Term
| What is incomplete dominance? |
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Definition
◦ Neither allele is completely
dominant over the other
Heterozygote has an
intermediate phenotype |
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Term
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Definition
◦ Occurs when a single gene has more than two alleles
◦ More than one may be dominant |
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Term
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Definition
◦ Two or more genes affecting the
inheritance of the same trait
◦ One gene alters the
expression of another |
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Term
| What is polygenic inheritance? |
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Definition
Two or more genes have
an additive effect on the
same phenotype |
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Term
| Give an example of quantitative traits |
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Definition
-Height
- Skin color
- Intelligence |
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Term
| What are environmental effects? |
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Definition
◦ Phenotypes are not solely determined by genes
Genes determine the range within which environment
can affect the phenotype
That phenotypic range is called “norm of the reaction”
More common for polygenic traits
Some are absolute, like blood type. Others are
‘Multifactorial’ – with both genetic and environmental
contributions |
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Term
| What is pleotropy and give an example |
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Definition
◦ One gene affecting multiple phenotypes
Observed as apparent perfect linkage between traits
Single gene can have multiple effects
PKU – phenylketonurea
Mutation of phenylalanine hydrolase (converts phenylalanine to
tyrosine)
Mental retardation - phenylalanine and other large neutral
amino acids cross the blood-brain barrier via a transporter.
Excess phenylalanine competitively inhibits transport of other
large neutral amino acids, necessary for brain development.
Lack of pigmentation - tyrosine is used by tyrosinase (Tyr) to
make melanin
Treated with a diet low in phenylalanine, high in tyrosine
A single gene, ABCC11, controls variation in both body odor and
ear wax |
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Term
| Describe pleotropy vs polygenic effects |
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Definition
Both are multisyllabic and begin with a ‘P’, but they represent the
converse of each other
Polygenic effect – many genes affecting one trait in an additive
manner
Pleiotropy – one gene affecting many traits |
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Term
| Describe pleiotropy vs epistasis |
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Definition
Both fancy scientific words having to do with genetics
Pleiotropy – one gene affecting many traits
Epistasis – one gene masking the effect of another |
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Term
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Definition
◦ Cells with different (effective) genotypes in the
same individual
Mutation after initial cell divisions
Fused zygotes/embryos
Chromosomal inactivation
Mammalian females randomly
inactivate one X chromosome
or the other
We are all mosaic
Birthmarks, moles & a lot of
differences we can’t see |
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Term
| Describe pedigree analysis |
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Definition
◦ Used to analyze inheritance
patterns based on extended family
information
Draw pedigree of known
individuals and their
phenotypes
Deduce inheritance pattern
(dominant/recessive)
Deduce genotypes
Particularly useful when you
have small numbers, or cannot
perform test crosses |
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