Lab:Mendel and the Gene Idea
Human genetics involves the inheritance of specific traits. These traits may involve physical,
mental or physiological characteristics unique to a particular individual and his or her relatives.
Why do some people look like their parent or grandparents? How is it possible for a
blond-haired child to have two brown-haired parents? Why do brothers in one family resemble
each other and in another family have no resemblance? These questions can be answered by a
study of heredity. The study of heredity is called genetics.
What is your phenotype? Phenotype is an observable physical characteristic, such as your hair
color, eye color, height, skin color etc. Your phenotype is the observable result of your genotype.
Genotype is your genetic make-up. It is the combination of alleles of a gene that will determine
your physical traits, your phenotype. Each gene can have a pair or a series of alleles. For
example, there are many alleles for eye color: blue; brown; green; grey; hazel etc. Gene’s for
which an individual has two different alleles is termed heterozygous; whereas gene’s for which
an individual has two identical alleles is termed homozygous.
Part I –What is your phenotype?
In this section, you will be identifying your phenotype for three specific human traits. After each
description of the trait, determine your phenotype for that specific trait. Record your
observations in the space provided below.
A. Tongue Rolling Ability
The ability to roll the tongue into a “U” shape when the tongue is extended from the mouth is a
dominant human trait. “Nonrollers” can do no more than produce a slight downward curve of the
tongue. A person can either roll the tongue easily or not at all.
tongue rolling
1. Are you a tongue-roller?
2. Can you tell whether the tongue-rollers are heterozygous or homozygous for tongue rolling?
Explain why or why not.
B. Attached Ear Lobes
In most people, the ear lobes hang free or are unattached. This is a dominant trait. When a
person is homozygous for the recessive trait, you will observe earlobes attached directly to the
side of the head or jaw line.
earlobes
3. Are your earlobes attached?
4. What could be your genotype?
C. Bent Little Finger
A dominant gene causes the last joint of the little finger to bend inward toward the fourth finger.
Lay both of your hands flat on the table, relax the muscles, and observe whether you have a
straight or bent little finger.
5. Is your little finger bent?
6. What is your genotype?
D. Eye Color
Eye color is controlled by many different genes.
eye color
7. What color are your eyes?
8. Why is it harder to know your genotype?
E. Hair
Straight hair, HH, is a dominant trait while curly is the recessive trait, hh. The heterozygote Hh
actually has wavy hair.
hair
9. Is your hair straight, curly or wavy?
10. What does that tell you about your genotype?
PART II– Making a Pedigree
Pick one of the traits from above and do a pedigree chart from your family members. A chart will
have circles for females and squares for males. If the family member has the trait, color that in.
If not, leave open. See figure 19.16a in your book for an example of a pedigree. You can make a
pedigree in WORD or PowerPoint. Go to “Insert” “Shapes” and choose a circle (female) and a
square (male). You can color it in by changing the “shape fill” color. You can connect the shapes
with lines. Make sure you have a key to your answers. If your family isn’t available, feel free to
use a hypothetical family or even your dog, horse (etc) if you know their breeding.
You can hand draw your pedigree and take a picture or scan it if you would like.
You can also do a pedigree chart on someone else- or even a pet! Be sure to describe in words
what your chart shows.
Here is an example of a pedigree chart.
pedigree.jpg
Blog:
Do it on lynch syndrome and make 500 words and cite sources in apa
There are so many different diseases that are caused by mistakes in the genes. Sometimes
there is a simple mutation, or change in one DNA base that results in a change in an amino
acid. Other mutations may involve deletion of many DNA bases and sometimes additional DNA
may be inserted into a gene.
For this week:
Choose a genetic diseases from the list below.
Go to Medline Plus and find some information on your disease.
Include:
A brief summary
frequency
Causes
Inheritance
Treatment
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Formatting
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