 If a disorder follows an autosomal inheritance pattern, which type of chromosome is it carried on?

 Genetic mutation is on an autosome

 A person only needs to get the abnormal gene from one parent in order to inherit the disease

 2 copies of an abnormal gene must be present in order for the disease or trait to develop

 Affect males & females differently  Female –XX  Male--XY

 Females with mild or no disease symptoms that have one mutated gene on an X chromosome and a normal version of the gene on the other X chromosome are called carriers.  Carriers are always heterozygous.

 Passed on the dominant gene through sex chromosomes  A female only needs to have one dominant allele for the disorder to be expressed

 Passed on the recessive gene though the sex chromosomes  A female needs to have both recessive alleles for the disorder to be expressed

 The most common error in meiosis occurs when homologous chromosomes fail to separate. This mistake is known as nondisjunction, which means “not coming apart.”  Nondisjunction may result in gametes with an abnormal number of chromosomes, which can lead to a disorder of chromosome numbers.

 The failure of a chromosome to split correctly during meiosis  Results in the production of gametes which have either more or less than the usual amount of genetic material

 Monosomy—one copy of a chromosome  Trisomy—three copies of a chromosome

 If two copies of an autosomal chromosome fail to separate during meiosis, an individual may be born with three copies of that chromosome.  This condition is known as a trisomy, meaning “three bodies.”  The most common form of trisomy, involving three copies of chromosome 21, is Down syndrome, which is often characterized by mild to severe mental retardation and a high frequency of certain birth defects.

 Common mechanism for trisomy or monosomy

 Results in the person presenting a female phenotype even though they possess an XY karyotype  Lack of the second X chromosome results in infertility

 Nondisjunction of the X chromosomes can lead to a disorder known as Turner’s syndrome.  A female with Turner’s syndrome usually inherits only one X chromosome.  Women with Turner’s syndrome are sterile, which means that they are unable to reproduce. Their sex organs do not develop properly at puberty.

 Female in appearance  Sex organs don’t develop at puberty  Person is sterile  Second sex chromosome is missing

 45X or 45XO ; instead of 46XX like a normal female  Most cases are not inherited; can result from an error in cell division (nondisjunction)

 In males, nondisjunction may cause Klinefelter’s syndrome, resulting from the inheritance of an extra X chromosome, which interferes with meiosis and usually prevents these individuals from reproducing.  There have been no reported instances of babies being born without an X chromosome, indicating that this chromosome contains genes that are vital for the survival and development of the embryo.

 47XXY  Person will appear male, but is sterile  Normal male  46XY  Most cases are not inherited; result from nondisjunction

 Aka Down Syndrome  There is an extra copy of chromosome 21; there are 3 copies of chromosome 21 instead of 2  Extra chromosome only occurs on the 21 st autosomal pair

 Most cases are not inherited; nondisjunction

 Genetic disorders characterized by progressive muscle wasting & weakness that begin with microscopic changes in the muscle

 The person’s muscle strength declines  One Type: Usually occurs in late 30’s or 40’s  X-linked recessive pattern

 Most times the person has a different mixture of cones from the normal  People with normal color perception have three different cones: blue, red, green  Complete loss of one cone type is dichromacy  X-linked recessive pattern

 X-linked recessive disorder  Characterized by the inability to properly form blood clots  X-linked recessive inheritance pattern

 Manifests itself in infancy & is fatal before the age of 5  Less severe juvenile & adult forms— developmental retardation, paralysis, dementia, blindness, retinal “cherry-red” spot, Startle reaction to sound

 Mapped to chromosome 15  Autosomal recessive  Fatal genetic disorder that is common among Jewish & French Canadian ancestry.

 Autosomal recessive condition  Affects mucus & sweat glands  Mostly—lungs, pancreas, liver, intestines, sinuses, sex organs

 Mucus is usually watery; keeps the linings of certain organs moist and prevents them from drying out or getting infected  In CF the abnormal gene causes mucus to become thick & sticky  Mucus builds up in the lungs & blocks the airways

 Most common fatal genetic disease in the U.S.

 Huntington’s disease is caused by a dominant allele for a protein found in brain cells.

 A progressive brain disorder that causes uncontrolled movements, emotional problems, and loss of thinking ability (cognition)  Most common form—adult-onset usually appears in the 30s or 40s

 Autosomal dominant  An affected person usually inherits the altered gene from one affected parent  In rare cases, an individual with Huntington’s disease does not have a parent with the disorder

 Affected people have little or no pigment in their eyes, skin, or hair  Inherited altered genes that do not make the usual amounts of pigment—melanin

 Autosomal Recessive  When both parents carry the gene & neither of them have albinism; 25% the child will  Disease is still a mystery

 Vision Problems  People with albinism always have problems with vision (not correctable with eyeglasses) and many have low vision. Vision problems in albinism result from abnormal development of the retina and abnormal patterns of nerve connections between the eye and the brain. It is the presence of these eye problems that defines the diagnosis of albinism.  While most people with albinism are fair in complexion, skin or hair color is not diagnostic of albinism. People with many types of albinism need to take precautions to avoid damage to the skin caused by the sun such as wearing sunscreen lotions, hats and sun-protective clothing.

 NF  A condition that causes tumors to grow on nerve tissue, producing skin and bone abnormalities  Autosomal dominant genetic disorders

 Most common causes of inherited mental impairment  Can range from learning disabilities to more severe cognitive or intellectual disabilities  X-linked Dominant Pattern

 A person of short stature as an adult—dwarf  Achondroplasia  Causes 70% of all dwarfism  Autosomal dominant  Makes legs & arms short in comparison to head & trunk

 Phenylketnuria  Tested for at birth  Characterized by an inability of the body to utilize the essential amino acid—phenylalanine

 Autosomal recessive  A person with this disorder must limit the protein in their diet  Left untreated can cause problems with brain development, leading to progressive mental retardation & seizures