Genetics+2+DB



Human Genetics 2 Homework 20.2c and 20.4 Define:
 * carrier**- a heterozygote that carries the recessive allele but does not show it in their phenotype


 * autosomal recessive disorder**-(RECOGNIZE A PEDIGREE)
 * Affected children can have unaffected parents
 * Heterozygotes have an unaffected phenotype (carriers)
 * Two affected parents will always have affected children
 * Affected individuals with homozygous unaffected mates will only have unaffected hcildren
 * Close relatives who reproduce (first cousins) are more likely to have affcted children
 * Both males and females are affected in equal frequency


 * autosomal dominant disorder**-(RECOGNIZE A PEDIGREE)
 * Affected children will usually have an affected parent
 * Heterozygotes are affected
 * Two affected parents can produce an unaffected child
 * Two unaffected parents will not have affected children
 * Both males and females are affected in equal frequency


 * X-linked disorder** (RECOGNIZE A PEDIGREE)
 * More males than females are affected
 * An affected son can have parents who have the normal phenotype
 * For a female to have the characteristic her father MUST have it and her mother must be a carrier or also have it.
 * The characteristic often skips a generation going from grandfather to grandson.
 * If a woman has the characteristic, all of her sons will have the characteristic.

autosomes- any chromosome other than the sex chromosomes (22 pairs)

sex chromosomes- chromosome that determines sex, females-XX, males-XY

sex linked- alleles that are on the sex chromosomes but determine a trait other than gender

X linked- sex- linked allele on the X chromosome

X linked dominant- a sex linked allele for a dominant gene on an X chromosome

X linked recessive- a sex linked allele for a recessice gene on an X chromosome

Describe diseases (You will need to know how they are inherited ie X-linked recessive or autosomal dominant. You will also need to know the gene that is mutated and what damage that causes to the body)

Tay-sachs- Autosomal recessive disorder in which an enzyme (Hex A) is missing. This enzyme breaks down lipids in lysosomes in certain brain cells. Neurological problems result from the problem including blindness and uncontrollable seizures. Children with tay-sachs eventually become paralyzed.

Cystic Fibrosis- Autosomal recessive disorder in which an enzyme that pumps chloride ions into cells does not function. Tis causes a build up of mucus in the lungs making breathing difficult.

PKU- Austosomal recessive disorder where the enzyme that breaks down phenylalanine is missing. High levels of phenylalanine can cause mental retardation.

Sickle Cell Disease- Autosomal recessive disorder in which the hemoglobin protein in red blood cells has an abnormal shape giving the red blood cells an abnormal shape. People with the disorder suffer from poor circulation, low immune system health, and anemia.

Mafan Syndrome- An **autosomal** **dominant** disorder in which the elastic connective tissue protein fibrillin is altered. People with the syndrome often have a dislocated eye lens, a caved in chest, and long limbs. They also have a thin aortal wall.

Huntington Disease- Neurological **autosomal** **dominant** disorder that leads to a mutated huntintin gene. The abnormal protein builds up in the brain and causes the break down of brain cells. Death results in patients after 10 to 15 years of having the disease.

Color blindness- An **x-linked recessive** disorder that causes men to see colors differently.

Muscular dystrophy- An **x-linked recessive** disorder due to a mutation in a gene for a muscle protein. The muscles deteriorate as a protein called dystrophin is missing. Frequent falls and difficulty rising results.

Hemophilia- An **x-linked recessive** disorder in which a blood clotting factor known as VIII is absent. A person with the disorder's blood either does not clot, or clots very slowly.