Medical Genetics Ii Modes Of Inheritance Of Single Gene Disorders

Front 1

Pedigree symbol: Empty square

Back 1

Male, unaffected

Front 2

Pedigree symbol: filled in circle

Back 2

Female affected

Front 3

Pedigree symbol: Square with a slash through it

Back 3

male, deceased

Front 4

Pedigree symbol: Diagonal square

Back 4

Sex not secified

Front 5

Pedigree symbol: Circle with a dot in it.

Back 5

Female, heterozygous for X-linked recessive trait

Front 6

Pedigree symbol: Square half filled in.

Back 6

Male, heterozygous for autosomal recessive trait.

Front 7

In pedigree analysis what characterizes autosomal recessive inheritance?

Back 7

Affected males=affected females
Horizontal transmission

Front 8

Are homozygotes common?

Back 8

Not in normal genetics, because this means that the two mates possess the exact same mutation.

Front 9

What are compound heterozygotes?

Back 9

Two 'mutant' alleles, help explain the different clinical manifestation and severity of inherited recessive disease.

Front 10

What two features characterize autosomal dominant inheritance?

Back 10

Vertical transmission
Affected males = affected females

Front 11

What are the three reasons why a mutation in an allele may be dominant?

Back 11

Haploinsufficiency
Dominant negative effect
Gain-of-function

Front 12

Explain the concept behind haploinsufficiency.

Back 12

Half of the normal amount of the protein is insufficient to maintain normal function

Front 13

Explain dominant negative effect as a reason behind autosomal dominant disorders.

Back 13

The product of the mutant allele interferes with the product of another, normal allele resutling in overall adverse outcome (such as seen in Osteogenesis imperfecta).

Front 14

Explain Gain-of-function as a reason behind Autosomal dominant disorders.

Back 14

Dominant disorders can result from achange in the elvel of activity of a protein or its expression int eh wrogn tissue or at the wrong time. Such as achondroplasia or Huntington (neurotoxin).

Front 15

What are the two characteristics of X-linked recessive inheritance?

Back 15

Affected males > affected females
no father to son transmission

Front 16

Name three diseases that are X-linked recessive.

Back 16

Duchenne muscular dystrophy
Hemophilia (A and B)
Red-green color blindness

Front 17

What are the two characteristics of X-linked dominant inheritance?

Back 17

Vertical transmission
affected males = 2 x affected females

Front 18

Give two examples of X-linked dominant inheritance where both sexes are affected.

Back 18

Fragile X syndrome
Vitamin D resistant rickets

Front 19

Define: Having different mutations in the same gene (either recessive or dominant)

Back 19

Allelic heterogeneity

Front 20

Explain how two individuals with autosomal recessive congenital deafness can have a normal child.

Back 20

Locus heterogeneity. Each parent is homozygous for a different nonallelic mutation (that is the alleles for the two types of deafness are found on separate genes loci).

Front 21

Explain the five reasons why dominant disorders may not show true vertical transimssion, that is they appear to skip generations.

Back 21

New spontaneous mutation
Penetrance
Delayed onset
Germline Mosaic
Pleitropic effects

Front 22

Give two examples of new spontaneous mutations.

Back 22

Type 1 neurofibromatosis,
Polycystic kidney disease
Duchenne muscular dystrophy

Front 23

Define: refers tot he clinical expression of the mutant gene. For some autossomal dominant diseases, an individual may carry the mutant gene, but be asymptomatic.

Back 23

Penetrance

Front 24

Define: When a muttion occurs in one cell of a multicellular embryo; Only some of the cells in that person would be mutant , and depending on which cells/tissues have the mutation, the individual couldb e clinically normal.

Back 24

Germline mosaic

Front 25

Give an example of Germline mosaicism.

Back 25

Type II OI

Front 26

Define: Affecting several organ systems or functions and frequnelty showing variable expressivity.

Back 26

Pleiotropic

Front 27

Explain how expressivity differs from penetrance.

Back 27

Penetrance referes to whether or not an individual exhibits the trait, and is an all-or-nothing phenomenon.
Expressivity refers to the nature and severity of the phenotype.

Front 28

Give an example of Germline mosaicism.

Back 28

Type II OI

Front 29

Give an exmaple of the pleiotropic effect.

Back 29

Marfan syndrome

Front 30

What syndrom is a connective tissue defect due to a mutation int eh cylcoprotein fibrillin with effects seen in the skeleton, cardiace system and eye? It is an example of pleiotropic effect.

Back 30

Marfan syndrome