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Ch 9. Patterns in Inheritance. Gregor Mendel. 1860’s Crossed pea plants Character vs trait. Purple. Flower color. White. Terminal. Axial. Flower position. Green. Yellow. Seed color. Seed shape. Round. Wrinkled. Pod shape. Inflated. Constricted. Green. Yellow. Pod color.

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Ch 9

Patterns in Inheritance


Gregor mendel

Gregor Mendel

1860’s

Crossed pea plants

Character vs trait


Genes

Purple

Flower color

White

Terminal

Axial

Flower position

Green

Yellow

Seed color

Seed shape

Round

Wrinkled

Pod shape

Inflated

Constricted

Green

Yellow

Pod color

Tall

Stem length

Dwarf

Genes

  • Mendel hypothesized that there are alternative forms of genes the units that determine heritable traits

    • Self-fertilization

    • Cross fertilization


Terms
Terms

  • True-breeding

  • Hybrid

    • Mono-hybrid

    • Dihybrid

  • Cross

  • P generation

  • F1 Generation

  • F2 Generation

  • Phenotype

  • Genotype


  • Mendel
    Mendel

    Mendel’s Observations of Inheritance Patterns

    • 2 alleles inherited

    • Mendel’s law of segregation

    • If the 2 alleles of an inherited pair differ

      • Heterozygous

      • Dominant allele

      • Recessive allele

    • If the 2 alleles are the same, no conflict

      • Homozygous


    Homologous chromosomes
    Homologous chromosomes

    • Two alleles for each characteristic.

    • Alternative forms of a gene reside at the same locus


    Dominance
    Dominance

    • Dominant

      • Gene that determines phenotype

    • Recessive

      • Gene that has no noticeable effect


    Disorders
    Disorders

    • Recessive

      • Carriers

    • Dominant

      • Some cases, homozygous dominant is lethal



    • Fetal Testing

      • Amniocentesis and chorionic villus sampling (CVS)

        • Allow doctors to remove fetal cells that can be tested for genetic abnormalities

    Amniocentesis

    Chorionic villus sampling (CVS)

    Needle inserted

    through abdomen to

    extract amniotic fluid

    Ultrasound

    monitor

    Ultrasound

    monitor

    Suction tube inserted

    through cervix to extract

    tissue from chorionic villi

    Fetus

    Fetus

    Placenta

    Placenta

    Chorionic

    villi

    Uterus

    Cervix

    Cervix

    Uterus

    Amniotic

    fluid

    Centrifugation

    Fetal

    cells

    Fetal

    cells

    Biochemical

    tests

    Several

    weeks

    Several

    hours

    Karyotyping

    Figure 9.10 A


    • Fetal Imaging

      • Ultrasound imaging

        • Uses sound waves to produce a picture of the fetus

    Figure 9.10 B


    Incomplete dominance
    Incomplete Dominance

    Intermediate phenotypes


    Hypercholestorolemia
    Hypercholestorolemia

    Figure 9.12 B


    Multiple alleles codominance
    Multiple Alleles/Codominance

    • ABO blood type in humans

    • Alleles for A and B blood types are codominant


    Pleiotropy
    Pleiotropy

    • A single gene which affects many phenotypic characteristics


    Polygenic
    Polygenic

    A single characteristic that is influenced by many genes


    Sex determination

    (male)

    (female)

    Parents’

    diploid

    cells

    44

    +

    XX

    44

    +

    XY

    22

    +

    X

    22

    +

    Y

    22

    +

    X

    Egg

    Sperm

    Offspring

    (diploid)

    44

    +

    XX

    44

    +

    XY

    Sex Determination


    22

    +

    X

    22

    +

    XX

    76

    +

    ZW

    76

    +

    ZZ

    32

    16

    Other systems of sex determination exist in other animals and plants

    Figure 9.22 B

    Figure 9.22 C

    Figure 9.22 D


    Independent assortment
    Independent Assortment

    • Mendels Law of Independent Assortment

      • Each pair of alleles segregates independently of other pairs during gamete formation

        ****Not entirely true


    Punnett squares
    Punnett Squares

    • A diagram that is used to predict an outcome of a particular cross or breeding experiment

    • Determine the probability of an offspring having a particular genotype


    Fig 9 3b

    Genetic makeup (alleles)

    P plants

    pp

    PP

    Gametes

    All

    All

    p

    P

    Fig. 9-3b

    F1 plants

    (hybrids)

    All Pp

    p

    P

    1

    2

    1

    2

    Gametes

    Sperm

    p

    P

    P

    PP

    Pp

    F2 plants

    Phenotypic ratio

    3 purple : 1 white

    Eggs

    Genotypic ratio

    1 PP : 2 Pp : 1 pp

    Pp

    pp

    p


    Practice problems
    Practice problems

    • Monohybrid cross

      • Blue eyes b, Brown eyes B

      • B is dominant

      • Both parents heterozygous brown eyed (Bb)

    • Homozygous for trait P

      • Mom is PP, dad is pp


    Linked genes

    Experiment

    Purple flower

    PpLI PpLI

    Long pollen

    • Observed Prediction

    • Phenotypes offspring (9:3:3:1)

    Purple long

    Purple round

    Red long

    Red round

    215

    71

    71

    24

    284

    21

    21

    55

    Explanation: linked genes

    P L

    Parental

    diploid cell

    PpLI

    P I

    Meiosis

    Most

    gametes

    P L

    P I

    Fertilization

    Sperm

    P I

    P L

    P L

    P L

    P L

    Most

    offspring

    P L

    P I

    Eggs

    P I

    P I

    P I

    P I

    P L

    3 purple long : 1 red round

    Not accounted for: purple round and red long

    Linked Genes

    • Linked genes are close to each other on the same chromosome and tend to be inherited together


    Sex linked genes
    Sex Linked Genes

    • Genes carried on sex chromosomes

    • XrX, XrY

    • Fruit Fly eye color- carried on X

      • R=dominant red eye (R)

      • R=recessive white eye (r)

        What proportion of offspring will have white eyes is mom is heterozygous red eyed and dad is homozygous red eyed?


    Fig 9 21c

    Female

    Male

    XR Xr

    XR Y

    Fig. 9-21c

    Sperm

    Y

    XR

    XR

    XR XR

    XR Y

    Eggs

    Xr Y

    Xr

    Xr XR


    Sex linked
    Sex Linked

    • Affect mostly males


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