 Pedigree Symbols male identical twins female fraternal twins (females) mating I II Roman numerals symbolize generations. Arabic numbers symbolize individuals within a given generation. affected individuals known heterozygotes for autosomal recessive Birth order within each group of offspring is drawn left to right, oldest to youngest.
34 Sample Pedigree I 1 2 II III 1 2 3