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Human Inheritance-text pp 106-110
i) Dominance and recessive-ii) Co dominance – Human Blood groupsOther Types of inheritance iii) Single Gene-Multiple alleles (Human Eye Colour)iv) Using Pedigreesv) Gender determinationvi) Sex Linkage – X Linked
i) Recessive trait
Dwarfism - dominant
• Dominant does not mean you will see lots of examples automatically in populations of individuals. It might be that it is a rare dominant form of a gene (allele) eg; dwarfism.
• The gene is said to have a low frequency in the human population
• Similarly recessive traits can be quite common in populations where the trait has a high frequency eg blue eyes in northern European populations eg; Danish, Swedish etc.
Dominant
Curved little finger - dominant
Observable Genetic TraitsCharacteristic dominant trait recessive trait
Earlobes Free ear lobes Attached ear lobes
Forelock White forelock No white forelock
Curve of thumb Straight thumb Curved thumb
Dimples Dimples No dimples
Pinky Bent pinky Straight pinky
Mid-digit hair Mid-digit hair No mid-digit hair
Tongue rolling Able to roll Not able to roll
Writing Hand right left
Crossing legs Left Leg up Right leg up
Second toe Length longer shorter
ii)Co dominance – Human Blood groups
ii)Co dominance – Human Blood groupsBoth Alleles are expressed in the phenotype
iii)Single Gene Inheritance-Multiple Alleles e.g Human Eye Colour
Discontinuous(one gene) VS Continuous(many genes)
Characteristics
iv)Using Pedigrees
Create Your own Pedigree for ear lobe attachment
v)Gender Determination
vi)Sex Linked Diseases eg Colour Blindness(can you see the number)
http://www.mediacollege.com/lighting/colour/colourblind.html
Comparison of X and Y chromosomes
X and Y chromosome Comparison
Colour Blindness(sex linked)Parents=Carrier female x Normal sited male
X X X XY
Now do
• Everyone read pp 106-110• If finding work hard complete Q 1-7• If finding easy -Completed • Q13,14,15,16,17,24