Test2: Lect 10 Susan Olson Flashcards
Degrees of relatedness:
primary = siblings, parents secondary = grandparents, uncles/aunts tertiary = cousins Quaternary = cousins kids
Double line on pedigree means:
Inbreeding
Autosomal dominant:
Doesn’t skip generations.
Can be male or female inheritance
Can appear even with marriage to someone who doesn’t have the phenotype
Autosomal recessive:
Only appears sometimes
X-linked recessive:
Females almost never have it, males do, but never pass it on (they do, but only to female carriers)
X-linked dominant:
All daughters of affected male will have it
No male to male transmission
50% chance daughter or son of affected female will have it
X-linked dominant inheritance male lethality:
Males die before birth when they inherent (when hemizygous)
Only females will have it and transmit it to other females (all of which are heterozygous, 50% chance)
Will have more female offspring than male offspring (1 male : 2 females)
How can a female have an x linked recessive trait?
X chromosome inactivation.
Usually 50 : 50 ratio of maternal vs chromosome reaction, but this is a normal distribution.
If majority of maternal or paternal is inactivated, then it is like being hemizygous, and the phenotype will be there
EXITS genes:
- Stands for:
- Define:
- Stands for:
Escapes X-inactivation tumor suppressor gene - Define:
Explains increased chance for men to get certain cancers.
Some tumor suppressors exist on X, if neither is inactivated then they would have to lose both to get cancer
Males would only have one copy of the tumor suppressor, and so would be vulnerable with a single knockout
Mitochondrial inheritance:
Only females pass it on.
May not pass it to all of their offspring (female has some normal and some abnormal mitochondria, so it just depends if the germ cell gets her normal or abnormal one)
Severity can fluctuate with the percentage of
‘bad’ mitochondria passed
Factors which may complicate inheritance patterns:
Delayed age of onset Variable expressivity Reduced penetrance Locus heterogeneity Allelic heterogeneity Complexity in monogenic diseases Oligogenic disorders Pleiotropy New mutation
Penetrance:
- Define:
- Implication:
- Define:
is all or nothing, they have the disease or they don’t. But reduced penetrance means that they are less likely to get the disease at all. - Implication:
A dominant disease may skip a generation
Locus heterogeneity:
- Define:
- Example:
- Define:
The same disease phenotype caused by mutations at two or more different loci - Example:
Recessive would require AAbb or aaBB or aabb to cause the disease.
Could also be x - linked recessive
Allelic heterogeneity:
- Define:
- Severity of phenotype?
- Define:
More than one version of a gene at the same locus can cause the disease (multiple allele types at the loci cause the disease) - Severity of phenotype?
Some alleles confer a more severe phenotype than others
Complexity in monogenic diseases:
One allele at one loci will always cause the disease.
However, depending on other loci the disease will manifest with different system
Oligogenic disorders:
Multiple loci contribute to whether one disease is seen
Pleiotropy:
Genes that exert effects on multiple aspects of physiology or anatomy
New mutation:
- What is it difficult to distinguish this from?
- What is it difficult to distinguish this from?
A new mutation or incomplete penetrance?
Genome Mutation:
- examples:
Aneuploidy (Trisomy, monosomy)
Polyploidy (triploidy)
Chromosome Mutation:
- examples:
Translocation
Inversion
Gene Mutation:
- examples:
Point mutations
Insertion
Deletion
Phenocopy:
Mimic of a phenotype that generally has a genetic cause by the interaction of an environmental factor with a normal genotype.
Mosaicism:
- Define:
Somatic mutation occurs, subsequent progeny differ from the rest of your cells, this is called Mosaicism
- Mosaicism can be present in a lot of your cells if the mutation occurred early enough in development
Mosaicism:
- Specificity:
- Specificity:
• Organism
• Tissue/ Organ
• Extraembryonic vs. embryonic
Gonadal mosaicism:
- Define:
- Testing:
- Define:
Mutation occurs in germline, children will have chance of getting disorder, parents will not have it if tested - Testing:
Test sample of skin or blood shows they don’t have disorder. Hypothesized child was a mutant, then the next child also has it, uh oh, looks like gonadal mosaicism.
Mosaicism by somatic reversion:
-
Heterozygous for two autosomal recessive alleles for a locus heterogeneity disease both of which happen to be on the same chromosome. Crossing over occurs, and now one daughter cell is homozygous for both autosomal recessive alleles, and has the disease, and the other daughter cell isn’t even a carrier.
Spoiler alert: cell with the disease causes the problems
Anticipation:
- Define:
- What could cause this?
- Define:
Phenotype presents more severely from one generation to the next.
E.G.
Phenotype looks worse each time.
Phenotype presents sooner each time. - What could cause this?
An example could be a sequence which keeps getting increased number of repeats in it from one generation to the next
Imprinted genes:
- Define:
- Define:
You either always receive the maternal or paternal copy of the gene. The other copy is always epigenetically silenced in males or in females.
Disorders with imprinted genes:
The same deletion could cover a maternal and paternal imprinted gene.
If you inherent this mutation from your mother you will have one syndrome, if you inherent the same mutation from your father you will have another syndrome.
