Gregor Mendel - ?· where a monk named Gregor Mendel documented inheritance ... •An organisms actual…

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  • 1

    Let there be

    PEAS ON EARTH!

    math.uit.no

    Unit 5 Notes: Genetics

    Modern genetics began in the mid-1800s in an abbey garden, where a monk named Gregor Mendel documented inheritance in peas

    used good experimental design

    used mathematical analysis

    collected data & counted them

    excellent example of scientific method

    Gregor Mendel

    Pollen transferred from white flower to stigma of purple flower

    anthersremoved

    all purple flowers result

    Bred pea plants

    cross-pollinate true breeding parents

    raised seed & then observed traits

    allowed offspring to self-pollinate& observed next generation

    ?

    self-pollinate

    When bred to themselves will always produce

    organisms with same phenotype.

    EX. White bred to white always produces white; purple bred to purple

    always produces purple.

    When a flower pollinates itself. No new genes are

    introduced.

    Mendels workMendel collected data for 7 pea traits

    Each of these

    traits is

    represented by a

    specific allele on

    a specific

    chromosome.

    Allele = genes

    that determine a

    specific trait.

    Flower color

    Seed color

    Seed shape

    Pod color

    Pod shape

    Flower location

    Plant size

    2ndgeneration

    3:175%purple-flower peas25%

    white-flower peas

    Parents

    100%1stgeneration(hybrids)

    100%purple-flower peas

    Xtrue-breeding

    purple-flower peastrue-breeding

    white-flower peas

    self-pollinate

    Some traits mask others purple & white flower colors are separate

    traits that do not blend purple x white = light purple

    purple masked white

    Dominant allele functional protein

    affects characteristic

    masks other alleles

    recessive allele no noticeable effect

    allele makes a non-functioning protein

    homologouschromosomes

    allele producing

    functional protein

    mutant allele

    malfunctioning

    protein

    What did Mendels findings mean?

  • 2

    Difference between how an organism looks & its genetics

    phenotype

    Form of the trait that gets expressedwhat you see

    genotype

    An organisms actual alleles

    Explain Mendels results using

    dominant & recessive

    phenotype & genotypeF1

    PX

    purple white

    all purple

    Genotype vs. phenotype Environment effect on genes

    Phenotype is controlled by both environment & genes

    Color of Hydrangea flowers

    is influenced by soil pH

    Human skin color is

    influenced by both genetics

    & environmental conditions

    Coat color in arctic

    fox influenced by

    heat sensitive alleles

    Phenotype is a result of both genetics and environment.

    www.safeandsoundlostandfound.org

    www.cats-central.com

    Cold Environment

    Warm Environment

    Siamese cats that grow

    up in a cold

    environment are

    darker

    than those that grow

    up in a warmer

    environment.

    Inheritance of genes On the chromosomes passed from Mom &

    Dad to offspring are genes

    may be same information

    may be different information

    eye color

    (blue or

    brown?)

    eye color

    (blue or

    brown?)

    Remember how Meiosis separates the alleles into sex cells?

    This separation is called the

    Law of Segregation.

    Effect of genes

    Genes come in different versions - alleles

    brown vs. blue eyes

    brown vs. blonde hair

    Alleles = different forms of a gene

  • 3

    Homozygous dominant = AA

    Homozygous recessive = aa

    Heterozygous = Aa

    Tt

    Bb

    WwYy

    rr

    RR

    Aa

    AB

    Ss

    bb EeBB

    aaXY

    Genes affect how you look

    X

    BBbb

    Bb Bb Bb Bb

    Where did the blue eyes go??

    X

    Bbbb

    Bb Bb bb bb

    Why did the blue eyes stay??

    X

    BbBb

    BB or Bb BB or Bb BB or Bb bb

    Where did the blue eyes come from??

    Genes come in versions

    brown vs. blue eye color

    Alleles (different forms of a gene)

    Alleles are inherited separately from each parent

    brown & blue eye colors are separate & do not blend

    either have brown or blue eyes, not a blend

    Some alleles mask others

    brown eye color masked blue

    People who have one recessive allele and one dominant allele are called CARRIERS (they carry the recessive allele, but do not express the trait)

    Carriers can pass on allele to offspring

    How does this work?

    eye

    color

    (brown?)

    hair

    color

    hair

    color

    eye

    color

    (blue?)

    Paired chromosomes have same kind of genes but may be different alleles

    gene

    allele

  • 4

    Traits are inherited as separate units For each trait, an organism inherits

    2 copies of a gene, 1 from each parent

    a diploid organism inherits 1 set of chromosomes from each parent

    diploid = 2 sets (copies) of chromosomes

    1 from Mom

    1 from Dad

    homologous chromosomes

    Making gametes

    BB = brown eyes

    bb = blues eyes

    Bb = brown eyes

    BB

    bb

    Bb

    brown is dominant over blue

    blue is recessive to brown

    Remember meiosis!

    B

    B

    b

    b

    B

    b

    Dominant = can mask others

    Recessive = can be hidden

    by others

    How do we say it?

    BB = brown eyes

    bb = blues eyes

    Bb = brown eyes

    2 of the same alleles

    Homozygous

    2 different

    Heterozygous

    BB

    B

    B

    bb

    b

    b

    Bb

    B

    b

    homozygous dominant

    homozygous recessive

    Punnett squaresBb (carrier) x Bb (carrier)

    male / sperm

    fem

    ale

    / e

    gg

    s

    X

    BB

    Bb bb

    BbB

    b

    B b

    Punnett square practice.

    Genetics vs. appearance

    There can be a difference between how an organism looks & its genetics

    appearance or trait = phenotype

    brown eyes vs. blue eyes

    genetic makeup = genotype

    BB, Bb, bb

    2 people can have the same appearance but

    have different genetics: BB vs Bb

    Genetics vs. appearance

    eye

    color

    (brown)

    eye

    color

    (brown)

    eye

    color

    (blue)

    eye

    color

    (brown)

    vs.

    BB

    B

    B

    Bb

    B

    b

    How were these

    brown eyes made?

  • 5

    Making crosses Can represent alleles as letters

    flower color alleles P or p

    true-breeding purple-flower peas PP

    true-breeding white-flower peas pp

    PP x pp

    PpF1

    PX

    purple white

    all purple

    Punnett squares

    Pp x Pp

    P pmale / sperm

    P

    p

    fem

    ale

    / e

    gg

    s

    PP

    75%

    25%

    3:1

    25%

    50%

    25%

    1:2:1

    %

    genotype

    %

    phenotype

    PP Pp

    Pp pp pp

    Pp

    Pp

    1stgeneration(hybrids)

    Aaaaah,phenotype & genotypecan have different

    ratios

    Using Punnett Squares

    Bb x Bbmale / sperm

    fem

    ale

    / e

    gg

    s

    X

    BB

    Bb bb

    BbB

    b

    B b

    A Punnett Square is a diagram used to identify possible combinations resulting from a mating.

    This married

    couple is

    considering

    having their first

    baby.

    The man is

    heterozygous for

    a disease. The

    woman is also

    heterozygous for

    the disease.

    The couple comes to you for counseling. They want

    you to know the chances they will have a healthy baby.

    You know that the disease they carry is a recessive

    trait and that both parents are heterozygous.

    RR Rr rrWhich of the above genotypes will you need to use?

    Man x Woman

    Rr RrRrR r

    RR

    r

    r

    RR rR

    Rr rr?

  • 6

    Man x Woman

    Rr RrR r

    R

    r

    RR rR

    Rr rr

    Genotype %RR =Rr =rr =

    25%50%25%

    Phenotype %Healthy =Carrier =Diseased =

    25%50%25%

    The chance that the

    couple will have a baby

    that has the disease is

    25%.Lets Practice!

    Not-so-bad Traits determined by Simple Inheritance

    Tongue rolling (dominant form)

    Widows peak (dominant form)

    Hitchhikers thumb (dominant form)

    Freckles (dominant form)

    Taste PTC (dominant form)

    Cleft chin (dominant form)

    Dimples (dominant form)

    No major consequences for these inherited conditions!

    Genetics Lab

    Work with a lab partner at a station

    Check out each others traits

    Write answers on your own paper

    PTC and Control papers go in trash, not in sink (this will get you detention)

    Complete the lab on your OWN paper

    Recessive Genetic Disorders

    Must inherit two faulty genes (one from mom, one from dad)

    Parents who do not express the trait, but pass it on are called CARRIERS (HETEROZYGOTES)

    Traits can be deadly

    Recessive Genetic Disorders

    Cystic fibrosis

    Any of 1000 different mutations of one gene found on chromosome 7

    Buildup of chlorine produces thick mucus around organs and in lungs

    Weakened immune system

    Life expectancy: 35 years

    Found mostly in Caucasians

    Recessive Genetic Disorders Tay-Sachs

    Mutation of one gene on chromosome 15

    Lack of an enzyme

    Buildup of lipids on

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