Lecture 3c: Lethal Genes Flashcards
- may result in a lethal
- phenotype when mutated.
needed for survival
essential genes
- makes up approximately 1/3 of all genes
- exists in the dominant and recessive condition
essential genes
- mutation in an essential allele that results in death.
- lethality due to absent or malfunctioning protein
- mostly recessive but can be dominant
lethal allele
causes lethality when homozygous recessive produce recognizable phenotype in heterozygote
Recessive lethal Gene - aa is Lethal
Manx cat- ML interferes with normal spine development
ML ML - __
ML M - __
MM - __
- death of embryo
- absence of tail
- normal
- heterozygotes fully viable
- with short legs
- better to raise since they can’t escape from fenced pastures
‘Dexter’ Condition in cattle
‘bulldog’ calves with extremely reduced features and aborted before birth
homozygous recessives of ‘Dexter’ Condition in cattle
Xeroderma pigmentosum in man
- __ show heavy freckling
- __ - with fatal skin cancer due to extreme sensitivity to UV, stunted growth, epilepsy
- heterozygotes
- homozygous recessive
Leads to fixation of heterosis in some plants
Balanced Lethal System
Recessive lethal alleles are __ in the population
- not eliminated
Rare alleles occur in the __ (protected or __).
- heterozygote
- balanced polymorphism
phenomenon by which more than one morph exists in the population at a stable frequency at a given time.
Balanced polymorphism or balancing selection
If dominant and immediate in expression - all individuals with genes will die and gene will be lost
Dominant lethal Genes- Aa and AA die
Dominant lethal Genes are not detected due to
- Rapid elimination in population
- usually with delayed effects
__ in humans
__ has tumor-like formation in various organs and skin, severe mental defects leading to early death
Epiloia
- heterozygote
