Chapter 3c - Lethal Genes Flashcards
- needed for survival
- makes up approx. 1/3 of all genes
- exists in the dominant and recessive condition
essential gene
essential gene makes up __ of all genes
1/3
- mutation in an essential allele that results in death
- lethality due to absent or malfunctioning protein
- mostly recessive but can be dominant
lethal allel
- cause lethality when homozygous recessive
- produce recognizable phenotype in heterozygote
recessive lethal gene
when was lethality first reported
1905 by Cuenot while working on mice (body color)
M^L interferes with normal spine development
Manx cat
- happens because of a mutation (change) in a gene called COMP
- change causes a problem with how bone and cartilage grow
- bones end up shorter than they typically would be.
Pseudoachondroplasia
- heterozygotes show heavy freckling
- homozygous recessive - with fatal skin cancer due to extreme sensitivity to UV, stunted growth, epilepsy
Xeroderma pigmentosum
situation where recessive lethal alleles are present on two homologous chromosomes
balanced lethal system
only expressed alleles are subject to __ __
natural selection
in diploid organisms, recessive alleles can be protected from being __ in __
eliminated in heterozygotes
sickle-cell disease is an example of what
balanced polymorphism
if dominant and immediate in expression, all individuals with genes will die and gene will be lost
dominant lethal genes
heterozygote has tumor-like formation in various organs and skin, severe mental defects leading to early death
epiloia
- disease attacks areas of the brain that help to control voluntary (intentional) movement, as well as other areas
- People living with this develop uncontrollable dance-like movements (chorea) and abnormal body postures, as well as problems with behavior, emotion, thinking, and personality
Huntington’s chorea
