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.