Chap 4- Alleles Flashcards
What are alleles?
alternative forms of the same gene
What is wild-type allele?
Allele that occurs more frequently in a population
mostly dominant, not always
What is mutation?
the source of alleles
contains modified genetic information and often specifies an altered gene product
What may mutation cause to an enzyme?
change shape and thus reduce/eliminate affinity for substrate
Loss of function mutation
Mutation may cause a complete loss of function
Null allele
Some mutations may enhance allelic function ; usually increases quantity of gene product by affecting regulation of transcription of gene
Gain of function mutation
Some mutations do not show any change in function
What may a cross between parents with contrasting traits generate?
Offspring with an intermediate phenotype in the heterozygote; incomplete or partial dominance ; phenotypic ratio identical to genotypic ratio
What is used if no dominance exist?
Italic uppercase and superscripts used to denote alternative alleles
How is incomplete dominance in humans revealed?
examining the gene product or proteins
What is Tay-sachs disease?
Lysosomal storage disease
What is codominane?
The joint expression of both alleles in a heterozygote
Example: MN blood group in humans
What do mutations modify?
the information stored in any gene by producing different alleles
-for any specific gene, there can be more than two alleles within members of a population
What do multiple alleles refer to?
three or more alleles of the gene
Where can multiple alleles be studied?
in populations, not individuals
What provides an example of multiple alleles in a population?
Human ABO blood groups
What does the ABO system exhibit?
the codominant mode of inheritance
Antisera?
Antisera contain antibodies against A or B antigen and reveal four phenotypes
The three alleles for ABO blood type?
Ia- A blood
Ib- B blood
I allele- O blood
What alleles produce their respective antigens?
IA and IB
Which allele does not produce antigen?
I allele; O
What IA and IB dominant and codominant to?
Dominant to i and codominant to each other
In Drosophila, what are phenotypes controlled by?
Multiple allelic inheritance
What are essential genes?
genes that are required for survival
What is huntington disease?
an autosomal dominant allele
Gene Interaction
the cellular function of numerous gene products contribute to the development of a common phenotype
Epigenesis
development concept where each step of development increases the complexity of the sensory organ and is under the control and influence of one or more genes
Hereditary deafness
mutations that interrupt the many steps of development
What is the hereditary deafness trait?
a heterogenous trait
What is epitasis?
the expression of a gene or gene pairs masks or modifies the expression of another gene or gene pair
Locus in first and second gene of epistasis
The first locus influences expression or alleles at a second gene locus; one dominant allele is required at each locus for phenotype expression
Dominant epistasis
when a dominant allele at one genetic locus masks the expression of the alleles in the second locus
