Transcript Human Heredit

Chromosomes
Every human cell has 46 chromosomes
(23 pairs of chromosomes)
 A karyotype is a picture of the 23 pairs
of chromosomes.

Autosomes are
the first 22 pairs
of chromosomes
(#1-#22)
Sex
Chromosomes
determine the sex
and are pair #23
Female (XX)
XX-female
XY-male
Male (XY)
•Muskopf, Shannan. Online Images. The Biology Corner. 8 May 2007.
http://www.biologycorner.com/bio1/celldivision-chromosomes.html
Pedigree Charts-shows genetic history of a
family over many generations
Generation I
Generation II
Generation III
•Muskopf, Shannan. Online Images. The Biology Corner. 8 May 2007.
http://www.biologycorner.com/bio2/humangenetics.html
Symbols in a Pedigree Chart
Female
• Male
Sick Female
Sick Male
 Married
Couple
 horizontal line connects a
married couple
• Siblings
 Shaded:
individual has
the trait
 Not
shaded: does not
have the trait
• Half-shaded: carries the
trait (heterozygous)
Pedigree Chart of a Dominant Trait
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Huntingtons disease is a dominant disease that damages the
nervous system
One dominant allele means you get the disease
HH (homozygous) and Hh (heterozygous) will have the disease
hh (homozygous) will not have the disease
One parent has to have it to pass on to child
What is the genotype of
the father?
What is the genotype of
the son?
Pedigree Chart of a Dominant Trait
The father does not have the
dominant disease so he must
have 2 recessive alleles; his
genotype is hh
The son has the dominant disease so
he has to have at least one dominant
allele. Is his genotype HH or Hh?
One allele came from his father so his
genotype is Hh.
Pedigree Chart of a Dominant Trait
What are the chances that future offspring
of this couple will have this dominant
disease? Use the genotypes of the
parents to draw a punnett square.
hh
HH
Hh
Pedigree Chart of a Dominant Trait
hh
H
H
Hh
Hh
HH
h
Hh
h
Hh
Hh
All of the offspring have the dominant allele
so 100% of their future children will have this
dominant disease.
Pedigree Chart of a Recessive Trait
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Cystic fibrosis is a recessive disease causing digestive problems
HH (homozygous) and Hh (heterozygous) will NOT have the disease
hh (homozygous) will have the disease
Must inherit recessive allele from each parent to have the disease
What is the genotype of the
father?
What is the genotype of the
daughter?
Pedigree Chart of a Recessive Trait
The dad does not have this
recessive disease so his genotype
is either CC or Cc. Since he
passed on one recessive allele to
his daughter, his genotype is Cc.
She must have 2 recessive
alleles to have this disease.
Her genotype is cc.
Pedigree Chart of a Recessive Trait
What are the chances that future offspring of
this couple will have this recessive disease?
Use the genotypes of the parents to draw a
punnett square.
Cc
Cc
cc
Pedigree Chart of a Recessive Trait
C
c
C
CC
Cc
c
Cc
cc
Only 1 out of 4 offspring have the
recessive disease (cc). There is a 25%
chance of future offspring having the
disease.
Cc
Cc
cc
Sex-Linked Traits (X-linked)
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Sex-linked genes are located on the sex
chromosomes (23rd pair) and deal with the X and Y
chromosome
A female is XX; a male is XY
Sex-linked genes are shown as superscripts on the
X chromosome
Sex-Linked Traits in females
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If a disorder is caused by a recessive gene, a
female’s genotype could be XBXB or XBXb and she
will not have the disorder. The XBXb female would
be a carrier.
A female with a sex linked disorder would be written
as XbXb because she must have both recessive
alleles.
Sex-Linked Traits in males
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The Y chromosome does NOT carry a gene. A male
without the recessive sex-linked disorder would be
XBY. A male with the sex-linked disorder would be
XbY.
Sex-linked disorders are more common in males
because males only need 1 copy of the recessive
allele since they have only 1 X chromosome.
Females must have 2 copies of the recessive allele
since they have 2 X chromosomes.
Common sex-linked disorders include color
blindness and hemophilia (a bleeding disorder)
Sex-linked pedigree for color blindness
What is this male’s genotype?
Colorblindness is a recessive sex-linked disorder
This is a male so his sex chromosome is XY
The square is shaded so this male is colorblind
His genotype is XbY (Remember, there are no superscripts on the Y
chromosome)
•Muskopf, Shannan. Online Images. The Biology Corner. 8 May 2007.
http://www.biologycorner.com/bio4/notes/inheritance3.html
Sex-linked pedigree for color blindness
What is this male’s genotype?
This is a male so his sex chromosome is XY
The square is not shaded so this male has normal vision
His genotype is XBY
•Muskopf, Shannan. Online Images. The Biology Corner. 8 May 2007.
http://www.biologycorner.com/bio4/notes/inheritance3.html
Sex-linked pedigree for color blindness
What is this female’s genotype?
This is a female so her sex chromosome is XX
This female is not colorblind so her genotype is either XBXB or XBXb
Her son is shaded so he is colorblind (XbY) and inherited the Y chromosome from
his father and the Xb chromosome from his mother.
The mother has to have a Xb in her genotype
Her genotype is
XBXb
•Muskopf, Shannan. Online Images. The Biology Corner. 8 May 2007.
http://www.biologycorner.com/bio4/notes/inheritance3.html
Practice
What percentages can be expected in
the offspring of a cross between a
female carrier for color blindness and a
male with a normal color vision? Show
your work with a punnett square.
Practice
What percentages can be expected in the offspring of a cross
between a female carrier for color blindness and a male with a
normal color vision? Color blindness is a recessive trait attached
to the X chromosome. A female carrier means heterozygous.
female carrier XBXb
male with normal vision XBY
XB
Xb
XB
XBXB
XBXb
Y
XBY
XbY
25% normal females
25% carrier females
25% normal males
25% colorblind males
Karyotypes are used to determine if an offspring has
the right number of chromosomes (46 in humans)
 Down Syndrome
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 47 chromosomes because there are 3 copies of
chromosome #21
 Causes mental retardation
3 copies of
#21
•Muskopf, Shannan. Online Images. The Biology Corner. 8 May 2007.
http://www.biologycorner.com/bio1/celldivision-chromosomes.html
Diagnosis of Chromosomal
Abnormality
• Amniocentesis-during pregnancy, a small
amount of fluid from the sac surrounding the
embryo is used to make a karyotype to
determine if the fetus has the correct number
of chromosomes
Amniocentesis
What is a karyotype?
Karyotype is a term in genetics. It refers
to the complement of chromosomes
either at the species level, or of
indivduals.
 The normal human karyotype comprises
23 pairs of chromosomes, making 46 in
total.
 In humans - and indeed in mammals,
the final pair varies between males (XY)
and females (XX)

Human Karyotype
Normal Male Karyotype
Normal Female Karyotype
Cystic Fibrosis
Is inherited disease of the secretory
glands. ( sweat and mucus)
 Inherited means the disease is passed
from parents to children through genes.
 May cause respiratory failure
 May affect :

 pancreas
 liver
 intestines
 sexual organs
 sinuses
Cystic Fibrosis
Mucus is a substance made by tissue
that line some organs in the body
cavities (lungs and nose)
 Buildup of mucus can cause bacteria to
grow and cause infection.
 People with CF will have a salty sweat.
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Huntington Disease
Huntington´s disease (HD) is an
autosomal dominant neurodegenerative
disease for which no cure is currently
available.
 Huntington's disease (HD) results from
genetically programmed degeneration of
brain cells, called neurons, in certain
areas of the brain.
 This degeneration causes uncontrolled
movements, loss of intellectual faculties,
and emotional disturbance.
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Huntington Disease
Huntington's disease is inherited in an
autosomal dominant fashion.
 The probability of each offspring
inheriting an affected gene is 50%.
Inheritance is independent of gender,
and the phenotype does not skip
generations.
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Tay Sachs
Tay-Sachs disease is caused by a
defective gene on chromosome 15.
 When both parents carry the defective
Tay-Sachs gene, a child has a 25%
chance of developing the disease.
 The child must receive two copies of the
defective gene -- one from each parent - in order to become sick
 Most common Eastern European Jews
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Tay Sachs
Infants with Tay-Sachs disease appear
to develop normally for the first few
months of life.
 As nerve cells become distended with
fatty material, a relentless deterioration
of mental and physical abilities occurs.
 The child becomes blind, deaf, and
unable to swallow
 . Other neurological symptoms include
dementia, seizures, and an increased
startle reflex to noise.
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Cri du Chat
Cri du chat syndrome is a group of
symptoms that result from missing a
piece of chromosome number 5.
 The syndrome’s name is based on the
infant’s cry, which is high-pitched and
sounds like a cat.
 1/20,000 individuals
 Less 20%
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Cri du Chat
Cri du Chat
Turner Syndrome
Turner Syndrome
Klinefelter Syndrome
Edwards Syndrome
Down Syndrome
Down Syndrome
Patau Syndrome
This the you need to known for the Quiz
Tay Sachs
 Huntington Disease
 Cystic Fibrosis
 Down syndrome
 Patau Syndrome
 Edwards Syndrome
 Turner Syndrome
 Klinefelter Syndrome
 Cri du Chat
 Karyotype
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