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Genetics
If molecule Y represents a DNA molecule, then
molecule W represents what?
Glucose
Nucleotide
Amino Acid
RNA
Lipid
1.
2.
3.
4.
5.
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Where in the cell does
transcription take place?
Cytoplasm
Mitochondria
Nucleus
Golgi Body
Vacuole
1.
2.
3.
4.
5.
1
2
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4
21
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mRNA is synthesized in the nucleus and
travels to the cytoplasm to meet up with
which organelle?
Mitochondria
Ribosome
Golgi Body
Lysosome
Nucleus
1.
2.
3.
4.
5.
1
2
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21
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Where in the cell does translation, the second
part of protein synthesis, take place?
Mitochondria
Nucleus
Golgi body
Cytoplasm
1.
2.
3.
4.
1
2
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4
21
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If molecule Y represents a protein, then
molecule W represents what?
Glucose
Nucleotide
Amino Acid
RNA
Lipid
1.
2.
3.
4.
5.
1
2
3
4
21
22
23
24
5
6
7
8
9
10
11
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13
14
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Chromosomal
Mutations
Mutations

Deletion


Occurs when part of a chromosome is left out
Most are lethal
Mutations

Insertion

Segment of a chromosome is removed and
inserted into another one
Mutations

Duplication

Segment of DNA is copied twice
Mutations

Inversion

Occurs when part of a chromosome breaks off
and is reinserted backwards
Mutations

Translocation

Occurs when segments of DNA on
2 chromosomes are rearranged
Genetics
Some Vocab first

Heredity


The passing on of characteristics from parents to
offspring
Trait

Characteristic that is inherited
What is a gene?




A region of DNA that controls a hereditary characteristic
Give me an example:
 Let’s take the gene for hair color
 How many different genes are present in this room?
Different forms of genes are called
 Alleles
For the gene for hair color how many different alleles do
each of you have?
 2
Where did it all begin?

With Gregor Mendel
Mendel




Mendel used pea plants to study what
genetics really was.
He would cross pollinate them to see what
kind of products he would get and then make
assumptions as to what was happening to the
genes.
Let’s look at how a plant reproduces
http://www.dnaftb.org/dnaftb/1/concept/index.
html
Mendel

What was Mendel seeing?

http://www2.edc.org/weblabs/Mendel/mendel.
html
Let’s take a trip down history
lane…

Mendel took two pea plants that were identical in every way
except for their heights, one was short and one was tall.

He called these two plants the parent generation, which
is some vocab that we still use today. It’s abbreviated –
P1
History Trippin

He cross pollinated them and took a look at
their offspring.
History Trippin

When he planted the seeds from the cross pollination the plants that were
produced were all tall.

He called the offspring from this first cross between the parents – the F1
generation
Filial is latin for son or daughter

History Trippin

Next, Mendel allowed the tall plants in the F1 generation to self pollinate.
He then planted these seeds and grew 1000 plants.

Mendel found in this F2 generation that ¾ of the plants grew tall and ¼
were short.
Why was this a big discovery
for Mendel?

1 trait of a pair seemed to disappear in the F1 generation, only to reappear
unchanged in ¼ of the F2 plants.
Mendel’s Conclusions


Gregor Mendel didn’t know much if anything about
DNA or what it was, and he didn’t even know how
much you know…so what was Mendel’s big
conclusion after seeing his offspring?
He figured out that each organism must have 2
factors that control each of its traits.
The Rule of Dominance

In Mendel’s F1 offspring plants, there were
only tall plants even though one of the
parents was a short plant.

1 of the alleles is dominant over the other.
The Rule of Dominance




The observed trait is DOMINANT and the trait that
disappeared is recessive.
In Mendel’s example which is the dominant trait and
which is the recessive trait?
The allele for tallness is DOMINANT
The allele for shortness is recessive
What does it mean to
be Dominant or
Recessive?
How many of you have 6
fingers on each hand?

6 fingers are dominant
How many of you have a
widow’s peak?

Widow’s peak is dominant
How many of you have
attached ear lobes?

Attached earlobes are recessive
How many of you have the
ability to roll your tongue?

Rolling your tongue is dominant
How many of you have a
straight thumb?

Straight thumb is recessive
How many of you have blue
eyes?

Blue eyes are recessive
How many of you can taste
PTC paper?

PTC tasting is dominant
How many of you have
freckles?

Having freckles are dominant
How many of you have a cleft
chin?

Having a cleft chin is recessive
How many of you have a
second toe longer than your
big toe?

Having a longer second toe is dominant
How many of you when clasping
your hands together, the left thumb
is on top of the right thumb?

Left thumb on top is dominant
How many of you have
broad/fuller lips?

Full lips are dominant
How many of you have an
immunity to poison ivy?

Poison ivy immunity is dominant
The Rule of Dominance

We label or designate alleles with letters.



(For example, a letter T for the trait of height)
An uppercase letter is used for the
Dominant allele (T for tall)
A lowercase letter is used for the recessive
allele (t for short)
The Rule of Dominance

Using the letter
T what can you
say about the
possible alleles
that the
following people
have on the
genes on their
chromosomes?
Mendel’s Law of Segregation
What happens during Meiosis?
Mendel’s law of segregation
explains the results of his cross
between F1 tall plants. He
concluded that the 2 alleles for
each trait must separate when
sex cells are formed. A parent,
therefore, passes on at random
only one allele for each trait to
each offspring.
Let’s Make Another Baby!


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How many chromosomes do we have in our cells?
How many came from Mom?
How many from Dad?
How many alleles for hair color did you receive from your mother?
How many alleles for hair color did you receive from your father?
If you have 2 alleles for hair color how come half of my head isn’t
blonde and half isn’t brown?
Genetics Vocabulary

Phenotype
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The way an organism looks
Give me an example
Genotype

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The gene combination an organism has
Give me an example
*Problem: You can’t always know an organism’s
genotype simply by looking at its phenotype
Genotype

Homozygous

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An organism’s 2 alleles are the same
2 capital letters would be homozygous dominant


2 lowercase letters would be homozygous
recessive


Give me an example
Give me an example
Heterozygous


An organism’s 2 alleles for a trait are different
Give me an example
Let’s revisit Meiosis again

What happens in Metaphase 1


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The law of independent assortment
Genes for different traits (for example seed
shape and seed color) are inherited
independently of each other.
In our class example we used hair color,
number of toes, and eye color

We saw depending on how they randomly lined
up with each other that you could tons of different
combinations.
Punnett Squares

In 1905, Reginald Punnett, an English
biologist, devised a way of finding the
expected proportions of possible
genotypes in the offspring of a cross.

If you know the genotypes of the parents,
you can use a Punnett square to predict
the possible genotypes of their offspring.
Monohybrid Cross


Let’s consider Mendel’s first monohybrid cross between his truebreeding Tall plants and his true-breeding short plants. (P1 -> F1)
Each letter (allele) separates into a possible gamete (sex cell).
Mendel’s Second Monohybrid
Cross

Now let’s look at Mendel’s second
monohybrid cross between his heterozygous
F1 generation self-pollinating themselves.
(F1 -> F2)
Probability

Punnett squares show all of the possible
combinations of gametes and the likelihood
that each will occur.



In reality, however, you don’t get the exact ratio of
results shown in the square. That’s because
genetics is like flipping a coin, meiosis leaves it up
to chance.
After completing a punnett square you are
able to calculate the probabilities of what
offspring will be produced.
Let’s calculate some probabilities
Sex Linked Inheritance
Sex Linked Genes




The X and Y chromosomes carry the genetic
information that makes us male and female
They also contain genetic information for
some other traits
What combination of sex chromosomes do
girls have?
What combination of sex chromosomes do
boys have?
Sex Linked Genes

Who determines the gender of the baby?
Sex Linked Genes

Since men only have 1 X chromosome they will display
the characteristics of these traits even if they are caused
by a recessive allele
Male
Female
The "a" recessive allele
will be
expressed in his
phenotype
The "a" recessive allele
will not
be expressed in her
phenotype
Sex Linked Genes



There are about 1,098 human X-linked genes.
Most of them code for something other than female
anatomical traits.
Many of the non-sex determining X-linked genes are
responsible for abnormal conditions such as hemophilia,
red-green color blindness, congenital night blindness,
some high blood pressure, duchene muscular dystrophy,
fragile-X syndrome, and male pattern baldness.
Sex Linked Genes
If a woman is a carrier of an X-linked
recessive allele for a disorder and her
mate does not have it, their boys will
have a 50% chance of inheriting the
disorder. None of their girls will have
it, but half of them are likely to be
carriers.
If a man has an X-linked recessive
disorder and his mate does not carry
the allele for it, all of their girls will be
carriers. None of their boys will
inherit the allele. Only girls receive X
chromosomes from their fathers.
Sex Linked Inheritance
Problems

In humans, red-green colorblindness is a
recessive sex-linked trait. It is found on the X
chromosome, not the Y. Because, males only
have one X chromosome, they have a much
greater chance of having red-green
colorblindness. Females would have to be
homozygous recessive in order to have redgreen colorblindness.
Colorblindness
Colorblindness

Normal vision – 8 red green color blind - 3
Colorblindness
Colorblindness
Colorblindness
Colorblindness
Sex Linked Inheritance
Sex Linked Inheritance
Practice

A recessive allele on the X chromosome is
responsible for red-green color blindness in
humans. A woman with normal vision whose
father is color-blind marries a color-blind
male. What is the probability that a son of this
couple will be color-blind?
Pedigre
Pedigrees



A pedigree is a diagram of family relationships
that uses symbols to represent people and lines
to represent genetic relationships.
These diagrams make it easier to visualize
relationships within families, particularly large
extended families.
Pedigrees are often used to determine the
mode of inheritance (dominant, recessive, etc.)
of genetic diseases.
Pedigrees

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Squares represent Males
Circles represent Females
Horizontal lines connecting a male and female
represent mating
Vertical lines extending downward from a couple
represent their children
Oldest individuals are found at the top and youngest
on the bottom
Pedigrees


Completely shaded in individuals posses the trait
Half shaded in individuals are carriers of the trait