Introduction to Genetics
Fact or Fiction?
Man is the highest of the animals; therefore,
he has the most chromosomes.
FALSE
No one really knows what determines the
number of chromosomes in an organism,
though related species tend to have similar
chromosome numbers. This is because
chromosomes may split or combine during
evolution and speciation. While humans
have 46, other great apes have 48. It is
important to remember that the
chromosome number has nothing to do
with how "advanced" a species is. Horses,
dogs, and several species of ferns have more
than we do.
An injury suffered in an accident will be
passed on to one’s children.
FALSE
You get 23 chromosomes from each parent. 1 of the
23 chromosomes determines whether you are male
or female. The other 22 chromosomes (Autosomal
DNA) pretty much determine your genetic profile.
You get Autosomal DNA 50-50 from both parents.
The two germ cells, male sperm and female egg,
have chromosomes with DNA in them. When the
germ cells get fused they form a zygote and this
process is responsible for transferring the character
from parent to offspring.
If your parents both have brown eyes, you
will definitely have brown eyes.
FALSE
Genetics is all about PROBABILITY. There is
a very high percentage that you will because
brown eyes is a dominant trait. But then
again you should also look at your
grandparents, aunts and uncles, because
anyone in your gene pool has had an affect
on what color eyes you will have. But in
most cases, yes, you will most likely have
brown eyes.
You have inherited traits, which are not
apparent.
TRUE
All the traits you are going to have in your
lifetime you have at the time of conception
and is outlined in your genetic map (DNA).
However, not all traits are visible at birth.
Most traits are “time released” meaning that
they present themselves at various stages of
growth and development.
In many organisms, the female determines
the sex of the offspring.
FALSE
The sex chromosomes carry genes that
determine whether a person is male or
female. The sex chromosomes are the only
chromosome pair that do not always match.
Since both of a female’s sex chromosomes
are X chromosomes, all eggs carry one X
chromosome. Males, however, have two
different sex chromosomes. Therefore, half
of a male’s sperm cells carry an X
chromosome, while half carry a Y
chromosome.
Each person inherits exactly half of his
genetic makeup from each parent.
TRUE
When the male sperm and female egg get
fused during fertilization the phenomena of
CROSSING OVER takes place which mix all
the characters of the parents and the child
gets a combination of both of them.
You inherit more from your mother if you
are a girl.
FALSE
You get 23 chromosomes from each parent.
The 22 chromosome pairs with the
Autosomal DNA pretty much determine your
genetic profile. Your Autosomal DNA is 5050 from both parents.
The 23rd chromosome pair, one from each
parent, determines your sex and are made
up of Y & Mitochondrial DNA. Y goes from
father to son only. Mitochondrial goes from
mother to both sons and daughters but only
the daughters pass it on to their children.
A parent may give a trait to his child without
ever having the trait himself.
TRUE
A person can carry an allele (code) for a
particular gene (trait) that is not visibly
present in them. But, because it is part of
their DNA they can pass it on to their
offspring and it may become visible in their
offspring or even future generations of
offspring within their family.
If you resemble one parent more than the
other, you probably inherited more from
that parent.
FALSE
Because children inherit alleles (codes) for
genes (traits) from their mother and father,
children often look like both of their
parents. If a child resembles one parent over
another it is because one parent may have a
stronger (dominant) gene pool.
You have all the hereditary traits you are
ever going to have at birth.
TRUE
All the traits you are going to have in your
lifetime you have at the time of conception
and is outlined in your genetic map (DNA).
Most traits are “time released” and will
present themselves at various stages of
growth and development.
Human Genetics Lab
Background Knowledge
• Gregor Mendel developed the basic
principles of genetics that are still used
today in our current study of heredity.
• Using pea plants, observing multiple
generations and thousands of offspring,
Mendel determined that most traits are
controlled by genes with two alleles.
– Dominant
– Recessive
Lab Objective
• How frequently do
certain dominant
and recessive
phenotypes occur
in humans?
• PHENOTYPE – AN
ORGANISM’S
PHYSICAL
APPEARANCE, OR
VISIBLE TRAITS.
Question / Hypothesis
• Does the dominant form of a trait
always occur more often within a
population than the recessive form?
Tongue Rolling
Polydactyly
Eye Wink
Mid-Digital Hair
Dimples
Hairline
Earlobes
Interlocking Fingers
General Procedure
• Read all instructions for this activity
before you begin your work.
• Collect and Analyze Data.
– Record your phenotype for each trait in
the data table.
– Report your data.
– Record the “class” data for each trait in
the table.
Data Table
Trait
2nd
D
2nd
R
3rd
D
3rd
R
4th
D
4th
R
6th
D
6th
R
7th
D
7th
R
TEAM
D
TEAM
R
Tongue Rolling
31
13
35
6
28
4
35
8
26
7
155
38
Polydactyl
0
44
2
39
0
32
1
42
0
33
3
190
Eye Wink
40
4
30
11
23
9
38
5
26
7
157
36
Mid-Digital Hair
14
31
9
32
18
14
24
19
7
26
72
122
Dimples
13
31
14
27
15
17
28
15
14
19
84
109
Hairline
17
27
12
29
12
20
18
25
14
19
73
120
Earlobes
35
9
30
11
24
8
31
12
25
8
145
48
Interlocking
Finger
33
11
23
18
20
12
32
11
25
8
133
60
Sample Graph
Dominant or Recessive
# of Students
200
150
TEAM-D
100
TEAM-R
50
0
Tongue
Rolling
Polydactyly Eye Wink Mid-Digital
Hair
Dimples
Trait
Hairline
Earlobes Interlocking
Finger