Heredity PBL

Jose Roque, Kit Crews, David Garang, Caleb Habtegebriel

Our Creature

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What is DNA and why is it important?

-DNA is a self-replicating material that is present in all living organisms and contains chromosomes. It carries genetic information. DNA helps make traits, characteristics that are present in one person in particular. These traits are made up of alleles which can be Dominant or Recessive. The Dominant allele is the allele that is present in the offspring if the parent contributes it. The Recessive allele is the allele that needs to be contributed by both parents in order to be expressed. The genotype, the genetic constitution of an organism, makes the phenotype, the observable traits of an organism.


-DNA is made up of two chains of repeating Nucleotides. Each nucleotide consists of three components. These components are:

  • Phosphate Group

  • 2-deoxyribose sugar

  • A nitrogen containing base

    • cytosine

    • adenine

    • guanine

    • thymine


- DNA is important in the inheritance of traits because the coils of DNA, chromosomes, are inherited and are matched up with the opposite parent's chromosomes to create the trait. If the DNA is wrong, then the trait is going to be fluctuated.

Mutations in DNA Sequence

Trans-location: The joining of a fragmented chromosome to a non-homologous chromosome

-The translocation of chromosome 8 causes Burkitt's lymphoma


Deletion: This mutation results from the breakage of a chromosome in which the genetic material becomes lost during cell division

-Deletion of part of chromosome 15 causes Angelman syndrome


Duplication: Duplications are produced when extra copies of genes are generated on a chromosome.

- Drosophia bar eye is caused from the duplication of a chromosome


Inversion: In an inversion, the broken chromosome segment is reversed and inserted back into the chromosome.

-Inversion of chromosome 9 may lead to infertility.


Insertions - Occurs when an extra nucleotide is added.

-Polyploidy, makes plants stronger by adding an extra set of chromosomes.

Mendelian Patterns of Inheritance

In Mendelian inheritance, the heterozygote expresses the dominant allele. the Punnett square below shows Mendelian inheritance because the heterozygote (Aa) has the phenotype as the homozygous dominant (AA).
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Non- Mendelian Patterns of Inheritance

Incomplete Dominance- the heterozygote phenotype is a blend of the homozygous dominant phenotype and homozygous recessive phenotype.


Codominance- both alleles are expressed in the heterozygote phenotype.


Sex-linked Inheritance- sex-linked traits are carried on one of the sex-determining chromosomes. Out of 23 pairs of chromosomes in humans, one pair contains the sex chromosomes.

What is Meiosis? What is Sexual reproduction?

Meiosis is a type of cell division that reduces the number of chromosomes in the parent cell by half and produces four gamete cells. This process is required to produced egg sperm cell for sexual reproduction. During reproduction, when the sperm and egg unite to form a single cell, the number of chromosomes is restored in the offspring. Meiosis is significant to sexual reproduction because it helps organisms make sex cells. Meiosis causes genetic variation among the population.


Independent Assortment

the genetic information a person receives from each parent is randomly divided and this random distribution of paternal and maternal chromosomes shows us that genes for different traits are inherited separately.


Crossing Over

The exchange of genetic material between homologous chromosomes. The regions exchanged are usually located at the tips of the chromosomes but may be located in any region of a chromosome.

What is karyotype? What is pedigree?

Karyotype- karyotype is an individual's collection of chromosomes.

Pedigree- a visual representation of how a trait is passed on through generations in a family. It is a graphic representation of a family tree. Chromosomal analysis can help us see whether if any of the family is affected or a carrier of a certain disease or change in a trait.

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The pedigree chart above shows us that the affected people are the black ones.The deceased ones are the ones with slash marks on them. The normal ones are the ones with nothing on them. This helps us interpret karyotypes and pedigrees.

Using these techniques, we can see how the future generations are slowing getting used to this new trait and how evolution is happening.