medical genetics
DESCRIPTION
Medical Genetics. Human Anatomy and Physiology II Oklahoma City Community College. Dennis Anderson. Produces daughter cells with 46 chromosomes Used in growth and repair. Mitosis. Mitosis. DNA is duplicated Doubled chromosomes form from duplicated DNA Each cms has 2 identical chromatids. - PowerPoint PPT PresentationTRANSCRIPT
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Medical Genetics
Human Anatomy and Physiology II
Oklahoma City Community College
Dennis Anderson
![Page 2: Medical Genetics](https://reader036.vdocuments.mx/reader036/viewer/2022062718/56812bd1550346895d903177/html5/thumbnails/2.jpg)
Mitosis
• Produces daughter cells with 46 chromosomes• Used in growth and repair
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Mitosis
• DNA is duplicated• Doubled
chromosomes form from duplicated DNA
• Each cms has 2 identical chromatids
Chromatid
Chromatid
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Chromosomes line up in a single row.
Mitosis Metaphase
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Chromosomes separate
Each chromatid becomes a single chromosome
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Meiosis
• Reduce the chromosome number to half that of body cells
• Produce gametes– Egg– Sperm
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Chromosomes line up in a double row.
Meiosis Metaphase
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Chromosomes separate
Each each daughter cell gets doubled chromosomes
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Doubled Chromosomes Separate in Second Meiotic Division
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Mitosis Metaphase
Meiosis Metaphase
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Cms 1 Cms 1
Cms 2 Cms 2
Double Filed Chromosomes
• Daughter cells receive ONE of each cms pair
• Daughter cells receive ONE allele for most traits
• New combinations of alleles possible
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Gene
• A unit of heredity that controls the development of one trait
• Made of DNA
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Allele
• Member of a paired gene– One allele comes from each parent
• Represented by a single letter
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Dwarfism = D
Normal height = d
DD = Dwarfism
Dd = Dwarfism
dd = Normal height
Examples of Alleles
Dwarf Band
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Dominant & Recessive Alleles
• Dominant alleles are expressed
• Recessive alleles are not expressed in the presence of a dominant allele– Recessive alleles are only expressed if both
recessive alleles are present
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Homozygous
• Both alleles alike
• AA or aa
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Heterozygous
• Alleles are different
• Aa
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Genotype
• Genetic make up
• Represented by alleles
• DD & Dd are genotypes for dwarfism
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Phenotype
• A trait
• Genotype determines the phenotype
• Dwarfism is a phenotype
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Codominant
• Two different alleles are both dominant
• A = allele for type A blood
• B = allele for type B blood
• AB = results in type AB blood
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Karyotype
• Picture of chromosomes from an individual
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Homologous Chromosomes
• Chromosomes of the same pair
• Karyotypes are usually arranged with homologous chromosomes paired together
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Mutation
• Change in a gene or chromosome
• Causes an abnormal trait
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MutagenAgent that causes mutations
Cigarette smoke
Pesticides
X-rays
Ulatraviolet light
Nuclear radiation
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Homologous chromosomes line up in a double file in metaphase I of meiosis
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Homologous Pairs Separate
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Four Gametes With Single Chromosomes
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Fertilization
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Nondisjunction
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Trisomy
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Sex Chromosomes
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Sex Chromosomes
• Male have Xy– Male gametes have either X or y
• Females have XX– Female gametes have X
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AutosomesChromosomes 1-22
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X-Linked Traits
• Alleles are on the X chromosome
• Females have two alleles
• Males have one allele– Only one X chromosome
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Normal Male
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Normal Female
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Trisomy 21Down Syndrome
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Down Syndrome
• Large tongue• Flat face• Slanted eyes• Single crease across
palm• Mental retardation
– Some are not
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Maternal Age & Down Syndrome
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Trisomy 18Edward Syndrome
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Edward Syndrome
• Heart defects• Displaced liver• Low-set ears• Abnormal hands• Severe retardation• 98% abort• Lifespan < 1 year
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Trisomy 13Patau Syndrome
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Patau Syndrome• Cleft lip and palate• Extra fingers & toes
– polydactylism
• Defects– Heart– Brain– Kidneys
• Most abort• Live span < 1 month
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Klinefelter Syndrome
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Klinefelter Syndrome
• Breast development• Small testes• Sterile• Low intelligence
– Not retarded
Klinefelter Website
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Turner Syndrome
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Turner Syndrome
• Short• Not go through
pruberty• Produce little estrogen• Sterile• Extra skin on neck
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Fetal Testing
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Sickle Cell Anemia
• RBCs sickle shaped
• Anemia
• Pain
• Stroke
• Leg ulcers
• Jaundice
• Gall stones
• Spleen, kidneys & lungs
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Sickle Cell Anemia
• Recessive allele, s codes for hemoglobin S – Long rod-like molecules– Stretches RBC into sickle shape
• Homozygous recessive, ss have sickle cell anemia
• Heterozygous, Ss are carriers
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Hemophilia
Blood clotting impaired
Recessive allele, h
carried on X cms
X-linked recessive trait
More common in males
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Albinism
• Lack of pigment– Skin
– Hair
– Eyes
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Amino Acids Melanin PigmentEnzyme
A a
AA = Normal pigmentation
Aa = Normal pigmentation
aa = Albino
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PKU Disease
• Phenylalanine excess• Mental retardation if
untreated
Molly’s Story
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Phenylalanine TyrosineEnzyme
P p
PP = Normal
Pp = Normal
pp = PKU
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A man & woman are both carriers (heterozygous) for albinism. What is the chance their children will inherit albinism?
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AA = Normal pigmentation
Aa = Normal pigmentation (carrier)
aa = Abino
Man = Aa Woman = Aa
A
a a
A
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A
a
a
A AA
Aa
Aa
aa
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AA
Aa
Aa
aa
Genotypes1 AA, 2Aa, 1aa
Phenotypes
3 Normal
1 Albino
Probability
25% for albinism
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A man & woman are both carriers (heterozygous) for PKU disease. What is the chance their children will inherit PKU disease?
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p
p
P PP
Pp
Pp
pp
P
PP = Normal
Pp = Normal (carrier)
pp = PKU disease
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PP
Pp
Pp
pp
Genotypes1 PP, 2Pp, 1pp
Phenotypes
3 Normal
1 PKU disease
Probability
25% for PKU disease
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A man with sickle cell anemia marries a woman who is a carrier. What is the chance their children will inherit sickle cell anemia?
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s
s
s Ss
Ss
ss
ss
S
SS = Normal
Ss = Normal (carrier)
ss = Sickle Cell
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Ss
Ss
ss
ss
Genotypes2 Ss, 2ss
Phenotypes
2 Normal (carriers)
2 Sickle cell
Probability
50% for Sickle cell
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A man with heterozygous dwarfism marries a woman who has normal height. What is the chance their children will inherit dwarfism? Dwarfism is dominant.
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d
d
D Dd
dd
Dd
dd
d
DD = Dwarf
Dd = Dwarf
dd = Normal
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Dd
dd
Dd
dd
Genotypes2 Dd, 2dd
Phenotypes
2 Normal
2 Dwarfs
Probability
50% for Dwarfism
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X-linked Recessive Traits
• Alleles are on the X chromosome
• Inheritance pattern different in males and females
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XH XH = Normal Female
XH Xh = Normal Female (Carrier)
Xh Xh = Hemophilic Female
XHy = Normal Male
Xhy = Hemophiliac Male
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A man with hemophilia marries a normal woman who is not a carrier. What is the chance their children will inherit hemophilia? Hemophilia is X-linked recessive.
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y
XH
Xh XH Xh
XH
Xh XH = Normal Female
XH Xh = Normal Female (Carrier)
Xh Xh = Hemophilic Female
XHy = Normal Male
Xhy = Hemophiliac Male
XH Xh
XHy XHy
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Genotypes
2 XH Xh, 2XHy
Phenotypes
2 Carrier Females
2 Normal Males
Probability
O% for Hemophilia
y
XH
Xh XH Xh
XH
XH Xh
XHy XHy
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A normal man marries a normal woman who is a carrier for hemophilia. What is the chance their children will inherit hemophilia?
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y
Xh
XH
XH
Xh XH = Normal Female
XH Xh = Normal Female (Carrier)
Xh Xh = Hemophilic Female
XHy = Normal Male
Xhy = Hemophiliac Male
XH XH XH Xh
XHy Xhy
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Genotypes
XH XH , XH Xh, XHy, XhyPhenotypes
2 Normal Females
1 Normal Males
1 Male Hemophiliac
Probability50% for Male Hemophilic
0% for Female Hemophilic
y
Xh
XH XH XH
XH
XH Xh
XHy Xhy
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The End