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43 Cards in this Set

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Are most traits determined by the allelic variations of a single gene or are they multifactorial?
multifactorial, arising from the action of two or more genes, or from interaction between genes and the environment
environment
In genetics, the encompasses all aspect of the outside world an organism comes into contact

e.g., temperature, diet, exercise, uterine environment, psychological environment
How common is the sickle cell allele?
1 in 13 African-Americans are a carrier of the allele
transgene
a gene or genetic material that has been transferred naturally or by any of a number of genetic engineering techniques from one organism to another.
AIDS
acquired immune deficiency syndrome
hematopoietic
the formation of blood cellular components
genotypic class
a grouping defined by a set of related genotpes that will produce a particular phenotype. The term is most useful in describing progeny of dihybrid or multihybrid crosses involving complete dominance; for example, in a cross between Aa Bb individuals, the genotypic classes are A- B-, A- bb, aa B-, and aa bb
complementary gene action
genes working in tandem to produce a particular trait

e.g., AA bb (white flowers) x aa BB (white flowers) producing Aa Bb (purple flowers)
What's the explanation for complementary gene action ?

(note: answer refers to the flower example)
It takes two enzymes catalyzing two separate biochemical reactions to change a colorless precursor into a colorful pigment.
epistasis
a gene interaction in which the effects of an allele at one gene hide the effects of alleles at another gene
epistatic
the allele that is doing the masking (in epistasis)
hypostatic
the gene that is being masked (in epistasis)
recessive epistasis
where homozygosity for a recessive allele of a second gene is required to hide the effects of another gene

e.g., in labradors, where --/ee results in a yellow coat
A 9:3:4 ratio might indicate:
recessive epistasis
Bombaby blood is an example of:
recessive epistasis
12:3:1 or 13:3 ratios may imply:
dominant epistasis
dominant epistasis
epistasis in which the dominant allele of one gene hides the effects of another gene
heterogeneous trait
a mutation at any one of a number of genes can give rise to the same phenotype

e.g., any one of 50 mutations for ear development all cause deafness
complementation test
method for discovering whether two mutations are in the same or separate genes

the method of discovering whether a particular phenotype arises from mutations in the same or separate genes
the occurence of complementation reveals:
genetic heterogeneity
With incomplete dominance, the interaction of two genes can produce ____ different phenotypes for a single trait
nine different


AA/BB, Aa/Bb, aa/bb, et cetera
Does the same genotype always produce the same phenotype?
No!
retinoblastoma
the most malignant form of eye cancer; dominant mutation, yet only 75% of carriers develope the disease
penetrance
how many members of a population with a particular genotype show the expected phenotype

can be complete (100%) or incomplete
expressivity
refers to the degree or intensity with which a particular genotype is expressed in a phenotype
modifier genes
have a more subtle, secondary effect; alter the phenotypes produced by the alleles of other genes
expressivity
refers to the degree or intensity with which a particular genotype is expressed in a phenotype

can be variable or unvarying
What leads to the visible effect of the coat on Siamese cats?
temperature; light areas where the temperature is warm, dark where the temperature is cool
conditional lethal
an allele that's lethal only under certain conditions
permissive
the range of condition (e.g., temperature) under which the allele remains viable
restrictive
the allele that's lethal under certain conditions (e.g., under temperature)
phenocopy
a change in phenotype arising from such environmental agents that mimics the effects of a mutation in a gene
homozygosity for the mutant PKU allele:
eliminates the activity of a gene encoding the enzyme phenylalanine hydroxylate
phenylalanine hydroxylate
converts the amino acid phenylalanine to the amino acid tyrosine
absence of phenylalanine hydroxylate causes:
buildup of phenylalanine, resulting in neurological problems
penetrance
the occurrence of a phenotype (e.g., heart disease from lack of exercise)
expressivity
the seriousness of a phenotype
(e.g., the degree of damage from heart disease)
century
a period of 100 years
quandary
a state of perplexity or uncertainty, esp. as to what to do; dilemma.
discontinuous trait
phenotypes that resulted from alternative alleles that were clear-cut, e.g., either short or tall
continuous trait
segregating allels of many different genes whose interaction with each other and the environment produces phenotypes showing continuous variation

e.g., height, weight, skin color in humans
quantitative traits
continuous traits
polygenic
controlled by multiple genes

they are, by definition, multifactorial
(note that not all multifactorial genes are polgenic)