GENETICS AND YOU

define heredity as the passage of genetic

instructions from one generation to the next

generation.[7.14A]

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The science we call Genetics* is the study of heredity

- passing of traits from parent to offspring

- has more than one theory (“point of view”)

--> most common/accepted is Mendelian Genetics

Mendelian Genetics is based upon the research of

Now credited as the

“Father of Genetics”

Mendel is most famous for his experiments with the pea plants (Pisum sativum)..

Plus, they reproduce quicklyAND have a fast LIFE CYCLE

Flowering plants can be eitherselfself or crosscross-pollinated

So What does it all mean to me?

• First you need to realize you are ½ of your mom and ½ of your dad.

• One gamete (reproductive cell) is 23 chromosomes for humans

• ALL other cells in your body have 46 chromosomes

• It all starts with your conception and the passing of their genes to you.

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Female egg cell…with half of “mom” DNA

Male sperm cell..with half of “dad” DNA

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First you need FERTILIZATION

They become one……fertilized cell with a completeSet of DNA

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Chromosomes!!! ..at this point all present and accounted for

Humans should have 46 chromosomes

The fertilized egg cell is now a ZYGOTE

• • tiny threadlike structures in nucleus of cell

* contain sections of DNA = GENES

*humans---> 20-25 THOUSAND genes

Alleles-form of a gene

• Chromosomes exist in pairs• Genes come in pairs- one on

each chromosome. Each member of the gene pair is an “allele”.

• Dominant allele- the one that will show up in the organism

• Recessive allele- will be hidden if paired with the dominant

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4. Some genes are dominant, while others are recessive.

• “Stronger” traits are called dominant.

• “Weaker” traits are called recessive.

• Geneticists use symbols (letters) to represent the different forms of a gene.

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Dominant traits are represented by a capital letter.

Yellow seeds are dominant……..

Y

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Recessive genes (for the same trait) are represented by THE SAME lower case letter.

Green seeds are recessive… lower case y.

Dominant allele (yellow) = Y

Recessive allele (green) = y

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• In pea plants, tall is dominant over short. The letter used to represent the tall allele is T.

• The short allele is represented by t.

Tall =T

Short = t

Tall =T

Short = t

In humans, brown eyes are dominant over blue.

Brown = B

Blue = b

5. Dominant alleles hide recessive alleles when both are inherited by an organism.

Y + y = yellow seeds (yellow is dominant)

•T + t = tall plant (tall is dominant)

•B+ b = brown eyes (brown is dominant)

Let’s Practice Pairing Alleles in Pea Plants

P-purple (dominant) p- white (recessive)

Plant 1 PP Plant 2 pp

genotype Pp purple phenotype

Genotype is heterozygous or hybrid for the trait b/c it has 2 different alleles

Pea plant 2nd generation

P-purple (dominant) p- white (recessive)

Plant 3 Pp Plant 4 Pp

genotype pp white phenotype

Genotype- homozygous or purebred for the trait

Pea Plant 3rd generation

*Offspring predictions can be done through using a Punnett Square

A PUREBRED organism has two of the same genes for a trait.

TT = homozygous

TALLtt = homozygous

SHORT

A HYBRID organism has two different genes for a trait.

Tt = heterozygous

TALL

(tall is dominant.)

Bb = heterozygous for black feathers (black is dominant.)

Will a hybrid human with the genes Bb have brown or blue eyes?

• Bb = Brown eyes • The dominant gene (brown), will be

expressed in a heterozygous genotype.

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Why must all blue eyed people be PUREBRED for that trait?

• If the dominant gene is present, it will always be expressed.

• The only possible gene combination for blue

eyes is bb.

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These basic laws of inheritance control the traits of all living organisms on Earth.

Can behavior be inherited too?

• Scenario 1 – Chimpanzee A has a very good technique for getting a banana out of a tree. This chimpanzee has an offspring which is taken away and raised in isolation. The offspring is not able to get the banana out of the tree.

• Scenario 2 – Bird A has a very specific way that it makes its nest. The bird has several offspring. One of the offspring is taken away and raised in isolation. The offspring begins making a nest in the exact same way as its parent.

• Scenario 1 is a learned behavior that a parent would pass on through teaching.

• Scenario 2 is an example of a behavior being inherited genetically

• Can you think of any examples of INHERITED behavior?