Chapter 18 and Chapter 20

Cell division and the Human Life Cycle + Chromosome Disorders

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

METAPHASE

CHROMOSOMES ARE ALIGNED ALONG THE CENTER OF THE CELL

ANAPHASE

SISTER CHROMATIDS ARE PULLED APART (CENTROMERE IS SEPARATED)

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

Inheritance Patterns

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

Polydactyly- DOMINANT

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

MULTIPLE ALLELIC TRAITS

HUMAN BLOOD TYPE A, B, O, AB USED IN PATERNITY SUITS TO

DISPROVE FATHERHOOD

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

SEX INFLUENCED TRAITS

PATTERN BALDNESS RECESSIVE IN FEMALES, BUT IN THE PRESENCE

OF TESTOSTERONE IT WILL BE EXPRESSED THIS MEANS THAT IT IS DOMINANT IN MALES MALE- Nn OR nn = BALD FEMALE- Nn= NORMAL because they don’t have

enough testosterone for it to be expressed nn= BALD WOMAN