Mendel’s Second Experiment Inheritance of Two Traits Dihybrid Cross.
Patterns of Inheritance Part 2 - Mrs. Ody's Biology Blog...Exceptions to Mendel’s Law •...
Transcript of Patterns of Inheritance Part 2 - Mrs. Ody's Biology Blog...Exceptions to Mendel’s Law •...
Patterns of
Inheritance Part 2
Exceptions to Mendel’s Law
• Mendel’s traits showed two distinct forms
• Most genes do not exhibit simple inheritance
• Genotypic and phenotypic ratios may vary
because of interactions between
– Alleles
– Other genes
– Segregation of genes on the same chromosome
– Environment
Complex Inheritance and Human Heredity
Incomplete Dominance
Pattern of inheritance in which one allele is not
completely dominant over another
RR=red
R1R1=white
RR1 =pink
Chapter 11
Complex Inheritance and Human Heredity
Codominance
Inheritance
pattern in which
both alleles show
at the same time
equally
BB=black
B1B1=white
BB1 =roan
Chapter 11
Roan horse is mix of
black and white hairs
Mix of red and
white petals
Complex Inheritance and Human Heredity
Multiple Alleles C=full color
ch=himalayan
c=albino
cch=chinchilla
Chapter 11
Some genes may
have more than
just two
alternative forms
of a gene
In rabbits, four
alleles code for
coat color:
Complex Inheritance and Human Heredity
Multiple Alleles
More than 2 alleles
determine genotype
Blood groups in
humans have 3 alleles
─IA
─IB
─i
11.2 Complex Patterns of Inheritance
Chapter 11
Complex Inheritance and Human Heredity
Multiple Alleles
Having 3 alleles
produces a total of 6
possible genotypes
and 4 possible
phenotypes.
Phenotype IS THE
SAME AS THE blood
type.
(A, B, AB, O)
11.2 Complex Patterns of Inheritance
Chapter 11
Complex Inheritance and Human Heredity
Epistasis
One allele hides the effects of another allele.
In Labs, black coat color is dominant over yellow
and how dark – very dark (B) or light (b).
E=dark pigment or not B=how dark pigment is
E=dark fur e=light fur B=very dark b=not dark
No dark pigment present in fur Dark pigment present in fureebb
eeB_E_bb E_B_
Chapter 11
Complex Inheritance and Human Heredity
Sex-Linked Traits
Genes located on the X chromosome –
XC = colorblind
Xh = hemophilia
Includes:
Red-green color blindness
Hemophilia: blood does not
clot
11.2 Complex Patterns of Inheritance
Chapter 11
Complex Inheritance and Human Heredity
Polygenic Traits
Polygenic traits arise from the interaction of
multiple pairs of genes. Includes height and
skin color in humans.
Chapter 11
Dihybrid CrossDihybrid cross
– Involves the
cross of TWO
traits
– Uses a 16 block
Punnett square
• “F.O.I.L.” to
produce
gametes
Complex Inheritance and Human Heredity
Environmental Influences
Environmental factors
Diet and exercise
Sunlight and water
Temperature
Chapter 11