Transcript Genetics PowerPoint - Lewiston School District

Genetics
Genetics
• Focus Question:
– If most organisms start from a single cell, than why
don’t we all look the same?
• Prediction:
– Why do you think species of organisms have different
characteristics. For example I have blue eyes, but
both of my parents have light green eyes.
The Father of Genetics
• The study of genetics is a very complicated
and technical process, but the basic
principal is quite simple. An Austrian
Botanist is considered to be known as the
“Father of Genetics” because of what he
learned from his scientific experiments with
pea pod plants.
• In the mid 1800’s Gregor Mendel carefully
studied seven traits of the pea plant; seed
shape, seed color, flower position, pod
shape, seed coat color, stem length, and
pod color. He discovered that crossing two
plants with the same trait did not guarantee
that those traits would show in their
offspring. He discovered that if there were
different traits in the plants’ history, those
traits might eventually show up.
Pea Pod Experiment
Mendel discovered that living organisms pass
down traits to their offspring that do not
physically show up from generation to
generation.
Mendel could not prove why this happened at the
time, but it did set the stage for further
investigation.
Physical traits are observable characteristics
determined by specific segments of DNA called
genes. Multiple genes are grouped together to
form chromosomes, thread-like parts which are
found in the nucleus of the cell. Genes carry the
information that determines the traits of an
organism.
Basic Animal Cell
Chromosomes
Nucleus
•A chromosome is an organized package of DNA found in
the nucleus of the cell. Different organisms have different
numbers of chromosomes. Humans have 23 pairs of
chromosomes. Each parent contributes one chromosome
to each pair so that offspring get half of their chromosomes
from their mother and half from their father
An example of possible
variations
A
Gene
•The gene is the basic physical unit of
inheritance. They are arranged, one after
another, on the chromosomes and contain the
information needed to specify traits. Humans
have approximately 23,000 genes arranged on
their chromosomes.
a
A
A
Allele
•An allele is one of two or more
versions of a gene. An individual
inherits two alleles for each gene, one
from each parent.
So How does Mendel's Peas Explain how we
Inherit our Traits?
•
If you think back to our cell
investigation we said that
organisms begin as one cell.
•
Because of the way cells divide
and join during reproduction,
each new offspring created
receives chromosomes (multiple
groups of genes) for specific
traits from the male and from the
female.
•
•
Parent
1st
Generation
The example to the right
demonstrates how Mendel’s pea
pods could pass down genes for
the specific trait of color.
From this we discovered that
some genes are recessive and
some genes are dominate.
2nd
Generation
Recessive and Dominate Genes
We discovered that some genes are recessive
and some genes are dominate because most
genes have two or more variations, called alleles
Parent
Alleles: The variation of genes for a trait. The
alleles for the color of a pea are referred to as
G: green and Y: yellow.
The green parent received 2 green alleles
The yellow parent received 2 yellow alleles
In this example each parent gives their offspring a
copy of one of their alleles. Depending on what
allele variations parents have to offer, offspring
may inherit two identical or two different alleles.
In this case each parent only had one type of allele
to offer, one G and one Y
As a result, all new 1st generation offspring are
yellow because the alleles interact in what is called
a dominant or a recessive manner.
1st
Generation
Recessive and Dominate Traits
Dominate Traits: The trait observed because a
dominant allele is present in the genes that the
offspring received from its parents.
Parent
In this example yellow color is a dominate trait
Recessive Traits: Traits due to recessive alleles
are only observed when two recessive alleles
are present. Recessive alleles may exist in the
genes of the offspring but the trait is not
observed.
1st
Generation
In this example green is a recessive trait
Depending on which alleles (gene variation) a
pea receives, future offspring could be green
although both parents are yellow.
If you cross the 1st generation of peas again, the
second generation could receive any of the
following allele combinations. 2nd generation
offspring could be yellow or green.
2nd Generation
Inherited Traits
•
You inherit many kinds of traits from
your parents that determine your
physical features. Many of these
traits cannot be changed and may
not even be present in your parents
or grand parents because they are
recessive genes.
•You are born with most of your
traits, but some such as
intelligence, personality, and
athletic ability, may be inherited
to a certain extent, but you are
greatly influenced by your
environment and your attitude.
For example; If your parents
were straight “A” students or
professional athletes, you are
not going to be just because
you have their genes.
Inherited Traits
•There are thousands of genes that
determine the traits each person has.
We know that these traits are inherited
from our parents and we know that
some are dominate and some are
recessive.
•Most physical traits result from a mix of
genes, but scientists believe that some
traits are due to one gene. When more
than one gene determines a trait it is
very difficult to predict an inheritance
pattern. For example Mendel couldn’t
easily predict the height and weight of
pea pods, but he could predict their
color.
This chart contains traits that
scientists have been able to
study and predict inheritance
patterns.
You would assume that dominant alleles are the most common in a population, but we
are going to complete an investigation to find out if this is always true.
Record the following in your scientist notebook
• What are examples of recessive and Dominate traits?
Create a large version of this table below. For each of the traits we are going to
identify and record the following:
Each step will be
•What is the Recessive or Dominate Trait?
explained in the next
•Fraction of Students With the Trait:
slides
•Fraction of Students Without the Trait:
•Most common or least common in our population?
Hairline Shape
Earlobe Attachment
Tongue Rolling
Cleft Chin
Dimples
Handedness
Freckles
Naturally Curly Hair
Hand Clasping
Hairline Shape
Hairline shape is reportedly due to a single gene with a widow’s peak
dominant and a straight hairline recessive.
Record and label in your table:
•What is the Recessive or Dominate Trait?
•Fraction Students With Widow Peak:
•Fraction Students Without Widow Peak:
•Most common or least common in our
population?
This image shows the possible
combinations of alleles you could
have received from your parents.
The only way you can get a
straight hairline is if both your
parents gave you a recessive
allele.
Earlobe Attachment
Some scientists have reported that this trait is due to a single
gene for which unattached earlobes is dominant and attached
earlobes is recessive.
Results of Allele Combinations
U is the Dominate Allele
u is the recessive Allele
Unattached = UU
Unattached = Uu
If earlobes hang free, they are
detached. If they attach directly to the
side of the head, they are attached
earlobes.
Record and label in your table:
•What is the Recessive or Dominate Trait?
•Fraction Students With unattached earlobes:
•Fraction Students With attached earlobes :
•Most common or least common in our
population?
Detached = uu
These are the possible
combinations of alleles you could
have received from your parents.
If you have detached earlobes,
both your parents gave you a
recessive allele.
Tongue Rolling
Tongue rolling ability may be due to a single gene with the
ability to roll the tongue a dominant trait and the lack of
tongue rolling ability a recessive trait.
Results of Allele Combinations
R is the Dominate Allele
r is the recessive Allele
Can Roll = RR
Can Roll = Rr
Can’t Roll = rr
Can you roll your tongue?
Record and label in your table:
•What is the Recessive or Dominate Trait?
•Fraction Students who can role tongue:
•Fraction Students who can’t role tongue:
•Most common or least common in our
population?
These are the possible
combinations of alleles you could
have received from your parents.
If you can’t roll your tongue, both
your parents gave you a
recessive allele.
Cleft Chin
This trait is reportedly due to a single gene with a cleft chin dominant and a
smooth chin recessive.
Results of Allele Combinations
C is the Dominate Allele
s is the recessive Allele
Cleft Chin = CC
Cleft Chin = Cs
Smooth Chin = ss
Record and label in your table:
•What is the Recessive or Dominate Trait?
•Fraction Students With Cleft Chin:
•Fraction Students Without Cleft Chin:
•Most common or least common in our
population?
These are the possible
combinations of alleles you could
have received from your parents.
If you have a smooth chin, both
your parents gave you a
recessive allele.
Dimples
Dimples are reportedly due to a single gene with dimples dominant (people may
exhibit a dimple on only one side of the face) and a lack of dimples recessive.
Results of Allele Combinations
D is the Dominate Allele
d is the recessive Allele
Dimples = DD
Dimples = Dd
No Dimples = dd
Record and label in your table:
•What is the Recessive or Dominate Trait?
•Fraction Students With Dimples:
•Fraction Students Without Dimples:
•Most common or least common in our
population?
These are the possible
combinations of alleles you could
have received from your parents.
If you have no dimples, both your
parents gave you a recessive
allele.
Handedness
Some scientists have reported
that handedness is due to a
single gene with right
handedness dominant and left
handedness recessive.
However, other scientists have
reported that the interaction of
two genes is responsible for this
trait.
Record and label in your table:
•What is the Recessive or Dominate Trait?
•Fraction Students who are Right Hand Dominate:
•Fraction Students who are Left Hand Dominate:
•Most common or least common in our population?
Results of Allele Combinations
R is the Dominate Allele
l is the recessive Allele
Right Handed = RR
Right Handed = Rl
Left Handed = ll
These are the possible
combinations of alleles you could
have received from your parents.
If you are left handed, both your
parents gave you a recessive
allele.
Freckles
This trait is reportedly due to
a single gene; the presence
of freckles is dominant, the
absence of freckles is
recessive.
Results of Allele Combinations
F is the Dominate Allele
f is the recessive Allele
Freckles = FF
Freckles = Ff
No Freckles = ff
Record and label in your table:
•What is the Recessive or Dominate Trait?
•Fraction Students With Freckles:
•Fraction Students Without Freckles:
•Most common or least common in our population?
These are the possible
combinations of alleles you could
have received from your parents.
If you have no freckles, both your
parents gave you a recessive
allele.
Naturally Curly Hair
Early geneticists reported that curly hair was dominant and straight hair was
recessive. More recent studies suggest that more than one gene may be
involved.
Results of Allele Combinations
C is the Dominate Allele
s is the recessive Allele
Curly = CC
Curly = Cc
Straight = ss
Record and label in your table:
•What is the Recessive or Dominate Trait?
•Fraction Students With Curly Hair:
•Fraction Students Without Curly Hair:
•Most common or least common in our population?
These are the possible
combinations of alleles you could
have received from your parents.
If you have straight hair, both
your parents gave you a
recessive allele.
Hand Clasping
A study of identical twins concluded that hand clasping has at least some genetic
component. However, other scientists have not found evidence that genetics plays
a significant role in determining this trait.
Fold your hands together by interlocking
your fingers without thinking about it. Which
thumb is on top – your left or your right?
Record and label in your table:
•What is the Recessive or Dominate Trait?
•Fraction Students with Left Thumb on Top:
•Fraction Students with Right Thumb on Top:
•Most common or least common in our population?
One study found that 55% of
people place their left thumb
on top and 45% place their
right thumb on top. 1% have
no preference. I was not able
to find evidence that supports
whether one is a dominate or
recessive allele.
Our Class Data:
Hairline Shape
Widows Peak Dominate
_______ Widows Peak
_______ No Widows Peak
Earlobe Attachment
Unattached is Dominate
_______ Unattached
_______ Attached
Tongue Rolling
Tongue Rolling Dominate
_______ Roll Tongue
_______ Can’t Roll Tongue
Which is most common in our
Classroom Population?
Which is most common in our
Classroom Population?
Which is most common in our
Classroom Population?
Cleft Chin
Cleft Chin Dominate
_______ Cleft
_______ No Cleft
Dimples
Dimples Dominate
_______ Dimples
_______ No Dimples
Handedness
Right Hand is Dominate Trait
_______ Right Handed
_______ Left Handed
Which is most common in our
Classroom Population?
Which is most common in our
Classroom Population?
Which is most common in our
Classroom Population?
Freckles
Freckles are Dominate Trait
_______ Freckles
_______ No Freckles
Naturally Curly Hair
Curly Hair Dominate Trait
_______ Curly Hair
_______ Straight Hair
Hand Clasping
Dominate vs. Recessive???
_______ Left Thumb
_______ Right Thumb
Which is most common in our
Classroom Population?
Which is most common in our
Classroom Population?
Which is most common in our
Classroom Population?
Does the dominate trait express itself more frequently then the recessive?
Classroom A Data:
Hairline Shape
Widows Peak Dominate
8/21 Widows Peak
13/21 No Widows Peak
Earlobe Attachment
Unattached is Dominate
14/21 Unattached
7/21 Attached
Tongue Rolling
Tongue Rolling Dominate
17/21 Roll Tongue
4/21 Can’t Roll Tongue
No Widows Peak Frequent
Unattached Most Frequent
Rolling is Most Frequent
Cleft Chin
Cleft Chin Dominate
6/21 Cleft
15/21 No Cleft
Dimples
Dimples Dominate
11/21 Dimples
10/21 No Dimples
Handedness
Right Hand is Dominate Trait
14/15 Right Handed
1/15 Left Handed
No Cleft Most Frequent
Dimples Most Frequent
Right Handed Appeared More
Freckles
Freckles are Dominate Trait
13/17 Freckles
4/17 No Freckles
Naturally Curly Hair
Curly Hair Dominate Trait
3/17 Curly Hair
14/17 Straight Hair
Hand Clasping
Dominate vs. Recessive
Unsure???
8/15 Left Thumb
7/15 Right Thumb
Freckles Appeared Most
Straight Hair Appeared the
Most
Classroom B Data:
Hairline Shape
Dominate: Widows Peak
Recessive: Straight Line
13/25 Widows Peak
12/25 Straight Line
Earlobe Attachment
Dominate: Unattached
Recessive: Attached
15/25 Unattached
10/25 Attached
Tongue Rolling
Dominate: Can
Recessive: Can’t
18/25 Can
7/25 Can’t
Widows Peak Showed Most
Unattached Showed Most
Can Showed Most
Cleft Chin
Dominate: Cleft
Recessive: No Cleft
5/25 Cleft
20/25 No Cleft
Dimples
Dominate: Dimples
Recessive: No Dimples
16/25 Dimples
9/25 No Dimples
Handedness
Dominate: Right
Recessive: Left
22/24 Right Handed
2/24 Left Handed
No Cleft Showed Most
Dimples Showed Most
Right Showed Most
Freckles
Dominate: Freckles
Recessive: No Freckles
19/24 Freckles
5/24 No Freckles
Naturally Curly Hair
Dominate: Curly
Recessive: Straight
8/24 Curly
16/24 Straight
Hand Clasping
Dominate vs. Recessive
Unsure??
13/24 Left
11/24
Freckles Showed Most
Straight Showed Most
Left Showed Most
Answer the following questions in your
scientist notebook
Use the data you collected from the table…
•Did most of the students in your class display dominate or
recessive traits?
Why do you think this happened?
•Do you think the results would be different if you had
surveyed the whole school?
Explain your opinion…
•Do you think the results would be different if you surveyed
people from different parts of the country or world?
Explain your opinion…
Claims and Evidence
• Focus Question:
– If most organisms start from a single cell, than
why don’t we all look the same?
I claim that…
I claim this because…
Conclusion
• Revisit your original prediction and explain
whether the evidence from our investigation
supports it or not.
Reflection
• Respond to some of the following
– What really surprised you
– What new questions do you have
– What would you really like to know more
about