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Co-dominance. By: M (athilde) dawg, L (iam) dawg, and G (eorge) dawg . Objectives. 4.3.3 – Multiple alleles 4.3.4 – Describe ABO blood groups as an example of co-dominance and multiple alleles. 4.3.5 – Sex Determination
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Co-dominance By: M (athilde) dawg, L (iam) dawg, and G (eorge) dawg
Objectives • 4.3.3 – Multiple alleles • 4.3.4 – Describe ABO blood groups as an example of co-dominance and multiple alleles. • 4.3.5 – Sex Determination • 4.3.6 – State that some genes are present on the X-chromosome and absent from the shorter Y chromosome in humans.
4.3.3 • Some genes have more than two alleles. • An individual can only possess two alleles. • The population may contain many alleles for a given gene. • Multiple alleles increases the number of different phenotypes. • Multiple alleles can be dominant, recessive or co-dominant to each other.
Video http://www.youtube.com/watch?v=mFbwOubQMgQ&list=ECE7B097006D38E249
4.3.4 -The ABO blood type system in humans has 4 possible phenotypes: A, B, AB, and O. -The red blood cell antigen is coded for by the gene I -I has three alleles three alleles IA, IB and IO -IAand IB are codominant, while IO is recessive.
The cross below shows how all four blood groups can arise from a cross between a group A and a group B parent.
4.3.5 • Determined by sex chromosomes • X and Y • In humans: - Homologous (XX) are females - Non- Homologous (XY) are males
Monohybrid cross • Demonstrates inheritance of X and Y chromosomes • There will be 1:1 ratio of male to females
X and y • Sex is determined solely by the sperm • Technique for separating X and Y sperm is using IVF
4.3.6 • These are called sex or linked X-linked genes • Female sex chromosomes are XX • Male sex chromosomes are XY • The Y chromosomes does not carry an allele
reference • http://static.ddmcdn.com/gif/blood-cells.jpg • http://2.bp.blogspot.com/-fnma529dqx0/URDOSarqpjI/AAAAAAAAADs/gxr1PLCKyyc/s1600/1-absolutely-innocent-princess1-baby-girl.jpg • http://2.bp.blogspot.com/-bpJf-4I0toQ/T7Zs9UU-BRI/AAAAAAAAAEo/lxo88YNM40s/s1600/Blog+10.jpg • http://imgc.artprintimages.com/images/art-print/victor-habbick-conceptual-image-cloning-where-we-see-cloned-babies-against-a-foreground-of-x-and-y-chromosomes_i-G-64-6462-1AVH100Z.jpg • http://i.telegraph.co.uk/multimedia/archive/01084/education-graphics_1084561a.jpg