Post on 14-Aug-2015
11.2 Complex
Inheritance
A. Incomplete DominanceA. Incomplete DominanceHeterozygous phenotype is
an intermediate phenotype between the two homozygous phenotypes
EX. Red x white = pink
Heterozygous phenotype is an intermediate phenotype between the two homozygous phenotypes
EX. Red x white = pink
B. Codominance B. Codominance Both alleles are expressed in the
heterozygous conditionExample: Sickle-Cell Anemia People who are homozygous have
abnormal red blood cells that are shaped like a half moon
Both alleles are expressed in the heterozygous condition
Example: Sickle-Cell Anemia People who are homozygous have
abnormal red blood cells that are shaped like a half moon
• Hemoglobin differs by one amino acid
• Results in slow blood flow and blocked vessels
Those heterozygous for this trait produce both kinds of blood cells (normal and sickle)—these individuals can lead relatively normal lives.
most common in black Americans whose families originated in Africa and white Americans whose families originated in countries surrounding the Mediterranean Sea
1 in 12 African Americans is heterozygous for this trait
Those heterozygous for this trait produce both kinds of blood cells (normal and sickle)—these individuals can lead relatively normal lives.
most common in black Americans whose families originated in Africa and white Americans whose families originated in countries surrounding the Mediterranean Sea
1 in 12 African Americans is heterozygous for this trait
C. Multiple Alleles C. Multiple Alleles
Example 1: Blood Typea.The gene I has three alleles:
IA, IB, & ib. These alleles determine your
blood type: A, B, AB, and O
Example 1: Blood Typea.The gene I has three alleles:
IA, IB, & ib. These alleles determine your
blood type: A, B, AB, and O
Blood TypesBlood Types
Importance of Blood Typing
Importance of Blood Typing
Your immune system recognizes the red blood cells that you have.
If cells with a different protein enter your body, your immune system will attack them!
Your immune system recognizes the red blood cells that you have.
If cells with a different protein enter your body, your immune system will attack them!
Blood TypesBlood TypesGenotype Surface
ProteinPhenotypes
IAIA or IAi A A
IBIB or IBi B B
IAIB A and B AB
ii none O
Example 2: Coat Color of Rabbits
Example 2: Coat Color of Rabbits
Multiple alleles can demonstrate a hierarchy of dominance
In rabbits, four alleles code for coat color: C, cch, ch, and c.
Multiple alleles can demonstrate a hierarchy of dominance
In rabbits, four alleles code for coat color: C, cch, ch, and c.
Coat Color of RabbitsCoat Color of Rabbits
Light gray
Dark gray
Chinchilla
Albino
Himalayan
D. EpistasisD. Epistasis Variety is the result of one allele hiding
the effect of another allele Example: Coat color in labrador retrievers
varies from yellow to black
Variety is the result of one allele hiding the effect of another allele
Example: Coat color in labrador retrievers varies from yellow to black
No dark pigment present in fur Dark pigment present in fur
eebb eeB_E_bb E_B_
E. Sex DeterminationE. Sex Determination
Sex chromosomes determine an individual’s gender
Sex chromosomes determine an individual’s gender
e. Sex Linked Traitse. Sex Linked TraitsExamples:1.Color Blindness
Carried on the X chromosome
Examples:1.Color Blindness
Carried on the X chromosome
2. Hemophilia; Inability of blood to clotCarried on X chromosome
2. Hemophilia; Inability of blood to clotCarried on X chromosome
f. Polygenic Inheritancef. Polygenic Inheritance1. Example: skin color2. Variation in skin color indicates
that between 3 and 4 genes are involved
1. Example: skin color2. Variation in skin color indicates
that between 3 and 4 genes are involved
11.3 Chromosomes and Human Heredity
11.3 Chromosomes and Human Heredity
A. Changes in Chromosome NumberA. Changes in Chromosome Number
What would happen if an entire chromosome was missing or if you had an extra chromosome?These mistakes often happen during meiosis. Nondisjunction=chromosomes fail to separate properly during cell division
What would happen if an entire chromosome was missing or if you had an extra chromosome?These mistakes often happen during meiosis. Nondisjunction=chromosomes fail to separate properly during cell division
1. Unusual Numbers of Autosomes
1. Unusual Numbers of Autosomes
Most people have 23 pairs of chromosomes;
• 22 autosome pairs & 1 pair of sex chromosomes
Some people have an extra chromosome (47 instead of 46)
Down SyndromeDown SyndromeCaused by an extra 21st chromosome Caused by an extra 21st chromosome
Karyotypes are used to locate extra chromosomes.
Unusual Number of Sex Chromosomes
Unusual Number of Sex Chromosomes
1. Many problems may exist: X missing
XO=Turner’s Syndrome, OY=death
Extra X: XXX=nearly normal female, XXY=Male with Klinefelter’s Syndrome
Extra Y: XYY=normal or nearly normal male
2. Any individual with at least one Y is male, and any individual without a Y is a female.
1. Many problems may exist: X missing
XO=Turner’s Syndrome, OY=death
Extra X: XXX=nearly normal female, XXY=Male with Klinefelter’s Syndrome
Extra Y: XYY=normal or nearly normal male
2. Any individual with at least one Y is male, and any individual without a Y is a female.