Term
| Why is genetic variation so important? |
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Definition
New alleles can be beneficial to population.
Leads to propagation of drug-resistant organisms
Implications to human health (susceptibility to disease, response to treatment, cancer) |
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Term
| What is the ultimate source of genetic variation? How do these occur? |
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Definition
Mutations; mistakes in DNA replication or repair, 1x10^-9,-7,-6 mistakes per nucleotide in bacteria/yeast/humans, respectively
Chromosomal rearrangements caused by inappropriate recombination/or insertion of mobile elements |
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Term
| How often does E. coli double in growth medium? How long would it take to form a significant population of antibiotic resistant bacteria? |
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Definition
| Every 20 mins; only 12 hrs or so |
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Term
| How does conjugation work? |
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Definition
| F+ bacteria mates with F- bacteria, forming sex pilus which transfers plasmid. Other bacteria is now F+, can spread antibiotic resistance this way |
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Term
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Definition
| when bacteria pick up DNA from surroundings and incorporate into their genome |
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Term
| How does homologous recombination in bacteria work? |
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Definition
| reciprocal exchange of DNA; one strand broken at a time until recombination has occured |
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Term
| What is bacterial transduction? |
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Definition
| a virus can be used to alter DNA sequence of bacteria; when the virus leaves later it can accidentally excise parts of bacterial chromosome. |
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Term
| What are some of the features of the bacterial transposons? |
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Definition
several hundred=several thousand base pairs
10-20 transposons per bacterium
at least codes for a transposase that catalyzes transposition
can carry antibiotic resistance by hopping into plasmids or bacteriophages |
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Term
| How do transposons contribute to genetic diversity in bacteria? |
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Definition
| can disrupt genes, can affect expression of neighboring genes, repeat sequences can confuse homologous recombination and lead to rearrangement of chromosome |
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Term
| What is the formula for possibilites at meiosis? |
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Definition
| 2N (where N is number of chromosomes), in humans possibilites from both parents is 2x2^23= 7.1 x10^13 outcomes |
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Term
| What proteins are involved in human recombination? What do they do? |
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Definition
| Rad50 resects the 4' ends leaving 3' overhangs, Rad51 facilitates strand exchange, ligase/resolvase connects the ends |
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Term
| How many recombination events are there per chromosome in meiosis? How many outcomes does that mean? |
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Definition
| 3 recombination events per chromosome; 3.5 x 10^41 per couple or 5.9x10^20 per person |
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Term
| How many loss of function alleles do we inherit? How many in-frame deletions? Premature stops? Splice-site disruptions? How many frame-shift deletions? How many variants that cause known inherited disorders? What is the rate of denovo base substitution? |
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Definition
Loss of function alleles: 250-300
in frame deletions: 190-210
premature stops: 80-100
splice site disruptions: 40-50
reading frame shifts: 220-250
inherited disorder variants: 50-100
rate of substitution: 10^-8 |
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Term
| What 3 major transposons are retrotransposons? When is transposition induced? |
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Definition
LINE1 6-8 kb, 21% of the genome (850k copies), have RT
SINEs 100-300 bp, 13% of genome (1.5 million copies), use the RT from LINEs to move
Alu sequence: 300 ncs long, 5% of genome, 500,000 copies per haploid genome, very few can transpose, transposition induced for all during meiosis |
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Term
| How can human transposons contribute to genetic instability? |
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Definition
-disrupt gene function by inserting in coding region of expressed gene
-affect expression of neighboring genes
-provide sites of illegitimate recombination |
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Term
| How do transposons cause unequal crossing over? |
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Definition
| Transposons create sites for miss-alignment during recombination and thereby unequal crossing over; once multiple gene copies exist, they can become specialized through genetic drift (eg, globin genes) |
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Term
| How do transposons cause exon duplication and deletion? |
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Definition
| Through unequal crossing over, can line up wrong and cause exon deletions and duplications |
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Term
| How was the dystrophin gene formed? What disorder does exon deletion of dystrophin cause? |
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Definition
| Exon duplication and amplification; muscular dystrophy |
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Term
| How does exon shuffling work? |
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Definition
| transposable elements shift exons into different places, causing different protein formations to occur (can make new proteins/genes this way) |
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Term
| What are infective insertion elements? |
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Definition
| retroviruses; they resemble retrotransposons |
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Term
| How can retroviruses cause disease? |
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Definition
| cell death eg AIDS, integration can disrupt a gene, viral promoters can inappropriately activate expression of genes, or virus can pick up important genes from previous hosts |
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