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MENDEL AND GENETICS

Miller Levine Macaw Book
by

Will James

on 23 February 2015

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Transcript of MENDEL AND GENETICS

Mendel and
Heredity

ESSENTIAL QUESTION: ARE THERE EXCEPTIONS TO MENDELS RULES?
Essential Question: What were Mendel's Principles?


inheritance
is
determined by factors
that are
passed from generation

to generation
.
was an Austrian monk who lived in the 1800s. (started the field of genetics)
Scientist that led the research into heredity.
1822 - 1884
ESSENTIAL QUESTION: WHO WAS GREGOR MENDEL?
Genetics
Gregor Mendel
is the
scientific study of heredity
.
Heredity
The
passing of traits from parents to offspring.
lead to great discoveries about genetics.
His research was done with pea plants.
Mendel's
experiments
Pea Plants
-Easy and fast growing
-7 distinct traits
Trait-
a specific
characteristic that varies from one individual to another.
studied seven pea plant traits, each with two possible characteristics.
Mendel
Examples
Then he
crossed plants with
each of the seven
different traits
and
studied which trait showed up in their offspring.
he is called the
"Father of Genetics"
Mendel's first conclusion:
Today, scientists call
these factors genes.
EQ: WHO WAS GREGOR MENDEL?
DO NOW: TRAITS
A distant relative is coming to stay with your family for a month. They have never met you or seen a picture of you. You go to the airport to pick them up and need to describe yourself to them so that they can find you in the crowd at the airport. In 2-3 sentences, how would you describe yourself so they would recognize you?



COMMON CHARACTERISTICS

Biological: Environmental:






EQ: WHO WAS GREGOR MENDEL?
EQ: WHO WAS GREGOR MENDEL?

EQ: WHO WAS GREGOR MENDEL?
REFLECTION: ANSWER THE FOLLOWING QUESTIONS IN YOUR NOTES. USE COMPLETE SENTENCES.
1. WHO WAS GREGOR MENDEL?

2. WHY WAS HE IMPORTANT TO THE STUDY OF GENETICS?

ESSENTIAL QUESTION: HOW DID MENDEL'S EXPERIMENTS SHOW THE PASSING OF GENES?
EQ: HOW DID MENDEL'S EXPERIMENTS SHOW THE PASSING OF GENES?
BLENDING THEORY
BEFORE MENDEL, SCIENTISTS BELIEVE THAT OFFSPRING WERE A MIX OF PARENTS GENES
FOR EXAMPLE:
BREED WHITE AND RED FLOWERS
AND YOU WOULD GET PINK FLOWERS
MENDEL'S EXPERIMENTS
SHOWED VERY DIFFERENT RESULTS THAN EXPECTED
EQ: HOW DID MENDEL'S EXPERIMENTS SHOW THE PASSING OF GENES?
INSTEAD OF BLENDING
EACH GENERATION SHOWED SPECIFIC RATIOS OF WHICH TRAIT SHOWED UP
EQ: HOW DID MENDEL'S EXPERIMENTS SHOW THE PASSING OF GENES?
GENES
EACH TRAIT IS CONTROLLED BY ATLEAST ONE GENE
EACH GENE HAS TWO POSSIBLE FORMS CALLED ALLELES
FOR EXAMPLE: THE GENE CONTROLLING THE TRAIT, FLOWER COLOR, HAD TWO POSSIBLE ALLELES, PURPLE OR WHITE
1st generation only showed one trait (tall)
2nd generation showed a 3 to 1 ratio (3 tall and 1 short)
He repeated this exact experiment for the 7 different traits of a pea plant and always got the same results!!
EQ: HOW DID MENDEL'S EXPERIMENTS SHOW THE PASSING OF GENES?
GENOTYPE
MENDEL HELPED US UNDERSTAND THAT GENES IN DNA COMBINE IN DIFFERENT WAYS TO CONTROL YOUR CHARACTERISTICS LIKE:
Your genetic order which gives you all of your characteristics
PHENOTYPE
What TRAIT you can
physically see; OR what you look like
EXAMPLES: BLUE EYES, RED HAIR, TALL, SHORT, ETC.
EQ: HOW DID MENDEL'S EXPERIMENTS SHOW THE PASSING OF GENES?
AFTER HE KEPT GETTING THE SAME RESULTS MENDEL CAME TO A FEW CONCLUSIONS
DOMINANCE VS. RECESSIVE
SINCE
EACH TRAIT HAD TWO ALLELES
(POSSIBLE VARIATIONS),
(TALL OR SHORT PLANTS.
BUT ONLY ONE TRAIT SHOWED UP IN THE PHENOTYPE
(EITHER TALL OR SHORT, NOT MEDIUM)
THEN ONE ALLELE WAS
DOMINANT
OVER THE OTHER
THE OTHER ALLELE IS RECESSIVE AND ONLY APPEARS IN THE PHENOTYPE IF THE DOMINANT ALLELE IS MISSING
EQ: HOW DID MENDEL'S EXPERIMENTS SHOW THE PASSING OF GENES?
REFLECTION: ANSWER THE FOLLOWING QUESTIONS AT THE BOTTOM OF TODAY'S NOTES.

1. FOR EACH PEA PLANT TRAIT WHAT WAS THE RATIO THAT MENDEL OBSERVED?

2. ONE TRAIT WAS CALLED DOMINANT, THE OTHER RECESSIVE. WHAT PERCENTAGE DID HE OBSERVE FOR EACH?

3. WHAT IS YOUR PHENOTYPE FOR THE FOLLOWING TRAITS.
EYE COLOR:
HAIR COLOR:
HEIGHT:
HAIR STYLE:

Essential Question: Can we predict the traits of offspring?
Essential Question: Can we predict the traits of offspring?
Probability
likelihood that a particular event will happen
Example: 50 % chance you will flip heads with a coin
can be used to predict the outcomes of genetic crosses
Essential Question: Can we predict the traits of offspring?
Genotype
= genetic makeup
Symbolized with letters
Ex.= Tt or TT or tt

capital letter = dominant allele/trait.

lowercase letter = recessive allele/trait

Example
Essential Question: Can we predict the traits of offspring?
Homozygous - Organisms
have two identical alleles for a particular trait.

Either two dominant alleles (RR) or two recessive alleles (rr)

The letter chosen for genotype is based off which trait is dominant. EX. if red is dominant over yellow then the Genotype would be a combination of R and r.
The genotype determines the phenotype
RR or Rr =
and
rr=
Heterozygous - Organisms
have two different alleles for a particular trait.

their genotype is one capital and one lower case
(ex= Rr).
they are called
hybrids
, a combination of both traits
Rr gives you what phenotype?
Essential Question: Can we predict the traits of offspring?
Essential Question: Can we predict the traits of offspring?
REFLECTION:
Use the information provided and your knowledge of genetics to answer each question.

For each genotype below, indicate whether it is a heterozygous (He) OR homozygous (Ho).

SS_____ Xx _____ KK _____ Ff _____ yy _____ uu _____

Dd _____ ff _____ aA _____ NN _____ nn _____ Ww _____

Which of the genotypes in #1 would be considered purebred?

Which of the genotypes in #1 would be hybrids?

Essential Question: Can we predict the traits of offspring?
Punnett square
USED TO PREDICT THE GENOTYPE AND PHENOTYPE OF OFFSPRING
Steps to using:
Reflection continued
Essential Question: Can we predict the traits of offspring?
Determine the phenotype for each genotype using the information provided about these cats.

Yellow eyes are dominant to blue.

YY ________________ Yy ________________ yy ________________

Silver stripes are dominant to orange.

SS ________________ Ss ________________ ss ________________

1. Determine genotype
of parents
2. Write genotypes on either side of box
Essential Question: Can we predict the traits of offspring?
3. move letters into the correct boxes
B
b
bb
bb
B
b
these boxes are the possible genotypes of the offspring
you can also determine what the possible phenotypes are too.
50% chance of Bb = blue AND 50% chance of bb = green
Examples of Punnett Squares
Essential Question: Can we predict the traits of offspring?
Essential Question: Can we predict the traits of offspring?
Reflection
Fill out the punnett square for
the cross of the following pea plants
Homozygous dominant for flower color
x
With a heterozygous plant for flower color
Purple is dominant to white
Essential Question: What were Mendel's Principles?
ALL OF MENDELS EXPERIMENTS LED HIM TO FORM 4 KEY IDEAS:
PRINCIPLE OF SEGREGATION
Genes are passed from parents to their offspring.

IF THERE is one or more alleles for a trait, then one is dominant and the others are recessive
Essential Question: What were Mendel's Principles?
Essential Question: What were Mendel's Principles?
PRINCIPLE OF INDEPENDENT
ASSORTMENT
PRINCIPLE OF DOMINANCE
HEREDITY
Genes that control different traits seperate from each other when gametes are formed.
ALLELES FOR THE SAME TRAIT (TALL AND SHORT) SEPARATE FROM EACH OTHER WHEN GAMETES ARE FORMED
this happens during meiosis
THIS MEANS THAT YOU GET ONE ALLELE FOR A TRAIT FROM EACH PARENT
EQ: ARE THERE EXCEPTIONS TO MENDELS RULES?
There are exceptions to Mendel's patterns of inheritance, but the still follow the idea that all genes are passed from parent to off spring.
1. Incomplete dominance
one allele is not completely dominant over another
means that the heterozygous genotype results in a BLEND of the dominant and recessive traits
EQ: ARE THERE EXCEPTIONS TO MENDELS RULES?
CODOMINANCE
both alleles contribute to the phenotype.
MEANS BOTH VARIATIONS FOR A TRAIT ARE SEEN
EQ: ARE THERE EXCEPTIONS TO MENDELS RULES?
MULTIPLE ALLELE
TRAITS
Genes that are controlled by more than two alleles
EXAMPLES: rabbit's coat color is determined by a single gene that has at least four different alleles
OR HUMAN BLOOD TYPE
 
Traits controlled by two or more genes are said to be polygenic traits.


Skin color in humans is a polygenic trait controlled by more than four different genes.

Copyright Pearson Prentice Hall

Polygenic Traits
EQ: ARE THERE EXCEPTIONS TO MENDELS RULES?
Being as descriptive as possible identify some characteristics/traits of the boy to the left
Being as descriptive as possible identify some characteristics/traits of the boy to the left
Do you think they are from a different family or the same?
They are the from the SAME family!
Using your knowledge of gametes and fertilization, explain (in 3-4 sentences) why this is possible!
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