Nurs310: Gene Genetic Diseases (Part Two)

What are Single Gene Diseases?

mutation in one specific gene leading to abnormal or absent protein

What is the mode of transportation?

how mutated gene transported

from parents to offspring

What is autosomal dominant?

one copy of mutated

gene is enough to cause disease

What is Autosomal Recessive?

two copies of mutated gene required for disease expression

Who passes on autosomal recessive disease?

heterozygous asymptomatic parents

Who inherits the disorder in children of Heterozygous asymptomatic parents? Who doesn't?

RECIEVES: homozygous recessive child (hh)

ASYMPTOMATIC: heterozygous child (Hh)

What is the recurrance rate for a child of heterozygous asymptomatic parents of a Autosomal RECESSIVE disease to pass it on to the child?

25%

Is there sex bias in autosomal diseases?

no, it is based on autosome, not sex chromosome so there is an equal chance for male and female

What is Consanguinity?

"incest"; mating between genetically related individuals

What is the risk of Consanguinity?

more likely to carry same recessive mutation, so the chance of homozygous recessive (hh) offspring is higher

What are the four examples of autosomal recessive disease?

1.) cystic fibrosis

2.) sickle cell anemia

3.) phenylketonuria (PKU)

4.) Tay-Sachs disease

What is cystic fibrosis?

mutation in CTFR affecting Cl- transport; too much mucus resulting in chronic cough and lung infection

What is sickle cell anemia?

abnormal Hg; RBCs sickle in low O2, increased infection risk

What is Phenylketonuria (PKU)?

deficiency of PAH; PAH accumulates and is toxic to brain, causing intellectual disability

What is Tay-Sachs disease?

mutation in HEXA, chromosome 15; lack of hexosaminidase A progressive in neurodegeneration

What is X-Linked Inheritance?

"sex linked"; caused by mutations on the X chromosome

What are the sex chromosomes of a female?

XX

What are the sex chromosomes of a male?

XY

Which gender is more likely to be affected by X-linked recessive disorders?

X-linked recessive disorders are more common and severe in males

Which gender is LESS likely to be affected by X-linked recessive disorders?

females because Y does not carry backup X-linked genes

How is it determined for males to be affected by X-linked recessive disorders?

if a male's X chromosome carry mutation, he is affected

Does a male who carries a X-linked recessive disorder pass it on to their son?

no, son inherits their father's Y. X is not affected.

Does a male who carries a X-linked recessive disorder pass it on to their daughter?

yes, daughter inherits X.

What happens to daughters who inherit an X-linked recessive disorder?

they are carriers but usually not affected unless it is skewed or X-linked dominant

How does X-linked recessive disorder affect females?

one normal X chromosome usually prevents disease

Does a female who carries a X-linked recessive disorder pass it on to their son?

50% risk of being affected and inheriting disorder

What are 4 examples of X-linked recessive disorder?

1.) hemophilia

2.) duchenne muscular dystrophy

3.) fradile X syndrome

4.) red-green color blindness

What is hemophilia?

impaired clotting

What is duchenne muscular dystrophy?

mutation in dystrophin gene; progressive muscle degeneration

What is fragile X syndrome?

mutation in FMR1 gene; impaired brain development

What is Red-green color blindness?

mutation in cone photopigment genes on X-chromosome

What is recurrance risk?

probability individual will develop disease

What are the characteristics of Klinefelter Syndrome?

thin facial hair, female physique

When one parent is affected by an autosomal dominant disease and the other half is normal, the occurrence and recurrence risks for year child are _____.

1/2

Every child born, regardless of siblings' outcome, has a recurrence risk of ____, because each birth is an ________ _______.

1/2; independent event