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Genes in Populations - Coggle Diagram
Genes in Populations
Principles of Mendelian genetics
Phenotype
= observable properties of an organism
Depends on type of allele
Dominant
- expressed if heterozygous or homozygous e.g. brown eyes
Recessive
- expressed only when homozygous e.g. blue eyes
Codominant -
incompletely dominant - expressed when heterozygous, but not to same degree as when homozygous e.g. A & B in ABO blood grouping
Genotype
= genetic constitution of an organism
Locus
= site of gene in chromosome
Allele
= different versions of a gene or DNA segment at locus
Heterozygous
= different alleles at a locus
Homozygous
= same alleles at a locus
Pedigrees and genetic aetiology
Familial disorder -
incidence among relatives of affected indiv greater than incidence in general population
Pedigree
- formal diagram of an indiv's ancestry
Proband or Index patient
- family member through which a family's medical history comes to attention
Types of genetic disorders
Chromosome disorders
Errors in chromosome replication during meiosis
Aneuploidy
- chromosome number not an exact multiple of haploid number e.g. monosomy, trisomy
Abnormal chromosome structure
Inversion -
chromosome segment inverted
Deletion -
chromosome segment deleted
Translocation
- change in position of chromosome segment
Single gene disorders
Types
Autosomal dominant
Autosomal recessive
Sex-linked dominant
Sex-linked recessive
Multifactorial (threshold) disorders
Genetic variation within populations
Population = group of interbreeding indiv
Genetic Variation = difference in genetic composition within a population
Arises from
Mutation - new alleles arising from point mutations and chromosome mutations
Rearrangement- mixing of existing alleles from segregation and recombination during meiosis
Gene flow - immigration of alleles from other populations
Examine measure of consanguinity
Explain how inbreeding depression arises