Download 11.2 Notes

Chapter 11: Human Heredity
Section 2: The Inheritance of Human Traits
Human Blood Groups


A gene that has three or more alleles is said to have _______________________
________________________
Although many alleles may exist, it is important to remember that only two
alleles are present in diploid (2N) organism

_______________ and ___________ blood groups are examples of human traits
determined by multiple alleles
ABO Blood Groups

In 1900, the Austrian physician _______________________________________
discovered that human blood could be classified into _____________ general
types
o Landsteiner blood groups
o Determined
by
the
presence
of
absence
of
specific
________________________________________________________
in
the blood

Landsteiner discovered that the red blood cells could carry two different
_______________________________, which he called _____ and _____
o Molecules that can be recognized by the __________________________
______________________

The presence or absence of the A and B antigens produces four possible blood
types
o _________________________________________

Type A blood – antigen _____

Type B blood – antigen _____

Type AB blood – antigen _____ and _____

Type O blood – _______________________________________

Especially important in ______________________________________________

A transfusion of the wrong type can cause a violent, even fatal, reaction in the
body as the immune system responds to an antigen not found on its own cells

People with _____________ blood can receive blood from any of the four types
because they already have both possible antigens on their blood cells

The ABO blood groups are determined by a single gene with three alleles:
___________________________________

EXAMPLE
o If type B blood is given to a person with type A or type O blood, a
reaction will occur against the red blood cells carrying the B antigen
Rh Blood Groups

In addition to the ABO antigens, there is another antigen on the red blood cells,
called the ___________________________________
o Named after the __________________________________________ in
which the antigen was first discovered

People who have the Rh antigen on their red blood cells are said to be Rh
positive _____________________

People who do not have the Rh antigen on their red blood cells are said to be Rh
negative ____________________

In blood banks, the ABO and Rh blood groups are often expressed together in
symbols such as ______________, or ________________
Huntington Disease

____________________________________________, which is produced by a
single dominant allele, is an example of a genetic disease

People who have this disease show no symptoms until they are in their
__________________________________________, when the gradual damage
to their _____________________________________________ begins

People who have the dominant allele for Huntington disease have the disease
and suffer painful progressive loss of __________________________________
and ____________________________________________ until death occurs
Sickle Cell Anemia

In 1904, Doctor _______________________________________ noticed an
unusual ailment afflicting one of his young patients
o Had been complaining of ______________________________ and dizzy
spells
o ________________________________ on legs
o Red blood cells were bent and twisted into shapes that resembled sickles
The Cause of Sickle Cell Anemia

Sickle cell anemia is caused by a change in one of the polypeptides found in
_____________________________________
o Protein that carries _________________________ in red blood cells

When a person who has sickle cell anemia is deprived of oxygen the
hemoglobin molecules join together and form fibers
o Cause the red blood cells to undergo dramatic changes in shape

More ___________________

Become ____________________ in capillaries

Movement of blood through these vessels is stopped and
damage to cells and tissues occur
o Serious injury or death may result
The Genetics of Sickle Cell Anemia

The allele for normal hemoglobin ____________ is codominant with the sickle
cell allele ___________
o Heterozygous (HAHS) individuals are carriers

________ of the hemoglobin is ___________________________

Suffer few ill effects of the disorder
o Homozygous (HSHS) individuals are sufferers

All hemoglobin molecules are affected by the sickle cell allele

___________________________________________
by
the disease
The Molecular Basis of Sickle Cell Anemia

The allele for sickle cell hemoglobin differs from the allele for normal
hemoglobin by a ______________________________________________

The substitution of one nucleotide in the allele results in the substitution of a
different amino acid in the sickle cell hemoglobin protein
o Makes hemoglobin _________________________________ in blood
The Distribution of Sickle Cell Anemia

In the US, people of ____________________________________________ are
the most common carriers of the sickle cell trait

In the rest of the world, sickle cell anemia is found in the tropical regions of
Africa and Asia

Approximately ____________ of Americans of African ancestry and as many as
_______________ of the population in some parts of Africa carry the trait

People who are heterozygous for sickle cell anemia (HAHS) are partially resistant
to ___________________________, a serious disease that affects red blood cells

Sickle cell hemoglobin is thought to offer this resistance because sickled cells are
frequently removed from the circulation and destroyed, killing any malaria
parasites with them

People who are homozygous for normal hemoglobin (HAHA) on the other hand,
have no _______________________________________________________

The incidence of sickle cell anemia parallels the incidence of malaria
throughout the tropical areas of the world
Polygenic Traits

Human traits that are controlled by a number of genes are called
___________________________________________
o _________________________________
o _________________________________
o _________________________________