Human Heredity

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Human Heredity
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• There are traits that are controlled by one gene
  with 2 alleles. Often, one is dominant and the
  other is recessive
• Example
• widows peaks and dimples.

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• Some traits are controlled by a gene with
  multiple alleles 3 or more for a single trait.
  
• For example blood types and skin color in
  humans.

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• There are 44 chromosomes that we call autosomal
  chromosomes.
• However, there are 2 chromosomes that determine
  our sex and we call them sex chromosomes.
• These 46 chromosomes all carrier genes on them
  that determine our traits.

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• Out of our 23 pairs of chromosomes, 1 pair is the
  sex chromosomes (X and Y).
• Female XX
• Male XY

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• Question What is the probability that your
  parents will have a boy or girl?
• XY (dad) x XX (mom)

Y
X


Phenotype 50 boy 50 girl
X
XX
XY
Genotype 50 XX 50 XY
X
XX
XY
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• Question?
• If my parents have 5 boys in a row, what is
  the chance they will have a girl the next time?

50
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• Human genes are inherited the same way that
  Mendel discovered. Some traits are controlled by
  one gene. Therefore, you can study inheritance
  of traits through a pedigree. A pedigree is a
  chart or family tree that traits a specific
  trait.

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Genetic counselors analyze these charts to infer
about genotypes of family member. Dominant
gene ?affected individuals have at least
one affected parent ?the phenotype
generally appears every generation
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Recessive gene ?unaffected parents can have
affected offspring ?affected progeny are
both male and female
                                                                                                              
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• Sex-linked gene
• Some traits are carried on the sex chromosomes.
  Genes on the X or Y chromosomes are sex-linked
  genes.
• These traits are passes on from parent to child.
  Sex- linked genes can be recessive or dominant.
• MALES are more likely to have a sex-linked trait
  because they only have ONE X and Y. The allele
  is USUALLY on the X chromosome.
• Ex. colorblindness, hemophilia, hairy ears,
  muscular dystrophy

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Are you colorblind?
What numbers do you see?
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• Carrier person who has one recessive allele and
  one dominant allele for a trait or heterozygous
  for that trait (only women can be carriers).
• Example
• Hemophiliac carrier XHXh
• Colorblind carrier XBXb

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• Carriers do not show that particular trait
  phenotypically but have a chance to pass the
  trait on to their child.

Carrier half colored
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Reading a Pedigree
Task 1 Genotyping a pedigree chart
Task 2 Take out your pedigree sheet and some
paper. Lets do the first one together. Do 2.
Come see me to get your paper starred.
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• Sex linked Punnett Squares
• Question
• What is the probability that a carrier female
  and a colorblind male will have a girl who is
  colorblind (b colorblind, B normal)?

Y
Xb
Phenotype 25 normal boy 25 colorblind boy 25
normal girl 25 colorblind girl


XBXb
XBY
XB
Xb
XbXb
XbY
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Try this one on your own

• Question
• What is the probability that a homozygous
  (normal vision) female and a colorblind male will
  have a girl who is colorblind (b colorblind, B
  normal)?

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Parents XBXB x XbY
Xb
Y
Phenotype 50 normal girls 50 normal boys


XBXb
XBY
XB
XB
XBXb
XBY
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?
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• Genetics Disorders and Mutations

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Mutations

• are changes in the genetic material
• can be good or bad
• can be on a single gene or the whole chromosome

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• Genetic Disorder
• abnormal condition that a person inherits
  through genes or chromosomes.
• They are caused by mutations or changes in a
  persons DNA.

Write down 3 disorders that have affected someone
you know.
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• Cystic Fibrosis
• Genetic disorder where the body produces
  abnormally thick mucus in the lungs and
  intestines making respiration and digestion
  difficult
• caused by a mutation in a gene. The product of
  this gene is a chloride ion channel important in
  creating sweat, digestive juices and mucus.
• One in four babies are born with cystic fibrosis
• Most common among Northern European descent

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• Sickle Cell Anemia
• Sickle cell is a genetic disorder that affects
  the bloods hemoglobin. Hemoglobin is the
  protein in your blood that carries oxygen.
• Sickle-cell anemia is caused by a point mutation
  in protein chain of hemoglobin, replacing the
  amino acid glutamic acid with the amino acid
  valine
• The sickle shape of the cell doesnt allow the
  red blood cell to carry very much oxygen.
• Most common among African American descent

Famous People with Sickle Cell Disease Miles
Davis, jazz musician. Paul Williams, singer (The
Temptations) Georgeanna Tillman, singer (The
Marvelettes) Tionne "T-Boz" Watkins, singer
(TLC)
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• Hemophilia
• Hemophilia is a genetic disorder in which a
  persons blood clots VERY slowly or not at all.
• A person with hemophilia can bleed to death from
  a paper cut or scrape.
• This is sex-linked disorder on the X chromosome.
• Queen Elizabeth suffered from this disorder.

This man received a vaccine. This is what having
hemophilia did to is body.
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• Down Syndrome
• Down Syndrome is a genetic disorder that occurs
  when an individual receives an extra copy of a
  chromosome.
• A mistake occurs during Meiosis I the
  chromosomes failed to separate correctly
  (non-disjunction) therefore leaving an extra copy
  of chromosome 21.

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• Doctors use tools like amniocentesis and
  karyotypes to help detect most diseases.

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?
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What is a karyotype?

• Picture of your chromosomes
• Arranged from largest to smallest
• quickly identify chromosomal changes

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• Diagnosis the karyotypes in the back of the room
  at your table.
• Make sure to include
• Case number
• Boy or girl
• Number of chromosomes
• Normal or abnormal
• (if abnormal, what is the
  problem?)

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4 Types of Genetic Disorders

• 1. Single gene
• Change in the DNA sequence
• More than 6000 known disorders
• Autosomal or sex linked
• 1 in 200 births
• Examples
• cystic fibrosis, sickle cell anemia, Marfan
  syndrome, Huntingtons disease

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Types of Genetic Disorders

• 2. Multi-factoral
• combination of environmental factors and
  mutations in multiple genes
• more complicated
• Examples
• heart disease, high blood pressure, Alzheimers
  disease, arthritis, diabetes, cancer, and obesity
  

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Types of Genetic Disorders

• 3. Chromosomal
• abnormalities in chromosome structure as missing
  or extra copies or gross breaks and rejoining
• Example
• Down Syndrome

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Types of Genetic Disorders

• 4. Mitochondrial
• rare type of genetic disorder
• caused by mutations in the non-chromosomal DNA of
  mitochondria

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Here are some genetics disorders, some you have
heard about and some you havent.
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Turners Syndrome
1 in 5,000 births 45 chromosomes X only 23
MonosomyNondisjunction
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Turners Syndrome
96-98 do not survive to birth No menstruation No
breast development No hips Broad shoulders and
neck
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Cri-Du-Chat Syndrome
1 in 216,000 births 46 chromosomes XY or XX 5
Deletion of lower arm
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Cri-Du-Chat Syndrome
Moon-shaped face Heart disease Mentally
retarded Malformed larynx Normal lifespan
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Aniridia-Wilms Tumor Syndrome
1 in 50,000,000 births 46 chromosomesXY or
XX 11 Deletion of upper arm
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Aniridia-Wilms Tumor Syndrome
Mentally retarded Growth retarded Blindness Tumors
on kidneys Short lifespan
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Thirteen Q Deletion Syndrome
1 in 500,000 births 46 chromosomesXY or XX 13
Deletion of lower arm
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Thirteen Q Deletion Syndrome
Mentally retarded Deformed face No thumbs Heart
disease Short lifespan
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Prader-Willi Syndrome
1 in 5,000,000 births46 chromosomes XY97
XX3 15 Deletion of lower arm
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Prader-Willi Syndrome
Small bird-like head Mentally retarded Respiratory
problems Obesity Short lifespan
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Eighteen Q Deletion Syndrome
1 in 10,000,000 births 46 chromosomesXY or
XX 18 Deletion of lower arm
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Eighteen Q Deletion Syndrome
Mentally retarded Heart disease Abnormal hands
and feet Large eyes Large ears Normal lifespan
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Cat-Eye Syndrome
1 in 1,000,000 births 46 chromosomesXY or
XX 22 Deletion of bottom arm
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Cat-Eye Syndrome
Fused fingers and toes Mentally retarded Small
jaw Heart problems Normal lifespan
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Four-Ring Syndrome
1 in 10,000,000 births 46 chromosomesXY or
XX 4 Inversion
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Four-Ring Syndrome
Cleft palate Club feet Testes dont descend Short
lifespan
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Down Syndrome
Down Syndrome Trisomy
1 in 31,000 births46 chromosomes XY97
XX3 14/21 Translocation
1 in 1,250 births 47 chromosomesXY or XX 21
Trisomy Nondisjunction
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Down Syndrome
Short, broad hands Stubby fingers Rough
skin Impotency in males Mentally retarded Small
round face Protruding tongue Short lifespan
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Pataus Trisomy Syndrome
1 in 14,000 births 47 chromosomesXY or XX 13
Trisomy Nondisjunction
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Pataus Trisomy Syndrome
Small head Small or missing eyes Heart
defects Extra fingers Abnormal genitalia Mentally
retarded Cleft palate Most die a few weeks after
birth
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Edwards Trisomy Syndrome
1 in 4,400 births47 chromosomes XX80
XY20 18 Trisomy Nondisjunction
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Edwards Trisomy Syndrome
Small head Mentally retarded Internal organ
abnormalities 90 die before 5 months of age
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Jacobs Syndrome
1 in 1,800 births 47 chromosomesXYY only 23
Trisomy Nondisjunction
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Jacobs Syndrome
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Normal physicallyNormal mentally Increase in
testosterone More aggressive Normal lifespan
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Klinefelter Syndrome
1 in 1,100 births 47 chromosomesXXY only 23
Trisomy Nondisjunction
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Klinefelter Syndrome
Scarce beard Longer fingers and
arms Sterile Delicate skin Low mental
ability Normal lifespan
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Triple X Syndrome
1 in 2,500 births 47 chromosomesXXX only 23
TrisomyNondisjunction
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Triple X Syndrome
Normally physically Normal mentally Fertile