| 1.
Genes can exist in different versions, which differ in
the nucleotide sequence; these versions are known as
alleles. |
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| 2.
The complete set of genes carried by an organism
is its genome;
the specific set of alleles it carries is known as its genotype. |
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| 3.
The specific features of an organism is known as its phenotype. |
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| 4.
The phenotype is a function of the genotype and environmental
and molecular events that occur during embryonic development
and thereafter. |
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| 5.
Some phenotypic traits are due to the allelic composition of a single gene, most
are based on a large number of different genes. |
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| 6.
During meiosis the process of recombination can lead
to the formation of new alleles and new combinations
of alleles along a chromosome. |
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| 7.
The process of sexual reproduction can generate vast
numbers of possible genotypes. |
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| 8.
All alleles have their origins as a mutation or
a recombination event. The original version of the gene, before the mutation,
is known as the wild type allele. |
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| 9.
A specific gene is also known as a genetic locus (position). In
a particular population of organisms, the number and frequency of alleles of
a
specific genetic locus will be determined by various factors, including founder
effects, genetic drift and natural selection. Generally the most frequent
allele will be considered the wild type, but this is an artificial convention. |
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| 10. Genes
produce products, either RNAs or (indirectly) polypeptides
(proteins). |
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| 11.
A
mutation can alter either the gene product itself, its
regulation (when, where and how much is produced). |
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| 12.
We can classify mutations formally, without even knowing
what the gene products do or how the mutation alters
them in the following terms. A mutation can be
amorphic (no
gene product produced), hypomorphic (the
gene product has the same function, but is less active
than the wild type), hypermorphic (the
gene product has the same function, but is more active
than the wild type), antimorphic (the
mutant gene product antagonizes the function of the wild
type product) or neomorphic (the
gene product has a new function, different from the wild
type gene produce). |
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| 13.
Haploid organisms
have a single copy of each genetic locus. Diploid organisms
have two copies (one inherited from the maternal
parent the other from the paternal
parent). In a diploid organism,
if a phenotypic trait is determined by one allele, irrespective
of the nature of the other allele at the genetic locus,
the determining allele is said to be dominant, the
other allele(s), recessive. |
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| 14
Most alleles are neither strictly dominant or recessive,
but interact in complex ways with each other and the
rest of the genotype to determine phenotype. |
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