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

CHAPTER 14 THE 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 XX Y 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

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.

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

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

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

Concept Map Section 14-1 Autosomol Disorders caused by Recessive alleles Dominant alleles Codominant alleles include include include Albinism Galactosemia Tay-Sachs disease Huntington’s disease Sickle cell disease Cystic fibrosis Phenylketonuria Achondroplasia Hypercholes- 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 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