M2.2 - Medical Genetics

Dizygotic twins share an average of ____ of the same alleles

50%

______________: -Absence or partial deficiency of melanin in the skin, eyes, and hair -It can also occur in a wide variety of animals

Albinism

What is the inheritance pattern for a trait that occurs with equal frequency in both sexes and will be inherited, on average, by 50% of the offspring of an affected individual who had only one affected parent?

Autosomal dominant

What is the inheritance pattern when the trait occurs with the same frequency in both sexes and two unaffected heterozygotes have, on average, 25% affected children?

Autosomal recessive

Vitamin __-resistant __________ is a disorder involving softening and weakening of the bones (of children primarily caused by lack of vitamin D

D, rickets

Which type of mutation causes a dominant genetic disorder through the production of an altered protein that works against the action of the normal protein?

Dominant-negative

_____________: the degree to which a penetrant gene is phenotypically expressed

Expressivity

What is syndactyly?

Fused fingers

______________________ is the phenomenon in which a person has only a single functional copy of a gene, and that single functional copy does not produce a normal phenotype.

Haploinsufficiency

There are three common explanation for autosomal dominant disorders... 1) ______________________ -The heterozygote has 50% of the normal protein -This is not sufficient for a normal phenotype 2) ________-____-__________ mutations -Mutation changes protein so it gains a new function 3) ___________ ___________ mutations -The altered gene product acts antagonistically to the normal product (so one copy in a negative state is enough to mask/block the normal gene product)

Haploinsufficiency, gain-of-function, dominant negative

Which disease has also been called "royal disease" because it has affected many members of European royal families?

Hemophilia

_________________: -The major symptom of the disease is that the blood cannot clot properly when a wound occurs -Common accidental injuries pose a treat of severe internal or external bleeding

Hemophilia

________________ disease: -The major symptom of the disease is the degeneration of certain types of neurons in the brain -This leads to personality changes, dementia, and early death

Huntington

__________ ________________ refers to the phenomenon that a disease can be caused by mutations in two or more different genes For example: _____________ -Blood clotting involves a cellular cascade that involves several different proteins -Thus, a defect in any of these proteins can cause the disease --Hemophilia A = defect in clotting factor VIII --Hemophilia B = defect in clotting factor IX --Hemophilia C = defect in clotting factor XI

Locus heterogeneity, hemophilia

X-Linked Dominant Traits _________ are often more severely affected

Males

What is true of X-linked dominant disorders such as Rett syndrome and Aicardi syndrome?

Males die at an early stage of development

Which of the following characteristics of inheritance for hemophilia can be observed in the pedigree for the family of Queen Victoria and Prince Albert? -________ are more likely to be affected than females -Mothers of affected males often have __________ with the disease

Males, brothers

______________ ________ share 100% of the same alleles

Monozygotic twins

________________: the proportion of individuals with a specific genotype who manifest the corresponding phenotype

Penetrance

______________: An organism whose phenotype has been modified to resemble the phenotype of a different mutant organism

Phenocopy

_________________: suppression of limb development -Caused by a _____________ allele with variable expressivity

Phocomelia, dominant

What is brachydactyly?

Shortened-fingers

_______________ disease: -Affected individuals appear healthy at birth, but then develop neurodegenerative symptoms at 4 to 6 months --Cerebral degeneration, blindness and loss of motor function -These patients typically die at 3 or 4 years of age

Tay-sachs

__________________: -Sedative -Between 1959-1962 children with shortened limbs were born to mothers who took the drug early in their pregnancy

Thalidomide

Approximately how many human diseases have a genetic basis?

Thousands

Autosomal Dominant Traits T/F: Members of both sexes are affected equally

True

True or false: Genetic diseases often show a specific age of onset

True

True or false: Identical twins share a genetic disease more often than fraternal twins

True

The following human diseases: 1) Vitamin-D resistant rickets 2) Rett syndrome 3) Incontinentia pigmenti are inherited in an ________________ _____________ manner

X-linked dominant

Vitamin D-resistant rickets is an _______________ ________________ disorder

X-linked dominant

The following human diseases: 1) Androgen insensitivity syndrome 2) Duchenne muscular dystrophy 3) Hemophilia A are inherited in an ________________ _____________ fashion

X-linked recessive

What is the inheritance pattern for a trait that more commonly affects males than females and can be observed in brothers or fathers of a woman who has affected sons?

X-linked recessive

What is the inheritance pattern for a trait that more commonly affects males than females and which will occur in about 50% of the sons born to the unaffected daughter of an affected male?

X-linked recessive Since the daughter is unaffected, the trait must be inherited as an X-linked recessive

Short-limed dwarfism is termed ________________________

achondroplasia

X-Linked Recessive Traits Affected FEMALES come from ___________ fathers and ____________ or ____________ mothers

affected, affected, carrier

X-Linked Recessive Traits Affected MALES result from ____________ mothers or mothers who are ___________

affected, carriers

Autosomal Recessive Traits Members of both sexes [are/are not] affected equally

are

Autosomal dominant compelling helio-ophthalmic outburst syndrome (aka achoo) is an ______________ _____________ disorder

autosomal dominant

Huntington Disease (HD) is an _________________ _______________ disorder

autosomal dominant

Penetrance and expressivity are used most often with _____________ ______________ traits

autosomal dominant

The following human diseases: 1) Huntington disease 2) Marfan syndrome 3) Aniridia are inherited in an ________________ _____________ fashion

autosomal dominant

Albinism is an ________________ _______________ disorder

autosomal recessive

Cystic fibrosis an an ____________ ______________ disorder

autosomal recessive

Phenylketonuria is an ______________ ______________ disorder -The defect is in the gene that encodes phenylalanine hydroxylase

autosomal recessive

Sickle cell disease is an ______________ ____________ disorder

autosomal recessive

Tay-Sachs disease is an ____________ ______________ disorder

autosomal recessive

The following human diseases: 1) Sickle cell disease 2) Phenylketonuria 3) Cystic fibrosis are inherited in an ________________ _____________ fashion

autosomal recessive

Autosomal Dominant Traits Two affected parents [can/cannot] product unaffected offspring Example: dad can be "Hh" and mom can be "Hh", offspring could be "hh" which is unaffected

can

Autosomal Recessive Traits Unaffected parents [can/cannot] have an affected child For example: If dad is "Rr" and mom is "Rr" - parents are unaffected but offspring could be "rr" --> affected

can

Autosomal Recessive Traits Two affected parents [can/cannot] have an unaffected child

cannot

Autosomal Recessive Traits Traits are more likely to occur in ________________________ marriages

consanguineous

What is the most common lethal genetic disease among caucasians?

cystic fibrosis

Siamese cats have a __________ fur at their extremities due to temperature

darker

X-Linked Dominant Traits Affected males have no normal _______________ and no affected _________

daughters, sons

X-Linked Dominant Traits Trait [does/does not] skip generations

does not

Autosomal Recessive Traits Healthy = ________________ Disorder = ___________________

dominant, recessive

Suppose a disease-causing allele shows autosomal recessive inheritance. How could a carrier of this disease-causing allele be identified? Carriers often show reduced activity for the _____________ encoded by the allele

enzyme

Disorders that involve defective ______________ typically have an autosomal recessive mode of inheritance

enzymes

X-Linked Recessive Traits Trait can NEVER be transmitted directly from __________ to _____

father, son

Y-Linked Traits Affected males get it from their ____________ and give it to their ______

fathers, sons

What are two reasons for incomplete penetrance and variable expressivity? 1) ________ interactions 2) ____________________ effects

gene, environmental

X-linked recessive inheritance poses a special problem for males -Males have only a single copy of most X-linked genes (XY) --They are termed _______________ -Therefore, a female heterozygous for an X-linked recessive gene will pass this trait to ______ her sons

hemizygous, half

X-Linked Dominant Traits Affected ___________________ females transmit the trait to approximately half of their children of either sex

heterozygous

Autosomal Dominant Traits The ___________________ for the disease-causing allele is generally more severely affected than the heterozygote

homozygote

X-Linked Dominant Traits Affected _____________________ females transmit the trait to all their children

homozygous

Autosomal Dominant Traits Trait [is/is not] usually present in every generation

is

A ______________ can be used to identify changes in chromosome number and structure associated with a disease condition

karyotype

Chromosomal abnormalities related to genetic diseases can be detected by producing a ____________________

karyotype

A situation where a disease may be caused by mutations in two or more different genes is called ____________ ____________________

locus heterogeneity

X-Linked Recessive Traits Most affected individuals are _________

male

Y-Linked Traits Trait only affects __________

males

X-Linked Dominant Traits Affected males must come from affected ______________

mothers

X-Linked Dominant Traits Affected females come from affected....

mothers or fathers

Autosomal Dominant Traits Sufferers must inherit only _____ allele to have the disorder

one

When a human disease is caused by a mutation in a single gene, scientists follow the pattern of inheritance by analyzing charts called human ______________

pedigrees

Chances are, if it's an enzymatic disorder, it's an autosomal _________________ disorder

recessive

Autosomal Dominant Traits Healthy = ________________ Disorder = ___________________

recessive, dominant

Autosomal Recessive Traits Trait tends to ______ generations

skip

X-Linked Recessive Traits Trait may _______ generations

skip

X-Linked Recessive Traits Affected females WILL have affected _______

sons

Autosomal Recessive Traits Sufferers must inherit _____ alleles in order to have this disorder For example: the offspring must inherit an "r" from the mom and an "r" from the dad in order for offspring to have to autosomal recessive disorder

two

Autosomal Dominant Traits Unaffected parents produce [affected/unaffected] offspring Example: dad is "hh" and mom is "hh", offspring will be "hh" --> unaffected, healthy

unaffected

Autosomal Dominant Traits On average, half the children of an affected parent [will/will not] be affected

will

Hemophilia is an ________________ _____________ disorder

x-linked recessive