Mendel

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GENETICS
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THE PASSING OF TRAITS FROM PARENT TO OFFSPRING
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Looking at Your Traits

• Number your paper 1-10
• Beside each number, write the Trait we are
  looking at.
• Tell whether you are dominant or recessive
  for this trait.

• Lastly, write your Genotypewhich will be
  represented by given letters
• Ex.
• PTC-Dominant-TT or Tt
• Tongue Rolling-Dominant-RR or Rr

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Looking at Your Traits

• 1. PTC is a chemical called phenylthio-carbamide
  and is harmless. It is used in medical genetics
  and as a diagnostic tool in medicine. The
  ability to taste the chemical is a dominant
  trait. People who cannot taste this chemical are
  recessive for the trait.

TPTC Taster t non PTC Taster
Dominant TT or Tt Recessive tt
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Looking at Your Traits

• 2. Tongue Rolling

RTongue Roller r non tongue roller
Dominant RR or Rr Recessive rr
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Looking at Your Traits

• 3. Earlobes

EUnattached Earlobes eattached earlobes
Dominant EE or Ee Recessive ee
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Looking at Your Traits

• 4. Earbump

DDarwin's Ear Point Present ddarwin's ear point
not present
Dominant DD or Dd Recessive dd
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Looking at Your Traits

• 5. Widows Peak

WWidow's Peak Present wwidow's peak not present
Dominant WW or Ww Recessive ww
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Looking at Your Traits

• 6. Hitchhikers Thumb

HHitchhiker's Thumb Present hhitchhiker's thumb
not present
Dominant HH or Hh Recessive hh
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Looking at Your Traits

• 7. Polydactyly

PSix Fingers or Toes pfive fingers or toes
Dominant PP or Pp Recessive pp
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Looking at Your Traits

• 8. Syndactyly

SWebbed Fingers or Toes snon webbed fingers or
toes
Dominant SS or Ss Recessive ss
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Looking at Your Traits

• 9. Cleft Chin

C Non Cleft Chin ccleft chin
Dominant CC or Cc Recessive cc
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Looking at Your Traits

• 10. Hair Whorl

LClockwise Hair Whorl lcounterclockwise hair
whorl
Dominant LL or Ll Recessive ll
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I. Terms

• Trait characteristic of an organism
• Gene a heredity unit that codes for a trait.
• Allele different gene forms
• Dominant the gene that is expressed whenever it
  is present
• Recessive the gene that is hidden. It is not
  expressed unless a homozygous condition exists
  for the gene.

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I. Terms

• Homozygous two identical (same) alleles for a
  given trait (TT).
• Heterozygous two different (opposite) alleles
  for a given trait (Tt).
• Gamete sexual reproductive cell.
• Fertilization the fusion of two gametes.
• Phenotype physical trait of an organism.
• Genotype the genes present in the cell.

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II. Gregor Mendel-The Father of Genetics

• A.Mendel was the first to come up with rules
  regarding heredity-which formed the basis of
  genetics.

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B. Mendels Hypotheses

• For each inherited trait, an individual has two
  factors that control heredity (these factors
  are called genes) which are inherited from each
  parent.

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B. Mendels Hypotheses

• There are alternative versions of genes(each
  version is called an allele).
• Ex. Purple flowers or white flowers
• Brown eyes or blue eyes

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B. Mendels Hypotheses

• When two different alleles occur together, one of
  them may be completely expressed, while the other
  may have no observable effect on the organisms
  appearance.
• --Dominant or recessive Purple flowers are
  dominant to white flowers

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B. Mendels Hypotheses

• 4. When gametes are formed, the alleles for each
  gene in an individual separate independently of
  one another. Thus, gametes carry only one allele
  for each inherited trait. When gametes unite
  during fertilization, each gamete contributes one
  allele.

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C. Laws of Heredity

• Law of Segregationthe two alleles for a trait
  segregate (separate) during the formation of
  gametes (meiosis).
• Law of Independent Assortmentthe alleles of
  different genes separate independently of one
  another during gamete formation.
• Ex. The alleles for height separate
  independently of the alleles for flower color

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III. Studying Heredity
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A. Punnett Square

• Determine the traits used.
• Determine the dominant vs. recessive trait.
• Determine the letters for each trait.
• Express the cross and determine the gametes
  formed.
• Set up Punnett Square.

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Punnett Square

• Place the two female gametes across the top
• Place the two male gametes down the side.
• Determine the offspring by filling in the squares.

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Ex. Problem
b
b

• Trait-Eye Color
• Brown is dominant to blue
• B Brown
• b blue
• Cross a homozygous brown eyed male with a blue
  eyed female.

B
b
b
B
B
B
b
b
B
B
0
0
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Genotypic ratio _________ Phenotypic
ratio________
4
0
BB
bb
x
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Passing on of Traits

• IV. Sexual Reproduction-reproduction where two
  gametes unite.

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Sexual Reproduction
--Two parents each form reproductive cells that
have one-half the number of chromosomesthese
cells are called gametes and the process that
they are made is called meiosis.
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A. MEIOSIS

• --A form of cell division that halves the number
  of chromosomes when forming specialized
  reproductive cells, such as gametes.

Four cells are produced, each with half as much
genetic material as the original cell.
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B. Chromosome Number in a Cell

• 1. Diploid number 2nthe number of chromosomes in
  a body cell of an organism.
• 2. Haploid number nhalf of the diploid number.
• The diploid number for a human is 46 (humans have
  46 chromosomes in each body cell)
• The haploid number for a human is ___ and is
  found only in the gamete cells (sperm/egg)

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Determine the Diploid or Haploid number of each
organism

• 2n n
• Homo sapiens (human) 46 23
• Mus musculus (house mouse) 40 ___
• Zea mays (corn or maize) 20 ___
• Drosophila melanogaster (fruit fly) ___ 4
• Xenopus laevis (South African clawed frog) ___
  18
• Caenorhabditis elegans (microscopic roundworm)
  ___ 6
• Saccharomyces cerevisiae (budding yeast) 32
  ___
• Canis familiaris (domestic dog) 78 ___
• Arabidopsis thaliana (plant in the mustard
  family) 10 ___
• Muntiacus muntjac (its Indian cousin) ___ 3
• Myrmecia pilosula (an ant) ___ 1
• Parascaris equorum var. univalens (parasitic
  roundworm) 2 ___
• Cambarus clarkii (a crayfish) 200 ___
• Equisetum arvense (field horsetail, a
  plant) 216 ___

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10
8
36
12
16
39
5
6
2
1
100
108
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Meiosis and Sexual Reproduction
Question What is the difference in the number of
cell divisions and the change in chromosome
number during mitosis and meiosis?
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Meiosis and Sexual Reproduction
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C. Mitosis VS. Meiosis

• Mitosis
• Produce identical cells
• Produce diploid cells
• Occurs in
• Plantsstems, leaves, roots
• Animalsskin, bones, digestive organs, etc.

• Meiosis
• Produce gametes (sex cells)
• Produce haploid cells
• Occurs in
• Plantsovules, spores
• Animalsovules (eggs), sperm

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V. Genetic Problems
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Genetic Diseases

• http//www.marchofdimes.com/pnhec/4439_4136.asp

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A. Pedigrees

• Pedigree help determine the inheritance and
  probability of human genetic disorders.

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Example Pedigree
Generation
Generation
Generation
Generation
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B. Karyotype

• --A picture of the paired chromosomes, arranged
  in order from largest to smallest.
• In humans, there are 23 pairs of chromosomes.
• -22 autosomes (chromosomes that code for regular
  body traits)
• -1 sex chromosome

Gender is determined by the combination of sex
chromosomes inherited in the zygote (the
fertilized egg). XX Female XY Male it
is the sex chromosome with in the sperm that is
the determining factor for gender.
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Karyotypes

• Karyotypes can be obtained by blood samples or by
  amniocentisis.
• Amniocentesis detects or rules out Down's
  syndrome. Amniocentesis also detects neural tube
  defects such as spina bifida. Babies born with
  spina bifida have a backbone that did not close
  properly. Serious complications of spina bifida
  can include leg paralysis, bladder and kidney
  defects, brain swelling (hydrocephalus), and
  mental retardation. If a pregnancy is complicated
  by a condition such as rh-incompatibility, your
  doctor can use amniocentesis to find out if your
  baby's lungs are developed enough to endure an
  early delivery.

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Amniocentesis
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C. Nondisjunction- the failure of chromosomes to
separate properly during meiosis.

• Karyotypes can also detect other chromosomal
  abnormalities such as
• Downs Syndromean extra 21 autosome.
• Klinefelters Syndromean extra sex chromosome
• Turners Syndromea missing sex chromosome

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