Inheritance Flashcards
(24 cards)
Darwin’s theory of natural selection
Natural variation in a population, some individuals have a fitness advantage, these have a higher chance of survival to reproduce, resulting in specific traits being passed onto offspring
Pea plant suitability for inheritance investigations
Variability, large family sizes, short generation times, easy and inexpensive growth, suitable for controlled matings
Mendel’s 7 characteristics of pea plants
Plant height, pod shape, pod colour, seed shape, seed colour, flower position, flower colour
First law of Mendelian inheritance
Genes can exist as variants known as alleles
Law of segregation
When any individual produces gametes, two copies of a gene separate, half the gametes receive one copy, half the other copy
Monogenic conditions
Diseases caused by variants in a single gene
Second law of Mendelian inheritance
Law of independent assortment - copies of different genes assort independently (not always true, does not apply to genes on the same chromosome)
Extensions to Mendel’s laws
More than two alleles can exist for any given gene, dominance is not an all or none phenomenon, some genes can have multiple affects on phenotype, some traits are determined by gene interactions or the environment
Incomplete dominance
Alleles that are not dominant or recessive to one another
Codominance
When phenotypes for both alleles appear in heterozygotes
The establishment of an ABO blood type involves…
Multiple alleles, complete dominance, codominance
Pleiotropic alleles
A single allele that can influence more than one phenotype
Phenylketonuria (PKU)
Caused by variant in the gene for a liver enzyme that converts phenylalanine into tyrosine, can result in intellectual disability and reduced hair/skin pigmentation if not treated through dietary restriction
Epistasis
Phenotypic expression of one gene affected by expression of another gene
Polygenic traits
Traits controlled by multiple genes
Penetrance
Probability that a specific genotype will lead to expression of the associated phenotype or trait
‘Variants’ over ‘mutations’
Better practice due to less negative connotations
Chromosomal variation
Deletion, insertion, duplication, inversion, translocation
Single nucleotide variations
Synonymous, missense, nonsense, frame-shift
Silent variants
Change in the DNA that has no impact on amino acid composition of protein
Missense variants
Nucleotide change in DNA that results in a different amino acid being incorporated into the protein
Benign genetic variants
Do not cause or increase disease/risk, considered harmless
Beneficial genetic variants
Provide a protective advantage (e.g. against disease)
Pathogenic genetic variants
Cause or increase risk of a genetic condition
