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Test 3 Flashcards

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1
Q

what are the units of transmission in meiosis

A

chromosomes

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2
Q

what cannot undergo independent assortment

A

linked genes

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3
Q

what is the frequency of crossing over on a single chromosome proportional to

A

the distance between them

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4
Q

when does crossing over occur

A

always happens in meiosis and mitosis

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5
Q

what can occur because of crossing over, but does not always occur

A

recombination

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6
Q

what is recombination a result of

A

crossing over

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7
Q

chromosome maps

A

indicate the relative location of genes on a chromosome

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8
Q

T/F A linkage map is a physical map

A

F - its a probability map

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9
Q

what is the consequences of linkage in meiosis

A

independent assortment does not occur (if it does then there is no linked genes)

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10
Q

what is linkage without crossing over

A

complete linkage

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11
Q

what does linkage with crossing over result in

A

generates recombinant gametes

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12
Q

complete linkage

A

produces parental gametes

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13
Q

results of crossing over

A

between 2 non-sister chromatids, both parental and recombinants produced

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14
Q

what is a linkage group

A

the haploid number of chromosomes

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15
Q

how many linkage groups in humans

A

24

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16
Q

Linkage effects expected ratios because it violates which of Mendel’s postulates?

A

Homologs independently assort in meiosis.

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17
Q

chiasmata

A

synapsed chromosomes in meiosis wrapped around each other

x shaped intersections with points of overlap (points of genetic exchange)

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18
Q

what does the percentage of recombinant gametes depend on

A

distance between 2 genes on the same chromosome

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19
Q

genes close to each other on a chromosome are more or less likely to have chiasmata and recombine

A

less likely

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20
Q

recombination frequencies between linked genes are

A

mostly additive

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21
Q

what is 1 cM equal to

A

1% recombination between 2 genes on the chromosome

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22
Q

single crossovers

A

the relative distance between 2 loci influences the amount of recombination and crossing over, 1 cross over results in 2 recombination events

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23
Q

what do we assume if the genes are more than 50 cM apart

A

that they are on different chromosomes

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24
Q

double cross over

A

results from double exchanges of genetic material, 2 chiasmata

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25
3 point mapping criteria
Genotype of organism producing crossover gametes must be heterozygous at all loci considered. Cross must be constructed to determine genotype of all gametes by observing phenotypes of offspring. Sufficient number of offspring must be produced for representative sample crossover.
26
steps for mapping a crossover
1. identify parental chromosomes 2. identify double cross overs 3. figure out what is in the middle 4. find which single cross overs pair up
27
how to know which criteria are the parents
highest numbers
28
how to determine the double cross overs
lowest number
29
how to figure out which gene is in the middle
compare parentals to double cross overs, the gene that doesn't move is in the middle
30
what do recombination frequencies do?
approximate the switches, measures the detectable recombinant combos in products of meiosis
31
what is the largest recombinant frequency
outermost genes of the trio
32
can crossovers always be detected why or why not
no, because a crossover event will not detect double exchange when an arrangement of alleles on non sister homologs are recovered
33
what are the complications of multiple gene exchanges
1. distance between gene is underestimated | 2. most accurate gene maps are when genes are closer together
34
interference
reduces the expected number of multiple crossovers when one cross over event in one region of the chromosome inhibits a second event nearby
35
coefficient of coincidence
quantifies disparities resulting from interference | c=o/e
36
what is the interferance equation
I=1-C
37
what is the value of I if interferance is complete and their are no double cross overs
I=1
38
what does it mean if i is positive
positive interference --> fewer DCO than expected
39
what does it mean if I is negative
negative interference --> more DCO than expected
40
what contributes to interference
physical constraints that prevent chiasmata
41
forward genetics
start with phenotype and find genotype
42
ways forward genetics is used
human genetic disease screens, linkage mapping
43
reverse genetics
start with genotype and figure out phenotype
44
ways reverse genetics is used
gene silencing, targeted mutagenesis, RNAi, CRISPR
45
morpholinos
synthetic oligonucleotides 25bps long, target mRNAs to block their transcription, do not destroy the mRNAs, base pairs are same as RNA, bound to methylenemorpholine rings linked through phosphoramidite groups instead of phosphates.
46
what is RNA interference
An ancient immunity pathway against transposable elements and/or viral elements Also used for gene-regulation Likely evolved at the base of the eukaryotes Utilizes dsRNA
47
siRNA
Double stranded Binds to the complementary portion of the target mRNA Targets the mRNA for degradation Each strand has a 2-3 bp overhang small interfering) - 21-22 bps,
48
miRNA
miRNA (micro) – 19-25 bps; encoded by the genome
49
RISC
RNA Induced Silencing Complex – cleaves the mRNA A complex of proteins; precise structure not yet resolved The main component is Argonaute
50
dicer
protein that cleaves the original dsRNA into siRNAs
51
Steps for RNAi
1. Inject dsRNA 2. Dicer chops dsRNA into siRNA 3. Argonaute puts siRNA in RISC 4. Guide strand is kept in RISC, partner strand is degraded outside of the complex 5. RISC uses a guide strand to recognize target mRNA 6. the Argonaute in RISC chops up target mRNA
52
what is miRNA
RNA interference that is indigenous, regulates gene expression
53
what processing is needed for miRNAs
expressed as long pri-miRNA, then processed to pre-miRNA
54
what cuts pri miRNA to pre miRNA
Drosha and posha
55
what happens to the pre-miRNA
enters the cytoplasma, cut into 22 bp long by dicer now mature miRNA Integrated into the RISC with argonaute argaunote can now use one strand as a guide
56
eRNAi
embryonic RNAi
57
mRNAi
maternal RNAi
58
how can dsRNAs be used in lab
can be synthesized, just need the sequence of the mRNA
59
main methods of reverse genetics
TALEN Zinc Finger nucleases CRISPR
60
Mutation by a double stranded break
non homologous end joining | because the break ends are directly ligated without the need for a template
61
What are zinc finger nucleases
artificial restriction enzymes made by fusion of zinc finger transcription factor domain and a DNA cleavage domain must be used in pairs very specific
62
What are TALENS
transcription activator-like effector nuclease restriction enzyme that can be engineered to cut specific sequences made by the fusion of the DNA binding domain of a bacterial transcription factor (TAL) to a DNA cleavage domain
63
how do TALs recognize DNA
through 34 AA repeat sequences, but the 12th and 13th position are hypervariable
64
how many breaks will one talen complete
one, two would make a double break
65
homologous recombination
sticky ends that look like donor and there are parts added to the break
66
how is CRISPR used in nature
to combat viruses in bacteria
67
how does CRISPR work in nature
Bacteria wants to remember it was attacked by a virus The b cells have a memory of what it has been attacked with before Bacterial genome has a CRISPR locus, after bacteria is infected by virus we have DNA and we put it into memory bank/CRISPR locus Spacers have the sequence specific to the virus
68
what is Clustered Regularly Interspaced Short Palindromic Repeats
These are DNA sequences Derived from bacteriophages that had previously infected the bacteria Used to detect and destroy DNA from similar viruses during subsequent infections.
69
What does CRISPR Cas do
Upon viral infection, bacteria use CRISPR-associated (Cas) proteins to cut off a piece of viral DNA This sequence is integrated into the bacterial genome in between specific spacer regions By storing it, the bacteria remember this virus and will be able to counter-attack it if it invades again Repeat sequences- separate the spacer/viral sequences
70
what are CRISPR spacer sequences
are transcribed into short RNA sequences (“CRISPR RNAs” or “crRNAs”) capable of guiding the system to matching sequences of DNA
71
what happens when target DNA is found in CRISPR
Cas9 binds to it and cuts it
72
tacrRNA
helps it get inot Cas9 machine and get it where it needs to go, partially complementary, helps it fit into the Cas 9 enzyme Partially complementary to the crRNA; base pairs with the crRNA Allows the formation of the Cas9-crRNA complex
73
crRNA
Made from the CRISPR locus Specific to the invading DNA virus Guides the Cas9 protein to the target sequence
74
what is the PAM
Protospacer Adjacent Motif DNA sequence immediately following the DNA sequence targeted by Cas9. PAM is a component of the invading virus or plasmid, but is not a component of the bacterial CRISPR locus Cas9 will not successfully bind to or cleave the target DNA sequence if it is not followed by the PAM sequence Cas9 cuts 3-5 bp upstream of the PAM sequence
75
how is the guide RNA form
fuse the tracrRNA and the crRNA into a single RNA called the “Guide RNA (gRNA)”
76
how to ... CRISPR hacking
We need to target specific sequences that will adhere to the CRISPR rules... The target site must be 20 bp- Not including PAM Must have a PAM

Genetics (4 decks)

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