Genetics

If molecule Y represents a DNA molecule, then molecule W represents what?

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1. Glucose

2. Nucleotide

3. Amino Acid

4. RNA

5. Lipid

Where in the cell does transcription take place?

1. Cytoplasm

2. Mitochondria

3. Nucleus

4. Golgi Body

5. Vacuole

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mRNA is synthesized in the nucleus and travels to the cytoplasm to meet up with which organelle?

1. Mitochondria

2. Ribosome

3. Golgi Body

4. Lysosome

5. Nucleus

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Where in the cell does translation, the second part of protein synthesis, take place?

1. Mitochondria

2. Nucleus

3. Golgi body

4. Cytoplasm

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If molecule Y represents a protein, then molecule W represents what?

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1. Glucose

2. Nucleotide

3. Amino Acid

4. RNA

5. Lipid

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! 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 The way an organism looks Give me an example

Genotype 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 An organism’s 2 alleles are the same 2 capital letters would be homozygous dominant

Give me an example 2 lowercase letters would be homozygous recessive

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 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 true-

breeding 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

 MaleThe "a" recessive allele

will beexpressed in his

phenotype   

FemaleThe "a" recessive allele

will notbe 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 red-green 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?

Pedigrees

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 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