Download Learning Goal: I will

Name
Period
Learning Goal: I will …
→ predict possible outcomes of various genetic combinations such
as non-Mendelian inheritance like incomplete dominance and
codominance.
Incomplete
dominance
Incomplete dominance = Blending
 Both alleles are partially expressed in the heterozygote
 Both traits are “weak”, so they blend together
 Notation uses the same capital letter, but one allele gets a “prime”
Ex: Red flower (RR) x White flower (R’R’)  Pink flower (RR’)
 Cross a Chestnut horse (HH) and a Cremello horse (H’H’)
Codominance
Codominance = Both Show
 Neither phenotype is dominant
 The heterozygous individual expresses both phenotypes
 Notation uses different capital letters because they are both strong
Ex: Black chicken (BB) x White chicken (WW)  Dominique
(BW)
 Cross two Dominique chickens (BW x BW)
Blood Types
 Blood type A and B are codominant
 Blood type O is recessive to both A and B
 Blood type is caused by a cell-surface marker protein called
Immunoglobulin
 the notation is IA, IB, or i (for type O)
 Cross a man homozygous for type A with a woman of type AB
Summary Word Bank

blending

blood type

codominance

incomplete

recessive
Summary of Learning
In incomplete dominance, neither phenotype is completely dominant, so
there is a blending of the traits in the heterozygote. In codominance,
both phenotypes are strong, so they are both expressed in the
heterozygote. Human blood type is an example of codominance between
the type A and type B alleles, and regular dominance with the recessive
allele for type O.
Name
Period
Multiple Alleles
Polygenic
Inheritance
Sex-linked
Inheritance
Summary Word Bank

homologous

multiple

polygenic

sex-linked
Learning Goal: I will …
→ predict possible outcomes of various genetic combinations such
as non-Mendelian inheritance like multiple alleles, polygenic
inheritance, and sex-linked inheritance.
Multiple Alleles
 Each individual has 2 homologous chromosomes that carry alleles
 One individual can only have 2 alleles
 There can be more than 2 alleles in the population
 Blood type is an example of this
Alleles for blood type: 1) IA 2) IB 3) I
 Coat color in rabbits exhibits multiple alleles
Some alleles are more dominant than others
 Complete the Punnett square that shows it is possible to have white
rabbit offspring if one parent is white and the other is chinchilla
Polygenic Inheritance
 A trait controlled by two or more genes
 Usually results in a wide range of possible phenotypes
Ex: Height in humans and skin color
 Graph of inheritance pattern usually forms a “bell curve”
Sex-Linked Inheritance
 X and Y chromosomes are sex chromosomes
 XX are female, and XY are male
 The X and Y chromosomes carry different genes, so they are NOT
homologous
 Traits on the X chromosome are called sex-linked
 Show the inheritance of the sex-linked recessive gene for the
recessive trait of hemophilia (XHXh x XHY)
Summary of Learning
A trait can have multiple alleles, although each individual can only have 2
alleles for each trait. A trait may be controlled by 2 or more genes, which
is called polygenic inheritance. A gene carried on the X chromosome is a
sex-linked trait, and will be more common in males because the X and Y
chromosomes are not homologous.