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Gen Chap 1
UC MED 2015
50
Medical
Graduate
09/27/2011

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Term
What is the difference between a diagnostic test and a predictive test?
Definition
a diagnostic test is used to determine if the patient has or is free from a disease

a predictive test is used determine if the person has the disease, but has yet to show any physical problems the disease as in Huntington's Disease
Term
What kind of conditions show up in a family history (pedigree) as a single isolated case?
Definition
recessive conditions
Term
A consanguineous marriage roughly ________the risk for abnormal children?
Definition
doubles
Term
What are the different genetic disorders that can occur?
Definition
1) chromosomal abnormality
2) autosomal dominant condition, fully or partially penetrant
3) autosomal recessive condition
4) X-linked condition, dominant or recessive
5) condition caused by a defect in mitochondrial DNA
6) multifactorial condition
7) non-genetic cause
Term
What are the four features of an autosomal dominant disorder?
Definition
1) vertical pedigree problem, with multiple generations affected
2) each affected person normally has one affected parent
3) each child of an affected person has a 1 in 2 chance of being affected
4) males and females are equally affected and likely to pass on the condition
Term
What are the 5 features of an autosomal recessive disorder?
Definition
1) horizontal pedigree problem, with one or more sibs affected; usually only see a single affection
2) parents and children of affected people are normally unaffected
3) each subsequent sib of an affected child has a 1 in 4 chance of being affected
4) males and females are equally affected
5) affected children are sometimes the product of a consanguineous marriage. If family has several of these might see several generations affected
Term
What are the 4 features of an X-linked recessive disorder?
Definition
1) a 'knights move' pedigree pattern, affected boys might have affected maternal uncle
2) parents and children of affected people are normally unaffected; never passed from father to son
3) affects mainly males: females can be carriers, and affected males in a pedigree are linked through females, not through unaffected males
4) subsequent brothers of affected males have a 1 in 2 chance of being affected; sisters are not affected, but have a 1 in 2 chance of being carriers
Term
What are the 2 features of X-linked dominant disorders?
Definition
1) features very similar to autosomal dominant pedigrees; except that all daughters, but no sons of an affected father are affected
2) condition is often milder and more variable in females than males
Term
What are 3 features of a Y-linked disorder?
Definition
1) a vertical pedigree pattern
2) all sons of an affected father are affected
3) affects only males
Term
What are 3 features of a mitochondrial disorder?
Definition
1) a vertical pedigree problem
2) children of affected males are never affected
3) all children of an affected female may be affected, but mitochondrial conditions are typically extremely variable even within a family
Term
In terms of penetrance, what are the two different ways to describe the passing on a trait when penetrance goes from (a) highly penetrant to (b) lowly penetrant?
Definition
a) Mendelian inheritance
b) Multifactorial inheritence
Term
What type of disorder shows an unusual pattern of inheritance: heterozygous females are more severely affected than than hemizygous males?
Definition
X-linked inheritance with cellular interference
Term
What is it called when an autosomal condition may affect just one sex for anatomical or physiological reasons?
Definition
sex-limited disorders
Term
present at birth
Definition
congenital
Term
runs in the family
Definition
familial
Term
a person whose body contains two or more genetically different cell lines
Definition
mosaic
Term
What are the 3 cases when mosaicism is clinically relevant?
Definition
1) if the mutant cells have a tendency to grow and take over
2) if the mutation arose sufficiently early in embryonic development so it makes up a big part of the body...person has features of the disease, but with milder phenotype
3) if the mutation affects the germ line (sperm or egg cells or their progenitors
Term
conventional abbreviation for "allelomorph". Refers to the form of a gene at a locus.
Definition
allele
Term
one of 22 pairs of chromosomes excluding the sex chromosomes (X & Y)
Definition
autosome
Term
the combination of proteins (such as histones) and nucleic acids that make up chromosomes.
Definition
chromatin
Term
threadlike structure (literally "colored body") consisting of chromatin. Genes are arranged along this.
Definition
chromosomes
Term
Alleles that are both expressed when they occur together in the heterozygous state. Examples are the A and B alleles of the ABO blood group system.
Definition
Co-dominant
Term
A statistic that measures the proportion of genes shared by two individuals as a result of descent from a common ancestor.
Definition
Coefficient of relationship
Term
the mating of related individuals
Definition
consanguineous
Term
Having two copies of each chromosome. In humans this number is 46.
Definition
diploid
Term
Allele that is expressed in the same way in a single copy (heterozygote) as in a double copy (homozygote).
Definition
Dominant
Term
A trait in which the same genotype may produce phenotypes of varying severity or expression. An example is neurofibromatosis type 1.
Definition
Expressivity
Term
The haploid germ cell (egg or sperm)
Definition
Gamete
Term
An individual's allelic constitution at a locus.
Definition
Genotype
Term
Cells having one copy of each chromosome, the typical state for gametes. In humans, this number is 23.
Definition
Haploid
Term
A gene present in only a single copy. Most commonly refers to genes on a single X chromosome in males, but can refer to other genes in the haploid state, such as the genes homologous to a deleted region of a chromosome.
Definition
Hemizygous
Term
Two or more distinct DNA sequences of the mitochondrial genome within the same cell.
Definition
Heteroplasmy
Term
An individual who has two different alleles at the same locus.
Definition
heterozygote
Term
An individual whom the two alleles are the same at the same locus.
Definition
Homozygote
Term
The chromosome location of a specific gene
Definition
Locus (loci)
Term
A proposal that one X-chromosome is randomly inactivated in each each somatic cellof the normal female embryo.
Definition
Lyon's Hypothesis...this process is called Lyonization and would create the barr body
Term
Cell division process in which haploid gametes are formed from diploid germ cells.
Definition
Meiosis
Term
An alteration in a genomic DNA sequence that is heritable
Definition
Mutation
Term
A diagram that describes family relationships, gender, disease status, and other attributes
Definition
pedigree
Term
In a population, the proportion of individuals possessing a disease-causing genotype who displays the disease phenotype. When this proportion is less than 100%, the disease genotype is said to have reduced or incomplete ___________.
Definition
Penetrance
Term
The observed characteristics of an individual, produced by the interaction of genes and environment.
Definition
Phenotype
Term
The first person in a pedigree to be identified clinically as having the disease in question. Synonymous with propositus and index case
Definition
proband
Term
a locus in which two or more alleles have gene frequencies greater than 0.01 in the population.
Definition
Polymorphism
Term
A table specifying the genotypes that can arise from the gametes contributed by a mating of individuals
Definition
punnett square
Term
An allele that is phenotypically expressed only in the homozygous or hemizygous state. This allele is masked by a dominant allele when the two occur together in a heterozygote.
Definition
Recessive
Term
refers to changes in the proportions of mitochondrial DNA alleles as the mitochondria reproduce
Definition
replicative segregation
Term
the occurrence of of a disease in a family with no apparent genetic transmission pattern, often the result of a new mutation
Definition
sporadic
Term
a trait in which the same genotype may produce phenotypes of varying severity or expression
Definition
variable expression
Term
process in which genes from one X-chromosome in each cell of the female embryo are rendered transcriptionally inactive
Definition
X-inactivation
Term
Refers to genes that are located on the X-chromosome
Definition
X-linked
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