Concept Introduction

What is heredity?

• why do children look like their parents?

• why do brothers and sisters resemble each other?

• This is because we 'inherit' traits from our parents.

• The passing of traits from parents to child is the basis of heredity.

Where are our traits?

• Our genes encode the instructions that define our trait. Each of us has thousands of genes, which are made of DNA and reside in our chromosomes.

• The environment we grow up and live in also helps define our traits.  For, example, while a person's genes may specify a certain hair color, exposure to chemicals or sunlight can change that color.

How do we get traits from our parents?

• Each parents contributes half of their DNA to their child.

What is a trait?

• A trait is a notable feature or quality in a person.  Each of us has a different combination of traits that makes us unique.

What types of traits exist?

• Physical traits are characteristics of one's physical makeup.  These include hair color, eye color and height.

• Behavioral traits are characteristics of the way one acts.  A sheepdog's herding instinct and a retriever's desire to fetch are good examples of behavioral traits.

• Predisposition to a medical condition.  An increased risk of getting a certain type of disease is also a type of trait that can be passed from parent to child.  Examples of such diseases include sickle cell anemia, cystic fibrosis, heart disease and certain types of mental illness.

What defines our traits?

• The instructions encoded in our genes play a role in defining traits.  But the non-genetic, or 'environmental', influences in our lives are just as important in shaping or traits.  Sometimes these environmental factors can even alter our traits. 

• Examples:

  • Physical traits:

            Genetics: Our genes determine or natural hair color

              Environment: Exposure to sun or hair dyes can  easily 
              change that color.

  • Behavioral traits:

            Genetics: People breed retrievers to chase things and bring
              them back.

             Environmental: You can train a retriever to instead roll over
              and play dead when you toss a ball.

  • Predisposition to a medical condition:

            Genetic: A person may be born with an increased risk of
              heart disease.

             Environment: Eating healthy foods and exercising can
              reduce this risk.

What is a DNA fingerprint?

• method of identification that compares fragments of deoxyribonucleic acid (DNA) It is sometimes called DNA typing. DNA is the genetic material found within the cell nuclei of all living things. In mammals the strands of DNA are grouped into structures called chromosomes. With the exception of identical twins, the complete DNA of each individual is unique.

  A DNA fingerprint is constructed by first extracting a DNA sample from body tissue or fluid such as hair, blood, or saliva. The sample is then segmented using enzymes, and the segments are arranged by size using a process called electrophoresis. The segments are marked with probes and exposed on X-ray film, where they form a characteristic pattern of black bars—the DNA fingerprint. If the DNA fingerprints produced from two different samples match, the two samples probably came from the same person.

 

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