2C- Autosomal Dominant/Recessive Flashcards
What is the principle of segregation?
sexually reproducing organisms possess genes that occur in pairs that only one member of this pair is transmitted to the offspring; it segregates
What is the principle of independent assortment?
genes at different loci are transmitted independently; transmission of a specific allele at one locus has no effect on which allele is transmitted at the other locus
What is a genotype?
An individuals genetic constitution (AA, Aa, aa, etc)
Does genotypes always correspond to a specific phenotype?
No. Genotypes do not uniquely correspond to phenotypes; because individuals with two different genotypes (dominant homozygote and heterozygote) can have the same phenotype
What are phenotypes?
The physical or clinical manifestations of genes and the environment.
In autosomal dominant diseases, what is the probability of having an affected child if one parent is heterozygous affected (Aa) and the other is unaffected (aa)?
1/2
In autosomal dominant diseases, what is the probability of having an affected child if one parent is homozygous affected (AA) and the other is unaffected (aa)?
- The child will be affected (Aa)
Is the prevelence of autosomal dominant diseases equal or unequal between men and women?
Equal
Are autosomal dominant traits present in every generation or can a generation skip a few?
Present in every generation
Is father-to-son transmission possible with autosomal dominant traits?
Yes
What is the most common cause of autosomal recessive inheritance?
parents are both heterozygous carriers
Having 2 heterozygous parents gives what % chance of having an autosomal recessive baby?
25%
Are autosomal recessive traits present in every generation or can a generation skip a few?
They can skip
Is the prevalence of autosomal recessive diseases equal or unequal between men and women?
Equal
Is father-to-son transmission possible with autosomal recessive traits?
Yes
What is the recurrance risk?
probability that an individual offspring will be affected by the disease; each birth is an independent event (such as a coin toss) and therefore the risk remains constant no matter how many affected or unaffected children are born.
What are “new” mutations?
results when a child is born with a genetic disease that has not occurred previously in the family.
What causes new mutations?
happens when a gene transmitted by one of the parents undergoes a change in DNA sequence, resulting in a mutation from a normal to a disease-causing allele
What are germline mosaicism?
type of mosaic (existence of 2 or more genetically different cell lines in an individual) in which the germ line of an individual contains an allele not present in the somatic cells
What is reduced penetrance?
situation in which a person has a disease causing genotype does not develop the disease phenotype.
What is penetrance?
Penetrance is the probability of expressing a phenotype, given that an individual has inherited a predisposing genotype; all-or-none phenomenon (either you have the phenotype or you do not)
What is delay in the age of onset?
age-dependent penetrance; some genetic disorders are not expressed until well into adulthood.
Ex: Huntington Disease
What is variable expression?
refers to the degree of severity of the disease phenotype; severity of expression of many genetic diseases can vary greatly
What is Locus heterogeneity?
diseases in which mutations at distinct loci can produce the same disease phenotype; single disease phenotype is caused by mutations at different loci in different families
What is a good example of Locus heterogeneity?
Osteogenesis imperfecta- Procollagen triple helix is enconded on two genes one on chromosome 17 and the other on chromosome 7
What is Pleiotropy?
describes genes that exert (multiple phenotypic effects) multiple aspects of physiology or anatomy; common feature of human genes
What is genomic imprinting?
describes process in which genetic material is expressed differently when inherited from the mother than when inherited from the father
What is anticipation?
a feature of pedigrees in which a disease is seen at earlier ages or with increased severity in more recent generations
What is repeat expansion?
a type of mutation in which a tandem trinucleotide repeat increases in number (ex: Huntington Disease)
What is consanguinity?
mating of related individuals; because relatives more often share disease genes inherited from a common ancestor, consanguineous unions are more likely to produce offspring affected by autosomal recessive disorders.
