Download Mendeloids

Mendeloids
Planning Form – Investigation 7
Eyebrows
X
P1
Bushy
Smooth
F1
All offspring have bushy eyebrows
Eyebrows
Bushy
Locus, Loci
METAPHASE OF MEIOSIS I
TELOPHASE OF MEIOSIS I
TELOPHASE
OF MEIOSIS II
Eyebrows
B
Bushy
BB
METAPHASE OF MEIOSIS I
TELOPHASE OF MEIOSIS I
B
B
TELOPHASE
OF MEIOSIS II
B
B
Eyebrows
b
METAPHASE OF MEIOSIS I
Smooth
bb
TELOPHASE OF MEIOSIS I
b
b
TELOPHASE
OF MEIOSIS II
b
b
Punnett Square
Possible gametes for the two parents
bb = homozygous recessive
b
B
Bb
b
Bb
BB = homozygous
dominant
B
Bb
Bb
Possible genotypes from these two parents
Bb = offspring are heterozygous
Eyebrows
• Bushy is the dominant allele
–B
• Smooth is caused by a recessive allele
–b
• Monotypic gene – either bushy or smooth,
no intermediate expressions
• Autosomal
Digits
• Number of toes – 2 or 3
– 2 digit x 3 digit = all 2 digits
– Which is dominant?
– Is this trait monogenic or polygenic?
– Sex-linked or autosomal?
Skin Color
solid
large
spots
medium
spots
small
spots
stippled
Skin Color
• Polygenic
– AABB = solid
– AABb or AaBB = large spots
– AaBb or aaBB or AAbb = medium spots
– Aabb or aaBb = small spots
– aabb = stippled
• Autosomal
Hearing
• Dominant = normal hearing
• Recessive = deaf
• Sex-linked (= gene is present on the X
chromosome but absent on the Y)
– XX = female; XY = male
A A
A a
XX
a
a
XX
XX
A
a
XY
XY