mendelian genetics Flashcards
(16 cards)
who was the first person to systematically investigate the principles of heredity
mendel
what did mendel allow us to understand?
to understand the underlying genetic mechanisms of inheritance but over-simplifies our understanding of the complex origins of traits.
how are gene names written?
upper case italics
how are mutant alleles written?
lower case italics
how are protein names written
upper case normal
how are mutant proteins written?
lower case normal
what are the effects of alleles?
Mutant alleles usually impair gene function (lower expression, less active protein)
* ‘Loss of function’
* But some mutant alleles increase gene function (higher expression, more active protein)
* ‘Gain of function’
homozygous
same allele for a given gene on both homologous chromosomes.
heterozygous
different allele for a given gene on homologous chromosomes
what are wild type alleles and loss of function alleles ?
usually ‘dominant’ compared to loss-of-function alleles
Loss-of-function alleles are therefore said to be ‘recessive’
what causes co dominance?
heterozygous plants show an intermediate phenotype.
* This can be because one wild-type allele is not enough - ‘haplo-insufficiency’.
* Or because of ‘dose-dependency’ of gain-of-function alleles.
* More alleles = stronger phenotype.
what is haplo-insufficiency?
when ne wild-type allele is not enough so co dominance occurs
what is Chromosomal linkage
two genes are ‘linked’ close together on the same chromosome
Can’t be independent assortment of genotypes
The further apart genes are, the more frequent recombinant phenotypes are
XY system
female XX
male XY
- There are 2 small ‘pseudo-autosomal’ regions shared between X and Y chromosomes.
- No sex chromosome recombination outside the pseudo-autosomal regions.
- The Y chromosome contains very few functional genes.
- By contrast, the X chromosome contains many functional genes
WZ system
female WZ
male ZZ
