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Chapter 18 and Chapter 20 Cell division and the Human Life Cycle + Chromosome Disorders
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DNA l INFORMATION IS WRITTEN IN A CHEMICAL LANGUAGE= DNA l OUR CELLS READ THE DNA IN THE NUCLEUS AND FOLLOW THE INSTRUCTIONS WRITTEN ON IT l LONG STRANDS OF DNA ARE CALLED CHROMOSOMES
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CHROMOSOMES l UNROLLED WHEN READ OR COPIED l WE HAVE 2 VERSIONS OF EACH TYPE OF CHROMOSOME (1 FROM MOTHER AND 1 FROM FATHER) l 23 TYPES x 2 VERSIONS= 46 TOTAL l THE 23RD PAIR (TYPE) ARE THE SEX CHROMOSOMES WHICH CONTAIN THE GENES THAT DETERMINE SEX
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CHROMOSOME PROBLEMS l MISTAKES ARE SOMETIMES MADE AS THE EGG AND SPERM ARE BEING MADE l SOMETIMES THE CHROMOSOMES IN THE EGG OR SPERM ARE DAMAGED OR TOO MANY OR TOO FEW CHROMOSOMES END UP IN THE EGG OR SPERM l PROBABLY MOST OF THESE TYPES AF CHROMOSOME ERRORS ARE NOT SURVIVABLE AND END IN A MISCARRAIGE l SOME OF THE EMBRYOS WITH DAMAGED/MISING/EXTRA CHROMOSOMES DO SURVIVE AND DEVELOP BUT WITH PROBLEMS
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CHROM. DISORDERS DOWN SYNDROME- SHORT STATURE, EYELID FOLD, ROUND HEAD, RETARDATION (VARYING LEVEL) ALSO CALLED TRISOMY 21- CAUSED BY AN EXTRA COPY OF CHROMOSOME #21 l MORE COMMON IN CHILDREN BORN TO OLDER MOTHERS
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CRI DU CHAT l FRENCH FOR “CRY OF CAT” l SMALL HEAD, MALFORMED LARYNX l OLDER- MISSHAPEN EARS, RETARDATION l CAUSE= PART OF CHROMOSOME #5 IS MISSING
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SEX CHROMOSOMES l X AND Y- THE 23RD PAIR l WOMEN- XX MEN- XY l EGG- X SPERM- X OR Y l 50/50 CHANCE OF PRODUCING A BOY VS. GIRL
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SEX CHROM. DISORDERS FRAGILE X SYNDROME- DAMAGED X CHROMOSOME l CHILD- HYPERACTIVE, AUTISTIC l ADULT- PROMINENT JAW AND EYES l MALES- RETARDATION MORE COMMON
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WRONG # OF SEX CHROM. XO- TURNER SYNDROME l FEMALE WITH NO SEXUAL CHARACTERISTICS- INFERTILE l SHORT, WEBBED NECK, BROAD CHEST l NORMAL INTELLIGENCE
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XXY- KLINFELTER Male with an extra X chromosome l STERILE MALE WITH LARGE HANDS AND FEET, LONG ARMS AND LEGS, MAY HAVE BREASTS l SOME ARE SLOW LEARNERS
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XXX- TRIPLO- X A female with an extra X chromosome l SOME HAVE MENSTRUAL IRREGULARITIES AND EARLY MENOPAUSE l OTHERS LIVE A NORMAL LIFE
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XYY- JACOB SYNDROME MALE WITH AN EXTRA Y CHROMOSOME l TALL MALE WITH PERSISTENT ACNE l SOME HAVE SPEECH AND READING PROBLEMS
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HUMAN LIFE CYCLE l GROWTH- MITOSIS- SIMPLE CELL DIVISION l SEXUAL REPRODUCTION- UNION OF GAMETES (SPERM AND EGG) l GAMETES HAVE ONLY ONE COPY OF EACH TYPE OF CHROMOSOME l ZYGOTE GETS TWO COPIES (VERSIONS) OF EACH CHROM.
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MITOSIS l THE DIVISION OF ONE BODY CELL INTO 2 IDENTICAL BODY CELLS l NORMAL BODY CELLS ARE DIPLOID (2N) l 2N 2N + 2N l 5 STEPS
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INTERPHASE l SOME CELLS STAY IN THIS PHASE FOREVER (example- brain and spinal cord cells- these are not replaced when they are damaged) l IF A CELL IS PREPARING TO DIVIDE, IT WILL COPY THE CHROMOSOMES l ID CHROMOSOMES ARE PRODUCED CALLED SISTER CHROMATIDS AND ARE JOINED AT THE CENTROMERE
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PROPHASE l NUCLEAR MEMBRANE FRAGMENTS l DNA COILS UP INTO VISIBLE CHROMOSOMES l SPINDLE FIBERS FORM FROM CENTRIOLS AND ATTACH TO CHROMOSOMES
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METAPHASE l CHROMOSOMES ARE ALIGNED ALONG THE CENTER OF THE CELL
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ANAPHASE l SISTER CHROMATIDS ARE PULLED APART (CENTROMERE IS SEPARATED)
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TELOPHASE l CHROMOSOMES ARRIVE AT THE POLES AND A LASSO-LIKE FIBER PINCHES THE CELLS APART l NUCLEAR MEMBRANE REFORMS l DNA UNCOILS INTO CHROMATIN AND IS READABLE AGAIN l RESULTS IN 2 ID DIPLOID DAUGHTER CELLS
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GAMETE PRODUCTION l GAMETES ARE HAPLOID (N) l CONTAIN ONLY ONE COPY OF EACH TYPE OF CHROMOSOME MEIOSIS- PROCESS THAT PRODUCES GAMETES l 2N CELL IN OVARIES OR TESTES HAPLOID GAMETES
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MEIOSIS l 2 SETS OF STAGES- MEIOSIS 1 AND 2 l PROPHASE 1 - RECOMBINATION (CROSSING OVER) OCCURS- HOMOLOGOUS CHROMOSOMES SWAP LEGS l RESULTS IN A NEW COMBINATION OF TRAITS IN 2 OF THE 4 GAMETES
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PROBLEMS IN MEIOSIS l NON- DISJUNCTION - FAILURE OF THE CHROMOSOMES TO SEPARATE PROPERLY DURING MEIOSIS l RESULTS IN AN UNEQUAL DISTRIBUTION OF CHROMOSOMES IN THE GAMETES l CAUSE OF DOWNS SYNDROME AND SEX CHROMOSOME DISORDERS
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Inheritance Patterns
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GENETICS l THE STUDY OF HOW TRAITS ARE INHERITED ALLELES- ALTERNATIVE FORMS OF THE SAME TRAIT THAT HAVE THE SAME POSITION ON HOMOLOGOUS CHROMOSOMES
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ALLELES DOMINANT ALLELE- WRITTEN AS A CAPITAL LETTER RECESSIVE ALLELE- WRITTEN AS A LOWERCASE LETTER l EVERYONE HAS 2 ALLELES, ONE ALLELE CAME FROM YOU MOTHER AND THE OTHER CAME FROM YOUR FATHER
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COMBINATIONS l 2 DOMINANT ALLELES= THE DOMINANT APPEARANCE (HOMOZYGOUS) l 2 RECESSIVE ALLELES= THE RECESSIVE APPEARANCE (HOMOZYGOUS) l 1 DOMINANT AND 1 RECESSIVE ALLELE= USUALLY THE DOMINANT APPEARANCE (HETEROZYGOUS)
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GENO AND PHENOTYPES GENOTYPE- THE ALLELES THAT ARE PRESENT PHENOTYPE- THE OUTWARD APPEARANCE OF AN ORGANISM
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GAMETE FORMATION l A RESULT OF MEIOSIS l THE 2 ALLELES ARE SEPARATED FROM EACH OTHER SO THAT EACH GAMETE CONTAINS ONLY ONE OF THE 2 ALLELES
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PUNNETT SQUARE l SHOWS THE POSSIBLE GENOTYPES OF THE OFFSPRING l ALL POSSIBLE PARENTAL GAMETES ARE WRITTEN ON THE EDGES l THE CENTER IS FILLED IN AND REPRESENTS THE POSSIBLE GENOTYPES OF THE CHILDREN
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PUNNETT SQUARE S= smooth s= wrinkled l Male parent genotype= Ss l Female Parent genotype= Ss l Genotypes- 25% of offspring will be SS (homozygous dominant) 50% will be Ss (heterozygous) and 25% will be ss (homozyg. recessive) l Phenotypes- 75% of offspring will be smooth and 25% will be wrinkled
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DOMINANT DISORDERS NEUROFIBROMATOSIS- l BIRTH- TAN SPOTS ON THE SKIN l SMALL BENIGN TUMORS GROW RANDOMLY THROUGHOUT THE BODY l CAN BE MILD OR SEVERE l CAUSE= A MUTATED GENE THAT CONTROLS CELL DIVISION
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DOMINANT DISORDERS HUNTINGTONS DISEASE- l DEGENERATION OF BRAIN CELLS IN MIDDLE AGED PEOPLE l MUSCLE SPASMS AND PERSONALITY DISORDERS l 10-15 YRS AFTER ONSET= DEATH l CAUSE= A DNA REPEAT ON CHROMOSOME #4
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Polydactyly- DOMINANT
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RECESSIVE DISORDERS l CYSTIC FIBROSIS- 1/20 CAUCASIANS IS A CARRIER- l THICK MUCUS IS PRODUCED IN THE LUNGS AND PANCREAS = DIFFICULTY BREATHING AND DIGESTING FOOD- AVERAGE LIFE SPAN= 28 YEARS l CAUSE= BAD GENE ON CHROMOSOME 7
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RECESSIVE DISORDERS PHENYLKETONURIA (PKU) l PERSONS LACK AN ENZYME THAT BREAKS DOWN PHENYLALANINE l UNLESS CHILDREN ARE PUT ON A DIET LOW IN PHENYLALANINE THEY WILL BECOME RETARDED l CAUSE= DAMAGED GENE FOR THE IMPORTANT ENZYME
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POLYGENIC TRAITS l ONE TRAIT IS DETERMINED BY 2 OR MORE SETS OF ALLELES l SKIN COLOR AND HEIGHT l SOME RESEARCH SUGGESTS THAT ALLERGIES AND CANCER MAY ALSO BE CONTROLLED BY POLYGENES
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MULTIPLE ALLELIC TRAITS l HUMAN BLOOD TYPE l A, B, O, AB l USED IN PATERNITY SUITS TO DISPROVE FATHERHOOD
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INCOMPLETE DOMINANCE l THE INDIVIDUALS WITH ONE OF EACH TYPE OF ALLELE HAVE A MIXTURE OF THE TWO TRAITS l Red x White = Pink
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SICKLE CELL ANEMIA l N= NORMAL n= SICKLE CELLS l nn= SICKLE CELL ANEMIA= DIE WITHOUT TREATMENT l Nn= CELLS WILL SICKLE ONLY UNDER STRESS= MALARIA PROTECTION l IN AFRICA- 60% ARE CARRIERS l TREATED BY BONE MARROW TRANSPLANTS
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SEX LINKED TRAITS l X- LINKED TRAIT= ONLY CARRIED ON THE X CHROMOSOME RED/GREEN COLOR BLINDNESS- 8% OF CAUCASIAN MALES MUSCULAR DYSTROPHY- MALE BABIES- POOR MUSCLE FUNCTION l SONS GET THESE X LINKED TRAITS FROM THEIR MOTHERS
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MORE X-LINKED TRAITS HEMOPHILIA- 1/15,000 MALE BIRTHS l LACK A BLOOD CLOTTING FACTOR AND TEND TO BLEED/BRUISE MUCH MORE WHEN INJURED
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SEX INFLUENCED TRAITS PATTERN BALDNESS l RECESSIVE IN FEMALES, BUT IN THE PRESENCE OF TESTOSTERONE IT WILL BE EXPRESSED l THIS MEANS THAT IT IS DOMINANT IN MALES l MALE- Nn OR nn = BALD l FEMALE- Nn= NORMAL because they don’t have enough testosterone for it to be expressed nn= BALD WOMAN
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