CHAPTER 14 THE HUMAN GENOME

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CH 14 THE HUMAN GENOME
14-1 HUMAN HEREDITY 14-2 HUMAN CHROMOSOMES 14-3
HUMAN MOLECULAR GENETICS
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CHAPTER 14THE HUMAN GENOME

• 14-1 - HUMAN CHROMOSOMES
• WHAT MAKES US HUMAN? LOOK INSIDE CELLS
  CHROMOSOMES ARE PRESENT
• CHROMOSOMES ARE PHOTOGRAPHED DURING MITOSIS
• A KARYOTYPE IS A PICTURE OF CHROMOSOMES ARRANGED
  INTO PAIRS
• KARYOTYPING ACTIVITY

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HUMAN CHROMOSOMES

• THERE ARE 46 CHROMOSOMES IN OUR BODY CELLS
• THEY ARE ARRANGED INTO 23 PAIRS
• THE 23RD PAIR IS CALLED THE SEX CHROMOSOMES
• THE REMAINING 22 PAIRS ARE CALLED AUTOSOMES
• FEMALE 46XX AND MALE 46XY

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HUMAN CHROMOSOMES

• EACH EGG CELL CARRIES ONE X CHROMOSOME (23 X)
• HALF THE SPERM CARRY AN X CHROMOSOME (23 X) AND
  HALF CARRY A Y CHROMOSOME (23 Y)
• THEREFORE, MALES DETERMINE THE SEX OF THE CHILD

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HUMAN TRAITS

• HUMAN TRAITS ARE INHERITED ACCORDING TO THE SAME
  PRINCIPLES THAT MENDEL DISCOVERED WITH HIS PEAS.
  
• NOT ALL TRAITS ARE INHERITED SOME ARE INFLUENCED
  BY THE ENVIRONMENT
• TO DETERMINE IF INHERITED, ONE MUST STUDY HOW THE
  TRAIT IS PASSED ON FROM GENERATION TO GENERATION

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PEDIGREE CHARTS

• A PEDIGREE CHART SHOWS RELATIONSHIPS WITHIN
  FAMILIES
• GENETIC COUNSELORS USE THEM TO DETERMINE
  GENOTYPES OF FAMILY MEMBERS

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Figure 14-3 A Pedigree
Section 14-1
A circle represents a female.
A square represents a male.
A horizontal line connecting a male and female
represents a marriage.
A vertical line and a bracket connect the parents
to their children.
A half-shaded circle or square indicates that a
person is a carrier of the trait.
A circle or square that is not shaded indicates
that a person neither expresses the trait nor is
a carrier of the trait.
A completely shaded circle or square indicates
that a person expresses the trait.
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Pedigree Practice

• http//www.zerobio.com/drag_gr11/pedigree/pedigree
  _overview.htm

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GENES AND THE ENVIRONMENT

• MANY GENES ARE STRONGLY INFLUENCED BY THE
  ENVIRONMENT
• NUTRITION AND EXERCISE

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HUMAN GENES

• OUR HUMAN GENOME OUR COMPLETE SET OF GENETIC
  INFORMATION INCLUDES OVER TENS OF THOUSANDS OF
  GENES
• ONE OF THE FIRST GENES TO BE IDENTIFIED WERE
  THOSE THAT CONTROL BLOOD TYPE

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BLOOD GROUP GENES

• RECALL THAT THERE ARE 3 ALLELES THAT CONTROL
  BLOOD TYPE A,B,O
• A IS DOMINANT TO O
• B IS DOMINANT TO O
• O IS RECESSIVE
• A AND B ARE CODOMINANT MEANING BLOOD TYPE AB

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Figure 14-4 Blood Groups
Section 14-1
Safe Transfusions
Antigen on Red Blood Cell
Phenotype (Blood Type
Genotype
From
To
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BLOOD GROUP GENES

• Rh BLOOD GROUP DETERMINED BY SINGLE GENE
• CAN BE POSITIVE OR NEGATIVE
• Rh/Rh OR Rh/Rh- ARE Rh POSITIVE INDIVIDUALS
• Rh-/Rh- ARE Rh NEGATIVE INDIVIDUALS

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RECESSIVE ALLELES

• MANY HUMAN GENES HAVE BECOME KNOWN THROUGH THE
  STUDY OF GENETIC DISORDERS
• SOME EXAMPLES ARE

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SOME AUTOSOMAL RECESSIVE DISORDERS IN HUMANS
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SOME AUTOSOMAL DOMINANT DISORDERS IN HUMANS
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AUTOSOMAL DISORDER CAUSED BY CODOMINANT ALLELES

• SICKLE CELL DISEASE SICKLE RED BLOOD CELLS
  DAMAGE TO MANY TISSUES
• SS NORMAL
• Ss SOME CELLS SHAPED LIKE SICKLES
• ss SICKLE CELL ANEMIA

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Concept Map
Section 14-1
Autosomol Disorders
caused by
include
include
include
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FROM GENE TO MOLECULE

• A SMALL CHANGE IN THE DNA OF A SINGLE GENE
  AFFECTS THE STRUCTURE OF A PROTEIN CAUSING A
  SERIOUS GENETIC DISORDER
• TWO EXAMPLES TAY SACHS DISEASE AND SICKLE CELL
  DISEASE

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CYSTIC FIBROSIS

• CAUSED BY RECESSIVE ALLELE ON CHROMOSOME 7
• THICK, HEAVY MUCUS THAT CLOGS LUNGS
• MOST CASES CAUSED BY DELETION OF 3 BASES IN A
  PROTEIN

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SICKLE CELL DISEASE

• COMMON GENETIC DISORDER FOUND IN AFRICAN
  AMERICANS
• SICKLE CELLS GET STUCK IN THE BLOOD VESSELS
  CAUSING DAMAGE TO BRAIN, HEART, AND SPLEEN
• PROTEIN HEMOGLOBIN IS ALTERED
• ONE DNA BASED IS CHANGED CAUSING AMINO ACID
  GLUTAMIC ACID TO SUBSTITUTE AMINO ACID VALINE

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14-2 HUMAN CHROMOSOMES

• FACTS ABOUT DNA AND CHROMOSOMES
• 1 CELL CONTAINS 6 BILLION BASE PAIRS
• ONLY 2 OF YOUR DNA FUNCTIONS AS GENES
• AVERAGE HUMAN GENE IS 3000 BASE PAIRS
• LARGEST GENE 2 MILLION BASE PAIRS

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HUMAN GENES AND CHROMOSOMES

• CHROMOSOME 21
• CONTAINS 225 GENES
• ALS LOU GEHRIGS DISEASE
• CHROMOSOME 22
• CONTAINS 545 GENES
• LEUKEMIA, AND TUMOR-CAUSING DISEASE

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SEX-LINKED GENES

• SEX-LINKED GENES GENES LOCATED ON SEX
  CHROMOSOMES
• GENETIC DISORDERS FOUND ON THE X CHROMOSOME

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SEX-LINKED RECESSIVE DISORDERS

• COLORBLINDNESS UNABLE TO DISTINGUISH CERTAIN
  COLORS MOSTLY RED-GREEN
• XCXC NORMAL FEMALE
• XC Xc CARRIER FEMALE
• Xc Xc COLORBLIND FEMALE
• XCY NORMAL MALE
• XcY COLORBLIND MALE
• http//www.toledo-bend.com/colorblind/Ishihara.htm
  l

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SEX-LINKED RECESSIVE DISORDERS

• HEMOPHILIA A PROTEIN MISSING FOR NORMAL BLOOD
  CLOTTING
• CAN BE TREATED WITH INJECTIONS OF NORMAL CLOTTING
  PROTEINS
• http//www.ygyh.org/hemo/whatisit.htm

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SEX-LINKED RECESSIVE DISORDERS

• DUCHENNE MUSCULAR DYSTROPHY DISORDER THAT
  RESULTS IN WEAKENING AND LOSS OF SKELETAL MUSCLE
• CAUSED BY A DEFECTIVE GENE THAT CODES FOR MUSCLE
  PROTEIN

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CHROMOSOMAL DISORDERS

• DUE TO NONDISJUNCTION AN ERROR IN MEIOSIS IN
  WHICH HOMOLOGOUS CHROMOSOMES FAIL TO SEPARATE
• RESULTS IN ABNORMAL CHROMOSOME NUMBER

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CHROMOSOMAL DISORDERS

• DOWN SYNDROME TRISOMY 21 HAVING 3 COPIES OF
  CHROMOSOME 21 RESULTING IN MILD TO SEVERE MENTAL
  RETARDATION

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SEX CHROMOSOME DISORDERS

• TURNERS SYNDROME - FEMALES WHO INHERIT 1 SEX
  CHROMOSOME (X)
• STERILE, SEX ORGANS DO NOT DEVELOP AT PUBERTY
• KLINEFELTERS SYNDROME MALES WHO INHERIT 3 SEX
  CHROMOSOMES (XXY)
• CANNOT REPRODUCE

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14-3 HUMAN MOLECULAR GENETICS

• HUMAN DNA ANALYSIS
• WAYS THAT BIOLOGISTS SEARCH THE HUMAN GENOME
• TESTING FOR ALLELES GENETIC TESTS THAT SCREEN
  FOR DIFFERENCES IN THE DNA CODE

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DNA FINGERPRINTING

• NO TWO INDIVIDUALS (EXCEPT FOR IDENTICAL TWINS)
  HAVE THE SAME DNA
• DNA FINGERPRINT ANALYZES SECTIONS OF DNA THAT
  VARY FROM INDIVIDUAL TO INDIVIDUAL

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HOW A DNA FINGERPRINT WORKS

• DNA IS CUT WITH RESTRICTION ENZYMES
• DNA IS SEPARATED BYSIZE USING GEL ELECTROPHORESIS
  
• VARIABLE REGIONS ARE DETECTED USING A DNA PROBE
• DNA SAMPLES CAN BE OBTAINED THROUGH BLOOD, SPERM,
  HAIR

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HUMAN GENOME PROJECT

• HGP AN EFFORT TO ANALYZE THE HUMAN DNA SEQUENCE
• OTHER ORGANISMS HAVE ALREADY BEEN SEQUENCED E.
  coli, YEAST, AND THE FRUIT FLY.
• IN JUNE 2000 HGP WAS ESSENTIALLY COMPLETE

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HUMAN GENOME PROJECT

• SEARCHING FOR GENES HUMANS HAVE ABOUT 25,000
  FUNCTIONING GENES
• THE FRUIT FLY HAS 14,000 GENES AND A TINY WORM
  ABOUT 20,000 GENES

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HUMAN GENOME PROJECT

• RESEARCH GROUPS AROUND THE WORLD ARE ANALYZING
  INFORMATION IN THE DNA SEQUENCE LOOKING FOR
  GENES THAT MAY PROVIDE CLUES TO THE PROPERTIES OF
  LIFE
• UNDERSTANDING THEIR STRUCTURE MAY BE USEFUL IN
  DEVELOPING NEW DRUGS AND TREATMENTS FOR DISEASES

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GENE THERAPY

• GENE THERAPY WHEN AN ABSENT OR FAULTY GENE IS
  REPLACED BY A NORMAL FUNCTIONING GENE
• FIRST USED IN 1990
• IN 1999, CELLS FROM A YOUNG GIRL WERE REMOVED,
  MODIFIED IN A LAB, AND INSERTED BACK IN THE BODY
  - CURED