Meiosis

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Meiosis
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MEIOSIS

• When __________ (sperm or egg) cells reproduce
  themselves the process is called MEIOSIS.
• During meiosis, a single __________ cell divides
  and produces FOUR __________ reproductive cells.
• In Meiosis there is one __________ duplication
  followed by two __________ divisions (into four
  cells) so Meiosis is broken down into Meiosis I
  and Meiosis II.

Upon fertilization, a 1N sperm meets a 1N egg and
a zygote (2N) is formed.
1 N sperm
1 N egg
2N zygote
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The steps of Meiosis I and Meiosis II
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What is the MAJOR difference between these two
processes?

• MITOSIS retains the same __________ number
• 2N 2N
• While MEIOSIS __________ the chromosome number
• 2N 1N

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Metaphases
Mitosis Meiosis
____________
____________ ____________
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Crossing Over

• Happens during ________________
• Chromosomes in ______________ ____________ form
  __________ and swap parts
• Is a source of ______________ ______________

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Purposes of Mitosis

• To produce ________________ cells with
  __________the genetic material.
• Humans have _____ chromosomes. Our sperm and
  eggs have _____ chromosomes.
• Grasshoppers have _____ chromosomes. Their sperm
  and eggs have _____ chromosomes.
• To produce cells that each have a
  ________________ set of genetic material.

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Mendelelian Genetics
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Gregor Mendel

• (1822-1884)
• Responsible for the __________ governing
  __________ of Traits

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Gregor Johann Mendel

• Austrian monk
• Studied the __________ of traits in ________
  ________
• Developed the laws of __________
• Mendel's work was not recognized until the turn
  of the __________ century

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Gregor Johann Mendel

• Between 1856 and 1863, Mendel cultivated and
  tested some __________ pea plants
• He found that the plants' offspring retained
  __________ of the parents
• Called the __________ of __________ "

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Particulate Inheritance

• Mendel stated that physical traits are inherited
  as __________
• Mendel did not know that the particles were
  actually __________ __________

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Genetic Terminology

• __________ - any __________ that can be passed
  from __________ to offspring
• __________ - passing of traits from parent to
  __________
• __________ - study of __________

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Types of Genetic Crosses

• __________ __________ - cross involving a single
  __________
• e.g. flower color
• __________ __________ - cross involving
  __________ traits
• e.g. flower color plant height

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Punnett Square

• Used to help solve __________ problems

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Designer Genes

• __________ - two forms of a __________ (dominant
  recessive) - one allele on each chromosome in a
  __________________ __________
• __________ - stronger of two genes expressed in
  the hybrid represented by a __________
  __________ ( ____ )
• __________ - gene that shows up less often in a
  cross represented by a __________ __________ (
  ____ )

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More Terminology

• __________ - gene __________ for a trait (e.g.
  RR, Rr, rr)
• Always two letters one for each _____________
• One for each __________ _____________
• __________ - the __________ __________ resulting
  from a genotype (e.g. red, white)

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Mendels Laws
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Law of Dominance
In a cross of parents that are __________ for
contrasting __________, only one form of the
trait will appear in the next generation. All the
offspring will be __________ and express only the
__________ trait. RR x rr yields all Rr (round
seeds)

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Law of Dominance
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Law of Independent Assortment

• When homologous pairs line up in ___________,
  they line up ___________.
• This is called a ___________ ___________.

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Law of Segregation

• During the formation of ________ (eggs or sperm),
  the two ________ ________ ________ responsible
  for a trait ________ from each other.
• Happens at the end of __________.

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Applying the Law of Segregation
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Genotype Phenotype in Flowers

• __________ of alleles______ red flower______
  yellow flower
• All genes occur in __________ , so 2 __________
  affect a characteristic
• Possible combinations are

__________ RR Rr rr __________
______ ______ ______
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Genotypes

• __________ __________ - gene combination
  involving 2 __________ or 2 __________ genes
  (e.g. RR or Rr) also called pure 
• __________ __________ - gene combination of one
  __________ one __________ allele    (e.g. Rr)
  also called __________

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Did the observed ratio match the theoretical
ratio?

• The theoretical or expected ratio of plants
  producing round or wrinkled seeds is ______
  __________ ______ __________
• Mendels __________ ratio was
• ______ ______
• The discrepancy is due to __________ __________

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Generation Gap

• __________ ______ Generation the __________
  __________ in a breeding experiment.
• ______ generation the __________ -generation
  __________ in a breeding experiment.
• ______ generation the __________ -generation
  __________ in a breeding experiment.

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Monohybrid Crosses
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P1 Monohybrid Cross

• Trait Seed Shape
• Alleles R Round r Wrinkled
• Cross Round seeds x Wrinkled seeds
• RR x rr

Genotype ______ Phenotype ______ GenotypicRatio
__________ PhenotypicRatio__________
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P1 Monohybrid Cross Review

• Homozygous dominant x Homozygous recessive
• Offspring all ____________ (hybrids)
• Offspring called _______ generation
• Genotypic Phenotypic ratio is ____________
  ____________

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F1 Monohybrid Cross

• Trait Seed Shape
• Alleles R Round r Wrinkled
• Cross Round seeds x Round seeds
• Rr x Rr

Genotype ___, ___, ___ Phenotype ________
________ G.Ratio
______ P.Ratio ____
R
R
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F1 Monohybrid Cross Review

• Heterozygous x heterozygous
• Offspring____ Homozygous dominant ________
  Heterozygous ________ Homozygous Recessive ____
• Offspring called ___ generation
• Genotypic ratio is _________
• Phenotypic Ratio is ______

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And Now the Test Cross

• Mendel then crossed a ________ a ______ from
  his ___ generation
• This is known as an F2 or ____ ____
• There are two possible testcrosses________
  ________ x ________ ________ ________ x ________

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F2 Monohybrid Cross (1st)

• Trait Seed Shape
• Alleles R Round r Wrinkled
• Cross Round seeds x Round seeds
• RR x Rr

Genotype ___, ___ Phenotype _______ GenotypicRa
tio ______ PhenotypicRatio ___________
r
R
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F2 Monohybrid Cross Review

• Homozygous x heterozygous (hybrid)
• Offspring___ ___________ RR___ ___________
  Rr
• _________ Ratio is ______
• Called _____ _____ because the offspring reveal
  genotype of the parents

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F2 Monohybrid Cross (2nd)

• Trait Seed Shape
• Alleles R Round r Wrinkled
• Cross Wrinkled seeds x Round seeds
• rr x Rr

Genotype ___, ___ Phenotype _______
________ G. Ratio ______ P.Ratio ______
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F2 Monohybrid Cross Review

• Homozygous x heterozygous(hybrid)
• Offspring___ ___________ rr___ ___________
  Rr
• Phenotypic Ratio is ______

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Practice Your Crosses

• Work the P1, F1, and both F2 Crosses for each of
  the other Seven Pea Plant Traits

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Dihybrid Cross

• A breeding experiment that tracks the __________
  of ______ traits.
• Mendels Law of ______________ ____________
• Each pair of alleles segregates _______________
  during gamete formation

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Dihybrid Cross

• Traits Seed shape Seed color
• Alleles R round Y yellow r
  wrinkled y green

RrYy x RrYy
___ ___ ___ ___
___ ___ ___ ___
All possible gamete combinations
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Dihybrid Cross
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Dihybrid Cross
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Dihybrid Cross
Round/Yellow 9Round/green
3wrinkled/Yellow 3wrinkled/green 1 9331
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Non-Mendelian Inheritance
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Incomplete Dominance

• ____ _____________ have an appearance somewhat in
  __________ the phenotypes of the two __________
  varieties.
• Example snapdragons (flower)
• red (RR) x white (RR)
• __ __ red flower
• __ __ white flower

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Incomplete Dominance
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Incomplete Dominance
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Codominance

• ______ _______ are expressed in __________
  individuals.
• Example blood type
• 1. type A ____ or ____
• 2. type B ____ or ____
• 3. type AB ____
• 4. type O ____

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Codominance Problem

• Example homozygous male Type B (____)
• x heterozygous female Type A
  (____)

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Another Codominance Problem

• Example male Type O (_____)
  x female type AB (_____)

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Codominance

• QuestionIf a boy has a blood type O and his
  sister has blood type AB, what are the
  genotypes and phenotypes of their parents?
• boy - type O (______)
• X girl - type AB (______)

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Codominance

• Answer

Parents genotypes ____ and ____ phenotypes
____ and ____
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Sex-linked Traits

• Traits (genes) located on the ________
  chromosomes
• Sex chromosomes are ___ and ___
• _____ genotype for females
• _____ genotype for males
• Many _____-_______ _______ carried on X chromosome

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Sex-linked Traits
Example Eye color in fruit flies
Sex Chromosomes
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Sex-linked Trait Problem

• Example Eye color in fruit flies
• (red-eyed male) x (white-eyed female) _____
  x _____
• Remember the Y chromosome in males does not
  carry traits.
• RR red eyed
• Rr red eyed
• rr white eyed
• Xy male
• XX female

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Sex-linked Trait Solution
50 _____ _____ female 50 _____ _____ male
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Female Carriers
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• Color blindness is a sex-linked trait that is
  carried on the X chromosome. If a boy is born
  color-blind, what would have to be true?
• A. His father had normal vision.
• B. His grandmother was colorblind.
• C. His mother carried at least one
• gene for color blindness.
• D. His grandfather passed on the
• color-blind trait to his father.

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Pedigrees

• Are a tool for tracking __________ through
  families.
• You can sometimes determine a persons genotype
  by their ____________________.
• Cystic fibrosis is a disease that only affects
  people with the ________________ ________________
  genotype.
• If a child has Cystic Fibrosis
  and the parents do not,
  what
  are the genotypes
  of the family members?

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Pedigree Symbols
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Pedigree Cystic Fibrosis (Recessive)
How to number individuals
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Pedigree Cystic Fibrosis (Recessive)
Start with the recessive individuals!
Cc
Cc
cc
cc
Cc
cc
Cc
Cc
cc
cc
cc
Cc
cc
Cc
cc
Then work from the bottom up!
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Pedigree Huntingtons Disease (Dominant)
Start with the recessive individuals!
hh
Hh
hh
hh
Hh
Hh
hh
hh
hh
Hh
Hh
Hh
hh
hh
Hh
Hh
Hh
Hh
Hh
Hh
Then work from the bottom up!
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The pedigree below represents a family in which
some members have the sickle cell allele.

• In the genetic pedigree, person U and her husband
  are considering having another child. What is the
  percent chance that this child will develop
  sickle cell disease?
• A. 25 B. 50
• C. 75 D. 100

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The pedigree below represents a family in which
some members have the sickle cell allele.

• Which person on the pedigree could not pass the
  allele for sickle cell disease to his/her
  offspring?
• A. V B. X
• C. Y D. Z

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The pedigree below shows the inheritance pattern
of a recessive allele (z) that results in a
genetic disease.

• Based on the inheritance pattern, what are all
  the possible genotypes for individual 6?
• A. Zz
• B. ZZ and zz
• C. ZZ and Zz
• D. ZZ, Zz and zz