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STUDY ON INHERITENCE PATTERN AND FREQUENCY OF GENETIC TRAIT FOR EARLOBES AMONG THE ETHNIC GROUP (BRAHMIN) IN RAJAPUR,BARDIYA ,NEPAL

Submitted as a part of practical course of Master of Science in Zoology Second Semester

Sumitted to Central Department of Zoology Institute of science, and technology Tribhuvan University Kirtipur, Kathmandu Nepal

Submitted by: Pradip Subedi Roll no:- 39 M.Sc. Second semester CENTRAL DEPARTMENT OF ZOOLOGY TRIBHUVAN UNIVERSITY 2014 A.D

Contents

1. Introduction2. Objectives3. Limitations4. Materials and Methods 5. Results6. Discussion7. Conclusion8. Acknowledgements9. References

1.IntroductionEarlobes also known as lobules auricular is the soft

fleshy lower part found at the base of the external ear. It is the only part of the auricle not supported by cartilage (Richard D. L. 2005). It is composed of the tough areola and adipose (fatty) connective tissues lacking the firmness and elasticity of the rest of the pinna (Chummy 1999; Keith and Arthur 2006). It is either attached directly to the lateral side of the head or detached hanging freely away from the lateral side of head. The detached type is slightly bigger than the attached earlobe Detached earlobe is considered a dominant trait while attached one is recessive. This variation in attachment of earlobe is a trait inherited from parents and its inheritance follows a pattern. The patterns of inheritance describes how a allele works together to produce traits.

The patterns described includes ;X-Y Linked traitsPolygenic inheritanceMitochondrial inheritanceDominant- Recessive inheritance

X-Y Linked inheritance results when the gene is located in the sex chromosome (X or Y).

In polygenic inheritance, a trait is controlled by multiple gene pairs. So there is a gradual variation of the trait in the population without a clear distinction. Examples include height, color etc.

Mitochondrial inheritance is when the chromosome is located in the mitochondrial of the cell instead of the nucleus like in the egg cells of humans (Nussbaum et al. 2007).

Dominant- Recessive inheritance involves two pairs of contrasting characters (allele) controlling one trait where recessive allele is masked by the dominant when they occur together. The recessive can only manifest in homogeneous form (Molly and Hougeton 2010).

Ear lobe attachment is a morphogenetic trait. There is conflict in the decision whether earlobes attachment is controlled by a single gene (Anshu et al. 2007) or influenced by many genes- a polygenic inheritance pattern (Dutta and Ganguly 1965) .

Table 1: Dominant- recessive Inheritance pattern of earlobes S.N. Father Mother Offsprings RATIO:

DE:ATRATIO OF Genotype FrequencyHOM0.

DOM. ( EE)HETER.

EeHOMO.

REC. (ee)

1. When Both Father and mother are with attached earlobesa. ee ee - - ee 0:1 0:1 0:0:12. When Father with attached earlobes and mother with detached earlobesa. ee EE - Ee - 1:0

3:10:1:0

b. ee Ee - Ee ee 1:1 0:1:13. When father with detached earlobes and mother with attached earlobes.a. EE ee - Ee - 1:0

3:10:1:0

b. Ee ee - Ee ee 1:1 0:1:14. When both Father and mother with Detached earlobes.a EE EE EE - - 1:0

15:1

1:0:0b Ee EE EE Ee - 1:0 1:1:0c EE Ee EE Ee - 1:0 1:1:0d Ee Ee EE Ee ee 3:1 1:2:1

Objectives

• To calculate the frequency of genetic trait (attached and detached earlobes).

• To know the inheritance pattern of genetic trait (attached and detached earlobes).

Limitations• Difficult to collect data from whole community• Unable to study on genotype level.

Materials and Methods• Direct interaction with people.

Data were collected starting with the children, then the mother and finally the father and arranged and is analysed. the expected frequencies are calculated from expected ofspring ratios from the mendellian crosss between different parental combinations given in table 1. Using chi-test, the significance of the observed frequencies are tested at p<0.05 (critical value=3.84;and degree of freedom=1) as shown in table 3.

Study site• Rajapur is located in mid-western region of Nepal which is also known as

island of Nepal which is bounded by Karnali river. Majority of people are Tharu and Brahmins were immigrants from different mountanious area were choosen for the study.

Both Father and mother

wth

attached

earlobes.

Family Individual Name Gender Detached earlobe Attached earlobe

1

1 M 2 F 3 M 4 F

2

5 M 6 F 7 M 8 M

3

9 M 10 F 11 F

12 M

Table 2: Observation of attached and detached earlobes in Rajapur, Bardiya

Results

4

13 M 14 F 15 M 16 M 17 F

Father with

attached earlobes

and mother

with detache

d earlobes

5

18 M 19 F

20 F

21 F 22 M

6

23 M 24 F 25 F 26 F

7

27 M 28 F 29 M 30 M

Father with

attached

earlobes and

mother with

detached

earlobes

8

29 M

30 F 31 F 32 M

9

33 M 34 F 35 F 36 F 37 M

10

38 M 39 F 40 F 41 M 42 M

11

43 M 44 F 45 F

46 M

Father with

attached

earlobes and

mother detache

d earobes

12

47 M

48 F 49 F 50 M 51 F 52 F 53 F

54 M

Father with

detached

earlobes and

mother with

attached

earlobes

13

55 M 56 F 57 M 58 M 59 F 60 F 61 F 62 M

1463 M 64 F

Father with detached

earlobes and

mother

with attach

ed earlobes.

15

65 M 66 F 67 M 68 M

16

69 M 70 F 71 F 72 M 73 M 74 F 75 M 76 M 77 M

17

78 M 79 F

80 F

81 M

82 M

Father with detached

earlobes and

mother

with attached

earlobes.

18

83 M 84 F 85 M 86 M 87 M 88 M

19

89 M 90 F 91 F 92 F

20

93 M 94 F 95 M 96 M

21

97 M 98 F 99 M

100 M

Both Father

and mother with Detach

ed earlob

es.

22

101 M 102 F 103 M

104 M

105 F 106 M

23

107 F 108 M 109 F

24

110 M 111 F 112 M 113 F 114 M 115 F

25

116 M 117 F

118 M

Both Father and moth

er with Detached

earlobes.

26

119 F 120 M 121 F 122 M

27

123 F 124 M 125 M 126 M 127 F

28

128 M 129 F 130 M 131 F 132 M

29

133 F 134 M 135 M

136 F

Both Fath

er and

mother

with Detached earlobes.

30137 M 138 F

31

139 M

140 F

141 M

142 F

143 M

32

144 F

145 M

146 F

147 M

33

148 F

149 M

150 F

151 M

152 F

153 M

154 F

Both

Father

and mother

with

Detached

earlobe

s.

34

155 F 156 M 157 F 158 M 159 F

35

160 M 161 F 162 F 163 F

36

164 F 165 M 166 M 167 F 168 F

37

169 M 170 F 171 F

172 M

both

Father

and mother

with

Detached

earlobe

s.

38

173 M 174 F 175 M 176 M

177 M

178 M

39

179 F 180 M 181 M 182 F 183 F 184 M 185 M

40

186 M 187 F 188 F 189 M

190 M

both Fath

er and

mother

with Detached earlobes.

41

191 M

192 F 193 M 194 M 195 F 196 M 197 M 198 F

42

199 M

200 F 201 M 202 M

43

203 M 204 F 205 M 206 F 207 F

208 F

both

Father

and mother

with

Detached

earlobe

s.

44

209 M

210 F

211 M

212 F

213 M

45

214 M

215 F

216 M

217 M

218 M

Parental Combination

Number of Families

Total Number of Offspring Chi square

Tab(df-1 p=0.05)

Chi square Cal.

Accept or Reject

Detached Attached Total

Father Detached Mother Attached

8 16 8 24 3.84 0.889 Accept

Mother Detached Father Attached

9 17 10 27 3.84 2.09 Accept

Both Parents Detached

24 63 5 68 3.84 0.1401 Accept

Both Parents attached

4 1 8 9 3.84 - -

Total 45 97 31 128

Table 3:- Frequency table showing offspring with attached and detached earlobes with their respective parents.

• Total Population: 218• People with Detached earlobes: 162• People with Attached earlobes: 56Frequency of Detached earlobes=Number of Detached Earlobes×100%

Total Population

= 162 × 100%

218= 74.31%

Frequency of Attached earlobes= Number of Attached earlobes ×100%

Total population

= 56 × 100%

218 = 25.68%

25%

75%

Attached earlobes Detached earlobes

Fig. 1:- Percentage of Brahmins people of Rajapur, Bardiya with detached and attached earlobes.

DiscussionOut of 218 individuals of 45 families used 74.31% had

detached earlobes while 25.68% had attached earlobe in the ratio of 3:1 . This is similar to the Mendelian monohybrid inheritance using the punnet square. But this result is in contrast to the study amongst the Chinese and Japanese that recorded 66.6% for attached earlobes (Lai and Walsh 1966).

It agrees with a record of 35.1%, 4.67% and 31.61% for Indian, Jats of Delhi and Ekpoma Nigeria populations for attached earlobe respectively (Sharma et al. 2007).

The current study also conforms to the result of Barut and Aktune (2006) where they found that 78.4% of Turkish students had detached earlobe.

Sixty three offspring had detached earlobe and Five had attached earlobe when both parents had detached earlobe (Table 3) with a high ratio of 13:1. Thirty three offspring had either parents with detached earlobe as shown in Table 3. These agree with the crosses shown as table 1.

One offspring had detached earlobe and Eight offspring had attached earlobe when both parents had attached earlobe. The one offspring is deviation from the cross shown in table which is statically not significant at p<0.05. This suggests that they occurred by chance and might not be true biological children of these parents (Ordu et al. 2014). Therefore is in conformity with single gene Mendellian dominant-recessive fashion.

The inheritance pattern then is unlikely to be sex linked or mitochondrial inheritance but rather controlled by autosomal genes which are recessive for attached and dominant for detached earlobe. Variations in the sizes of earlobes was observed amongst the individuals and within families which might suggest polygenic inheritance, these earlobe variations are due to the differences in the ages of offspring since earlobe increases with age (Anshu et al. 2007) and not polygenic inheritance which is a great find in opposite of Dutta and Ganguly (1965) who concluded that earlobes attachment is polygenic inheritance.Therefore the pattern of inheritance amongst brahmins is a dominant recessive single gene Mendellian pattern which was also found to be same in Nigerian tribe found by Williams and Hughes (2008) and Ordu et al. (2014).

Conclusion

The present study provides comprehensive database of 218 samples of 45 families on the inheritable trait for Detached earlobes and attached earlobes people of Brahmins of Rajapur, Bardiya.

From the above results, it has been found that the presence of Detached earlobes people have higher frequency about 74.31% are the dominant and attached earlobes people about 25.69% are the recessive .

On the basis of data of this community it is seen that the most of the Brahmins of Rajapur, Bardiya have dominant Detached earlobes and inheritance pattern is of simple dominance-recessive pattern.

AcknowledgementsFirstly, I would like to express my immense gratitude to our

respected Associate prof. Dr. Nanda Bahadur Singh and Associate prof. Dr. Kumar Sapkota for a great encouragement, motivation and suggestion during the planning and preparing of this report. In addition to this, I would like to thanks Prof. Dr. Ranjana Gupta, the Head of the Department of Zoology, Tribhuvan University.

This report includes the data and information on human trait for earlobes that transferred from parents to their offspring genetically through gene.

I would also like to thanks to the Brahmin Community of Rajapur, Bardiya for supporting and providing me the data for this study.

Lastly i would like to express my gratitude to Miss Binita Pandey for helping me for preparation of this report and to all my classmates for their valuable cooperation and comfortable relation.

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