Genetics

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Genetics
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Section 2 vocabulary

• 1. Genetics
• 2. Allele alternate forms of the gene
• 3. Dominant appears in the F1
• 4. Recessive not present in the F1
• 5. Homozygous same alleles
• 6. Heterozygous different alleles
• 7. Genotype alleles
• 8. Phenotype physical
• 9. Law of segregation
• 10. Hybrid
• 11. Law of independent assortment

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• Additional Vocabulary

monohybrid cross true-breeding P generation F1
generation F2 generation Punnett square test
cross probability pedigree sex-linked gene
polygenic inheritance incomplete dominance
multiple alleles codominance
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The Father of Genetics!

• Genetics the science of heredity.
• Gregor Mendel

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Gregor Johann Mendel (1822 - 1884) was a member
of an Augustinian order (Monastic) in Brunn
Austria
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Mendel began studying plant breading by trying to
find the effects of crossing different strains of
common garden pea

• He carried out his research with more precision
  than had yet been used. He also used the new
  science of statistics to analyze the results of
  his experiments. This use of mathematics to
  describe biological phenomena was a new concept.

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• Gregor Mendel bred varieties of the garden pea in
  an attempt to understand heredity.
• Mendel observed that contrasting traits appear in
  offspring according to simple ratios.

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allele

• Alternate forms of a gene
• Such as blue, brown or green for the eye color
  gene
• Or yellow and
• green for
• pea color

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Phenotype

• The observable or outward expression of the
  allele pair that an organism has what it looks
  like.

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genotype

• The organisms allele pairs what genes it has
  to produce the outward appearance it has.

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Homozygous genotype

• An organism with two of the same alleles for a
  trail. Both alleles are the same

Dominant
Recessive
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Heterozygous genotype

• An organism with 2 different alleles for a trait.

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Hybrid 279

• Heterozygous genotypes

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Monohybrid crosses

• Two parents differ by only one trait.
• Height tall or short
• or
• smooth/ wrinkled
• Green/ yellow

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Monohybrid traits
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Monohybrid crosses
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Results of a monohybrid crossfirst generation F1

• One of the characteristics would kind of take
  over the other and the offspring would all look
  like only one of the parents.
• Example green and yellow
• All offspring were yellow!

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Second generation F2

• When the parents from the F1 are crossed.
• Yellow X Yellow
• ¾ were Yellow but ¼ was green .
• The green trait reappeared!!!!

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• Mendel collected 6022 yellow peas and 2001 green.
• this was almost a perfect 31 ratio of yellow
  green
• He studied several traits and each gave this
  ratio!

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F2 generation
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What did Mendel learn from this?

• Each organism has two factors for each of its
  traits.
• Factors are forms of the Genes on chromosomes.
• These are the alleles

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alleles

• An alternative form of a single gene passed from
  generation to generation.
• Example the yellow or the green form of the
  color of peas are each alleles of the gene for
  the color of peas.

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• In Mendels experiments, only one of the two
  contrasting forms of a character was expressed in
  the F1 generation.
• The other form reappeared in the F2 generation
  in a 31 ratio

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• Factors are Genes on chromosomes
• Forms are called alleles

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Rule of Dominance

• By definition,
• the trait that shows up in the F1 generation is
  dominant
• the trait that disappears is recessive

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What do these mean?

• P
• F1
• F2

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Out of Mendel's work came two "Laws" of
inheritance

• 1) Mendel proposed that heredity was controlled
  by paired factors that segregated when gametes
  formed and rejoined at fertilization and,
• 2) The principle of independent assortment
  indicates that the segregation of one pair of
  factors, or Alleles, has no influence over the
  way any other pair segregates.

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Gregor Mendel approached problem-solving in new
and different ways.
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• 1. He worked with pure strains of garden peas.
• The flowers have both male (stamen- anther and
  filaments) and female (pistil- stigma, style and
  ovary) reproductive parts.

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• He removed (emasculated) the male part (anthers
  and filaments that produce the male sex cells) so
  he could control the way each plant was
  fertilized.
• This was done artificially by mechanically
  transferring the male sex cells from the desired
  plant to the stamen of the emasculated plant.
• The offspring using this procedure are referred
  to as "crosses".

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• 2. He only worked with traits of the peas that
  could easily be seen.
• He experimented using only one trait at a time.
• Traits included a) stem length, b) flower color
  or c) seed shape.

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• 3. Mendel kept detailed records of his "crosses".
  
• He counted the pea offspring and calculated,
  using mathematics, how often the trait occurred
  in the offspring.

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• Mendel believed that traits were determined by
  individual units called factors.
• He believed that each offspring received a factor
  from each parent.
• Today these factors are called genes.

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Punnett Squares
Dad Mom Allele allele
Allele
Allele

• The square shows how the alleles separate when
  gametes are formed.
• It shows the possible combinations of the alleles
  when fertilization occurs.

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Punnett Square

• G green peas g yellow peas
• pure breed green

G G
g
g
Pure breed yellow
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What are the results?

• 100 are phenotype green
• 100 are genotype heterozygous

4/4
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Both parents are heterozygous genotype and
brown hair phenotype



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What are the results?
Brown hair
blonde hair
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Chances for Genotypes
1/4
1/4
2/4
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Chances for Phenotypes
¾ Brown
¼ blonde
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Flower color

• R red
• r white

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Mendel's First Law Law of Segregation

• Mendel guessed that the TWO genes for flower
  color separate or segregate, when the sex cells
  form during meiosis.
• In the case of the hybrid pea flowers (RR), each
  plant would have one gene (allele) for red color
  (R) and one gene (allele) for white color (r).
• These two genes would separate or segregate from
  each other during the formation of the sex cells.
  About half of the sex cells would receive the
  gene for red color and the other half the gene
  for white color.

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Meiosis/ sex cell formation
Sperm cells each get one allele
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Mendel's Law of Segregation states-

• The two genes that determine a particular trait
  will separate when sex cells form.
• Half of the cells will receive one gene (allele)
  and half of the cells will receive the other gene
  (allele) of the allelic pair.

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Law of segregation
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• _ The law of segregation states that the two
  alleles for a gene separate when gametes are
  formed.

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Mendel's Second Law

• - the law of independent assortment
• Random distribution of alleles occurs during
  gamete formation. Genes on separate chromosomes
  sort independently during meiosis.
• during gamete formation the segregation of the
  alleles of one allelic pair is independent of the
  segregation of the alleles of another allelic
  pair

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• The law of independent assortment states that two
  or more pairs of alleles separate independently
  of one another during gamete formation.

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In other words

• Where the allele for color goes is not connected
  to where the gene for height goes.

Color r
Color R
Height T
Height t
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R
r
r
R
T
T
t
t
t
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Mendels Theory

• _ Different versions of a gene are called
  alleles. An individual usually has two alleles
  for a gene, each inherited from a different
  parent.

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• _ Individuals with the same two alleles for a
  gene are homozygous those with two different
  alleles for a gene are heterozygous.

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Studying Heredity

• _ The results of genetic crosses can be predicted
  with the use of Punnett squares and
  probabilities.
• _ A test cross can be used to determine whether
  an individual expressing a dominant trait is
  heterozygous or homozygous.
• _ A traits pattern of inheritance within a
  family can be determined by analyzing a pedigree.

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Linked genes

• Unless. The genes are located on the same
  chromosome and then they are called linked genes
  and they do travel together to the same gamete.

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Genes on the same chromosome will always travel
together into the same gamete

• red hair r
• freckles f

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2 traits

• Dihybrid cross
• When you look at two traits at a time the Punnett
  square gets bigger because the possible
  combinations get bigger!

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dihybrid

• A attached ears
• a unattached ears
• B brown hair
• b blonde hair
• So when we look at the chances of getting two
  traits the possibilities increase

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Heterozygous hybrid

• So 2 pure breed parents for both traits would be
• P generation AABB X aabb
• All of the kids would be AaBb

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Dihybrid cross means hybrid for two traits so

• F1 generation
• AaBb X AaBb
• What are the possible combinations of gametes?
• Remember the law of segregation only one letter
  or allele for a trait.
• Only A or a but not both!

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A
a
B
b

• The gene alleles for attached or unattached ears
  must segregate from each other during meiosis.
• In other words. You will only have one or the
  other in the gametes.

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a
B
b
A

• The same is true for the alleles for hair color.
• gametes

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Possible gametes

• AB
• Ab
• aB
• ab

A
a
B
b
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Place the possible gametes on the sides of the
square
AB
Ab
aB
ab




AB
Ab
Which becomes AABB
aB
ab
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What are the phenotypic results?

• ___/16 attached ears and brown hair
• ___/16 attached ears and blonde hair
• ___/16 unattached ears and brown hair
• ___/16 unattached ears and blonde hair

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You always get

• 9331

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The genotypic results?

• Homozygous dominant for both traits ___/16
• Heterozygous for both traits
  ___/16
• Homo recessive for both traits ___/16
• Homo dominant for first hetero for 2nd ___/16
• Homo recessive for 1st hetero for 2nd ___/16
• Homo recessive for 1st homo dom 2nd ___/16
• Hetero for 1st homo/dom for 2nd ___/16
• Hetero for 1st homo rec for 2nd ___/16
• Complete the list

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Reflections

• The genetics questions will be part of your
  reflections for benchmark 16.1
• After completing them and checking your answers
  tomorrow, write a statement about your level of
  understanding . Can you do them? Which types do
  you still have trouble with? Have you studied the
  vocabulary? Do you understand the question, how
  to set up the question? Be specific so I know how
  to help you! These will be due after we go over
  the answers to the problems!

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Corn Questions

• Write the answers on your own paper.
• Draw the punnett squares.

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Now that you have determined the predicted
percentages of phenotypes and genotypes, you will
examine an ear of corn resulting from two
heterozygous parents and compare the observed
percentage to the predicted percentage.

• Procedure Count the number of red and yellow
  kernels on the ear of corn pictured below. Count
  FIVE rows of kernels. Record the numbers of red
  kernels, yellow kernels, and total kernels.

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Analysis

• Calculate the percentage of red and yellow
  kernels from your data.
• Compare your observed percentages with the
  theoretical percentage you predicted from the
  Punnett Square you completed in Part A, 4.
• Hypothesize Would you have calculated the same
  ratio if you had counted only half the kernels on
  the ear of corn above? Explain.
• Apply How could you determine whether a
  particular red kernel is homozygous dominant or
  heterozygous? Hint Look at the Punnett squares
  in Part A.
• This is due today!

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Do the Worksheet 1 Monohybrid cross questions.

• Write the answers on your own paper.
• Draw punnett squares for each question to show
  your work.
• Use the following letters for each question.
• 1. Cc
• 2. Gg
• 3. Bb
• 4. Bb
• 5. Aa
• 6. Ff
• 7. Ll
• 8. Y yellow y grey
• 9. P p
• 10. B b
• These are due tomorrow!

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Reflections

• The genetics questions will be part of your
  reflections for benchmark 16.1
• After completing them and checking your answers
  tomorrow, write a statement about your level of
  understanding . Can you do them? Which types do
  you still have trouble with? Have you studied the
  vocabulary? Do you understand the question, how
  to set up the question? Be specific so I know how
  to help you!

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Section 3

• Section 3 vocabulary
• Genetic recombination
• Polyploidy

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Genetic recombination

• New combinations of genes produced by crossing
  over and independent assortment.
• Add variations
• 2n n is the number of chromosome pairs

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Gene linkage

• Genes close together on the same chromosome are
  said to be linked and travel together!
• These are exceptions to the independent
  assortment law!

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• Crossing over happens more when genes are far
  apart than those that are close together.
• Chromosome maps show the location of genes on
  chromosomes.

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Polyploidy

• One or more sets of chromosomes.
• Triploid organisms 3n have 3 sets
• this is rare in animals but more common in
  plants.
• In humans this is lethal deadly!
• 1/3 plants are polyploids.
• Wheat, oats, sugar are all polyploids, this
  increases their vigor and size.

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polyploid
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Kleinfelder Karyotype
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• Question 1
• Let's say that in seals, the gene for the length
  of the whiskers has two alleles.  The dominant
  allele (W) codes long whiskers the recessive
  allele (w) codes for short whiskers.
• a)  What percentage of offspring would be
  expected to have short whiskers from the cross of
  two long-whiskered seals, one that is homozygous
  dominant and one that is heterozygous? b) If one
  parent seal is pure long-whiskered and the other
  is short-whiskered, what percent of offspring
  would have short whiskers?

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• P-sqARE PraCTice qUesTiON 2
• In purple people eaters, one-horn is dominant and
  no horns is recessive. Draw a Punnet Square
  showing the cross of a purple people eater that
  is hybrid for horns with a purple people eater
  that does not have horns. Summarize the genotypes
  phenotypes of the possible offspring.

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• Question 3
• A green-leafed luboplant (I made this plant up)
  is crossed with a luboplant with yellow-striped
  leaves.  The cross produces 185 green-leafed
  luboplants. Summarize the genotypes phenotypes
  of the offspring that would be produced by
  crossing two of the green-leafed luboplants
  obtained from the initial parent plants.

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P-squARE PRacTice qUeStION 4

• Mendel found that crossing wrinkle-seeded plants
  with pure round-seeded plants produced only
  round-seeded plants.  What genotypic phenotypic
  ratios can be expected from a cross of a
  wrinkle-seeded plant a plant heterozygous for
  this trait (seed appearance)?

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Gene Linkage

• Genes on the same chromosome are linked.
• Linked genes are inherited together.
• Linked genes do not undergo independent
  assortment.
• THEREFORE, MENDELS LAW OF INDEPENDENT ASSORTMENT
  ONLY IS TRUE IF THE GENES ARE ON DIFFERENT
  CHROMOSOMES.
• Studies have shown that linked genes on the same
  chromosome sometimes can separate. This occurs by
  a process called "crossing over".
•  

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Crossing Over

• Occurs at prophase during the first part of
  meiosis (Anaphase I)
• Chromosomes pair before they divide
• Chromosome pairs wind around each other
• Each pair of chromosomes duplicates itself
• Chromosomes break and exchange equal amounts of
  chromosome material. The newly exchanged pieces
  are enzymatically "glued" together.
• Chromosomes separate (to individual chromatids).
  Each chromatid now has different traits or
  genes/alleles.

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Purpose of crossing over

• provides new combinations of genes/alleles
  (traits) in male and female sex cells (gametes)
  so that when fertilization occurs the offspring
  demonstrate increased genotypic and phenotypic
  variability.

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Sex-linked genes

• Genes located on one of the sex chromosomes.
  Usually the X
• Most often expressed in males because they only
  have one X chromosome

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• The inheritance of abnormal genes found on the 22
  pairs of human chromosomes (autosomes) obey the
  principles of Mendelian genetics.

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• The inheritance of abnormal genes on the
  X-chromosomes also are based on Mendel's
  principles.

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Gender issues

• complicate this process only in regard to the Y
  chromosome.
• Males have only one X chromosome whereas females
  have a pair of X-chromosomes. The expression of
  genetic abnormalities in the offspring of
  affected people takes on a new dimension when the
  Y-chromosome is included in the "equation".  

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•  

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• Traits which are determined by one or more genes
  show
• dominance,
• recessiveness,
• sex linkage,
• phenotypes,
• genotypes
• and incomplete dominance

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Complex Patterns of Heredity

• _ Characters usually display complex patterns of
  heredity, such as incomplete dominance,
  codominance, and multiple alleles.
• _

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• Mutations can cause genetic disorders, such as
  sickle cell anemia, hemophilia, and Huntingtons
  disease.
• _ Genetic counseling can help patients concerned
  about a genetic disorder.

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Section 3 vocabulary

• 1. Genetic recombination 2. Polyploidy

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Summary of genetics video

• http//www.bing.com/videos/search?qgeneticvideos
  viewdetailmidE7AEA272F3FDDB885163E7AEA272F3FDD
  B885163first0FORMLKVR19