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Pedigree Lab

Free essay example:

  • DATA COLLECTION:

A pedigree chart shows a record of the family of an individual. It can be used to study the transmission of a hereditary condition. It is particularly useful when there are large families and a good family record over several generations.

A pedigree chart is a chart which tells one all of the known phenotypes for an organism and its ancestors, most commonly humans. The word pedigree is a corruption of the French "pied de gru" or crane's foot, because the typical lines and split lines (each split leading to different offspring of the one parent line) resemble the thin leg and foot of a crane.

In a pedigree chart, generations are identified by Roman numerals (I, II, III…). Individuals in each generation are identified by Arabic numerals numbered from the left (1, 2, 3…).

TABLE 1:The gene controlled character observed in father’s family:

Tongue Rolling

No Tongue Rolling

1st Generation

Grandmother

Grandfather

2nd Generation

Aunt 1

Aunt 2

Uncle 1

Uncle 2

Uncle 3

Father

3rd Generation

Cousin 1

Cousin 2

Sister

Me

TABLE 2:The gene controlled character observed in mother’s family:

Tongue Rolling

No Tongue Rolling

1st Generation

Grandmother

Grandfather

2nd Generation

Mother

Aunt

Uncle

3rd Generation

Sister

Me

After collecting the required data, we need interpret whether the pedigree chart of my family with the single controlled gene character of rolling the tongue is autosomal or X-linked.

If the disorder is X-linked most of the males will have the disorder because the Y-chromosome cannot mask the affects of an affected X-chromosome.  A female can have the disorder, but it would be a very low percentage.  For a female to be affected, she would have had to receive an affected gene from the mother and the father.  This means that the father would have the disorder and the mother was a carrier.

In an autosomal disorder, the disorder is not found on the X or Y chromosome.  It is found on the other 22 chromosomes in the human body.  This means that men and women have an equal chance of having the disorder.  The mother and father can be homozygous dominant, heterozygous, and homozygous recessive.  If a person is homozygous dominant, the person has two of the same dominant genes.  

The second step is to determine if the disorder is dominant or recessive.  It is important to find out if a disorder is dominant or recessive.  

If a disorder is dominant, one parent must have the disorder (either homozygous dominant (TT) or heterozygous recessive (Tt).  Both parents do not have to have the disorder.  One parent might not have the disorder or be a carrier.  If a disease is dominant, it does not skip a generation unless one parent is heterozygous dominant (Tt) and the other parent is homozygous recessive (tt).  In this case the child has a chance of not receiving the dominant gene.

If the disorder is recessive, a parent does not have to have the disorder, but could still pass it to their offspring.  This would happen when a parent is heterozygous recessive (Tt) and passes on the recessive (t) gene.  This means this disorder can skip generations.  An example of a recessive disorder would be sickle cell anemia.

  • DATA PROCESSING AND PRESENTATION:

Predicting possible phenotypes and genotypes:

  1. Fathers Family

             Let:

         B= Tongue rolling        ,        b= No tongue rolling

Grandmother      ×      Grandfather

Parents:                           bb                              Bb

Gametes:                          b                           B        b                  

*BY USING A PUNNET GRID, WE CAN PREDICT THE OFFSPRING OF THE GENETIC CROSSES

Punnet Square:

image00.png

Genotype:                          Bb                ,                bb

Phenotype:               Able to roll tongue                        Unable to roll tongue

  1. Mothers Family

             Let:

         B= Tongue rolling        ,        b= No tongue rolling

Grandmother      ×      Grandfather

Parents:                           Bb                              bb

Gametes:                     B       b                            b                  

*BY USING A PUNNET GRID, WE CAN PREDICT THE OFFSPRING OF THE GENETIC CROSSES

Punnet Square:

image01.png

Genotype:                          Bb                ,                bb

Phenotype:               Able to roll tongue                        Unable to roll tongue

image02.png

  1. My Family

             Let:

         B= Tongue rolling        ,        b= No tongue rolling

    Mother          ×          Father

Parents:                               Bb                           Bb

Gametes:                         B       b                    B         b                  

*BY USING A PUNNET GRID, WE CAN PREDICT THE OFFSPRING OF THE GENETIC CROSSES

Punnet Square:

image03.png

Genotype:               BB         ,         Bb         ,          Bb          ,         bb

Phenotype:       Able to roll tongue            Able to roll tongue             Able to roll tongue            Unable to roll tongue

image04.png

Based on the above Punnet Square, my genotype could not be predicted. The genotypic ratio is 3:1, meaning that three have the ability to roll their tongue and 1 does not. My genotype could be in the form of BB or Bb, but this could not be known until my offspring’s are present.

Family Genetic Pedigree of three generations representing a one gene controlled character, tongue rolling.

image05.png

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