Transcript Unit 8: Human Inheritance

UNIT VIII - HUMAN INHERITANCE
I. HUMAN GENETICS (pp. 270 – 271, 299 - 301)
A. Human Somatic Cells
body cells) are _______
diploid or 2n.
 Human somatic cells (_____
46 chromosomes, or 23 pairs
 Each human somatic cell has ___
of chromosomes. Of these 23 pairs, 22 pairs are called
homologous pairs, meaning they contain the same
_____________
genes in the same order.
 The 44 chromosomes that make up the 22 homologous
pairs in each cell are called ____________.
autosomes
sex chromosomes.
 The 23rd pair of chromosomes are the ____
XX
o In female somatic cells, the sex chromosomes are ___.
XY
o In a male’s somatic cells, the sex chromosomes are ___.
 All human somatic cells contain:
o ____
44 autosomes and
2 sex chromosomes.
o ___
1. Karyotypes
homologous
 A karyotype is a micrograph of _______________
chromosome pairs. Arranged in decreasing size.
B.




Human Gametes
Gametes are haploid
_______ or n, and contain 23
___ chromosomes.
egg cells, and male gametes are sperm
Female gametes are ____
______ cells.
meiosis in the ovaries or testes, respectively.
Gametes are produced through the process of ________
In meiosis, when the tetrad, or homologous pairs of chromosomes separate in anaphase I of
meiosis, the sex chromosomes separate also.
X chromosome, while the sperm cell produced has a
 The resulting egg cell can ONLY contain an __
MALE
50% chance of containing an __,
X and a 50% chance of containing a __.
Y Therefore, the ______
determines the sex of the offspring.
C. Analyzing Human Inheritance
Pedigree chart is a diagram that follows the inheritance of
A _________
a single _____
generations of a family.
trait through several ___________
Pedigree Rules:
squares and
• In a pedigree, males are represented by ________,
females are represented by ______.
circles
Horizontal
• _______
Vertical lines connect parents to children. __________
lines connect siblings or spouses. Children are placed in
birth order, from left to right.
• Roman numerals show ___________.
generations
• Individuals who are affected by the trait are represented
with shaded
_______ symbols. Individuals that are not affected
non-shaded figures.
by the trait are shown by ___________
• Half shaded = _____________
carrier of
heterozygous or a “_________”
the trait.
• Circle with a ____
female
dot = X-linked carrier (always _______)
(Video: What are Pedigree Charts? (Mark Drollinger 4:23))
An attached ear lobe is a recessive trait. Determine the genotypes of each individual
below. Hint: label all homozygous recessives first!!!
Analysis Questions:
1. How many are males have attached
earlobes? 3
2. How many are females have free
earlobes? 5
3. How many aunts are in this family?
2
4. How many heterozygous traits
exist? 5 How many are possible? 7
A widow’s peak hairline is a dominant trait. Determine the genotypes of each individual below. Hint: label all
homozygous recessives first!!!
Key: W = widow’s peak
w = no widow’s peak
The following pedigree shows the inheritance of a recessive trait.
rr
R?
Rr
R?
rr
R?
R?
R?
Rr
R?
R?
rr
R?
Rr
Rr
R?
R?
rr
rr
rr
rr
Rr
rr
R?
• How many generations are shown in this
pedigree? 5 (V)
• How many children did Parents I-I and I-2
have? 3
• How many were boys? 1 Girls? 2
• How many children did Parents II-1 and II2 have? 3
• How many were boys? 2 Girls? 1
• Key: R = non-affected; r = affected
• Determine the genotypes of each person
in this pedigree.
II. AUTOSOMAL DISORDERS (pp. 296 – 304)
autosomes the 44 chromosomes other than the 2 sex
• Most genes are carried on the __________,
chromosomes. So it follows that most genetic disorders are autosomal disorders.
equally
• These disorders affect males and females _______.
• Autosomal disorders can be divided into:
A. Recessive
________
1. Albinism
2. Cystic Fibrosis
3. Tay-Sachs Disease
4. Phenylketonuria
B. Dominant
_________
1. Huntington Disease
2. Marfan’s
C. _______
Number Disorders
A. AUTOSOMAL RECESSIVE DISORDERS
(https://www.youtube.com/watch?v=_oVvTkjDm6g)
melanin
1. Albinism – Characterized by failure to produce the pigment, _______.
hair and _____.
eyes
• Affected individuals lack coloration in skin, ____,
cancer and are very sensitive to light.
• Very susceptible to skin _______
• Symptoms appear at _____;
birth they have a normal life expectancy.
• Mode of Inheritance:
o From recessive alleles on chromosome # ___
11
mucus production in lungs & respiratory system.
2. Cystic Fibrosis – Characterized by excess _______
• Symptoms appear just after birth which include frequent respiratory infections, poor
nutrition due to blockage of pancreas & can cause liver failure..
20’s & 30’s
• With treatment, patients can survive to their ____
____.
fatal genetic disorder in the US among Caucasians.
• Cystic fibrosis is the most common _____
(1:30)
7
• Recessive allele on chromosome # ___
3. Tay-Sachs Disease – Characterized by the inability of nerve cells to break down a specific
type of lipid
____.
3-6 months.
• Symptoms appear between the ages of ____
blindness degeneration of mental & motor skills, and
• Lipid build-up causes seizures
_______, _________,
5
_____
death at or before age ___.
Jewish population, although genetic testing has decreased its
• Historically associated with ______
incidence.
• Recessive allele on chromosome # 15
___
PKU – Characterized by an inability to breakdown the amino acid,
4. Phenylketonuria or ____
phenylalanine
_____________.
brain damage & mental impairment.
• Build-up results in severe ______
easily treated with a diet
• All babies born in US hospitals are tested for PKU because it is _____
low in phenylalanine.
12
• Recessive allele on chromosome # ___
B. AUTOSOMAL DOMINANT DISORDER https://www.youtube.com/watch?v=yANF0bxHpzU
brain cell degeneration
1. Huntington
_________ Disease – characterized by genetically programmed _____
psychological
• Affects ______,
motor cognitive & ____________changes.
• S/SX: mood swings, depression, loss of memory and ability to learn. As well as loss
of muscle control, difficulty swallowing, speech impairment, and eventually death.
normal
• Genotypes: hh = _______
one parent must have it for the
• HH
___ or ___=
Hh will have disease (therefore, only ____
child to inherit the disease.)
4
• Affiliated with Chromosome # __
2. Marfan Syndrome – Dominant disorder that affects the __________
connective tissue
______of the
skeletal system, eyes, and circulatory system. Affected individuals have very long
limbs ______
aortic
vision problems, and are susceptible to ______rupture.
_____,
C. NUMBER DISORDERS
• Number disorders occur because of a failure of a
separate correctly in
chromosome pair to _________
Anaphase I or II of meiosis. This is referred to as
nondisjunction
______________.
• Nondisjunction can occur during Meiosis I, in
homologous _____
pairs fail to separate or in
which ___________
sister__________
chromatids fail to
Meiosis II, in which _____
separate.
• In both cases, the gametes produced have an
abnormal number of chromosomes.
_________
• **Number disorders are NOT inherited;
therefore, they CANNOT be Predicted with
Punnett _______**
square
________
• Can involve autosomal chromosomes or sex
chromosomes
A. Autosomal Number Disorders https://www.youtube.com/watch?v=ze_6VWwLtOE
lethal The ONLY autosomal number disorder that
Most autosomal number disorders are ______.
Down syndrome
allows survival into adulthood is ______
_________.
3 chromosomes at the
21 because there are __
1. Down syndrome is also known asTrisomy
___________
21st position, instead of just ___.
2
____
• Individuals have characteristic facial features; growth, behavior, and mental development
impaired There is also a higher risk of congenital heart defects. The incidence
are all _________.
older mothers.
of babies with Down syndrome is much higher in _____
2 . Edward’s Syndrome
Also called _________ ____, is a chromosomal
condition associated with abnormalities in many parts
of the body.
• Slow growth before birth (intrauterine growth
retardation) and a low birth weight.
• May have heart defects & abnormalities of other
organs that develop before birth.
• Other features are a small, abnormally shaped
head; a small jaw and mouth; and clenched fists
with overlapping fingers. Due to the presence of
several life-threatening medical problems
• Many die before birth or within their first month.
Five to 10 percent of children with this condition
live past their first year, and these children often
have severe intellectual disability.
3. Patau Syndrome
Also called _______
Trisomy ___,
13 is a chromosomal condition
associated with severe intellectual disability and physical
abnormalities in many parts of the body. Occurs in about
1 in 16,000 newborns
• _____
Heart ______,
defect brain or spinal cord abnormalities, very
small or poorly developed _____
eyes (microphthalmia)
• Extra fingers or toes
lip (a cleft lip) with or without an
• An opening in the ___
opening in the roof
____ of the mouth (a cleft palate)
• Weak muscle tone (hypotonia).
Due to the presence of several life-threatening medical
problems, many infants with trisomy 13 die within their
first
5-10
____ days or weeks of life. Only ______%
of children with
this condition live past their _____
first year
B. Sex Chromosome Number Disorders https://www.youtube.com/watch?v=YQG8o5b4lKg
nd sex chromosome
45 XO because individuals lack a 2____________________.
1. Turner Syndrome – Also called _______
females typically short in stature, underdeveloped sexually, sterile, with a
• Patients are ________,
normal life expectancy.
47XXY https://www.youtube.com/watch?v=6qTPdSJc9Cs
2. Klinefelter Syndrome – Also called ______.
extra sex chromosome. Symptoms do not appear until _______
puberty at which
• Individuals inherit an _____
males show poor sexual development and infertility. Treated with hormone
time affected ______
therapy. Normal life expectancy.
• Most common sex disorder (1 out of 500 males)
III. SEX-LINKED INHERITANCE
X or ___).
Y
A gene is referred to as “sex-linked” if it is located on a sex chromosome ( ___
X chromosome.
In humans, sex-linked genes are almost always located on the larger ___
Y chromosome is much smaller and carries only a few genes related to sexual
The __
two X chromosomes; males have one
development. Females have ___
___ X.
• Females will only show recessive traits located on the X chromosome if they are
homozygous
__________ recessive.
higher incidence of sex-linked disorders.
• But a male will always having a much ______
• Genotypes for sex-linked traits are written using the X and Y chromosomes to
show path of inheritance.
• For example: red-green color blindness is a sex-linked recessive trait. If C = normal
vision and c = colorblindness:
XcY colorblind female = ____.
carriers
XcXc Females can be _______
• KEY: colorblind male = ____;
for sex-linked recessive disorders. A carrier someone who has the defective allele,
show the trait The genotype of a female carrier is _____.
XCXc Males
but doesn’t ___________.
_______
CANNOT be carriers for a sex-linked trait because they only have one X
chromosome.
A. Sex-linked Disorders – All of these disorders are sex-linked __________.
RECESSIVE
Normal life span
1. Color Blindness – Inability to differentiate and distinguish colors. ______
• Example: red-green colorblindness
2. Hemophilia – Missing an enzyme required for normal blood clotting
______.
a. Have uncontrolled bleeding episodes. Main Symptom:
bruising and/or bleeding
• Blood fails to clot properly leading to excessive _______
internally
________.
• Treated with blood __________.
transfusions
b. Hemophilia can be traced through a pedigree of the _____
Royal family
3. Duchenne’s Muscular Dystrophy
3-6 years of age.
• Symptoms develop at ____
breakdown of muscle fibers, leading to eventual
• Causes muscle weakness
________ and the __________
cure Death usually occurs before _________.
adulthood
death. There is no available treatment or ____.
Sex-Linked Punnett Squares Practice: In sex-linked traits, probabilities for male and female offspring
must be calculated separately because traits are inherited differently.
1. 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 = ____________
2. A genetics counselor interviews a couple with a family history of
hemophilia to evaluate the possibility of having offspring with the disorder.
The woman does not have hemophilia, but states that her father had the
disorder. The man is normal.
• Key: ________________________________________
• Cross: _______________________________________
• Probability of having a daughter with hemophilia = _____
• Probability of having a son with hemophilia = ___________