chapter 4 part 1 Flashcards
types of interactions in which genes interact to influence a phenotype
-may be more than two alleles for a given locus within a population
-dominance of one allele over another may be incomplete
-two or more genes may affect a single trait
-the expression of a trait may depend on the interaction of more than one gene &/or the interaction of genes with non-genic factors
two alterative forms that mendel chose
-one form was completely dominant over the other so the heterozygous for the 2 alleles showed the dominant phenotype
-research in the early & mind-20th century was aimed at better understanding the molecular nature of dominance
the terms dominant & recessive have a ________ basis
biological
what is dominance of one allele over another determined by?
the protein product
haplosufficient
-when making one copy of the normal allele is enough for normal function (mutant allele is recessive)
haploinsufficinet
when making one copy of the normal allele is not enough (Tt) for normal function (you need two copies of the normal one to be sufficient) so the mutant allele is dominant
wild-type allele
always produced when an organism has two copes of the wild type allele
what are the categories that mutant alleles can be?
-gain-of-function
-loss-of-function
gain-of-function
when the gene produce aquires a new function or shows an increased level
loss-of-function
when there is a significant decrease or complete loss of functional gene product
null/amorphic mutations
loss of function mutations that produce no functional product
-often are lethal when homozygous
leaky/hypomorphic mutations
-loss-of-function mutations that result in a partial loss of function
-severity of the phenotype of these depends on the level of activity of the leaky mutation
what are particularly subject to dominant negative mutations
multimeric proteins, composed of two or more polypeptides that join together to form a functional protein
why are dominant negative dominant?
due to loss of function of the multimeric protein complex due to an amino acid change of one subunit
why are dominant negative mutations “negative”?
-due to their “spoiler effect” on the protein as a whole
are gain of function mutations usually dominant or recessive?
usually dominant and can be hypermorphic or neomorphic
hypermorphic mutations
produce more gene activity than wild type
neomorphic mutations
aquire novel gene activities not in the wild type
incomplete dominance or partial dominance
when heterozygous individuals display intermediate phenotypes between either homozygous type
-typically the heterozygote will be more similar to one of the homozygous types than the other
how many different ABO blood types resulting in how many different combinations of alleles?
4
3
Blood type A
-RBCs have type A Antigen on their surface IAIA or IAi
Blood type B
-RBCs have type B antigen on their surface
IBIB or Ibi
blood type AB
-RBCs have both A and B antigens on surface
-IbIA
blood type O
-RBCs have neither A or B antigens
-ii
