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25 Cards in this Set
- Front
- Back
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genome
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all of the DNA in a nucleus of a cell; humans have a lot of foreign DNA scattered throughout the genome, including transposons...as cellular DNA amounts increase there is a correlation in an increase in cell complexity and cell size
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genome evolution
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differences in species generation times lead to different rate of evolution
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genes and gene families
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many highly conserved during evolution; others are unique to each species
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looking at conserved sequences allow.
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comparison of two species and offers information about genetic basis of human diseases.
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human vs/ tiger pufferfish
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- last common ancestor 450 mya
- overall, the pufferfish genome has less DNA than the human genome - 25% human genes have no counterpart in pufferfish - repetitive DNA: 97% in humans, less than 16% in pufferfish but gene rearranging has been extensive in the genomes of the two vertebrates - genes regulating the basic cellular metabolism are conserved in both species |
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human vs/ mouse
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- human has 400 million more nucleotides but have about the same number of genes
- share a common ancestor more recently than humans with pufferfish - share about 99% of genes - 300 genes unique to either (only 1%) - conservation of genes has been great in both genomes - mouse genome has experienced a greater rate (2x) of chromosomal rearrangements than humans have |
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human vs/ chimp
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- diverged 4.1 mya
- estimated genome sizes and number of genes is very similar in humans and chimpanzees - less than 1% difference in protein coding genes confirms that humans and chimps are sibling species - some insertion-deletions (indels) lead to loss of function changes in the two genomes - mutations have led to major differences in gene expression |
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synteny
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conserved arrangement of segments of DNA in related genomes which can be seen when linear order of genes is preserved over long sequences with a chromosome
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polyploidy
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caused when an entire genome duplicates in one species or from hybridization of two different species so that 3 or more complete copies of the genome exist in each cell
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allopolyploids
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results from hybridization and subsequent duplication of the genomes of two different species
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duplicate genes
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- can share the ancestral function of the original gene but usually do not share the same pattern of gene expression
- can lose their ancestral function and/or gain a derived function through subsequent mutation - duplication is most likely to occur in growth and development genes, immune system genes, and cell-surface receptor genes |
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Arabidopsis vs/ Oryza
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- distant relatives but share 80% genes
- they each have very high copy numbers (slightly divergent copies of a gene), probably indicating episodes of polyploidy and/or segmental duplication |
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duplication of DNA segments
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when gene duplicates, the most likely fates of the duplicate gene are
1. loosing function through subsequent mutation 2. gaining a novel function through subsequent mutation 3. having the total function of the ancestral gene partitioned into the two duplicates |
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genes controlling basic metabolism
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least likely to be duplicated
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loss of gene function
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- evolutionary mechanism
Consider: 60% of human OR (olfactory receptor) genes are pseudogenes (sequences of DNA that are very similar to functional genes but do not produce a functional product)...this inactivation may be because we rely on other senses so selection pressure against loss of OR genes reduced. |
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vertical gene transfer (VGT)
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genes are passed from generation to generation
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horizontal gene transfer (HGT)
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genes are transferred from one species to another; this infrequently happens but happened more frequently in the distant past
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pseudogenes
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DNA sequences similar to functional genes, but which appear not to produce functional products; often created by gene inactivation
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paralogues
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two genes within an organism that have arisen from the duplication of a single gene in an ancestor and may be pseudogenes or evolve new functions
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orthologues
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reflects conservation of a single gene from a common ancestor therefore are likely to have the same function
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evolution of speech
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- the protein coded by the FOXP2 gene differs by only two amino acids in humans and chimps
- the FOXP2 gene is involved in the control of the neuromuscular pathway leading to complex sound formation - in humans a single point mutation in the FOXP2 gene impairs speech and grammar - FOXP2 may be involved in songbird singing and mouse vocalization |
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Plasmodium falciparum
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- P. falciparum has many genes with similar function clustered together on its chromosomes
- P. falciparum is difficult for the immune system to target because it "cloaks" itself inside of red blood cells |
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plasmodium apicoplast
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chloroplast-like organelle inherited from chloroplast of an alga and found only in plasmodium and its relatives; site where 12% of its proteins produce fatty acids; may offer vulnerability
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transposons
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small segments of DNA that move from one part of the genome to another part
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transposase
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- recognizes inverted repeast
- cleaves at both ends of the transposable element - carries the transposable element to a new site on the DNA - cleaves the target DNA at staggered sites |
