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· The role of DNA duplication in evolution is not confined to the __, but can also act on a smaller scale to create __ by stringing together short duplicated segments of DNA
o The proteins encoded by genes generated in this way can be recognized by the presence of repeating similar __ which are covalently linked to one another in series
- expansion of gene families
- single genes
- protein domains,
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· In genes that have evolved in this way, as well as in many other gene, , each __ often encodes an __, or domain
· The organization of DNA coding sequences as a series of __ has greatly facilitated the evolution of new proteins
- separate exon
- individual protein folding unit
- such exons separated by long introns
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o The duplications necessary to form a __, for example, can often occur by __ anywhere in the __ on either side of an exon: without __there would be only a few sites in the original gene at which a __ could duplicate the domain
§ By enabling the duplication to occur by __at many potential sites rather than just a few, introns do what?
- single gene coding for a protein with repeating domains
- breaking and rejoining the DNA
- long introns
- introns
- recombinational exchange between DNA molecule
- recombination
- increase the probability of a favorable duplication event
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· More generally, we know from genome sequences that the various parts of gene—both their __ and __—have served as __ that have been duplicated and moved about the genome to create the great diversity of living things
- individual exons and their regulatory elements
- modular elements
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· The __ differences of distantly related organisms overshadow __ variation even more dramatically
o Each fixed difference between the human and the chimp started out as a __ in a single individual
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- inter-species
- intra-species
- new mutation
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· If the mutation is deleterious, its eliminated by __. If it is advantageous, its inherited
· There are __ that can be fixed, but less rapidly, about 1/2N, N being the population
purifying selection
neutral mutations
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· One important source of variation is the presence of many __ of large blocks of DNA. A human should have roughly 100 differences involving long sequence blocks
o Some of these “__” will be common, while others are not
§ Nearly half will contain known gene
- duplications and deletions
- copy number variations
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· The __ that have been most extensively characterized are __
o These are what?
- intra-species variations
- single-nucleotide polymorphisms (SNPs)
- simply points in the genome sequence where one large fraction of the human population has one nucleotide, while another substantial fraction has another
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· Mapped sites in the human genome that are __(meaning there is a reasonable probability that the genomes of two individuals will differ at that site) are useful
polymorphic
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