5 Mendelian inheritance Flashcards
Autosome
chromosomes that are not considered sex chromosomes
Allosome (gonosome)
sex chromosomes (X and Y)
Gametes
Sex cells,
contain one copy of each chromosome and either X or Y
Haploid
cells having one copy of each chromosome
Diploid
cells having two copies of each chromosomes
Allele
a form of a gene.
Polymorphism
when a locus has multiple alleles present at one locus
Hemizygous
One allele, example x linked genes in males
Pleiotropism
A single mutant gene results in many phenotypes.
A single disease causing mutation affects multiple organ systems.
Occulodentodigital Dysplasia (ODD)
Connexin mutation ( one gene). form of pleiotropism
Clinical features: thin nose, microcephaly, micropthalmia, microcornea, microdontia, partial adontia, hand and foot abnormalities
Incomplete dominance
expression of two different alleles results in an intermediate phenotype. (Red + white = pink is expressed)
Codominant
Each allele results in an observable phenotype
ex. blood type- both AB are expressed.
haploinsufficiency
Normal physiology contains more than half of full functioning gene PRODUCT. Need more than one gene.
affected individuals do not have affected parents.
Resulting form new mutation (in sex cells)
Penetrance
How frequently the allele expresses itself phenotypically
50% penetrance= 50% of people carrying allele will express trait.
X-linked disorders
Most are X-linked recessive (all males express it)
X inactivation
One X chromosome in all females is inactive. Random process 50/50 maternal or paternal.
Inactive one is targeted by noncoding RNA. Recruits chromatin remodeling machinery > heterochromatic > gene regions methylated > Barr body
Dependent- once inactivated every daughter cell will have the same X chromosome inactivated.
Incomplete- some genes from inactivated X can ‘leak out’
Genetic Mosaicism
cells with different genotypes or chromosome constitutions are present in one individual
Due to X inactivation.
Types of problems related to gene inheritance
Enzymes defects- build up of substrates, inhibition of pathways, failure to inactivate damaging substrates
Receptors- wrong concentration, altered signaling
Non enzyme- changes in carriers and structural proteins
Adverse reaction to drugs- drug metabolizing enzymes, transporters, and receptors.
Myotonic Dystrophy
Autosomal dominant condition with variable expression of clinical severity and age of onset.
ex. grandma has cataracts no face weakness, mom developed face weakness cataracts later in life, son congenital and severe case.
Due to expressivity- genes can express differently within the same genotype.
How is incomplete penetrance different from variable expression?
incomplete penetrance- Some individuals have disease genotype but do not display the phenotype
Variable expression- shows different degrees of phenotype.
Locus Hetorogeneity
single disorder caused by mutations at different loci.
New mutation
passed form unaffected parent to offspring.
Must be a gremline mutation to pass on. would occur during cell proliferation stage of somatic cells or in sex cells.
Often high mortality and infertility rates.
Missense mutation
Alters meaning of sequence so that it codes for a different amino acid.
May or may not affect overall protein structure.
Nonsense
Alters meaning of the code to stop codon
Truncated protein.
