CHAPTER%207%20EXTENDING%20MENDELIAN%20GENETICS

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CHAPTER 7 EXTENDING MENDELIAN GENETICS
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SECTION 1 CHROMOSOMES AND PHENOTYPES

• Two copies of each autosomal gene affect
  phenotype.
• One copy comes from the Father, the other from
  the mother
• ? What cellular process forms gamete cells?
  (aka haploid cells?)
• Some disorders are caused by recessive alleles.
• The Heterozygous form of these conditions are
  known as CARRIERS because they do not portray the
  disease, but can pass it on to the next
  generation.

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DISORDERS CAUSED BY ALLELE COMBINATIONS

• Recessive
• ex. Sickle Cell Anemia

• Dominant
• ex. Huntingtons disease

• Homozygous recessive to have the disease/disorder
• The Heterozygous form of these conditions are
  known as CARRIERS because they do not portray the
  disease, but can pass it on to the next
  generation.

• less common than recessive disorders.
• Since caused by a dominant allele, there is a 50
  chance of the next generation having the disease.

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SEX LINKED TRAITS

• Sex chromosomes the X and Y
• Females XX, Males XY
• In X-linked traits
• women can be carriers, normal, or affected
• males are either affected or not since they have
  only 1 X
• In Y-Linked traits
• Only seen in males, and all the males in a family
  will be affected from father to son.
• The X chromosome is SUPER HUGE as compared to
  the Y chromosome and must be present in either
  sex.

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X CHROMOSOME INACTIVATION

• X chromosome is HUGE, and in cats controls color.
• The cells randomly turns one of the Xs off
  allowing one color to show through.
• The Turned off X is called a BARR BODY.
• This is how you get calico cats! ?

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PATTERNS OF INHERITANCE REVIEW

• Incomplete dominance-
• occurs when neither of the dominant nor the
  recessive allele is masked during the
  heterozygous stage.
• The phenotypes seem to BLEND
• Codominance-
• both alleles of a gene are expressed completely,
  neither is dominant or recessive.
• Polygenic traits- ex skin color, eye color,etc
• phenotype that is controled by two or more genes.
• Epistasis occures when there is one gene that can
  mask/ interfere with ALL the rest. Example
  Albinism

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POP QUIZ

• What term do we use when there is a blending of
  phenotypes due to the heterozygous genotype? ex
  white, pink, Red
• INCOMPLETE DOMINANCE
• What term is used to describe the state where
  BOTH alleles are expressed completely, where
  neither is dominant or recessive?
• CODOMINANCE
• What term is used to describe a trait that is
  controlled by two or more genes?
• POLYGENIC TRAIT

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POP QUIZ

• 4. What do we call the polygenic gene that can
  mask all the rest?
• Epistatic gene
• 5. What is the term used to describe the X
  chromosome that has been turned off in female
  cells?
• Barr Body
• 6. Why are dominant trait disorders less common
  in a population than recessive trait disorders?
• Dominant trait disorders generally cause server
  damage and death for the creature, generally
  before it can pass on its genetic information

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POP QUIZ BONUS

• Sunlight can cause a persons hair to become
  lighter in color. Is this an example of an
  interaction between genes and the environment?
  Why or why not?
• YES! because phenotype is altered by environment
• Give an example of a trait that is considered to
  be polygenic.
• Eye color, skin color, etc

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HOME WORK

• Read Chapter 7 sections 3 4 pages 209 217
• Screen notes assignment Part one
• Fold your 2 pieces of notebook paper so that each
  side has 6 boxes.
• Everytime you come to a BOLD BLUE or BLACK
  paragraph heading you will do the following.
• In the LEFT BOX you will write the page number
  and notes to sum up that section.
• minimum of 12-15 words!
• In the RIGHT box you will sketch a picture to
  illustrate what you wrote in the left box.
  Something to help you remember it.
• You must have 8 box sets of words pictures.
• Part two Investigation on page 219 s 1-4, must
  show work and use COMPLETE SENTENCES!!!

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GENE LINKAGE ,MAPPING, PEDIGREES

• chapter 7 sections 34

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THOMAS HUNT MORGAN AND HIS FRUIT FLYS

• Gene linkage was first studied by Morgan in fruit
  flies because they were easy to raise and had few
  characteristics to easily study.
• He expected the Mendelian 9331 ratio but his
  results did not always follow that.
• He observed that some of the triats seemed to be
  inherited together in four groups.
• we later learned that they only had four
  chromosomes
• He called these genes LINKED GENES because they
  were on the same chromosome, and found out that
  the CHROMOSOMES not the GENES assorted
  independently during meiosis.

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• He called these genes LINKED GENES because they
  were on the same chromosome, and found out that
  the CHROMOSOMES not the GENES assorted
  independently during meiosis.
• He also concluded that chromosomes must exchange
  homologous genes during meiosis CROSSING OVER

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LINKAGE MAPS

• Are used to estimate distances between genes.
• The CLOSER together two genes are, the MORE
  likely they will be inherited together.
• The FARTHER apart two genes are, the LESS likely
  they will be inherited together.
• On a linkage map, one map unit is equal to one
  cross-over for each 100 offspring, or one point.

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MAP CHALLENGE USE THE DATA BELOW TO ANSWER THE
QUESTIONS

• Gene A and B cross over 6.0 of the time.
• Gene B and C cross over 12.5 of the time.
• Gene A and C cross over 18.5 percent of the time.
• Which two genes are closest together?
• Which two genes are farthest apart?
• Draw a map showing the location of each gene and
  its / map unit distance from the next.
• ex. ______A__________B__C_________
• 25 2
• so A to C 27

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PEDIGREES

• Human genetics, or any mammals genetics follow a
  set of patterns that can be easily recorded in
  pedigrees.
• A Pedigree is a chart that can help trace the
  phenotypes and genotypes in a family for a
  particular trait.
• Autosomal traits are easily traced since the
  traits will follow a Mendelian punnett square.
• Sex linked traits leave a distinct pattern that
  requires the observed to remember if the trait is
  dominant or recessive, X-linked or Y linked

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• squares male
• circles females
• Half filled means carrier
• Filled means affected

I
A
II
B
III
C
Give the Genotypes for IA, IIB, and IIIC
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KARYOTYPES

• Are pictures of ALL the chromosomes in a cell.
• Chemical stains produce a pattern of stains on
  the chromosomes to help identify them.
• Karyotypes can be used to show whole or partial
  chromosome deletions or additions.
• Ex. Downs syndrome is caused by an extra 21
  chromosome.

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HOMEWORK

• Complete the at home investigation on page 219.
  Answer ALL the Analyze and conclude questions.
  (1-4)