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1/16/20 1 NGSS UNIT 2 – HEREDITY: INHERITANCE AND VARIATION OF TRAITS UNIT 2: MENDELIAN GENETICS Part 2 WHAT IS INHERITANCE? o White Board Responses o Guidelines- Everyone participates o White board is ONLY used when directed (it is NOT a doodle board) o Write down ONE genetic trait you share with a family member (or you shared with someone in class Friday) . o All living things have a set of characteristics inherited from their parents. o Eye color o Hair color/texture (straight or curly) o Height o Nose shape o Diseases and disorders (asthma, diabetes) Genetics: The scientific study of HEREDITY MENDEL THE MONK HOW MENDELS PEA PLANTS HELPED US UNDERSTAND GENETICS Watch the TedEd video short and answer the questions in your fill in notes. ! Gregor Mendel was a monk born ______ century in who lived in _________ ! What is the name for the “hidden” trait Mendel described? ! The combinations of alleles is called __________________. ! The trait that you can “see”, such as pea color, is called the ________________. ! What is the name fore the tool used to predict offspring genotypes?

NGSS UNIT EREDITY INHERITANCE AND VARIATION OF TRAITS

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1/16/20

1

NGSS UNIT 2 – HEREDITY: INHERITANCE AND VARIATION

OF TRAITS

UNIT 2: MENDELIAN GENETICS

Part 2

WHAT IS INHERITANCE?

o  White Board Responses o  Guidelines- Everyone participates o  White board is ONLY used when directed (it is NOT

a doodle board)

o  Write down ONE genetic trait you share with a family member (or you shared with someone in class Friday) .

o  All living things have a set of characteristics inherited from their parents. o  Eye color o  Hair color/texture (straight or curly) o  Height o  Nose shape o  Diseases and disorders (asthma, diabetes)

Genetics: The scientific study of HEREDITY MENDEL THE MONK HOW MENDEL’S PEA PLANTS HELPED US UNDERSTAND GENETICS

Watch the TedEd video short and answer the questions in your fill in notes.

!  Gregor Mendel was a monk born ______ century in who lived in _________

!  What is the name for the “hidden” trait Mendel described?

!  The combinations of alleles is called __________________.

!  The trait that you can “see”, such as pea color, is called the ________________.

!  What is the name fore the tool used to predict offspring genotypes?

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MENDEL’S PEAS

o  Worked on ordinary peas o  He knew about the male (pollen) and female (egg) parts of

the plant that cause fertilization. o  Fertilization produces a new cell that develops into a tiny

embryo encased in a seed o  When pollen fertilizes an egg cell, a seed for a new plant is

formed. o  Pea plants normally reproduce by self-pollination.

SELF-POLLINATING

o  Usually pea plants are self pollinating so they basically have one parent o  All their characteristics would be

the same as their parent

MASTER OF THE MONASTERY…GARDENS

o  Mendel had several pea plants in his garden

o  They were true-breeding: meaning that if the plants are allowed to self-pollinate, they will produce offspring identical to themselves

o  These plants were the basis of Mendel’s experiments

OFFSPRING IDENTICAL TO PARENTS

o  One stalk produced only tall plants

o  Another only short ones o  One only had green seeds o  Another had only yellow

o  He had to prevent Self-pollination. o  Cross Pollination: He cut away the pollen from a flower

and then dusted the female part with pollen from another plant

o  This produced seeds with 2 parents

Mendel wanted to produce seeds from male and female of different plants GENES AND DOMINANCE

o  Mendel studied several different pea plant traits o  Trait: a specific characteristic that varies from one

individual to another o  Flower color, pea shape, plant height

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CHECK FOR UNDERSTANDING ON YOUR WHITE BOARD….

1.  If a pea plant is true breeding for purple flower color, what color with the offspring be?

2.  What is the name for the process that leads to these true breeding plants?

o  Each trait Mendel studied has contrasting characters o  Green seed color and yellow seed color o  Tall plant and short plant o  Round peas and wrinkled peas

THE 7 TRAITS

o  Mendel crossed plants with each of the seven contrasting characters o  Seed shape o  Seed color o  Seed coat color o  Pod shape o  Pod color o  Flower position o  Plant height

GENERATIONS AND HYBRIDS

o  Original pair of plants are P (parental) generation

o  Offspring are called F1 (first filial) generation

o  Offspring of parents with different traits are called hybrids.

o  What F1 Generation like?

o  Did the characters blend?

o  Did they look at all like the parents?

F1 GENERATION

o  Mendel was surprised! o  In each cross the character seemed to have

disappeared from one of the parents

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MENDEL CONCLUDED 2 THINGS…

o  1) Biological inheritance is determined by factors that are passed from one generation to the next o  Today we call these genes o  Each gene studied was controlled by a gene

that occurred in 2 contrasting forms o  Plant height (gene) = tall (form 1) and short (form2)

o  These different forms for the same gene are called alleles o  2 alleles for the gene of plant height are short and

tall

MENDEL CONCLUDED 2 THINGS

o  2) The principle of dominance. o  1. Some alleles are

dominant and some are recessive

o  2. An organism with a dominant form of a trait will exhibit that trait

o  3. An organism with a recessive form will only exhibit the trait when no dominant form is present

o  In Mendel’s experiments the allele for tall was dominant and short was recessive. Yellow was dominant and green recessive.

MENDEL HAD A QUESTION… Did the recessive disappear?! Where did the recessive trait go? He couldn’t see it, did that mean it was gone forever? Or were they still somehow present in the F1

generation?

ANOTHER EXPERIMENT FOR ANOTHER QUESTION… o  He allowed all seven kinds of F1 generation plants to

produce an F2 generation by self-pollination. o  He crossed the F1 generation with itself to produce an F2

generation.

THE RESULTS

"  The traits controlled by recessive genes reappeared! "  About ¼ of the F2 plants showed the trait controlled by

recessive allele "  Why did recessive traits disappear in F1 and reappear

in F2?

THE ANSWER… !  The recessive trait is masked

in F1 but shows up in F2 !  This reappearance indicates

that the allele for short somehow got separated from tall

!  This separation of alleles is called segregation.

!  Mendel suggested that alleles for short and tall in F1 segregate during sex cell or gamete formation.

!  Law of segregation ! Organisms inherit two copies of

each gene, one from each parent. ! Organisms donate only one copy

of each gene in their gametes. Thus the two copies of each gene separate, during gamete formation.

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BREAK IT DOWN…

o  Each F1 plant flowers and produces gametes o  pollen-male o  egg-female

o  2 alleles segregate from each other so that each gamete carries only a single copy of each gene

o  Therefore, each F1 plant produces 2 types of gametes o  Tall alleles and short alleles

GENETICS AND PROBABILITY

�������������������������������������������������������������������������������������������������������������������������������� Probability: the likelihood of an event happening

�������������������������������������������������������������������������������������������������������������������������������� 2 possible outcomes to flipping a coin �������������������������������������������������������������������������������������������������������������������������������� Heads �������������������������������������������������������������������������������������������������������������������������������� Tails

�������������������������������������������������������������������������������������������������������������������������������� The chances or probability of getting heads or tails is equal

�������������������������������������������������������������������������������������������������������������������������������� The probability of getting a heads in a single coin flip is 1 chance out of two possibilities (heads or tails).

��������������������������������������������������������������������������������������������������������������������������������  This is 1:2 or 50% chance

o  Each coin flip is a single event o  So what’s the probability of landing on head three

times in a row? o  Probability of heads is 1/2 o  Flipped 3 times o  1/2 x 1/2 x 1/2 = 1/8

o  You have 1 chance out of 8 to flip heads 3 times in a row!

"  How is coin flipping related to genetics?

"  The way in which alleles segregate is completely random, like a coin flip.

"  The principles of probability can be used to predict the outcomes of genetic crosses.

ALLELES AND TRAITS

o  Organisms that have 2 identical alleles for a trait are homozygous.

o  They are true-breeding for the trait. o  Organisms with 2 different alleles for the same

trait are heterozygous. o  They are hybrid for the trait.

PHENOTYPE VS. GENOTYPE

o  Phenotype: physical characteristic

o  All tall plants have the same phenotype.

o  Genotype: genetic makeup

o  All tall plants do not have the same genotype.

TT Tt

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MONSTER GENETICS

! Determine who is mom and who is dad. BOTH parent fill out a data sheet

! Each parent flips the coin to determine if they give a dominant or recessive allele

! All Monsters Have: !  Four legs !  Three eyes !  One pair of ears !  One mouth !  One pair of hands

! A good monster drawing clearly shows the traits, includes colors, and the parents names

It’s all about probability…

PUNNETT SQUARES Mendel discovered that inheritance follows certain rules of chance.

PUNNETT SQUARES

o  Gene combinations that MIGHT result from a genetic cross can be determined from a Punnett square diagram

o  Shows segregation of genes o  Parent Generations are shown along the

top and side of the diagram (square) o  F1 appear in the 4 boxes

o  Letters in the diagram represent alleles o  T = Tall t= short

o  Punnett squares can be used to predict and compare the genetic variations that will result from a genetic cross

O PROBABILITY AND SEGREGATION

o  ¼ have 2 alleles for tallness (TT)

o  2/4 have 1 for tallness and 1 for shortness (Tt)

o  The allele for tallness is dominant over shortness so ¾ of the plants will be tall

o  ¼ of the plants have two alleles for shortness (tt)

o  Therefore for every 3 TALL plants there is one short plant.

o  Mendel performed this punnett square cross to predict the ratio of tall to short plants.

o  When the seeds grew he was RIGHT! o  His ratio worked out to

be 1 short plant for every 3 tall ones.

o  This proved Mendel’s assumptions about segregation to be correct!

o  All 7 alleles proved this true!

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GENETICS AND PROBABILITY

�������������������������������������������������������������������������������������������������������������������������������� The punnett square is used to predict probability.

BEYOND MENDELIAN GENETICS There are many variations of inheritance patterns.

A SUMMARY OF MENDEL’S PRINCIPLES

�������������������������������������������������������������������������������������������������������������������������������� The inheritance of biological characteristics is determined by individual units known as genes, which are passed from parents to offspring.

��������������������������������������������������������������������������������������������������������������������������������  In cases in which 2 or more alleles of the gene for a single trait exist, some forms of the gene may be dominant and others may be recessive.

��������������������������������������������������������������������������������������������������������������������������������  In most sexually reproducing organisms, each adult has 2 copies of each gene- one from each parent. These genes are segregated when gametes are formed.

�������������������������������������������������������������������������������������������������������������������������������� The alleles for different genes usually segregate independently of one another.