lecture 9 Flashcards
what influences phenotypic characters ?
many different genes and their products
gene interaction
several genes influence a particular characteristic
what does the cellular function of numerous gene products contribute to?
the development of common phenotypes
epistasis
interaction of genes that are not alleles; suppression of the effect of one such gene by another
is epistasis similar or different from dominance and recessiveness
different
what is the bombay phenotype?
a rare recessive mutation at locus that is from an incomplete formed H substance: causes different phenotype for blood type
dominant epistasis
dominant allele at one loci masks an allele at a second loci
recessive epistasis
when the homozygous recessive gene masks the “dominant” allele
complementation analyses
when two strains of an organism with different homozygous recessive mutations that produce the same mutant produce off-spring with the WT phenotype
what are the three possible outcomes if a combination of two genomes containing different recessive mutations yield a mutant phenotype?
- mutations occur in the same gene
- one mutation affects the expression of another
- one mutation may result in an inhibitory product
pleiotropy
expression of a single gene has multiple phenotypic effects
what’s an example of pleiotropy?
marfan syndrome- an autosomal dominant mutation in gene encoding connective tissue protei fibrillin
what influences phenotypic expression?
environment and genotype
do gene products function in different ways within the cell?
yes
penetrance
percentage of expression of mutant genotype in population
expressivity
range of expression of mutant phenotype
what type of mutation is the eyeless mutation in drosophila?
homozygous recessive
what else can influence gene expression
physical location in relation to other genetic material
what modifies expression?
translocation or inversion
what does physical location impact gene expression?
euchromatin can become heterochromatin or vice versa
in conditional mutations, what can effect phenotype?
temperature
what are examples of conditional mutations?
evening primrose, Siamese cats, and Himalayan rabbits
extranuclear inheritance
vary from traditional biparental inheritance of nuclear genes
organelle heredity
organism’s phenotype is affected by genes in the mitochondria and the chloroplasts
what is the material effect?
an organism’s phenotype is determined by genetic information expressed in maternal gamete
what is organelle heredity?
inheritance patterns related to chloroplast and mitochondrial function
what pattern of inheritance is organelle heredity?
extranuclear
how is organelle heredity transmitted from the maternal parent?
ooplasm
heteroplasmy
the cell may or may not have mutant genes in the organelles but the phenotype may not be revealed; more than one type of organellar genome
mitochondrial mutations
DNA found in human mitochondria completely sequenced
what must the mitochondrial gene product include?
13 proteins (unless aerobic cellular respiration), 22 transfer RNAs (for translation), and 2 ribosomal RNAs (for translation)
what does MERRF stand for?
Myoclonic epilepsy and ragged-red fiber disease
what is MERRF?
the gene encoding tRNAlys, it interferes with translation which leads to disorders
what happens to cells that are affected by MERRF?
exhibit heteroplasmy; they contain a mixture of normal and abnormal mitochondria
