- Email: [email protected]
Location of the Pea Comb Gene1
Location of the Pea Comb Gene1 D . L. ZARTMAN
Dairy Department, New Mexico Slate University, Las Cruces, New Mexico 88003 (Received for publication November 3, 1972)
POULTRY SCIENCE 52: 1455-1462,1973
T
were involved here. Each male had an Xray induced translocation between the largest autosome (hereafter called chromosome no. 1) and a Z sex chromosome. The aberrations appeared to differ only in the magnitude of the segment translocated. The exchange appears to be mostly from 1 to Z and little, if any, of the Z to 1. The karyotypes and characteristics of the aberrations used for this study are described in Figures 1-3 and Table 1. As shown in the leukocyte karyotypes and meiotic diakinesis photographs, there were definitely translocations present. The fertility and hatchability figures of about 85% and 40%, respectively, confirm that observation from a statistical point of view. The proportion of fertile eggs which hatched, ca. 50%, conforms to A pair of aberrations meeting these the usual expectations where translocaqualifications were obtained in two hy- tion induced mortality prevails due to brid males. By testing transmission fre- deletion and duplication meiotic segrequencies and chromosome spreads in the gants. progeny of the two males an association The two aberrant hybrid males origbetween the aberrations and pea comb inated from X-irradiated semen (7092 inheritance was detected. had 500r., 7659 had 300r.). The parent breeds were Single Comb White Leghorn MATERIALS AND METHODS and homozygous pea-comb Dark Cornish. Two hybrid males (7092 and 7659) Male 7092 came from Cornish semen and 7659 came from Leghorn semen. The 1 Journal article 447, Agricultural Experiment genetic designation for these comb types Station, New Mexico State University, Las Cruces, is 'P' for the dominant pea comb strucNew Mexico 88003. HE composition of six genetic linkage groups in chickens was identified long ago (Hutt and Lamoreux, 1940). More recently, this was condensed to five (Somes, 1971). However, aside from the linkage group on the Z sex chromosome, no linkage group has been definitely ascribed to any one of the autosomes visible in cytological preparations. To accomplish this task of matching genes and chromosomes, aberrant marker chromosomes are fundamental tools. These markers have been rare and even now only a few are being tested (Bernier, 1971; Shoffner, 1972; Zartman, 1972a). Secondly, since the number of genes which have been identified is also small, the combination of a useful gene with an aberration is all the more scarce.
1455
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ABSTRACT Two hybrid males were available, each having an X-ray induced translocation between the largest autosome and a Z chromosome. In one male the translocated genome was Single Comb White Leghorn. The other male had a Dark Cornish genome translocated. The genetic markers for this study were single comb from the Leghorn ancestor and pea comb from the Cornish ancestor. Observations of the chromosome structures and phenotypes of the progeny of these males when mated to similar hybrid females showed non-random distributions of comb types. From the data obtained it was concluded that the pea comb gene resides on the largest autosome in chickens and it probably is distally positioned on the longer arm.
1456
D. L. ZARTMAX
i
.«;,. »i«*».ft
a ililBJil'
,^
:
is., ^ P
S«r ,$i.A
FIG. 1. A karyotype for male 7092. The translocated no. 1XZ chromosomes are indicated by arrows.
ture and ' p ' for the recessive single comb type. These two males were mated with hybrid females from the same cross which were heterozygous P p like the roosters and all pea comb. The progeny derived were the subjects of this study. Leukocyte chromosome preparations
were in accordance with the technique of Z a r t m a n (1972b), and meiotic preparations followed the process of Shoffner el al. (1967) except that cells were airdried instead of squashed. At least 20 well prepared leukocytes were observed for each chick. Comb structures were denoted when about 6 weeks old.
Downloaded from http://ps.oxfordjournals.org/ at Uniwersytet Warszawski Biblioteka Uniwersytecka on May 8, 2015
•ilk
1457
PKA COJIH ( , I . M :
il
II
/
+/
It
€'
41 I*
5W FIG. 2. A karyotype for male 7059. The translocated no. 1XZ chromosomes are indicated by arrows.
Statistical analyses of the d a t a were based on the procedure of Freund el al. (1960) for testing the equality of a proportion to a specified value. RESULTS AND DISCUSSION As mentioned before, the males used were heterozygous P p ; and one had a translocated ' P ' bearing genome while
the other had a translocated ' p ' bearing genome. Because these males were mated to P p females, it was expected t h a t the progeny would be distributed as f pea comb and \ single comb. However, when the progeny were separated in accordance with their possession or failure of possession of the sire's translocation, it was seen that this 3:1 ratio did not exist
Downloaded from http://ps.oxfordjournals.org/ at Uniwersytet Warszawski Biblioteka Uniwersytecka on May 8, 2015
I
1458
D. L. ZARTMAN
f •:-^-;f: : „ :: ;,:..Y
• -,:• •
w
B FIG. 3. Diaklnesis of meiosis. Quadrivalents are indicated by arrows. (A) Cell from male 7092. (B) Cell from male 7659.
Downloaded from http://ps.oxfordjournals.org/ at Uniwersytet Warszawski Biblioteka Uniwersytecka on May 8, 2015
n
1459
PEA COMB GENE TABLE 1.—Viability measurements for gametes produced by the subject males 7092 and. 7695 Male jMaie
7092 7659
No
- E SS S Exposed 59 100
N ?' Fertilized1 47(79.7%) 88(88.0%)
No. Hatched
Hatched/ Fert.
24(40.7%) 42(42.0%)
51.1% 47.7%
1 Fertilization is estimated on the basis of visible embryonic development.
TABLE 2.—Progeny test information for male 7092 1. Heterozygous (Pp) pea comb sire, 7092. 2. Derived from X-rayed Cornish sperm X Leghorn egg. 3. 7092 has a 1XZ translocation. 4. Test matings with Pp females. Carrier Progeny Non-carrier Progeny Male Female Male Female Pea Single
7 0
11 2
18:-2 (90%)
Pea Single
10 7
16:-14 (53.3%)
Tests for random assortment at pea locus. Hypothesis: P p X P p ^ 7 5 % P - and 25% pp Carriers: 90% vs. 75% - - - P = .06 Non-carriers: 53.3% vs. 75% - - - P = .003
TABLE 3.—Progeny test information for male 7659 1. Heterozygous (Pp) pea comb sire, 7659. 2. Derived from X-rayed Leghorn spermXCornish egg. 3. 7659 has a l X Z translocation, larger than 7092 but otherwise similar. 4. Test matings with Pp females. Carrier Progeny Non-carrier Progeny Male Female Male Female Pea Single
17:-12 (58.6%)
Pea Single
0
Tests for random assortment at pea locus. Hypothesis: P p X P p ^ 7 5 % P - and 25% pp Carriers: 58.6% vs. 75% - - - P = .02 Non-carriers: 96.7% vs. 75% - - - P = .003
21 1
29:-l (96.7%)
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within the two groups (see Tables 2 and 3). No progeny were found to have received only one member of the translocated pair of chromosomes. The translocation was always transmitted in balanced form. That is, progeny were either normal or like their sires—carriers. The ratios of comb types not only differed among carriers and non-carriers but
the ratios were distributed in reverse for one male's progeny as compared to the other's. For 7092, almost all carriers were pea comb and among non-carriers only about half were pea comb. Whereas, for 7659, about half the carriers were pea comb and nearly all the non-carriers were pea comb. If the pea comb gene were independent of the translocation, the ratios of pea to single should have been 3:1 in both carriers and non-carriers. Statistical tests were applied to the data and it was found that in all cases (P < .06) the ratios were significantly different from a 75% pea comb distribution. A new hypothesis was constructed based upon the chromosome distributions
1460
D. L. ZARTMAN
TEST FEM A L
7659
14II
t
y i
Z W
Z tZ GAM E T p
41 tl tZ
4! PI
t
p
- or t
tl tZ 1 Z pea
W
! or-*-
i 1 Z
\u
t
1 Z PROGEN Y ~^r
jorf
tl tZ 1 Z
W
single
W
~~Y~
U}or|
1 Z 1 Z pea
1 Z
W
W t t
f-Rl
1 Z
•for
t
1 Z
W
pea
FIG. 4. The chromosomal constituents derived from male 7659 and the heterozygous test females. The only gametes shown for male 7659 are those derived from alternate segregation of a quadrivalent meiotic structure. No other segregants were observed. The progeny left of center are called 'carriers' because they have the translocation.
presented in Figures 4 and 5. Accordingly, carriers from male 7092 should be 100% pea comb and non-carriers should be 5 0 % pea comb. Progeny distributions for male 7659 should be vice versa. The pea comb gene was arbitrarily positioned on the no. 1 chromosome since it is not in the sexlinked group. Now, the ratios of comb types fit the hypothesis under statistical examination ( P > . 1 8 ) for all cases.
One question remained. How did single comb chicks come to be present in the groups t h a t theoretically should have been 100% pea comb? The natural answer is t h a t crossing-over between P and p loci must have occurred in the meiotic processes of the sires. This could then cause an inordinate combination of gene and translocation. All feasible conceptions of pea gene
Downloaded from http://ps.oxfordjournals.org/ at Uniwersytet Warszawski Biblioteka Uniwersytecka on May 8, 2015
1 1 1 tl
PEA COMB GENE
1461
TEST F E M A LE I
7 0 9 2
if Z tZ
1
1
Z W
GAMET
i! tl tZ
!
I 1 Z PROGENY "V
-v
J!
H
tl tZ 1 Z pea
W
I!
i
<
tl tZ 1 Z
W
v
r
j
I ' P
pea
1 Z 1 Z P sa
P
P
}t P
W
jcrj
'P
1 Z
z
w
s i n <3 l e
FIG. 5. The chromosomal constituents derived from male 7092 and the heterozygous test females. The only gametes shown for male 7092 are those derived from alternate segregation of a quadrivalent meiotic structure. No other segregants were observed. The progeny left of center are called 'carriers' because they have the translocation.
locus and cross-over position were tested The only one which could give the single comb individuals in question is illustrated in Figure 6. This figure was designed for male 7092; for 7659 the 'P' and 'p' genes would be reversed. Under the conditions shown in Figure 6, an unusual combination of 'p' gene and translocation could occur as designated by the arrow. If that sperm cell fertilized a 'p' bearing egg cell from a heterozygous test female, then a single comb chick would appear in the
carrier group which would otherwise be all pea comb. Therefore, it is concluded that the pea gene is located distally on the long arm of chromosome 1. Referring back to Tables 2 and 3, the crossover incidence was about 10% for 7092 and 3 % for 7659. Notice that the size of the translocation for 7659 is greater than the 7092 exchange. Why is the crossover incidence smaller for the greater exchange? It may be a matter of chance. Contrarily, there may be enough
Downloaded from http://ps.oxfordjournals.org/ at Uniwersytet Warszawski Biblioteka Uniwersytecka on May 8, 2015
1 tl
H
1462
D . L. ZARTMAN
probably half of the real rates since their
709 2 MEIOTIC
CROSSING-OVER
expression is dependent upon the 5 0 % probability of meeting a ' p ' egg.
SYNAPSIS
Although it can not be stated definitely it is now highly likely t h a t the linkage
i —i—n»_^.tZ PRIMARY
group containing the pea gene belongs to
a. JC SECONDARY
SPERMATOCYTES
the largest autosome. When other genes of t h a t group have been tested by these or similar translocations, this assertion can be resolved. REFERENCES Bernier, P. E., 1971. Personal communication. Oregon Stale University, Corvallis, Oregon. Freund, J. E., P. E. Livermore and I. Miller, 1960. Manual of Experimental Statistics. PrenticeHall, Inc., Englewood Cliffs, N. J. Hutt, F. B., and W. F . Lamoreux, 1940. Genetics of the fowl. 11—A linkage map for six chromosomes. J. Heredity, 31:231-235. Shoffner, R. N., A. Krishan, G. J. Haiden, R. K. Bammi and J. S. Otis, 1967. Avian chromosome methodology. Poultry Sci. 46: 333-344. Shoffner, R. N., 1972. Personal communication. Leader of the Minn, contingent of the North Central States Regional Poultry Breeding Project, Univ. of Minn., St. Paul, Minn. Somes Jr., R. G., 1971. Callus domesticus registry of genetic stocks in the United States. Bulletin 420, Storrs Ag. Exp. Sta., Univ. of Conn. Zartman, D. L., 1972a. Work in progress. New Mexico State University Ag. Exp. Sta., New Mexico State University, Las Cruces, New Mexico Zartman, D. L., 1972b. Manuscript submitted to Cytogenetics.
11 I! 0 P ^1
PI
P
4 FIG. 6. The only satisfactory scheme to allow for the appearance of single comb chicks where only pea comb chicks are expected. The crossover involves single chromatids of the synapsed homologous portions of 1 and tZ. double crossing-over with the
lengthier
exchange segment to reduce the observed frequency of recombination. This answer seems credible and indicates t h a t the pea gene m u s t be very distally located. Anyway, the observed recombination rates are
NEWS AND
NOTES
(Continued from page 1454) 1971, and boosted sales by 17 percent over a six: week period. The judges gave the Goldenlay scheme top place on the grounds that it was not: only a tremendous success, but the follow-up publicity on the winning recipes introduced housewives to new ways of cooking eggs. They felt thatt an increase in U.K. egg consumption depended1 very much on persuading people to look beyond1 the traditional boiled or fried breakfast egg. In the Goldenlay competition the first prize off
a dream kitchen or £1,000 went to a Cheshire farmer's wife, Mrs. Sheila Jones, and she, with 10 other housewives had come to London for the grand final. The winning recipe for a kipper flan, using two large eggs, had been used with a number of other recipes in Goldenlay advertisements in women's magazine. At the time of the competition the Goldenlay marketing consortium consisted of Thames Valley, Yorkshire Egg Producers, West Cumberland
(Continued on page 1481)
Downloaded from http://ps.oxfordjournals.org/ at Uniwersytet Warszawski Biblioteka Uniwersytecka on May 8, 2015
1
SPERMATOCYTES
Dairy Department, New Mexico Slate University, Las Cruces, New Mexico 88003 (Received for publication November 3, 1972)
POULTRY SCIENCE 52: 1455-1462,1973
T
were involved here. Each male had an Xray induced translocation between the largest autosome (hereafter called chromosome no. 1) and a Z sex chromosome. The aberrations appeared to differ only in the magnitude of the segment translocated. The exchange appears to be mostly from 1 to Z and little, if any, of the Z to 1. The karyotypes and characteristics of the aberrations used for this study are described in Figures 1-3 and Table 1. As shown in the leukocyte karyotypes and meiotic diakinesis photographs, there were definitely translocations present. The fertility and hatchability figures of about 85% and 40%, respectively, confirm that observation from a statistical point of view. The proportion of fertile eggs which hatched, ca. 50%, conforms to A pair of aberrations meeting these the usual expectations where translocaqualifications were obtained in two hy- tion induced mortality prevails due to brid males. By testing transmission fre- deletion and duplication meiotic segrequencies and chromosome spreads in the gants. progeny of the two males an association The two aberrant hybrid males origbetween the aberrations and pea comb inated from X-irradiated semen (7092 inheritance was detected. had 500r., 7659 had 300r.). The parent breeds were Single Comb White Leghorn MATERIALS AND METHODS and homozygous pea-comb Dark Cornish. Two hybrid males (7092 and 7659) Male 7092 came from Cornish semen and 7659 came from Leghorn semen. The 1 Journal article 447, Agricultural Experiment genetic designation for these comb types Station, New Mexico State University, Las Cruces, is 'P' for the dominant pea comb strucNew Mexico 88003. HE composition of six genetic linkage groups in chickens was identified long ago (Hutt and Lamoreux, 1940). More recently, this was condensed to five (Somes, 1971). However, aside from the linkage group on the Z sex chromosome, no linkage group has been definitely ascribed to any one of the autosomes visible in cytological preparations. To accomplish this task of matching genes and chromosomes, aberrant marker chromosomes are fundamental tools. These markers have been rare and even now only a few are being tested (Bernier, 1971; Shoffner, 1972; Zartman, 1972a). Secondly, since the number of genes which have been identified is also small, the combination of a useful gene with an aberration is all the more scarce.
1455
Downloaded from http://ps.oxfordjournals.org/ at Uniwersytet Warszawski Biblioteka Uniwersytecka on May 8, 2015
ABSTRACT Two hybrid males were available, each having an X-ray induced translocation between the largest autosome and a Z chromosome. In one male the translocated genome was Single Comb White Leghorn. The other male had a Dark Cornish genome translocated. The genetic markers for this study were single comb from the Leghorn ancestor and pea comb from the Cornish ancestor. Observations of the chromosome structures and phenotypes of the progeny of these males when mated to similar hybrid females showed non-random distributions of comb types. From the data obtained it was concluded that the pea comb gene resides on the largest autosome in chickens and it probably is distally positioned on the longer arm.
1456
D. L. ZARTMAX
i
.«;,. »i«*».ft
a ililBJil'
,^
:
is., ^ P
S«r ,$i.A
FIG. 1. A karyotype for male 7092. The translocated no. 1XZ chromosomes are indicated by arrows.
ture and ' p ' for the recessive single comb type. These two males were mated with hybrid females from the same cross which were heterozygous P p like the roosters and all pea comb. The progeny derived were the subjects of this study. Leukocyte chromosome preparations
were in accordance with the technique of Z a r t m a n (1972b), and meiotic preparations followed the process of Shoffner el al. (1967) except that cells were airdried instead of squashed. At least 20 well prepared leukocytes were observed for each chick. Comb structures were denoted when about 6 weeks old.
Downloaded from http://ps.oxfordjournals.org/ at Uniwersytet Warszawski Biblioteka Uniwersytecka on May 8, 2015
•ilk
1457
PKA COJIH ( , I . M :
il
II
/
+/
It
€'
41 I*
5W FIG. 2. A karyotype for male 7059. The translocated no. 1XZ chromosomes are indicated by arrows.
Statistical analyses of the d a t a were based on the procedure of Freund el al. (1960) for testing the equality of a proportion to a specified value. RESULTS AND DISCUSSION As mentioned before, the males used were heterozygous P p ; and one had a translocated ' P ' bearing genome while
the other had a translocated ' p ' bearing genome. Because these males were mated to P p females, it was expected t h a t the progeny would be distributed as f pea comb and \ single comb. However, when the progeny were separated in accordance with their possession or failure of possession of the sire's translocation, it was seen that this 3:1 ratio did not exist
Downloaded from http://ps.oxfordjournals.org/ at Uniwersytet Warszawski Biblioteka Uniwersytecka on May 8, 2015
I
1458
D. L. ZARTMAN
f •:-^-;f: : „ :: ;,:..Y
• -,:• •
w
B FIG. 3. Diaklnesis of meiosis. Quadrivalents are indicated by arrows. (A) Cell from male 7092. (B) Cell from male 7659.
Downloaded from http://ps.oxfordjournals.org/ at Uniwersytet Warszawski Biblioteka Uniwersytecka on May 8, 2015
n
1459
PEA COMB GENE TABLE 1.—Viability measurements for gametes produced by the subject males 7092 and. 7695 Male jMaie
7092 7659
No
- E SS S Exposed 59 100
N ?' Fertilized1 47(79.7%) 88(88.0%)
No. Hatched
Hatched/ Fert.
24(40.7%) 42(42.0%)
51.1% 47.7%
1 Fertilization is estimated on the basis of visible embryonic development.
TABLE 2.—Progeny test information for male 7092 1. Heterozygous (Pp) pea comb sire, 7092. 2. Derived from X-rayed Cornish sperm X Leghorn egg. 3. 7092 has a 1XZ translocation. 4. Test matings with Pp females. Carrier Progeny Non-carrier Progeny Male Female Male Female Pea Single
7 0
11 2
18:-2 (90%)
Pea Single
10 7
16:-14 (53.3%)
Tests for random assortment at pea locus. Hypothesis: P p X P p ^ 7 5 % P - and 25% pp Carriers: 90% vs. 75% - - - P = .06 Non-carriers: 53.3% vs. 75% - - - P = .003
TABLE 3.—Progeny test information for male 7659 1. Heterozygous (Pp) pea comb sire, 7659. 2. Derived from X-rayed Leghorn spermXCornish egg. 3. 7659 has a l X Z translocation, larger than 7092 but otherwise similar. 4. Test matings with Pp females. Carrier Progeny Non-carrier Progeny Male Female Male Female Pea Single
17:-12 (58.6%)
Pea Single
0
Tests for random assortment at pea locus. Hypothesis: P p X P p ^ 7 5 % P - and 25% pp Carriers: 58.6% vs. 75% - - - P = .02 Non-carriers: 96.7% vs. 75% - - - P = .003
21 1
29:-l (96.7%)
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within the two groups (see Tables 2 and 3). No progeny were found to have received only one member of the translocated pair of chromosomes. The translocation was always transmitted in balanced form. That is, progeny were either normal or like their sires—carriers. The ratios of comb types not only differed among carriers and non-carriers but
the ratios were distributed in reverse for one male's progeny as compared to the other's. For 7092, almost all carriers were pea comb and among non-carriers only about half were pea comb. Whereas, for 7659, about half the carriers were pea comb and nearly all the non-carriers were pea comb. If the pea comb gene were independent of the translocation, the ratios of pea to single should have been 3:1 in both carriers and non-carriers. Statistical tests were applied to the data and it was found that in all cases (P < .06) the ratios were significantly different from a 75% pea comb distribution. A new hypothesis was constructed based upon the chromosome distributions
1460
D. L. ZARTMAN
TEST FEM A L
7659
14II
t
y i
Z W
Z tZ GAM E T p
41 tl tZ
4! PI
t
p
- or t
tl tZ 1 Z pea
W
! or-*-
i 1 Z
\u
t
1 Z PROGEN Y ~^r
jorf
tl tZ 1 Z
W
single
W
~~Y~
U}or|
1 Z 1 Z pea
1 Z
W
W t t
f-Rl
1 Z
•for
t
1 Z
W
pea
FIG. 4. The chromosomal constituents derived from male 7659 and the heterozygous test females. The only gametes shown for male 7659 are those derived from alternate segregation of a quadrivalent meiotic structure. No other segregants were observed. The progeny left of center are called 'carriers' because they have the translocation.
presented in Figures 4 and 5. Accordingly, carriers from male 7092 should be 100% pea comb and non-carriers should be 5 0 % pea comb. Progeny distributions for male 7659 should be vice versa. The pea comb gene was arbitrarily positioned on the no. 1 chromosome since it is not in the sexlinked group. Now, the ratios of comb types fit the hypothesis under statistical examination ( P > . 1 8 ) for all cases.
One question remained. How did single comb chicks come to be present in the groups t h a t theoretically should have been 100% pea comb? The natural answer is t h a t crossing-over between P and p loci must have occurred in the meiotic processes of the sires. This could then cause an inordinate combination of gene and translocation. All feasible conceptions of pea gene
Downloaded from http://ps.oxfordjournals.org/ at Uniwersytet Warszawski Biblioteka Uniwersytecka on May 8, 2015
1 1 1 tl
PEA COMB GENE
1461
TEST F E M A LE I
7 0 9 2
if Z tZ
1
1
Z W
GAMET
i! tl tZ
!
I 1 Z PROGENY "V
-v
J!
H
tl tZ 1 Z pea
W
I!
i
<
tl tZ 1 Z
W
v
r
j
I ' P
pea
1 Z 1 Z P sa
P
P
}t P
W
jcrj
'P
1 Z
z
w
s i n <3 l e
FIG. 5. The chromosomal constituents derived from male 7092 and the heterozygous test females. The only gametes shown for male 7092 are those derived from alternate segregation of a quadrivalent meiotic structure. No other segregants were observed. The progeny left of center are called 'carriers' because they have the translocation.
locus and cross-over position were tested The only one which could give the single comb individuals in question is illustrated in Figure 6. This figure was designed for male 7092; for 7659 the 'P' and 'p' genes would be reversed. Under the conditions shown in Figure 6, an unusual combination of 'p' gene and translocation could occur as designated by the arrow. If that sperm cell fertilized a 'p' bearing egg cell from a heterozygous test female, then a single comb chick would appear in the
carrier group which would otherwise be all pea comb. Therefore, it is concluded that the pea gene is located distally on the long arm of chromosome 1. Referring back to Tables 2 and 3, the crossover incidence was about 10% for 7092 and 3 % for 7659. Notice that the size of the translocation for 7659 is greater than the 7092 exchange. Why is the crossover incidence smaller for the greater exchange? It may be a matter of chance. Contrarily, there may be enough
Downloaded from http://ps.oxfordjournals.org/ at Uniwersytet Warszawski Biblioteka Uniwersytecka on May 8, 2015
1 tl
H
1462
D . L. ZARTMAN
probably half of the real rates since their
709 2 MEIOTIC
CROSSING-OVER
expression is dependent upon the 5 0 % probability of meeting a ' p ' egg.
SYNAPSIS
Although it can not be stated definitely it is now highly likely t h a t the linkage
i —i—n»_^.tZ PRIMARY
group containing the pea gene belongs to
a. JC SECONDARY
SPERMATOCYTES
the largest autosome. When other genes of t h a t group have been tested by these or similar translocations, this assertion can be resolved. REFERENCES Bernier, P. E., 1971. Personal communication. Oregon Stale University, Corvallis, Oregon. Freund, J. E., P. E. Livermore and I. Miller, 1960. Manual of Experimental Statistics. PrenticeHall, Inc., Englewood Cliffs, N. J. Hutt, F. B., and W. F . Lamoreux, 1940. Genetics of the fowl. 11—A linkage map for six chromosomes. J. Heredity, 31:231-235. Shoffner, R. N., A. Krishan, G. J. Haiden, R. K. Bammi and J. S. Otis, 1967. Avian chromosome methodology. Poultry Sci. 46: 333-344. Shoffner, R. N., 1972. Personal communication. Leader of the Minn, contingent of the North Central States Regional Poultry Breeding Project, Univ. of Minn., St. Paul, Minn. Somes Jr., R. G., 1971. Callus domesticus registry of genetic stocks in the United States. Bulletin 420, Storrs Ag. Exp. Sta., Univ. of Conn. Zartman, D. L., 1972a. Work in progress. New Mexico State University Ag. Exp. Sta., New Mexico State University, Las Cruces, New Mexico Zartman, D. L., 1972b. Manuscript submitted to Cytogenetics.
11 I! 0 P ^1
PI
P
4 FIG. 6. The only satisfactory scheme to allow for the appearance of single comb chicks where only pea comb chicks are expected. The crossover involves single chromatids of the synapsed homologous portions of 1 and tZ. double crossing-over with the
lengthier
exchange segment to reduce the observed frequency of recombination. This answer seems credible and indicates t h a t the pea gene m u s t be very distally located. Anyway, the observed recombination rates are
NEWS AND
NOTES
(Continued from page 1454) 1971, and boosted sales by 17 percent over a six: week period. The judges gave the Goldenlay scheme top place on the grounds that it was not: only a tremendous success, but the follow-up publicity on the winning recipes introduced housewives to new ways of cooking eggs. They felt thatt an increase in U.K. egg consumption depended1 very much on persuading people to look beyond1 the traditional boiled or fried breakfast egg. In the Goldenlay competition the first prize off
a dream kitchen or £1,000 went to a Cheshire farmer's wife, Mrs. Sheila Jones, and she, with 10 other housewives had come to London for the grand final. The winning recipe for a kipper flan, using two large eggs, had been used with a number of other recipes in Goldenlay advertisements in women's magazine. At the time of the competition the Goldenlay marketing consortium consisted of Thames Valley, Yorkshire Egg Producers, West Cumberland
(Continued on page 1481)
Downloaded from http://ps.oxfordjournals.org/ at Uniwersytet Warszawski Biblioteka Uniwersytecka on May 8, 2015
1
SPERMATOCYTES