Download Heredity Inherited Traits - Saint Mary Catholic School

Heredity
Inherited Traits
• Have you ever wondered…..
Why do people have babies?
Why do dogs have puppies?
Why do birds have baby birds?
Why do seals have pups?
We inherit our traits from our
parents!
What is a trait?
• A trait is any notable feature or quality in a
person or organism.
• Physical traits
• Behavioral traits
• Some traits can be influenced by our environment or
the things we do.
• For example:
hair color
skin color
predisposition for certain medical conditions
What defines our traits?
• Our Genes determine our traits.
• NO, NOT YOUR BLUE JEANS!
• The genes located on the chromosomes that
are found in the nucleus of our cells…
• We inherited these from our parents
Let’s look at some of the dominant
traits listed below.
• Free earlobes •
• Cannot fold •
tongue up
•
• Clockwise
•
hair whorl
•
• Bushy, thick
eyebrows
•
• Brown Eyes
Dark Hair
Dimples
Curly Hair
Freckles
Dark
eyebrows
Turned up
nose
• Widow’s peak
• Straight little
finger
• Can roll
tongue
• Straight little
finger
Which ones do you have?
If you have a dominant trait, that
means you inherited the trait from at
least one of your parents.
For instance Ff or FF for freckles.
F + f = freckles
F + F = freckles
Alleles for dominant traits are usually
represented with a capital letter.
If you have a recessive trait, that
means you had to inherit the trait
from both of your parents.
For instance ff for no freckles.
f + f = no freckles
Alleles for recessive traits are usually
represented with a lower case letter.
The Mask
• Dominant genes mask, hide, or overpower the
trait of the recessive gene. The recessive gene
is still present, but it is not expressed…..
It does not show up in the form of a trait
that can be seen or noticed by others.
• There are other traits that occur in degrees
such as the color of carnation flowers. A
white flower and a red flower can produce a
pink flower.
Gregor Mendel
The Father of Genetics
Click the picture to link
to Mendel’s biography.
Gregor Mendel, 1863
The Father of Genetics
• While studying pea plants, a monk named Gregor
Mendel discovered that traits are passed from
parent to offspring, that traits can be hidden for a
generation, and that hidden traits can reappear in
later generations.
• He theorized that the plant received an allele
from each parent. The allele was the form of a
gene and produced the trait.
• He created the Punnett Square, a mathematical
square to predict the possible traits of offspring
from certain parents.
Punnett Square
• Let’s work one on the board together for the
freckles.
• If mom has FF and dad has ff, what happens?
• F mom is Ff and dad is Ff, what happens?
Homozygous vs. Heterozygous
Homozygous means the alleles for the trait are
the
same:
• FF or ff
Heterozygous means the alleles for the trait are
different:
• Ff
Where do the alleles come from?
• Alleles come from the genes that are located on the
chromosomes inside the nucleus.
• Chromosomes are made of long molecules of DNA
representing thousands of genes
• Build a DNA molecule.
• Click here to learn more about DNA, genes, and proteins.
• Francis Crick and James Watson figured out how a DNA
molecule fit together. Click on the underlined names to meet them!
How are genes passed from parent to
child?
• Through reproduction.
• The child receives a set of chromosomes from
the mom and a set of chromosomes from the
dad.
• Humans have 46 chromosomes or 23 pairs of
chromosomes.
• Other organisms have different numbers of
chromosomes.
Each organism received its genes from
its parents.
• Let’s use a critter to explore….
• This critter has 8 chromosomes.
• Let’s see if you can determine the traits a critter
would have if it had the chromosomes and alleles
in your bag.
• Yellow chromosome BLUE green eye color
• Pink chromosome BROWN orange spots or not
• Orange chromosome PURPLE yellow skin color
• Purple chromosome RED lt blue curly tongue
Now lets watch meiosis
• Demonstration by Mrs. McNeill.
Mrs. McNEill
4 Daughter Cells from One Parent Cell
HALF THE CHROMOSOME NUMBER FOR EACH CELL!!!!
4 Daughter Cells from One Parent Cell
HALF THE CHROMOSOME NUMBER FOR EACH CELL!!!!
Sex Cells are Haploid or Half
• The gametes are the sex cells of the parents.
When formed they undergo meiosis. In the
process, the chromosomes are duplicated,
then separated and packaged as separate sets
in the sex cells.
• If this were not the case, the number of
chromosomes would double every time a new
organism was created.
Meiosis
More meiosis
Cells dividing in meiosis
Mrs. McNeill’s Critters underwent
Meiosis
• Duplicate, split, make 4 new cells
• Now 4 daughter cells or 4 sex cells
• Does each daughter cell have the same alleles
for the traits?????
YOUR TURN!
• You will not duplicate yours, just separate them
so you have 2 sets of half.
• The left side of the table will pick one half to
simulate meiosis.
• The right side of the table will pick one half to
simulate meiosis.
• Now put the two chosen cells together. Do not
plan, put them together randomly.
Congratulations!
• CONGRATULATIONS…..you have a new critter!
• Draw a baby picture of your critter.
•
•
•
•
Yellow chromosome BLUE green eye color
Pink chromosome BROWN orange spots or not
Orange chromosome PURPLE yellow skin color
Purple chromosome RED lt blue curly tongue
Quiz
• How did you know which traits to draw?
• Where are chromosomes located?
• Do all organisms have the same number of
chromosomes?
• Is there only one gene on a chromosome or
many?
• Explain dominant and recessive.
• Explain heredity.
Homework
•
•
•
•
Ask your family to show you their traits.
Can they roll their tongues?
Do they have dimples?
What other traits will you notice?
• Whether through sexual or asexual reproduction,
traits are passed from the parent to the offspring
on the genes that are inherited.