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14-1:
HUMAN
HEREDITY
HUMAN CHROMOSOMES
Karyotype: set of photographs of
chromosomes grouped in order and in pairs.
SEX CHROMOSOMES*
Sex Chromosomes: 2 chromosomes that determine an
individual’s sex on the 23rd pair of chromosomes.
Females– XX on 23rd pair
Males– XY on 23rd pair
AUTOSOMES
Autosomes: chromosomes that are not sex
chromosomes (everything except for pair #23).
POST-IT-NOTE CHECK
1. How many total pairs of
chromosomes do humans have?
2. Which pairs are autosomes?
3. Which pair(s) is/are sex
chromosomes?
PEDIGREE
Pedigree: Chart that shows the relationships
within a family.
BLOOD GROUP GENES
•
Transfusion of the wrong blood group can be fatal.
•
ABO and Rh are the best known blood group genes.
•
Rh positive (Rh+) is dominant to Rh negative (Rh-).
•
ABO blood group produces different antigens on
red blood cells.
BLOOD TYPES CHART*
*Type O: Universal Donor
*Type AB: Universal Recipient
THINK-PAIR-SHARE
SCENARIO
Imagine Person A is rushed to the ER because they
have just been in a major car accident. They are losing
a lot of blood in a short amount of time and you have to
decide what to do next as the only doctor in the ER.
Issues
• Person A has type AB blood.
• There are no more available blood bags for a blood transfusion.
• There are plenty of nurses, technicians on staff etc.
How are you going to keep this person alive?
RECESSIVE ALLELES
A normal, functioning gene is often revealed only when
abnormal/nonfunctioning allele affects the phenotype.
PKU: recessive allele on chromosome
12 causes severe mental retardation and
inability to break down phenylalanine
(found in milk and other foods).
Tay-Sachs: recessive allele
that results in the breakdown
of the nervous system.
DOMINANT ALLELES
A dominant allele for a genetic disorder will be expressed in
the phenotype.
Achondroplasia:
form of dwarfism
Huntington’s Disease: causes loss
of muscle control & mental function in
middle age until death.
CODOMINANT ALLELES
Sickle cell disease is caused by a codominant allele and
found in 1 in 500 African Americans.
T-Boz From TLC has sickle
cell disease
Codominance in Panda Bears
CYSTIC FIBROSIS (CF)
•
•
•
Caused by a recessive
allele on chromosome 7
where 3 bases are
deleted resulting in a
nonfunctioning chloride
ion channel protein.
Causes serious digestive
problems and a thick
heavy mucus to clog the
lungs and breathing
passageways.
About ½ of children born
with CF survive into their
20’s.
SICKLE CELL DISEASE
•
A change in just one DNA base in the hemoglobin gene
causes the protein to clump together resulting in bent
and twisted red blood cells.
•
Causes physical weakness, damage to brain, heart and
spleen- may be fatal.
•
Carriers are usually healthy and resistant to malaria.
CHECKING FOR
UNDERSTANDING
1. What is the difference between autosomes and
sex chromosomes?
2. List 1 disease associated to each: dominant,
recessive and codominant alleles (3 total).
3. In terms of blood type groups, why is it possible
for Type O people to donate blood to any blood
type group? (HINT: Think about antigens/
antibodies)