Download Human Inheritance

Human Inheritance – Part I
Review – What is Heredity?
• Heredity is the passing of _____________ from _____________ to _________________
• ______________ are passed from parents to offspring (**Remember a ___________ is the ________ that controls
______________**)
• ______________ are located on our _______________________
Autosomes vs Sex Chromosomes
•
•
•
All human cells contain ____ chromosomes or _______________ of
chromosomes
The first ______ chromosomes (or ______________) are called
___________________
The __________ of chromosomes are the ____________________________
– In female the sex chromosomes are ______
– In males the sex chromosomes are ______
Karyotypes
• A karyotype is a _____________________ of ________________________________.
• A normal human karyotype is the result of a _____________________________ containing _____ chromosomes
fertilizing a ______________________ also carrying ___ chromosomes (__________________)
• Karyotypes are used to detect ___________________________ and to determine the __________________________
Normal Female Karyotype
This karyotype would be labeled:____________
Normal Male Karyotype
This karyotype would be labeled:_____________
**Circle and label the sex chromosomes on each karyotype
**Label an autosome on each karyotype
Pedigrees
• A pedigree is a diagram that follows the ___________________ of a ______________________ through several
generations of family
• How to Read a Pedigree
=
=
=
=
=
=
**Remember children are placed in birth order from left to right
Practice
The following pedigree shows the inheritance of a recessive trait.
1. How many generations are shown in the above pedigree?
2. How many children did Parents 1-1 and 1-2 have?
How many were boys?
How many were girls?
3. How many children did Parents II-1 and II-2 have?
How many were boys?
How many were girls?
4. If R = non-affected and r = affected; determine the genotypes of each person in this pedigree. (Hint: label all
homozygous recessives first)
Chromosome Number Disorders
• Number disorders occur because of a ______________ of the chromosomes to ___________________________
during __________________
• _________________________ – chromosomes ________________________
– Nondisjunction in __________________: ___________________________ fail to separate
– Nondisjunction in __________________: ___________________________ fail to separate
• In either case, gametes have an _____________________________________
Nondisjunction in Anaphase I
Chromosome Number Disorders
**Number disorders are ______ inherited; therefore they ___________________________ using
__________________________**
Two Types of chromosome number disorders: 1) Autosomal Number Disorders 2) Sex Chromosome Disorders
1. Autosomal Number Disorders
• Most autosomal number disorders are ____________
• The only autosomal number disorder that allows survival into adulthood is ________________________
Down Syndrome
• Also known as ____________________ because there are ___ chromosomes in the _________________________
• Characteristics:
– ____________________ nose and face; __________________ slanting eyes
– Growth, behavior and mental development are all _____________________
– Risk of _________________________
• Incidence of having a baby with Down syndrome is high in ______________________
2. Sex Chromosome Number Disorders - Caused by _____________________ of the chromosomes
in the ______________________ or the ___________________________
Turner Syndrome
• Also called __________ because individuals lack a ________________
______________________________.
• Characteristics:
– Female
– ______________ stature
– Underdeveloped sexually
– ___________________ (unable to bear children)
– ______________________ life expectancy
Klinefelter Syndrome
• Also called _______________ because individuals inherit an ______________________________.
• Characteristics:
– Symptoms appear at ________________
– Males shows _____________ sexual development
– ______________
– ________________ life expectancy
Human Inheritance – Part II
Sex-Linked Inheritance
• A gene is referred to as “_________________” if it is located on a _____________________ (either __ or __)
• In humans, sex-linked _____________ are almost always located on the _______________________________.
• The _________________________ is much ______________ and carries only a few genes related to
______________________________________
• Females have _______ chromosomes; males have ______ chromosome.
Sex-Linked Inheritance – Who is Affected?
• Females will only show _________________________ located on the _____________________________ if they are
______________________________.
• Males will ALWAYS show a __________________________ located on the __________________________ because
he only has _______.
• Females can be _________________ for _________________________________.
– A carrier someone who has the _____________________, but doesn’t show the _______________.
Sex-Linked Disorders
**Important – all of these disorders are sex-linked RECESSIVE**
1. Color Blindness: the ________________ to differentiate and distinguish _______________
Ex: red-green colorblindness
2. Hemophilia: Patients are missing an _________________ required for normal ___________________________.
– Have _______________________________ episodes
– Treated with blood _________________________
3. Duchenne’s Muscular Dystrophy
– Symptoms develop at _________________ of age.
– Causes _________________________ and the _____________________________________, leading to eventual
death.
– There is no available ____________________ or cure.
Sex-Linked Disorders – How to Write Genotypes
• Genotypes for _________________________ are written using the ________________ chromosomes to show
___________________________________.
C = normal vision c = colorblindness
Colorblind male = XcY
Colorblind female = XcXc
Carried female = XCXc
**REMEMBER – In sex-linked disorders males CANNOT be carriers**
Using Punnett Square to Determine Inheritance of Sex-Linked Disorders
• In _____________________ traits, ______________________ for male and female offspring must be calculated
_______________________ because traits are inherited ________________________.
Practice: A colorblind female marries a man with normal vision. What is the probability of them having colorblind children?
Key: ________________________________________
Cross: _______________________________________
Probability of having a colorblind daughter = ___________
Probability of having a colorblind son = ____________
Practice: A genetics counselor interviews a couple with a family history of hemophilia to evaluate the possibility of having
offspring with the disorder. The wife does not have hemophilia, but states that her father had the disorder. The husband is
normal.
Key: ________________________________________
Cross: _______________________________________
Probability of having a colorblind daughter = ___________
Probability of having a colorblind son = ____________
Autosomal Disorders
• Most genes are carried on the autosomes, the 44 chromosomes other than the sex chromosomes.
•Most genetic disorders are autosomal disorders.
•These disorders affect males and females equally.
Autosomal Disorders
•Autosomal disorders can be divided into three groups based on the pattern of inheritance.
–Autosomal Recessive: Person needs two recessive alleles to have the disorder
–Autosomal Co-dominant: People with a heterozygous genotype expresses similar symptoms to the homozygous dominant
genotype
–Autosomal Dominant: the dominant allele will causes the disorder; only need one dominant allele
Autosomal Recessive Disorders
•Albinism: characterized by failure to produce the pigment, melanin.
–Lack coloration in skin, hair and eyes
–At risk for skin cancer
–Symptoms appear at birth
Autosomal Recessive Disorders
2. Tay-Sachs Disease: characterized by the inability of nerve cells to break down a specific type of lipid.
–Symptoms appear between 3-6 months of age
–Lipid build-up causes seizures, blindness, degeneration of mental & motor skills
–Death usually occurs at or before age 5
–Historically associated with the Jewish population
Autosomal Recessive Disorders
3. Cystic Fibrosis: characterized by excess mucus production in the lungs & respiratory system
–Symptoms appear just after birth
–Suffer from frequent respiratory infections and poor nutrition
–Treatment helps patients live to their 20’s & 30’s
Cystic Fibrosis
Autosomal Recessive Disorders
4. Phenylketonuria or PKU: characterized by the inability to breakdown the amino acid, phenylalanine.
–Build-up results in severe brain damage & mental retardation
–All babies born in US hospitals are tested for PKU because it is easily treated with a diet low in phenylalanine
Phenylketonuria or PKU
Autosomal Co-Dominant Disorders
•Sickle Cell Anemia affects hemoglobin production.
–Hemoglobin is the protein that carries oxygen in our red blood cells (RBCs)
–Individuals that are homozygous dominant (SS) produce an abnormal hemoglobin which causes RBCs to “sickle” during
periods of low oxygen
•Ex: stress, high altitudes
–Sickled RBCs block vessels causing severe pain and brain damage
Sickle Cell Anemia
Autosomal Dominant Disorders
•Marfan Syndrome: affects the connective tissue of the skeletal system, eyes and circulatory system
Characteristics:
–Long limbs, vision problem, susceptible to aortic rupture
Autosomal Dominant Disorders
2. Huntington’s Disease: characterized by deterioration of the nervous system
Characteristics:
–Fatal disorder
–Symptoms arise in the 40’s-50’s
–Mental deterioration
–Uncontrollable movements