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Patterns of Inheritance Knew that two parents contributed hereditary material Thought it was...

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Page 1: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.
Page 2: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.

Patterns of Inheritance

Page 3: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.

Knew that two parents contributed hereditary material

Thought it was blending of fluidsBut blending couldn’t explain some traits (a

black horse and white horse should only produce gray horses)

Page 4: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.

Austrian Monk, mid-1800s Math, physics, botany at

University of Vienna Studied Pisum sativum, garden

pea plant Self-fertilizes—produces both male

& female gametes Can cross-fertilize—done by plant

breeders Observed that white-flowered

parent plants produce white flowers

Observed that when bred w/ different-colored plant, different traits emerged.

Page 5: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.

Genes—sequence of DNA on a chromosome that gives information on inheritable traits (i.e. hair color gene)

Allele—all forms of the same gene. Reside at the same location (locus) on homologous chromosomes. (i.e. alleles for red, brown, blonde, and black hair)

Locus—location of a gene on a chromosome

Hybrid—offspring of two “parents” who each breed true for different forms of a trait

Page 6: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.
Page 7: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.

Homozygous—identical alleles on homologous chromosomes (AA, aa)

Heterozygous—non-identical alleles on homologous chromosomes (Aa)

Dominant allele—masks effect of recessive allele when pairedCapital letter for dominant (“A”)Lower-case letter for recessive (“a”)

Page 8: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.

Homozygous dominant—AA Homozygous recessive—aa Heterozygous—Aa True-breeding parents—P First-generation offspring—F1 Second-generation offispring—F2

Genotype—particular alleles in an individual; genetic make-up

Phenotype—Individual’s observable traits (what they look like)

Page 9: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.

Sperm in pollen grains, originate in stamen

Carpel—female flower part, has eggs, fertilization, seed development

Brush pollen onto carpel for artificial fertilization

Page 10: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.

Assume each P was homozygous AA for one trait, aa for other trait Breed true for a phenotype

F1 only show “A” trait, not “a” trait

F2 show 1 “a” trait for every 3 “A” traits

Page 11: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.
Page 12: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.

Mendel tracked 7 observable traits on pea plants Seed shape (round or wrinkled) Seed color (yellow or green) Pod shape (inflated or wrinkled) Pod color (green or yellow) Flower color (purple or white) Flower position (on stem or at tip) Stem length (tall or dwarf)

Noted that F1 had all same trait, some of F2 had different trait

Approximately 3:1 ratio of traits

Page 13: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.

Law of Segregation“A sperm or egg carries only one allele for

each inherited characteristic because allele pairs separate from each other during the production of gametes.”

Each homologous chromosome carries one allele. During meiosis, these chromosomes separate so that only one ends up in each gamete.

Page 14: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.
Page 15: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.

Dominant (A) genotype suppress recessive (a) phenotype

Page 16: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.

Monohybrid cross—a single phenotype (“Mono” = 1)

Page 17: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.

Dihybrid cross—two phenotypes (“Di” = 2)

Page 18: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.
Page 19: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.

Law of Independent Assortment“Each pair of alleles segregates

independently of other pairs of alleles during gamete formation.”

The alleles for a given trait (on homologous chromosomes) separates during meiosis independently of other traits. E.g. Hair color alleles will segretate during

meiosis independently of eye color alleles

Page 20: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.

Autosomal RecessiveRecessive

phenotype only shown with homozygous recessive

Heterozygous is “carrier”

Page 21: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.

AlbinismLack of normal

amounts of melanin (pigment) in body

Cystic fibrosisThick mucus in lungs

& digestive tractBreathing & digestion

difficultMost common lethal

genetic disorder among Caucasians

Page 22: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.

Autosomal DominantAllele expressed in

heterozygotesAA or Aa show

dominant phenotype

Page 23: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.

AchondroplasiaEmbryonic cartilage in skeleton

doesn’t develop properly“Dwarf”, average 4’ tall

Huntington’s DiseaseNervous system deterioratesSymptoms often not seen until

after 30Die in 40s or 50s

Page 24: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.

Phenotype treatmentsPhenylketonuria (PKU)—lack of enzyme,

can’t convert certain amino acid, brain function problems

Restrict intake, can lead normal life Genetic screening

Detect alleles that can cause disorders Prenatal diagnosis

Amniocentesis—collect fluid from around fetus

Cells in fluid from fetus, can analyze for certain disorders

Page 25: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.

Heterozygous phenotype between the two homozygotes

One trait doesn’t completely dominate the other

Hybrid is a blend of the two phenotypes

Page 26: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.

Nonidentical alleles expressed at same time

Multiple allele system—3 or more alleles for a single gene locus

Blood types

Page 27: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.
Page 28: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.

Phenotype results from interaction among products of 2 or more gene pairs

Labrador retriever colorsB (black) & b (brown)EE or Ee—melanin

(pigment) production. Black or brown

ee—no melanin produced. Always yellow!

Page 29: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.

One gene may affect multiple systems or traitsSickle-cell anemia

Page 30: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.

Continuous variation—range of small differences in a traitDue to polygenic inheritance—

inheritance of multiple genes that affect the same trait

Skin color—due to different kinds & amounts of melanin

Page 31: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.
Page 32: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.
Page 33: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.

Responsible for genetic variation

Can result in nonparental combinations

The closer the genes on a chromosome, the more likely to stay togetherLinked genes

Page 34: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.

HumansXX = FemaleXY = Male

Page 35: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.

Different species have different systems

X-Y XX = Female, XY = Male Humans

X-O XX = Female, X = Male Grasshoppers, roaches, many

insects Z-W

ZW = Female, ZZ = Male Fish, butterflies, birds

Haplo-Diploid 2n = Female, n = Male Ants, bees

Page 36: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.

Recessive, found on X chromosome

Only present if XAY or XAXA, Not XAX

Baldness Red-Green Color

Blindness Hemophilia A

Lack of certain clotting factors

Blood cannot clot, bleed uncontrollably

Page 37: Patterns of Inheritance  Knew that two parents contributed hereditary material  Thought it was blending of fluids  But blending couldn’t explain some.

XXB XY

XXB XY

XB YX

X

XB = Bald, recessive trait X, Y = Non-bald, dominant trait

XBXB

XBY

XXB XY

XB YXB

X

XXB XBY

XX XY

X YXB

X

XBXB = bald womanXXB = carrier womanXX = normal womanXBY = bald manXY = normal man


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