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Genetics 7th Grade - Begoyan

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William Begoyan

on 20 January 2016

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Transcript of Genetics 7th Grade - Begoyan

Foundations of Genetics
by: Mr Begoyan
Page 35 in your Interactive Notebook
AVID: What makes me different than everyone else?
Gregor Mendel
Born in 1822 in the Austrian Empire (modern Czech Republic).
He spent most of his adult life in a monastery as a monk.
At those times, monasteries contained and taught most of the knowledge in Europe.
During his time as a monk, Mendel tended a flowering pea garden.
Studying the peas, Mendel discovered what we now call the field of
Genetics
.
Genetics

is the study of

heredity
.
Heredity
is the passing of traits of an organism from parent to offspring.
Mendel's Peas
(and his experiments)
Mendel worked with peas because they were quick and easy to grow, came in different varieties, and were edible (monks had to eat!).
Mendel used
true breeding
plants.
These plants have
pure
genes (if they have, for example, color purple, all their offspring will always have the color purple, no exceptions).
Traits that Mendel studied in peas.
Who is Gregor Mendel?
The passing of traits from parent to offspring is called:
Genetics is the study of ____________
What organism did Mendel study (and consequently eat...)?
Why were peas a good experimental organism?
What does "true breeding" mean?
In his experiments, Mendel crossed a true breeding
white
plant with a true breeding
purple
plant.
The resulting offspring were 100%
purple
.
Mendel knew that both plants contributed genetic information, so why were there no
white
plants?
Mendel's reasoning was that traits from one parent may be more
powerful
than that of the other parent.
Traits are controlled by genes.
Genes
are different parts of a DNA, like song tracks on a CD, but imagine that a CD had 100000+ tracks!
Each plant received a version of the trait/gene from each parent.
We call these different versions
Alleles
.
DNA is broken down in to small parts called _______
Different versions of a trait/gene are called_______
Genes and Alleles
Each gene/trait has at least two different versions of itself, we call these different versions
alleles.

Each gene will have a
dominant
and a
recessive
allele.
Dominant
alleles are strong, and will block recessive alleles if they are ever together.
Recessive
alleles are weak and shy, they will hide in the presence of dominant alleles.
Since each gene/trait must have at least two alleles, you can have three combinations:

1.
Dominant
+
Dominant
= only
dominant
trait expressed (
Homozygous
dominant
)

2.
Dominant
+
Recessive
=
dominant
blocks
recessive
, only
dominant
expressed (
Heterozygous
)

3.
Recessive
+
Recessive
= No
dominant
to block,
recessive
expressed (
Homozygous

recessive
)
Traits that have the same type of alleles (
dominant+dominant
or
recessive+recessive
) are called
Homozygous
(Homo = same).
Traits that have the different type of alleles (
dominant
+
recessive
) are called
Heterozygous
(Hetero = different).
Phenotype vs Genotype
Phenotype
is the expression of the trait/gene that we can observe in the world.
Genotype

is the specific combination of alleles.

Example
: In eye color,
brown
is the dominant trait,
blue
is recessive.
A person with
brown
eyes can be homozygous dominant (two dominant
brown
alleles) or heterozygous (
brown
allele and
blue
allele). You would never be able to tell them apart, they both have the same
phenotype
but different
genotypes
.
Each gene/trait must have at least ____ alleles
What are the two different types of alleles?
Will the recessive allele express itself if a dominant allele is present?
Can a heterozygous combination ever express the recessive trait? Why?
How are phenotype and genotype different?
Inheritance, Pedigrees, and Punnet Squares
To understand inheritance (passing of traits from parent to offspring), scientists use a pair of tools:
Pedigrees
and
Punnet squares.
Punnet squares
help us model possible genotypes and phenotypes of any given trait from two parents.
Scientists use single letter abbreviations for alleles.
A capital letter designates the dominant allele, while a lower case letter designates the recessive allele (same letter must be used).
For example: We are looking at the color of the pea plant flowers.
Purple
is dominant and
white
is recessive.
I can designate
P
as the dominant allele, while
p
is the recessive.
A
Pedigree
shows and tracks traits that were inherited by members of a family tree.
On a Pedigree, males are represented by squares, females by circles.
Individuals who have the trait, are shaded in.
Lines connect members of a family.
Mendel's Laws of Heredity
Mendel created 2 laws:
1. Mendel's laws of independent assortment
2. Mendel's laws of segregation

-They essentially state that every trait, and every version of the trait (alleles), can move independently of each other.
-In short, we can get an incredible combination of traits and trait types.
The End
Questions
What is a Punnet Square?
In Pedigrees, males are represented with ________, while female are represented by _________
In Punnet Squares, capital letters represent the _______ allele, while lower case letters represent the _______ allele.
What is a Pedigree?
In Pedigrees, individuals that are shaded in represent _________
To set up a Punnet square, draw a 2x2 box.
The alleles of one parent are placed on the left of the box, the alleles of the other parent are placed on the top of the box (doesn't matter which parent goes where).
You then cross match to obtain the resulting combinations.

Gene 1
Gene 2
Gene 3
Gene 1 = Hair color
Homework on page 34
:
Using visuals, tell me about
Gregor Mendel
, what are
genes
and what are
alleles
.
Full transcript