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