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Genetics > Chapter 14: Genetic Mapping in Eukaryotes > Flashcards

Chapter 14: Genetic Mapping in Eukaryotes Flashcards

1
Q

Syntenic?

A

genes that are on the same chromosome

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2
Q

Linked genes?

A
  • genes on the same chromosome that do not seem to assort independently
    -loci that are on the same chromosome
  • inherited together and do not assort independently
  • these genes belong to a linkage group
    #linkage groups = # chromosomes
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3
Q

Genetic recombination?

A

the process by which recombinants are produced ( progeny showing non parental combinations of alleles)

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4
Q

Genetic recombination
L> An exchange event between?
L>reshuffling of?

A

homologous chromosomes
- alleles
L> daugther chromosomes carry combos of alleles not present in parental chromosomes …aka recombinants

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5
Q

Genetic recombination:

Parentals?

A
  • progeny showing parental combination of alleles…aka non-recombinants
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6
Q

Genetic recombination:

-recombinants?

A
  • progeny showing non-parental combination of alleles …aka non-parentals
  • crossing over occurs here
    L> two homologous chromosomes line up…
    chromatids…breakage and crossing over occurs…reunion: exchange is complete…recombinants have formed
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7
Q

Hz(frequency) of recombination:

-The Hz of crossing over between two linked genes is ?

A

proportional to their location on the chromosome
L> the closer the genes are the less likely there is going to be any crossing over…the farther away they are the more crossing over will occur in that region.

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8
Q

Hz(frequency) of recombination:

-interlocus distance?

A

the percentage of recombinant offspring produced between two loci and is defined as the interlocus distance

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9
Q

Hz(frequency) of recombination:

- 2% recombination = what in map units or centimorgans?

A
  • 2 map units (mu)
  • 2 centimorgans (cM)
  • *0.002 frequency of recombination
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10
Q

Linkage ratio?

A

if two linked loci are far enough apart the # of recombinants will be approximately 50%
- there would be a 1:1:1:1 ratio for all four phonos

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11
Q

Are the loci involved in linked genes different or similar to those seen in unlinked genes?

A

L> these loci are indistinguishable from unlinked genes

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12
Q

Linked Autosomal Genes
1. Cross wild-type parent with non wild type parent.
a+b+/a+b+ x ab/ab

A

F1: a+b/ab

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13
Q

Linked autosomal genes:

2. Cross a+b+/ab x ab/ab (test cross)

A

Parental progeny:
a+b+/ab (wild type)…. ab/ab
Recombinant progent:
a+b/ab ab+/ab

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14
Q

What is the formula for map distance?

A

map distance = (# recombinant progeny/total # progeny) x 100

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15
Q

Nomenclature for synteny:
double heterozygote for w and m alleles, label if they are trans or cis!
- w+m+/wm
- w+m/wm+

A
  • cis ( when two dominant alleles are on one homolog and the two recessive mutant alleles are on the other homolog…aka coupling)
  • trans ( each homolog carries the dominant allele of one gene and the mutant allele of the other gene, called repulsion)
  • crossing over of cis loci = w+m and wm+ recombinants
  • crossing over of trans loci= w+m+ and wm recombinants
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16
Q

Order of linked genes:

- Explain the three point test cross approach!

A
  • tripe heterozygote crossed with a triple homozygote recessive
  • note the phenotypic classes seen in progeny
    L> 2 ^n = phenotypic classes
  • single and double crossovers to consider
16
Q

Order of linked genes:

- Explain the three point test cross approach!

A
  • tripe heterozygote crossed with a triple homozygote recessive
  • note the phenotypic classes seen in progeny
    L> 2 ^n = phenotypic classes
  • single and double crossovers to consider
17
Q

Recombination Hz for linked genes:

- whats the formula?

A

(Single cross over region (w+x) + double cross over region (#+#)/ total progeny )100
**this also = map distance

17
Q

Recombination Hz for linked genes:

- whats the formula?

A

(Single cross over region (w+x) + double cross over region (#+#)/ total progeny )100
**this also = map distance

18
Q

Whats the formula for the total map distance when examining recombination Hz for linked genes?

A

(single crossover region (w+x) + double crossover (#+#) + single crossover region (y+z) + double crossover (#+#)/ number of progeny)100

18
Q

Whats the formula for the total map distance when examining recombination Hz for linked genes?

A

(single crossover region (w+x) + double crossover (#+#) + single crossover region (y+z) + double crossover (#+#)/ number of progeny)100

19
Q

Interference:
- what is this expressed as?
- what is interference?
L>underestimation of what?

A
  • expressed as coefficient of coincidence
  • when one crossover event interferes with a second crossover event
  • an underestimation of the number of double crossovers
19
Q

Interference:
- what is this expressed as?
- what is interference?
L>underestimation of what?

A
  • expressed as coefficient of coincidence
  • when one crossover event interferes with a second crossover event
  • an underestimation of the number of double crossovers
20
Q

Formula for interference? (cc)

A

cc= observed double crossover Hz/ expected double crossover Hz
….Interference = 1-cc
If cc= 1 then there is no interference and all double crossovers were observed..

20
Q

Formula for interference? (cc)

A

cc= observed double crossover Hz/ expected double crossover Hz
….Interference = 1-cc
If cc= 1 then there is no interference and all double crossovers were observed..

21
Q 
Interference example: 
- expected # of double crossovers = 0.208(0.1)
- observed double crossovers= 6/500
L> what is CC?
L> whats the interference?
L> explain answer
A

cc= 0.023/0.0308= 0.577
interference= 1-0.577= 0.423
cc does not equal interference…
Therefore, in this case, only 57.7% of the double crossovers were observed.

21
Q 
Interference example: 
- expected # of double crossovers = 0.208(0.1)
- observed double crossovers= 6/500
L> what is CC?
L> whats the interference?
L> explain answer
A

cc= 0.023/0.0308= 0.577
interference= 1-0.577= 0.423
cc does not equal interference…
Therefore, in this case, only 57.7% of the double crossovers were observed.

Genetics (14 decks)

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