Transcript Mendels Geneticsx

Mendel’s Genetics
I’m a freak—
Yay!
Who was Gregor Mendel?

A 19th century Monk and Scientist who is called
the Father of the Genetics: the study of how living
things get their DNA and how DNA works.
Who was Gregor Mendel?

Mendel was the Gardener/Farmer of the
monastery he lived in, and observed and
experimented on the pea plants he grew for food.
Who was Gregor Mendel?

Mendel discovered that something in living things
determines what they look like. (later called
Genes)
Who was Gregor Mendel?
Genes are parts of DNA that determine things
like…
A. Eye Color
C. Tallness/shortness
B. Hair Color
D. Ear Shape
Who was Gregor Mendel?

Mendel also discovered that parents can pass on
their Genes to their offspring, creating children
that share the same traits as their 2 parents.
Wolf
Huskies
Who was Gregor Mendel?
He called these offspring
Hybrids, meaning that they
have DNA created when 2
different DNA codes were
combined.
Mendel’s 4 genetic Hypothesizes
During his studies, Gregor Mendel developed 4
hypothesizes that explain how Genetics work, that
are still true today.
Mendel’s 4 genetic Hypothesizes

1. All Genes have Alleles.
--Alleles are different
versions of the same Gene.
Alleles, continued
Ex: A flower Gene that determines its petal color.
--For that flower species, there may be Purple
flower Genes, White flower Genes, and Orange
flower Genes.
Alleles, continued
--These 3 different versions the Flower Color
Gene are the Alleles.
Mendel’s 4 genetic Hypothesizes
2. Principle of Segregation (3 parts to this)
A. All traits/Genes must have 2 parts.
Mendel’s 4 genetic Hypothesizes
2.
Principle of Segregation
B. During Meiosis, the 2 parts of the Gene are
Segregated (separated) into 2 separate cells
Mendel’s 4 genetic Hypothesizes
2. Principle of Segregation
C. The Offspring’s Genes are the combination of 1
gene from each of the 2 parents.
Who was Gregor Mendel?

Remember, that all chromosomes in DNA get
paired with a matching half.

Each of the Gene’s 2 parts is on 1 of the 2
chromosomes in the same pair.
Who was Gregor Mendel?

For example, Each Eye Color gene have 2 parts,
the 1st part is on the first chromosome in a pair,
and the 2nd part lies inside the 2nd chromosome.
The Principal of Segregation means that…

1. During Meiosis (similar to mitosis, but makes sex
cells) the Parent’s DNA/gene pairs are separated
into 2 egg/sperm/pollen cells.
The Principal of Segregation means that…

2. Cell Fertilization combines each parents’
DNA/Gene Pair halves into 1 complete DNA
Code/Gene pair.
The Principal of Segregation means that…

3. The children of the parents now have DNA/Gene
Pairs that is part Mother DNA, part Father DNA.
Mendel’s 4 genetic Hypothesizes

2. Genes/alleles can be Homozygous or
Heterozygous.
Mendel’s 4 genetic Hypothesizes
Homozygous Alleles =
2 of the same(homo-)
alleles.

Ex: having 2
Brown Hair genes

Mendel’s 4 genetic Hypothesizes

Heterozygous Alleles = having 2 different (hetero-)
versions of the gene/allele
together.
Ex; having 1 Brown Hair
Gene and 1 Blonde Hair
Gene together in DNA.

Mendel’s 4 genetic Hypothesizes

3. Alleles come in 2 Types: Dominant
Genes/alleles and Recessive Genes/alleles.
Mendel’s 4 genetic Hypothesizes
Dominant—”stronger gene”
 If the trait is Heterozygous (having 2 different
alleles), the Dominant gene will overpower the
Recessive, and the trait appearance would be
whatever the Dominant Gene is.


Dominant Genes are represented with CAPITAL
LETTERS
Mendel’s 4 genetic Hypothesizes
Ex: If you carry 1 Blue
Eye Gene(b) and 1
Brown Eye Gene(B)…

the Brown is Dominant, and the Blue is Recessive:
so your eye color would be Brown, even through
you have a Blue Eye Allele.
Mendel’s 4 genetic Hypothesizes

If you have Heterozyous Genes (Bb), you could
have a child with blue eyes, even if you have
Dominant Brown eyes.
Mendel’s 4 genetic Hypothesizes
Recessive—”weaker gene”
 The gene that would be “covered up” in the
Presence of another Dominant Gene.
 Represented with a lower-case letter.

Mendel’s 4 genetic Hypothesizes

To have a recessive characteristic, such as Blonde
hair, or blue eyes, both of the 2 genes for hair/eye
color MUST be the recessive Blonde Hair genes.
Punnett Square How-to (simple)
The Punnett Square is a diagramming tool used for
years to show Mendel’s Principal of Segregation at
work.
Punnett Square How-to (simple)
The punnett square can predict…
A.
% of the children that show a certain trait.
(phenotype)
Punnett Square How-to (simple)
Phenotypes are the appearance of the
plant/animal’s traits.
Punnett Square How-to (simple)
The square can also predict…
B. % of the children with
Homozygous or
Heterozygous Genes.
(Genotype)
Punnett Square How-to (simple)
Genotypes are the unseen, lettering that represents
the gene-pair.
Short Hair
hair
SS or Ss
Examples:
Phenotypes
Genotypes
Curly
ss
Punnett Square How-to (simple)
This lesson teaches how to do a Punnett Square
“Mono-hybrid Test-cross” which is fancy for “1
gene from 2 parents gets tested once.”
Reminder: The Principal of Segregation
explains….
1.
All genes have 2 parts—1 part on each
chromosome in each pairs.
Reminder: The Principal of Segregation
explains….
2. All gene (and chromosome) pairs are divided
during sex cell production (meiosis)
Reminder: The Principal of Segregation
explains….
3. During cell/seed fertilization, parent DNA halves
are combined into the child’s DNA
Punnett Square How-to (simple)
Step 1: Draw the Punnett Square.
Punnett Square How-to (simple)
Step 2: insert the parent’s gene pairs for whatever
trait you are testing.
--Parent 1 Genes
are on the top,
Parent 2 Genes
are on the side
of the square.
Punnett Square How-to (simple)
Step 3: Combine the genes in the squares
wherever they “cross”
(its called a Testcross)
Punnett Square How-to (simple)
Step 4: “analyze the data”
Punnett Square Sample problem
A farmer wants to have a barn full of spotted pigs
for a show. Unspotted pigs
will be sold to the butcher!
Spotted is Dominant (S)
Unspotted is Recessive (s)
The Farmer has 2 pigs—1 Homozygous-unspotted,
and 1 Homozygous Spotted.
What percent of the litter would be sold to the
butcher?
Punnett Square Sample problem
Steps 1, 2, and 3: Draw the square, insert the parents’
genotypes,
and do the test-cross.
____________are Ss (4 out of 4)
____________are ss
____________ are SS
Punnett Square Sample problem
Since Spotted is Dominant, then the whole
litter will be Spotted, BUT carry Unspotted
genes in their DNA.
Punnett Square Sample problem 2
The same farmer tries again, this time he will breed
with 2 Heterozygous Spotted Pigs.
Spotted is still Dominant
Unspotted is still Recessive.
What % of the litter will
be sold to
the butcher?
Punnett Square Sample problem 2
Complete the test-cross…
Punnett Square Sample problem 2
1 out of 4 are Spotted Homozygous (SS = 25%)
2 out of 4 are Spotted Heterozygous (Ss = 50%)
1 out of 4 are Unspotted Homozygous (ss = 25%)
Punnett Square Sample problem 2
So, 1 out of 4 (25%) of the litter will be sold to the butcher!!