Polydactyly Down Syndrome Hemophelia Progeria Hypertrichosis Sickle Cell Anaemia INTRODUCTION What is genetic diseasesdisorders The human body is composed up of cells each one specializing a particular function like sensing light smelling ID: 910721
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Slide1
Genetic Disorders
Slide2Human Inheritance and Genetic Disorders
Polydactyly
Down Syndrome
Hemophelia
Progeria
Hypertrichosis
Sickle Cell Anaemia
Slide3INTRODUCTION
What is genetic diseases/disorders?
The human body is composed up of cells , each one specializing a particular function like sensing light, smelling
etc
, So the chromosomes which are the sub cellular structure that exist in the nucleus of each cell that makes a human body .There are 23 pairs of chromosomes in human, these chromosomes are responsible for transferring genetic information from one generation to another.
Most people have the concept that genetic disease must be the one which is transmitted from one generation to next. Actually this is not totally correct. In medicine genetic disease refers to one that is caused by abnormalities of the genetic material at the stage of germ cells or early embryo.
Slide4Pedigrees
Geneticists use
diagrams that trace the inheritance of particular traits through several generations
called
pedigrees.
A pedigree uses symbols to illustrate different meanings on the pedigree.Males
are represented by a square.
Females are represented by a circle.
Usually someone who expresses a trait is dark.
Usually someone without the trait is light.
Usually a carrier is half dark and half light.
Slide5Pedigrees
Horizontal lines
between symbols represent
parents of the offspring
in the lines below them.Offspring are ordered from first to last.
Roman numerals represent generations.
Slide6Pedigrees
A
Pedigree
is a chart or “family tree” which maps genetic disorders
in a family.
Slide7Karyotypes
A Karyotype
is a
picture of all the chromosomes in a cell.
Modern scientists can take a blood sample from an unborn child to an adult, create a karyotype by
separating chromosomes, and be able to determine if any genetic disorders are present.
A couple who wishes to have children can receive genetic counselling
where a doctor looks at both parents karyotypes to see if any disorders will pass to offspring.
Slide8ALLELE
Is one member of a pair or series of different forms of a gene.
Homozygous
-an organism in which 2 copies of genes are identical i.e. have same allelesHeterozygous-an organism which has different alleles of the gene
Slide9Chromosomes:
Chromatin: DNA, RNA & proteins that make up
chromosme
1. Chromatids: one of the two
identical parts of the chromosome. 2. Centromere: the point where two
chromatids attach46 chromosomes. 22 pairs Autosomes and 1 pair Sex chromosomes.
Slide10Genetic
Disorders
A
Genetic Disorder
is an abnormal condition that a person inherits through their genes.
Genetic disorders can be caused by either changes in the DNA, or an extra,
or a missing chromosome.
Slide11Normal Karyotype
Slide12Congential
Disease.
Diseases which are present at
birth.Hereditary/Familial Disease. Diseases which are derived from one’s parents and transmitted in the gametes through the generations.
Not all congenital diseases are genetic( congenital Syphilis) and not all genetic diseases are congenital (Huntington disease).
Slide13Human
Inheritance
Review:
Each individual trait (characteristic) of an organism is
controlled by a gene which is a part of a chromosome.
Each gene is controlled by two allelles; one from mother,
one from
father.
Allelles
are patterns of DNA that tell the body how to make certain amino
acids which form proteins.
Proteins control how an organism looks and functions.
Slide14Human
Inheritance
Some traits are controlled by just one gene, two alleles.
A widow's peak for example.
Multiple alleles are
three or four forms of a gene that code for a single trait. Our blood type is an example:
Still other traits are controlled by
multiple genes.
Skin type, eye
color,
hair color and many others are controlled
by multiple genes.
Slide15Sex
Chromosomes
Sex Chromosomes
are 1 pair of the 23 pairs of chromosomes in the body.
Sex Chromosomes carry the genes that makes a person male or female, but also carry genes which determine other traits.
Slide16Sex
Chromosomes
The 'Y' chromosome (male)
is much smaller than
the 'X' chromosome.
Because the 'X' is bigger,
it carries a lot more genetic information
than the 'Y'
Sex-Linked Genes
have alleles that pass from parent to child on a sex chromosome.
Slide17Sex-Linked Genes
A common sex-linked gene is
colorblindness
.
Slide18Are you Color Blind?
Slide19Is anyone unable to see the image in this circle?
If so, you have red-green
color
blindness!
This is a sex-linked recessive trait.
Slide20Are you color blind?
Cause: x-linked recessive
1/10 males have, 1/100 females have. Why the difference?
Individuals are unable to distinguish shades of red-green.
Sex-Linked
Genes
Slide22This
Punnet Square
shows
sex-linked genes for
color blindness
. Only the X chromosome carries the gene, so if a male gets a recessive
Xc
and a Y, he automatically has the disease. Females, however, can be
carriers of the disorder with one dominant X
C and one recessive
Xc, but only have the disorder if she has both recessive:
Xc
Xc
A carrier is a person who has
one recessive and one dominant allele for the trait.
Slide23Environment
Environmental factors also determine
how genes are expressed.
A person can have genes to be really tall, but if they do not have
proper nutrition, they will not reach their optimal height.
A person can even have genes which wire the brain to be good at making music, but if they never try to play an instrument,
they will never know.
This is why everyone should try everything at least once; you could end up being really great at
anything!
Slide24CATEGORIES OF GENETIC DISORDERS
a)
Chromosomal Disorder
: Abnormalities in chromosome structure such as missing or extra copies.
b)
Single Gene Disorder: Disorders caused by abnormality or mutation in the sequence of a single gene. The pure genetic diseases are caused by a single gene in the human DNA. These are classified as Dominant, Recessive and X-linked diseases.
c) Multifactorial Disorders: That are caused by the result of the combined effect of genetic and environmental factors.
d) Mitochondrial Disorders: Caused by mutation in the non chromosomal DNA of mitochondria.
Slide25Patterns Of Inheritance:
Autosomal Dominant.
Autosomal Recessive.
X-Linked Recessive.X-Linked Dominant
.
Slide26Mendelian Disorders
A genetic disease caused by a single mutation in the structure of DNA, which causes a single basic defect with pathologic consequences
Slide27Trinucleotide
Repeat Mutations:
A set of genetic disorder caused by trinucleotide repeat in certain genes exceeding normal, stable threshold e.g. Huntington disease
Fragile X Syndrome Myotonic dystrophy
Slide28Autosomal Dominant
Dz’s
Huntington’s Disease
Gene located on Chromosome 4
, trinucleotide repeat disorder (CAG)nNormally 9 to 35 repeats but people with Huntingtons have 36 to 121 repeats
Affects the folding of Huntingtins protein which accumulates and clumps.Clumps kill the neuron producing GABA & ACHDecreased levels of GABA and Ach in the brain
Slide29HUNGTINGTON’S DISEASE
It results from genetically programmed degeneration of nerve cells in certain areas of the brain
This degeneration causes uncontrolled movements , loss of intellectual functions
Emotional Disturbance
The Symptoms of this disease are ;
Mood Swings, irritability , depression, loss of memory As this disease progresses walking and speech become more difficult, the memory and intellectual functions continue to decline.
Slide30Huntington Disease
It is a neurodegenerative genetic disorder that affects muscle coordination and leads to cognitive decline and dementia
Autosomal dominant :
Symptoms do not appear until age 30-40.
Death takes about 5-10 yearsNo treatment, no cure – but there is a test to see if you have it before symptoms beginResults in mental impairment and uncontrollable spastic movements
Slide31Huntington's chorea. Chorea means "dance-like movements" and refers to the uncontrolled motions often associated with the disease.
Slide32Autosomal Dominant Disorders.
Slide33Manifested in heterozygous
states.
Individuals with these diseases usually have one affected parent .
Variable to late onset.These disorders usually involve non-enzymatic proteins;
Proteins involved in metabolic pathway regulation. Structural Proteins.
Slide34Inheritance Pattern:
Typical mating pattern is a heterozygous
affected
individual with a homozygous unaffected individual.Every child has one chance in two of having the disease Both sexes are affected equally..
Slide35Disorders:
Slide36Structural Protein Defects:
Marfan’s Syndrome
.
Ehler-Danlos Syndrome.
Slide37Marfan’s Syndrome
:
Mutation in the
fibrillin gene.Chromosom 15 Fibrillin
important component of microfibrils in Elastin.Tissues affected are Skeleton, Eyes and the CVS. C/F include tall stature, long fingers, pigeon breast deformity, hyper-extensible joints, high arched palate, subluxation of lens, floppy Mitral valve, Aortic aneurysm , defects in skin, lungs.
Slide38Marfan’s Syndrome
Slide39Marfanoid Habitus
Marfanoid
(or
Marfanoid habitus) is a group of symptoms resembling those of Marfan syndrome, including long limbs, with an arm span that exceeds the height of the individual, and a crowded oral maxilla, sometimes with a high arch in the palate, arachnodactyly, and
hyperlaxity.
Slide40Ehler-Danlos
Syndrome(Cutis
Hyperelastica
):Characterized by defects in collagen synthesis.Clinical Features include fragile, hyper-extensible skin, hyper-mobile joints, rupture of internal organs like the colon, cornea and large arteries, poor wound healing.
Slide41Slide42Defects in metabolic proteins pathway
:
Familial
Hypercholesterolemia:
One of the most common mendelian disorders. Mutation in the LDL receptor gene.Hypercholesterolemia due to impaired LDL transport into cells.
Increased risk of atherosclerosis and coronary artery disease. Increases Cholesterol leads to formation of Xanthomas.
Slide43Autosomal Dominant Dz’s
Familial hypercholesterolemia (HLP type 2A)
Phenotypic Traits:
Xanthelasma palpebrarumtendon xanthomas (classically on the Achilles tendon) severe atherosclerotic
dz MI may develop early
Slide44Autosomal Recessive Disorders
Slide45Largest group of
Mendelian
Disorders
Affected individuals usually have unaffected (carrier) parents.
Uniform, early age of onset.These disorders usually involve Enzymatic Proteins.
Slide46Pattern Of Inheritance:
Typical mating pattern is two heterozygous
unaffected
(carrier) individuals.
The trait does not usually affect the parent, but siblings may show the diseaseSiblings have one chance in four of being affected Both sexes affected equally
.
Slide47Recessive Genetic Disorders
Cystic Fibrosis
Albinism
Galactosemia
Tay
-Sachs disease
Slide48Albinism
Patients are unable to produce skin or eye pigments, and thus are light-sensitive
Autosomal recessive
Therefore, is it monogenic or chromosomal?
Slide49Albinism
Mother of five, with three albino children
Slide50Disorders:
Slide51Glycogen Storage Diseases.
Category
Disease
Enzyme
Hepatic Type.
Von Gierke’s Disease type 1.
Glucose-6-phosphotase.
Myopathic Type.
McArdle Syndrome.
Muscle Phosphorylase.
Miscellaneous Type.
Pompe’s Disease type II
Lysosomal Glucosidase.
Slide52Dominant Genetic Disorders
Dominant genetic disorders.
Caused by
dominant alleles.
If
only one parent has one dominant allele (heterozygous), 50% of the children will inherit the disease.
Slide53Dominant Genetic Disorders
Huntington's disease
– Causes nerve cells in the brain to degenerate, causing a gradual loss of brain function. Occurs most commonly in people ages 30 – 50 years old.
Achondroplasia
– A disorder that affects the growth of bones and causes dwarfism.
Polydactyly – A condition resulting in an extra number of fingers and toes.
Slide54Polydactyly
Slide55Albinism and Polydactyly Pedigrees
Slide56END