Genetics Refresher Flashcards
What determines the individual’s risk for a disease?
The interactions between genetic risk factors (predisposition) and environmental risk factors.
Define a TRAIT.
Describes a characteristic BUT also used to describe a group of symptoms of a disease or disorder.
Define a DISEASE.
Refers to an illness which produces specific symptoms or affects a specific body function/structure.
Define a DISORDER.
Disruption to regular bodily structure/function usually causing a disease.
Define a CONDITION.
An abnormal state of health that interferes with normal wellbeing.
Define a SYNDROME.
A collection of symptoms associated with a specific disease (usually affect multiple organs).
Define a COMPLEX DISEASE.
A disease where one or more alleles, acting alone or in concert increase or reduce the risk of developing a trait.
What kinds of alterations can genetic disorders make?
1 gene
Multiple genes.
Chromosomes.
What types of genetic disorders are there?
Monogenic (mendelian) disorders.
Polygenic (multifactorial) complex disorders.
Chromosomal disorders.
What are monogenic (mendelian) disorders?
Mutations which occur due to singular gene mutation which can be transferred from parent to offspring.
What are some examples of monogenic/mendelian disorders?
Cystic fibrosis
Sickle cell anaemia
Some cancers
What are polygenic (multifactorial) complex disorders?
Common disorders which occur due to multiple risk alleles along with environmental risk increasing risk.
What are some examples of polygenetic (multifactorial) complex disorders?
Most cancers
Type 2 Diabetes
Cardiovascular Disease
Arthritis
What are chromosomal disorders?
Very rare diseases which are caused by a structural or numerical abnormality on the chromosome.
When does the risk of chromosomal disorders increase?
When the mother gets older.
What kinds of disorders are chromosomal?
Trisomy (3 types of a chromosome rather than 2)
Monosomy ( 1Chromosome rather than 2)
What does DE NOVO mean?
Not inherited, occurring new inside the body.
What kind of disorders are cancer?
Mostly complex diseases and may also involve de novo/somatic mutations.
What are mitochondrial disorders?
Very rare disorder caused by mutations in mitochondrial DNA or nuclear DNA.
What are chromosome abnormalities?
Changes resulting in visible alteration of the chromosomes.
An abnormality produced by chromosomal mechanisms.
What happens when a chromosomal abnormality occurs in a gamete cells?
Results in constitutional abnormalities which affect all cells.
What happens when chromosomal abnormalities occur later in life?
Results in somatic abnormalities (not all cells) which results in mosaicism.
What types of chromosome abnormalities are there?
Numerical or Structual.
What kinds of numerical chromosome abnormalities exist?
Triploid
Aneuploidy
What is triploid?
Containing homologous sets of chromosomes, it is lethal.
What is aneuploidy?
Loss or extra copy of one/more chromosomes, can be lived with.
What kinds of structural chromosome abnormalities exist?
Deletion
Duplication
Translocation
Inversion
What are monogenic disorders caused by?
A rare mutation at a single locus.
What kinds of gene mutations cause mendelian disorders?
Point mutations
Deletion
Insertion
What is a point mutation?
Replace 1 base with another.
What kind of mutation is sickle cell anemia?
Point mutation.
What kinds of point mutations are there?
Silent
Missense
Nonsense
Other regulatory regions.
What is a silent point mutation?
No change in the protein sequence (change for a pair).
What is a missense point mutation?
A change in an AA sequence, causes a codon to code for a different amino acid. (sickle cell anaemia)
What is a nonsense point mutation?
Creates a STOP codon.
What is a STOP codon?
Signals the termination of the translation process.
What kind of mutation is cystic fibrosis?
Deletion
What kind of mutation is Huntington’s Disease?
Insertion
What is include in Mendel’s Law?
Law of segregation
Law of independent assortment
Law of dominance
What is the Law of Segregation?
During gamete formation, the 2 alleles for each gene (locus) segregate from each other so that each gamete carries only one allele for each gene (locus).
What is the Law of Independent Assortment?
Alleles for different traits segregate independently during the formation of gametes.
What is the Law of Dominance?
An organism with at least one dominant allele will display (phenotype) the
effect of the dominant allele.
What is penetrance?
The proportion of individuals carrying a particular genetic variant that also expresses an associated trait.
What does high penetrance mean?
More space for prophylactic intervention.
What is the impact of environmental factors on mendelian (monogenic)?
Weak but can impact progression.
What kind of penetrance do Mendelian disorders have?
HIGH
What kinds of cells undergo mutations?
Somatic (body) cells
Gamete cells.
What does a mutation in a somatic cell lead to?
Can cause malignant transformation and some congenital diseases.
What does a mutation in a gamete cell lead to?
Can give rise to inherited disease.
Where do inherited mutation come from?
Passed from one or both parents.
De novo mutations in gametes.
When are inherited mutations present?
All through life and in ALL cells.
Are inherited mutations passed?
YES
When do Somatic (de novo) mutations occur?
Very early stages of development mean they are present through life but can also occur later in life.
What are mosaics?
Somatic mutations which occur later in life, are only present in some cells resulting in a mosaic of affected and unaffected cells.
Are somatic mutations passed?
NO
What are multifactorial disorders?
Common disorders caused by the combined effects of multiple genetic variants interacting with environmental factors.
What does polygenetic mean?
Multiple SNPs
What is the impact of environment on Multifactorial Complex disorders?
A very strong effect works alongside the genetic aspect.
What is the penetrance of Multifactorial Complex disorders?
Very low so no prophylactic approaches available.
What is the individual risk for a multifactorial disease determined by?
The combination of the genetic
+
Environmental risk portfolio for this individual
Define AETIOLOGY.
Cause or set of causes of a condition.
What does it mean to have a genetic susceptibility to a complex disease?
The likelihood of developing disease increases but doesn’t always directly cause it.
