14-1 HUMAN HEREDITY14-2 HUMAN CHROMOSOMES14-3 HUMAN MOLECULAR

GENETICS

CH 14: THE HUMAN GENOME

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

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

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

X X

X XX XX

Y XY XY

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

PEDIGREE CHARTS A PEDIGREE CHART SHOWS

RELATIONSHIPS WITHIN FAMILIES GENETIC COUNSELORS USE THEM

TO DETERMINE GENOTYPES OF FAMILY MEMBERS

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 completely shaded circle or square indicates that a person expresses 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.

Section 14-1

Figure 14-3 A Pedigree

Pedigree Practice http://www.zerobio.com/drag_gr11/pedigree/pedigree_overview.htm

GENES AND THE ENVIRONMENT MANY GENES

ARE STRONGLY INFLUENCED BY THE ENVIRONMENT NUTRITION

AND EXERCISE

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

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

Phenotype(Blood Type Genotype

Antigen on Red Blood Cell

Safe Transfusions

To From

Section 14-1

Figure 14-4 Blood Groups

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

RECESSIVE ALLELES MANY HUMAN GENES HAVE BECOME

KNOWN THROUGH THE STUDY OF GENETIC DISORDERS

SOME EXAMPLES ARE:

SOME AUTOSOMAL RECESSIVE DISORDERS IN HUMANS

ALBINISM LACK OF PIGMENT IN SKIN, HAIR, AND EYES

CYSTIC FIBROSIS EXCESS MUCUS IN LUNGS, AND DIGESTIVE TRACT

GALACTOSEMIA BUILD UP OF GALACTOSE (SUGAR) IN TISSUES; MENTAL RETARDATION AND LIVER DAMAGE

PHENYLKETONURIA

BUILD UP OF PHENYLALANINE IN TISSUES; MENTAL RETARDATION

TAY-SACHS LIPID BUILD UP IN BRAIN; DEATH IN EARLY CHILDHOOD

SOME AUTOSOMAL DOMINANT DISORDERS IN HUMANS

ACHONDROPLASIA DWARFISM

HUNTINGTON’S DISEASE

MENTAL DETERIORATION AND UNCONTROLLABLE MOVEMENTS: ONSET OVER AGE 35

HYPERCHOLESTEROLEMIA

EXCESS CHOLESTEROL IN BLOOD: HEART DISEASE

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

caused by

Section 14-1

includeincludeinclude

Concept Map

AutosomolDisorders

Recessive alleles

Dominant allelesCodominant

alleles

Albinism Galactosemia Tay-Sachs disease

Huntington’s disease

Sickle cell disease

Cystic fibrosis

Phenylketonuria AchondroplasiaHypercholes-

terolemia

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

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

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

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 – 2.4 MILLION BASE

PAIRS (Dystrophin-associated with Muscular Dystrophy)

HUMAN GENES AND CHROMOSOMES CHROMOSOME #21: CONTAINS 225 GENES ALS – LOU GEHRIG’S

DISEASE

CHROMOSOME #22: CONTAINS 545 GENES LEUKEMIA, AND

TUMOR-CAUSING DISEASE

SEX-LINKED GENES SEX-LINKED GENES – GENES

LOCATED ON SEX CHROMOSOMES

GENETIC DISORDERS FOUND ON THE X CHROMOSOME

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.html

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

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

CHROMOSOMAL DISORDERS DUE TO NONDISJUNCTION – AN

ERROR IN MEIOSIS IN WHICH HOMOLOGOUS CHROMOSOMES FAIL TO SEPARATE

RESULTS IN ABNORMAL CHROMOSOME NUMBER

NONDISJUNCTION IN DAUGHTER CELLS

CHROMOSOMAL DISORDERS DOWN SYNDROME

– “TRISOMY 21” – HAVING 3 COPIES OF CHROMOSOME 21 RESULTING IN MILD TO SEVERE MENTAL RETARDATION

SEX CHROMOSOME DISORDERS TURNER’S SYNDROME - FEMALES

WHO INHERIT 1 SEX CHROMOSOME (X)

STERILE, SEX ORGANS DO NOT DEVELOP AT PUBERTY

KLINEFELTER’S SYNDROME – MALES WHO INHERIT 3 SEX CHROMOSOMES (XXY)

CANNOT REPRODUCE

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

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

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

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

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

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

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