GENETIC DISORDERS

• A genetic disorder is a disease that is

caused by an abnormality in an

individual's DNA.

• Abnormalities can range from a small

mutation in a single gene to the addition

or subtraction of an entire chromosome

or set of chromosomes.

Gene Mutations

• Can either be inherited from a parent or acquired

• Failure of chromosome pairs to separate properly is called NON-DISJUNCTION

• Non-disjunction will result in an imbalance of chromosomes

• Having more or less genetic material is detrimental and is the resulting cause of Genetic Disorders

•There are four major

types of chromosomal

mutations:

#1 DELETIONS:

• involve deletion of a small portion of

a chromosome

#2 DUPLICATIONS:

• produces an extra exact copy of a

specific region of a specific

chromosome

#3 INVERSIONS:

• re-order a segment of chromosome

in backwards order

• Not as detrimental as deletion or

insertion

#4 – TRANSLOCATIONS: • Occurs when the information from one of two

homologous chromosomes breaks and binds

to the other

• Usually this sort of mutation is lethal

• In humans, non-disjunction is most often associated with the 21st chromosome, producing a disorder known as Down's syndrome (also referred to as trisomy 21).

Individuals with Down's syndrome display the

following characteristics:

• mild to severe cognitive mental delays

• short stocky body type

• Upward slant to the eyes

• large tongue leading to speech difficulties

Kleinfelter’s Syndrome

• Males with Kleinfelter’s have an extra X

chromosome (XXY)

• Infertile – do not produce sperm

• Enlarged breasts

• Small penis and testicles

• Sparse facial and body hair

Turner’s Syndrome

• Missing or damaged X chromosome in

females (Momosomy X)

• Underdeveloped ovaries

• Short stature, webbed neck

• Sterile

• Lacking secondary sexual characteristics

Cystic Fibrosis

• Hereditary disease primarily affecting the

lungs, pancreas and intestines

• Caused by faulty channel proteins

• Excess mucous clogs lungs causing a

difficulty in breathing, prevents food from

being digested

• Diagnosed with a “sweat test”

• Life expectancy of patients ~ 36 years

Duchenne’s Muscular Dystrophy

• Generalized weakness and muscle

wasting first affecting hips, pelvic area,

thighs and shoulders

• X linked recessive disorder

• Eventually even muscles of the lung may

weaken which may lead to respiratory

failure

Albinism

• Characterized by little or no pigment in the eyes,

skin and hair

• Major vision problems

• Inherited altered genes do not make usual

amounts of pigment melanin

• Both parents must carry a defective OCA

(oculocutaneous albinism) gene to have a child

with albinism

Red-Green Colour Blindness

• X-linked recessive

disorder

• Person cannot

distinguish shades

of red and green

• Visual acuity is

normal

Progeria

• A rare disorder in

where a person

ages rapidly.

• Caused by

random,

spontaneous

mutation of one

gene.

• The mutated gene

must be dominant

over it’s recessive

normal partner.

• It is an autosomal

disorder.

Progeria – Physical features.

Phenylketonuria or

PKU People with PKU cannot consume any product that

contains aspartame.

PKU is a metabolic disorder that results when the

PKU gene is inherited from both parents

(autosomal recessive disorder)

Caused by a deficiency of an enzyme which is

necessary for proper metabolism of an amino

acid called phenylalanine.

PKU • Phenylalanine is an essential amino

acid and is found in nearly all foods which contain protein, dairy products, nuts, beans, tofu… etc.

• A low protein diet must be followed.

• Brain damage can result if the diet is not followed causing mental retardation…and mousy body odor (phenylacetic acid is in sweat).

PKU

Phenylalanine. Free diet

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