GENETICS Pedigree LabSummary

8/13/2019 GENETICS Pedigree LabSummary

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Results:

Legend:

Figure 1:pedigree of paternal and maternal side showing affected and unaffected family members for the single genetrait, tongue rolling

The Pedigree developed for the single gene trait, tongue rolling showed high incidence for the trait, as well

persistence in each generation as opposed to skipping 1 or more generations. The pedigree clearly

demonstrates that the trait was passed from both mothers and fathers to offspring. The paternal lineage,

brother #5 shows a male parent positive for the trait of tongue rolling, mating with an unaffected female and

9

Dad Mom

8654321 7

?

?

?

?

?

Mom

??

?

??Maternal Side

Paternal Side

3 54

Dad

Unborn offspring

Separated/divorced

Male no tongue rolling

(unaffected)

21

?

Male tongue rolling

(affected)

Female no tongue rolling

(unaffected)

Female tongue rolling

affected


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both sons expressed the tongue rolling trait. Affected female #3 on the maternal side produced affected

offspring, a daughter, with an unaffected male.

On the paternal side 7 of 10 offspring were shown to be affected by the tongue rolling trait and from these 10

siblings that were married and produced offspring, 16 out of 16 offspring (cousins) showed the trait tongue

rolling (this excludes the 17th

offspring that was reported to be unknown). 4 out of 5 offspring on the maternal

side reported to have the tongue rolling trait and of these 4 affected offspring, 5 out of 5 of their children

showed the trait as well (excluding the 6th

and 7th

children of affected off spring that were reported as unknown

Figure 2:pedigree demonstrating the inheritance pattern of the single gene trait, attached ear lobes

The pedigree constructed for the single gene trait, attached ear lobes, shows the trait for attached ear lobes wa

passed from mother to both son and daughter and the father was unaffected(free ear lobes). The Student, an

affected female, produced off spring with an unaffected male that yielded a son who was unaffected and two

daughters that were affected.

Conclusion:

It was concluded that the pedigree created for Tongue rolling (Fig. 1) showed tongue rolling to be a dominant

trait as it was present in all generations as is consistent with autosomal dominant traits. Autosomal traits

demonstrate no preference for gender of the receiver or donor of a gene. Fig1 shows an affected father (#5) on

the paternal side, with an unaffected female transmitted the tongue rolling gene to his two affected sons. Also

MomDad

Student female - attached ear lobes

(affected)

female - free ear lobes

(unaffected)

male attached ear lobes

(affected)

male free ear lobes

(unaffected)

monozygotic twins

Legend:


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on the maternal side, an affected female (#3), with an unaffected male, produced a daughter who was

demonstrated the tongue rolling trait. Both of these inheritance patterns show that the gene for tongue rolling

must be found on an autosomal chromosome. In X-linked (sex-linked) recessive traits, in addition to skipping a

generation, females typically pass the trait to their sons. In X-linked dominant traits the father will often pass the

condition or trait to their female offspring.

It was clear the grand parents were either heterozygotic dominant or homozygotic dominant, but further

exploration of the offspring was needed to confirm this. Out of ten children, 7 were said to possess the

dominant allele for tongue rolling which seemed to close to predictions made based upon heterozygotic

dominant crosses of the grandparents. This also shows that both of the grandparents must possess one

recessive (t) allele in order to have 3 homozygotic recessive, non-tongue rolling children. Had the either 1 of the

grandparents been homozygotic dominant (TT) for the trait, 100%, all 10 of their children would be affected, and

demonstrate the tongue rolling trait. A cross between heterozygotic dominant (Tt) parents should show a 3:1

phenotypic ratio (3/4 or 0.75) in favor of the dominant trait; however we saw a 7/10 ratio (0.7) for the dominant

trait. While this is close to the predicted .75, it is possible that an error in self reporting had occurred. The first

aunt claimed she was unable to roll her as well as all of her children. However the claim that all three of her

children could not as well is consistent with the aunt and her husband both being homozygotic recessive (tt) for

the tongue rolling trait. The maternal lineage was consistent with being autosomal dominant just as the

paternal lineage and also showed that 4 out of 5 offspring were dominant for the tongue rolling gene having at

least one (T) allele. The grandparents were said to be unknown however the appearance of 1 of 5 offspring

being unaffected and therefore homozygotic recessive for the trait shows that both of the maternal

grandparents must be heterozygotic dominant (Tt) for the tongue rolling trait. The offspring of maternal son (#2

must be heterozygotic dominant as his mother (maternal #3) was homozygotic recessive for the trait and

procreated with a male who was positive for the tongue rolling trait (either Tt or TT).

The pedigree showing the inheritance patterns of attached ear lobes was consistent with predicted ratios. The

father was homozygotic recessive (ee) and thestudents

mother was either heterozygotic or homozygoticdominant for the trait (without further information or more offspring produced) it is impossible to tell which).

Both the student and her brother were affected by the trait confirming they are heterozygotic dominant (Ee) for

the attached ear lobes trait. While the aunt did not report any information it was certain that she also is in

possession of at least one dominant allele (E), as they are monozygotic twins and possess identical alleles for

every trait.


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The gene responsible for attached ear lobes appear to be on an autosomal chromosome as there were no classi

patterns noted that are typically associated with sex-linked traits (patterns mentioned earlier in reference to

tongue rolling). The traits were seen in every generation and not passed from mother to son, or father to

daughter confirming our conclusions that both tongue rolling and attached ear lobes dominant traits and their

genes are found on autosomal chromosomes.

GENETICS Pedigree LabSummary

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