Inheritance Flashcards
Locus
Chromosomal location defining the position of a gene or DNA sequence
Allele
Alternative versions of a gene
Genotypes
List of alleles present at one or several loci
Phenotypes
characters or traits- observable properties in an organism
Homozygous
Both alleles at the locus are the same
Heterozygous
Alleles at a locus are different
Gene
-Functinal unit of DNA
-Physical and functional unit of heridetary
-It is a determinant or co-determinant of a charcater that is inheritied
-Dos not always encode for proteins
Monogenic (Mendelian)
Character programmed by one pair or set of genes at a single locus that are co-inherited
-Expression from both genes required- paricular genotype at locus
-Mendelian characters are recognised by pedigree inheritance patterns
OMIM database
Online Mendelian Inheritance in Man database
-Has sequenced genes
-sequences of genes associated with diseases
-Charaters inherited in mendelian pattern with no identified genes
Non-Mendelian inheritance
Characters that depend on a large number of genes and environmental factors governed at more than one locus
-Mendelian pedigree not shown
Multifactorial In
Non mendelian characteristics
Depend on 2,3 or many loci
Oligogenic
Refers to the fact that genetic determination is based on a small nuber of loci
Polygenic
Refers to many loci, with each individually small effect
-single primary locus with polygenic background- effect modified by cumulative effect at many loci
-Especially found in psychiatric disorders
Dichotomous
Phenotype present or absent
Mendelian Characteristics
eg cystic fibrousis
Continous or quantitative
Most human characteristics
-Height or weight- characterisitics that all have but differ to a degree
Quantitative trait loci (QTLs)
-At the molecular level-individual genes may have a Mendelian pattern of inheritance
-Character determined in a more complex way
-None-communicable diseases such as metabolic disorders like diabetes or psychiatric diseases- some cases caused in Mendelian way, some based on environment, a majority- multifactoral
Mendelian pedigree
This is when a phenotype/character is determined by a variation at a single locus
Symbols of pedigree
Characteristic Mendelian pedigree patterns
Autosomal Domiant Inheritance
Autosomal Recessive Inheritance
X-linked Recessive Inheritance
X-Linked Dominance
Y-Linked Inheritance
Mitochondrial Inheritance
Autosomal recessive carriers
Variable expression
Types of abnormalities
-Constitutional
-Mosaicism
-Chimerism
Constitutional
-Present in all cells of the body
-Inherited or developed very early during embryonic development
Mosaicism
-Two or more genetically different cell lines derived from one zygote
-Post-Zygotic change in developing embryo
Chimerism
Fusion of two zygotes to form single embryo- rare
Non-mendelian characters
-Polygenic theory- quantitative traits van be genetically determined
-Additive action- Large no. of small independant causes
-Shows Gaussian distribution
-Conceptua framework for the distribution of a polygenic trait in a population
-statistical method
