Lecture 2 - Mendelsassumptions 1. 1. 1. 1. 1.

Info iconThis preview shows pages 1–10. Sign up to view the full content.

View Full Document Right Arrow Icon
Mendel’s assumptions 1. For every pair of alleles, one allele is completely dominant to the other allele. 1. For each trait, there can only be two alleles. 1. Each gene can affect only one phenotype. 1. The phenotype determined by one gene is completely independent of the phenotype  determined by a different gene. 1. The phenotype of a given genotype is always observed (for example, an rr pea will always  be wrinkled). 1. Alleles behave the same whether no matter which parent they        are inherited from. 7.   Genes always assort independently . It turns out these assumptions are not always correct!
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
INCOMPLETE or PARTIAL DOMINANCE : Exception 1:  Not every pair alleles exhibit complete dominance/recessive relationships
Background image of page 2
Note that because the phenotype of the heterozygote is  different from either homozygote, the genotypic ratio is  equal to the phenotypic ratio. The 1:2:1 ratio  indicates that the F1 mating was a mono- hybrid cross.
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
CO-DOMINANCE: The MN blood group is determined by two L M L M 1         2             1 Because the phenotype of the heterozygote is unique, the genotypic ratio is equal to the phenotypic ratio.
Background image of page 4
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 6
Exception 2:  For some genes, more than two alleles exist in a population. LOCUS (plural, LOCI): G1 G2 For diploid organisms, the number of alleles in an individual is two.  However,  within a population, there may be more than two alleles that can be present at that  locus. G2 G3 G2 G2 G1 G4
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
The ABO blood groups display four phenotypes:  A, B, AB and O . These phenotypes arise from different sugars present on the surface of red blood cells. The body makes antibodies against sugars that it does not have on its own red blood cells, causing rejection of blood containing those sugars. AB person:  Has no antibodies, is a universal recipient                     A person:  Has antibodies against the B sugar, can receive blood                  from A and O people B person:  Has antibodies against the A sugar, can receive blood                  from B and O people O person:  Has both A and B antibodies, therefore is a universal                  donor but can only receive blood from O people
Background image of page 8
The ABO blood groups are determined by three alleles:  I A , I  and i, that create four 
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 10
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 01/27/2010 for the course BIO 89329 taught by Professor Hollingsworth during the Spring '10 term at SUNY Stony Brook.

Page1 / 38

Lecture 2 - Mendelsassumptions 1. 1. 1. 1. 1.

This preview shows document pages 1 - 10. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online