HUMAN GENETIC DISORDERS

A look into a few different types

About Human Genetic Disorders Any illness caused by abnormalities in

genes or chromosomes Most are rare May or may not be heritable

Broad Types of Genetic Disorders

Single Gene Disorder – result of a single mutated gene. X-Linked Dominant – mutations on genes of the X

chromosme Men and women are equally likely to get it Rett Syndorme (degenerative brain disorder) Fragile X

X-Linked Recessive – again, mutations on the genes of the X chromosome Males way more likely to get these than women Duchenne Muscular Dystrophy Hemophilia

Y-Linked – mutations in genes on the Y chromosome ALL males will have these disorders Rare since the Y chromosome is small

Autosomal dominant – only one mutated copy of the gene is needed Marfan Syndrome Huntington’s Disease Retinoblastoma

Autosomal recessive – two mutated copies of the gene are needed to be affected Sickle cell anemia Cystic fibrosis Tay-Sachs

LET’S TAKE A LOOKInsight to a few human genetic disorders

Achondroplasia

Mutation in a gene on chromosome #4 that makes a protein that is involved in converting cartilage to bone

A form of dwarfism

In MOST cases is it NOT inherited but in rare cases that it is, it is autosomal dominant

Achondroplasia

Occurs in 1 in ever 15,000-40,000 live births

Often these children are born to normal sized parents

Not fatal No treatment but monitoring of height,

weight, and head circumference.

Achondroplasia

Symptoms: Abnormal bone growth Short stature with disproportionately short

arms and legs Short fingers Large head Prominent forehead Bowed legs Weak muscles

Causes delays in walking and other motor skills

Duchenne Muscular Dystrophy A disease characterized by progressive

loss of muscle function and weakness beginning in the lower limbs.

A sex-linked recessive disorder – body does not make the muscle protein dystrophin

Occurs mostly in boys Affects 1 in 3500 births

Duchenne Muscular Dystrophy Symptoms (appear between ages 1-6):

Delays in motor skill milestones like sitting or walking

Progressive muscle weakness in the legs and pelvic muscles

Loss of muscle mass Abnormal bone development By age 10, leg braces are required for walking By age 12, confinement to a wheelchair In the early teens, complications due to an enlarged

heart appear and few individuals live past their 30’s/

Turner’s Syndrome

A disease characterized by females having only ONE X-Chromosome instead of two The second X-Chromosome may be entirely

missing or severely mutated Causes delays in the development of

females

Turner Syndrome

Occurs in 1 in ever 2500 births but is more common in non-surviving pregnancies

This is NOT an inherited disorder, it is due to nondisjunction during meiosis – chromosomes do not separate properly

Turner Syndrome

Symptoms Extra skin on neck Short stature Swelling of hands and feet Skeletal abnormalities Heart defects Developmental delays Most females with this disease are infertile

and do not go through puberty unless they are given hormones

Cri-du-Chat

Part of chromosome #5 is missing. The more genes missing, the more severe the symptoms

Characterized by infants with this syndrome having a high pitched cry that sounds like that of a cat

Occurs in 1 in every 20,000 – 50,000 births

NOT in inherited disorder

Cri-du-Chat

Delayed development Small head size Low birth weight Weak muscle tone in infants Low set ears Widely set eyes Small jaw Round face Possibility of heart defects

Huntington’s Disease

An autosomal dominant disorder caused by a CAG repeat on chromosome #4. Normally this gene should have 10-28 repeats but people with HD have between 36-120. The more repeats, the more likely your symptoms will start earlier and be more severe.

IS an inherited disorder. If one of your parents has it you have a 50% chance of getting it.

Huntington’s Disease

Most common form begins in adults in their mid 30-40’s.

Symptoms Behavior changes

Hallucinations Moodiness Paranoia Psychosis

Huntington’s Disease

Symptoms Dementia

Disorientation or confusion Loss of memory Loss of judgement Personality changes

Abnormal or Unusual Movements Jerky, sudden movements of the limbs Slow, uncontrolled movements Unsteady walk

Huntington’s Disease

Can use a neurological exam, MRI, or genetic exam to detect symptoms

Eventually for a person with HD, 24 care will be needed and death occurs 15-20 years after the symptoms first present themselves

There is no treatment, it is 100% fatal however many different medications can be prescribed to treat the symptoms Antipsychotics Dopamine blockers

HD BRAIN NORMAL BRAIN