Download X b

Variations on Mendel
1. INCOMPLETE DOMINANCE
• Neither trait is completely
dominant over the other
• Get a BLEND of the two traits
• The new phenotype is
somewhere between the original
two
W
•I
R
I
= white
= Red
• White Carnation x Red Carnation
• Parent Genotypes?
W
W
R
R
–I I x I I
–Do the Punnett Square
• What do you get????
IWIR = 4 / 4 are pink carnations
IW
IW
IR
IW IR
IR
IW IR IW IR
IW IR
•What happens if you cross 2
Pink Carnations?
W
R
–I I
x
W
R
I I
–Do the Punnett Square
–What phenotypes occur?
IWIW = 1 / 4 white
IWIR = 2 / 4 pink
IRIR
IW
= 1 / 4 red
IR
IW
IW IW IW IR
IR
IW IR IR IR
Another Incomplete Dominance
example…..
• White bunny x brown bunny = ??
• IWIW x IBIB = IWIB
I
I
• IWIB = tan
IW IB
IW IB
W
W
IB
IB
IW IB
IW IB
2. CODOMINANCE
• Two traits are dominant at the
same time
• Both traits are fully expressed at
the same time
• EX: Speckled Chickens
•These birds have BOTH black
and white feathers
•Both black and white are
dominant
B
B
•I I
= black feathers
W
W
• I I = white feathers
B
W
• I I = speckled
• Cross a black with a speckled-what are possible phenotypes?
IBIB = 2 / 4 black
IBIW = 2 / 4 speckled
IB
IB
IB
IB IB
IW
IB IW IB IW
IB IB
• Blood Type: based on 2 gene groups
(1)ABO:
--Two dominant ( IA and IB )
--One recessive ( i )
–
–
–
–
IA IB
IA i or IA IA
IB i or IB IB
ii
makes ______
makes ______
makes _______
makes _______
• Can a Type A and a Type B have:
–Type AB child?
•Yes
–Type A child?
B
•Yes..if Type B parent is I i
–Type B child?
•Yes…. if Type A parent is IA i
–Type O child?
•Yes…if both are heterozygous
• Blood Type: based on 2 groups of
genes
(2) Rh Factor:
-- One dominant gene (I+)
-- One recessive gene (I-)
IA i I+ IIB i I+ Ii i I- I-
makes _________
makes __________
makes __________
5. Sex-Linked Genes
• X & Y = sex chromosomes
• X X = female genotype
• X Y: male genotype
• “X” –carries traits
–Colorblindness, hemophilia
• “Y” --no corresponding traits
• Males are more likely to have these
recessive traits than females
5. Sex-Linked Genes
• XB = normal sight
b
• X = colorblind
b
b
Colorblind Female = X X
Normal Female= XB XB or XB Xb
Colorblind Male= Xb Y
Normal Male = XB Y