chapter 8 “heredity” 8 heredity 2016 student edition.pdfgregor johann mendel !was an austrian...

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Chapter 8 “Heredity”

copyright cmassengale 1

Learning Target(s):

ò  I Can…….

ò  A) explain the differences between dominant and recessive traits.

ò  B) explain the differences between phenotypes and genotypes.

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Why don’t you look exactly like your parents?

ò  You don’t look exactly like your parents because of what is known as “ heredity’.

ò  Heredity is the passing of traits from parent to offspring.

ò  You may have curly hair while both your parents have straight hair or blue eyes while both of your parents have brown eyes

ò  People have investigated this question for a long time.

ò 

ò  About 150 years ago, Gregor Mendel performed an important experiment which helped find answers to many of our questions.


Gregor Mendel (1822-1884)

Is credited for the theories that explain how are traits are inherited from generation to generation.

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Gregor Johann Mendel § Was an Austrian monk who studied the inheritance of traits in pea plants. He was also great in Math, which helped him to better understand his research.

§ He developed the laws of inheritance

§ He is known as the “Father of Genetics."


Mendel’s Pea Plant Experiments


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How Mendel Began Mendel produced pure strains of plants by allowing plants to “self-pollinate” for several generations

Mendel’s experiments…

ò  From working with these plants, Mendel noticed that the patterns of inherited traits were not always clear.

ò  Sometimes traits would appear in one generation and be absent in another generation. In generations afterwards, the trait would “reappear” again.

ò  Mendel noticed this also occurred in other organisms as well, so he wanted to learn more about “what caused these patterns”

ò  To keep his investigation simple, Mendel decided to study plant, since he had already done research on them before.

ò  How do you think Mendel’s experiment relates to you and your family?

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Mendel studied only one characteristic at a time…

ò  A characteristic is a feature that has different forms in a population. (ex: hair color)

ò  What are some more examples of characteristics a person may have?

ò  Any characteristic that can be passed from a parent to his/her offspring are called “Traits”. These traits can come in different forms such as red hair, brown hair, etc…

ò  .

“Trying it all”…..

Mendel used different plants

that had different traits for each of the characteristics

he studied. ò  ?

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Dominant and Recessive..

ò  Mendel noticed that from crossing the plants, one trait was always present and the other seemed to have disappeared.

ò  Mendel chose to call these traits:

ò  A) Dominant

ò  B) Recessive

ò Dominant traits are those that appear or are “visible”.

ò Recessive traits are those that are “hidden”.

Back to Gregor Mendel…

ò  Mendel knew that from his experiment there must be two sets of instructions (one given from each parent).

ò  We now call these instructions “genes”.

ò  Each parent gives one set of genes to the offspring. The offspring then has two forms of the same gene for every characteristic –(one from each parent)

ò  .

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What’s in your “genes”…….

ò B= brown-eyed

ò b= blue-eyed

ò  The different forms of a gene (such as “dominant” or recessive” is called an allele.

ò  Dominant alleles are represented by a Capital letter.

ò  Recessive alleles are represented by a lower-case letter.

Quick check:

ò  How many genes make up an allele?

ò  Where does each gene come from?

ò  Scenario: You have “freckles”. Your mom has rosy cheeks, but dad has freckles also. What is the dominant gene in this example?

ò  Now write an example of an allele to represent the freckles and an example to represent the rosy cheeks.

ò  Possible Answer:

ò  FF= freckles

ò  ff= rosy cheeks

ò  Ff= freckles

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Genes affect the traits of offspring….


An organism’s “physical appearance” is known as its phenotype. ( ex: color of plants: purple or white Shapes : round or wrinkled

In humans phenotypes are little more complicated. (Ex: Albinism in humans is even considered a phenotype).

Describe the phenotype of this flower.

Red and Yellow

Genes affect the traits of offspring….


An organism’s “genetic make-up appearance” is known as its genotype. All genes occur in pairs, so 2 alleles affect a characteristic

Possible combinations are:

Genotypes RR Rr rr Phenotypes RED RED YELLOW

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Genotypes §  Homozygous genotype - gene combination

involving 2 dominant or 2 recessive genes Homozygous genotypes are also called “purebreed” genotypes.

§  (e.g. RR or rr)

§  Heterozygous genotype - gene combination of one dominant & one recessive allele. These are also called “hybrid” genotypes.

§  (e.g. Rr) copyright cmassengale 17

If T is the allele for tall and t is the allele for

short, write the 3 possible genotypes.

Ready for the

Countdown!

Quick check: .

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Genotypes represent the “genetic make-up” of the organism

Remember!!!

Phenotypes represent the

“physical appearance” in the organism

Remember!!!

What are some words you can use to Describe the phenotypes in this slide?

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What does “homozygous” mean?

“Heterozygous”? How many of each

type is shown here?

Quickcheck????

Corny “pic” of the day…

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Learning Target(s):

ò I Can…….

Use a punnet square to predict possible outcomes when crossing different traits.

24 copyright cmassengale

Punnett Squares: What are they and why do we use them?

1)  Are used to help solve genetics problems

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2) It organizes all the possible combinations of offspring from particular parents.

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25 25

Y= yellow pea y= green pea

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Get some practice…. ò  Create a Punnet Square

to predict the offspring of two plants that produce round seeds. The “genotype” for each parent is Rr.

ò  Round seeds are dominant and wrinkled seeds are recessive.

ò  R=round

ò  r= wrinkled

ò  What will the offspring look like?

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Practice problem …. ò  Trait: Seed Shape

ò  Alleles: R – Round r – Wrinkled

ò  Cross: Rr x Rr


R

r

r R

RR

rr Rr

Rr

What will the offspring look like?

What are the Genotypes?:_________

What are the Phenotypes?:________

What percent is “round”? “Wrinkled”?

Here’s your answer…. ò  Trait: Seed Shape


ò  Cross: Rr x Rr


R

r

r R

RR

rr Rr

Rr

Three of the offspring are Round and one is wrinkled.

What are the Genotype?: RR, rr, Rr

What are the Phenotype?: Round & Wrinkled

What percent is round? Wrinkled? 75% Round 25% wrinkled

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Sample Problem #1 ò  Trait: Seed Shape


ò  Cross:

ò  “homozygous”Round seeds x “Heterozygous” Round seeds

ò  RR x Rr


What are the Genotypes?__________

What is the Phenotype(s)? _______________

What percent is round? Wrinkled? ________

Sample problem #2: ò  Trait: Seed Shape


ò  Cross: Wrinkled seeds x Round seeds

ò  rr x Rr


What is the Genotype(s)?

What is the Phenotype(s)?

What percent is Round? What percent is Wrinkled?

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More practice: on your notebook paper, predict the offspring of the plants

crossed below.


Cross 2 Pure Plants TT x tt

a) What are your results?

b) What are your results by Crossing two of the offspring?

T= Tall plants t = short plants

Here’s your Answer: How did you do????


Cross 2 Pure Plants TT x tt

a) What are your results?

b) What are your results by Crossing two of the offspring?

All of the Offspring are (Tt)

3 Tall & 1 short (TT, Tt, & tt)

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Objectives:

ò  I can:

ò  Analyze and interpret a pedigree chart.

ò  Explain the differences in genetic disorders and sex-linked traits.

Pedigree Charts…

ò  A pedigree chart is a tool for tracing a trait through generations of a family. It is used to predict if a person is a carrier of a particular disease (or trait).

ò  You can even use a pedigree chart to trace how you inherited your hair color.

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How to read a pedigree chart….

ò  Vertical lines connect children to their parents.

ò  A solid square or circle indicates a person has a certain trait.

ò  A half-shaded circle indicates a person is a “carrier” of the trait.

ò  Not shaded: they don’t have nor carry the recessive trait (homozygous dominant, TT)

SQUARES= MALES CIRCLES= FEMALES

chapter 8 “heredity” 8 heredity 2016 student edition.pdfgregor johann mendel !was an austrian...

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