Term
| predicting the pheno mean of the next gen |
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Definition
IF h2 = 0
*cant predict what P-bar will be
*the ind would have inc pheno due to non add genetics (ex: env)so not necessarily better than average
*P-bar(G2) = P-bar(G1)
IF h2 = 1
*the ind had inc pheno due to BV (perfect relation bet BV & P)
*ind selected would transmit their entire deviation to the next gen b/c all of it is caused by additive genetics
NOTE: P-bar(G2) depends on heritability
*↑h2 = most of deviation transferred
*↓h2 = not transferred b/c its due to nonadditive effects |
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Term
| Question: Predict the pheno mean deviation due to additive genetics |
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Definition
BV-cap = h2(P - P-bar)
*BV-cap: ____% of pheno variation is due to additive genetics |
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Term
| Question: Predict the mean phenotype of offspring? |
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Definition
BV-cap = 1/2BV(P1) + 1/2BV(P2)
P-bar(G2) = BV-cap + P-bar(G1)
*AKA P=M+BV+GCV+E (but GCV and E = 0) |
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Term
| selection differential (S) |
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Definition
*pheno diff between the selected ind and the total pop we are selecting from
S = (P-bar,s) - P-bar
P-bar,s : mean pheno of selected ind
P: total pop mean pheno b4 selection
S: selected ind have a mean pheno of ____ above/below pop mean
S = σP * i |
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Term
| Response to selection (R)/ genetic change (ΔBV) |
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Definition
*how the pop changes genetically or pheno
-genetic and pheno are same b/c pheno tracks genetics
*the change in mean BV or pheno in a pop from selection
R = ΔBV |
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Term
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Definition
*reveals ways to overcome less accurate selection
R = ΔBV = h2*S
ΔBV: additive genetic change
S: selection differential
R: pop responded to selection by inc/dec mean additive genetics by ___ and the pheno tracked it
R = ΔBV = h2 * σP * i
R = ΔBV = h * σBV * i (use ratio of narrow sense)
R = ΔBV = rBv,P * σBV * i (use h2-correlation relationship)
ΔBV/t = (h2 * σP * i)/L (for rate of genetic change) |
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Term
| Factors that influence response to pheno selection |
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Definition
1) S
2) h2
* h2 has huge influence of resp to selection
-b/c its proportion that is transmitted
*H2 does not have influence
-b.c effects are not transmitted (nonadditive) |
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Term
| h2 influence on pheno selection |
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Definition
LOW h2
*R would be low
*mean pheno would only change slightly (calc R) even if pick highest ind b/c high P due to nonadd genetics
HIGH h2
*mean pheno would be high
*would have a lrg pheno shift in sing gen of selection
*ind would have ↑P --> good indicator of ↑BV --> ind transmit alleles and have strong resp to selection
* ↑h2 = ↑ resp to selection (R) |
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Term
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Definition
| *define a pt, and select all ind above, cull below |
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Term
| Question: When using trunk selection, what is S? |
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Definition
*mean of the colored region (P-bar,s)
*goes from mid of bell curve to mid of colored region |
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Term
| Question: Truncation selection, what is the resp to selection / where will the mean be in the next gen |
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Definition
*should fall w/in the rage of S (depends on h2)
*R goes from mid of bell curve to start of the colored region |
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Term
| Question: how does truncation selection point influence response? |
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Definition
| *if choose further down x-axis, S would be greater --> R would be greater |
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Term
| Visual representation of Breeder's equation w/ truncation selection |
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Definition
| *selected ind have a mean pheno and they transmit some pheno difference |
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Term
| factors that influence pheno respons |
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Definition
FOR SIT
*allele, geno freq
FOR QUANT
*pheno response
*R = ΔBV = h2 * σP * i
* so if increase h2, variation, or intensity --> inc response to selection |
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Term
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Definition
*represents the S as a SD
*represents the strength of selection
*the mean of selected ind in SDs
i = S / σP |
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Term
| Improving the rate of genetic change (PART 1) |
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Definition
R = ΔBV = h * σBV * i
*inc h, σBV, or i to improve resp
1) INCREASE σBV
2) INCREASE i |
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Term
| How to inc σBV (#1, Part 1) |
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Definition
A. USE + ASSORTATIVE MATING TO ↑σBV
*changes distrib of alleles:↑homo, ↓hetero
*changing syst doesnt change allele freq, changes how alleles disrtib across phenos (creates more extremes)
*✔ can easily control, X dec in uniformity
B. BRING NEW GENETIC VARIATION BY CROSSING IN DIFF BREED/STRAIN/LINE
*bring in new alleles --> if alleles have + pheno effect --> inc variation --> inc resp
* X could inc one trait but could dec another
C. GENE EDITING
*EX: dairy cows that are pulled produce less milk
D. NEW MUTATION
*ultimate source of genetic variation
*X random, not guaranteed; slow process |
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Term
| How to inc i (#2, Part 1) |
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Definition
*theres a relationship between i and proportion of ind saved
EX:
if select top 10%, i= 1.76
if select top 1%, i= 2.67
*with more intense selection you get a better response |
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Term
| Improving the rate of genetic change (PART 2) |
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Definition
R = ΔBV = rBv,P * σBV * i
*use selection accuracy (h = rBV,SC) |
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Term
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Definition
| *the info forming the basis of a selection decision |
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Term
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Definition
*making selection w/ pheno values of an ind
* SC would be the phenotypes themselves (SC = P)
*resp to selection refers to BV and pheno
(rBV,P = rBV,SC) |
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Term
| Phenotypic selection using truncation pts |
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Definition
*if have mod-low h2, cause some ind w/ low BV to be chosen
*only looking at x-axis b/c dont see BV (b/c in low h2 cant use P to predict BV)
*for weak h2, truncation with pheno selection bot good b/c ind high pheno caused by nonadd (not passed) |
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Term
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Definition
*correlation between BV and SC
*determines resp to selection (↑ accuracy --> ↑ resp)
h = rBV,SC
*if have strong correlation between BV-cap and BV, then BV-cap would be better criterion to use for selection (inc accuracy)
-slection will be more accurate if rank ind based on BV-cap w/ lots of info (strong corr bet BV-cap and true BV)
*can get better selection h if compile all info have and use more than just P |
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Term
| Using more info vs pheno selection |
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Definition
*using more info would produce a higher response to selection
*pheno selection (SC = P), more info (SC ≠ P)
-SO for more info rBC,SC ≠ rBV,P b/c not basing selciton on pheno records
*selection using more info: gathering lots of info to estimate BV and make a selection on that (which inc accuracy of selection)
*even if have low h2, can get a better resp to slection if gather more info |
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Term
| Improving the rate of genetic change (PART 3) |
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Definition
*change BEQ to incorporate diff time frames (EX: years)
ΔBV/t = (h2 * σP * i)/L
ΔBV/t: rate of genetic change
L: generation interval
↑ RATE
1. can inc numerator
2. dec denominator
*will give ind with best improvement for next gen |
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Term
| Question: What is the resp under x gen of selction? |
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Definition
EX: 10 gen
ΔBV = (lbs / 1gen ) = (x / 10gen) |
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Term
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Definition
*average age of all parents (when offspring are born) in a pop
* ↓ L = ↑ rate of genetic change (ΔBV/t)
*for a species, cant go below a certain amount b/c takes awhile for an ind to mature
*BUT can ↓ mean gen interval by choosing younger ind (not a fixed value)
*want to have a smaller L (young ind) b/c allows to go through more amount of cycles in same amount of time |
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Term
| How to ↑ Numerator (#1, Part 3) |
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Definition
SELECTION INTENSITY (i)
*if ↓ % of ind saved --> ↑ intensity
GENETIC VARIATION (σBV)
*can be inc by 1)bringing in outside alleles, 2)perform + mating
SELECTION ACCURACY (rBV,SC)
*pheno vs selection w/ more info
*selection with more info give higher accuracy
*if have strong relationship bet SC and BV-cap, get the truly best ind |
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