Transcript 19,20INHERITANCEnoaudio

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
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CHROMOSOME PROBLEMS
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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
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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
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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.
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MITOSIS
THE DIVISION OF ONE BODY CELL
INTO 2 IDENTICAL BODY CELLS
 NORMAL BODY CELLS ARE DIPLOID
(2N)
 2N
2N + 2N
 5 STEPS
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INTERPHASE
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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
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METAPHASE
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CHROMOSOMES ARE ALIGNED
ALONG THE CENTER OF THE CELL
ANAPHASE
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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
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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
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MEIOSIS
2 SETS OF STAGESMEIOSIS 1 AND 2
 PROPHASE 1 - RECOMBINATION
(CROSSING OVER) OCCURSHOMOLOGOUS CHROMOSOMES
SWAP LEGS
 RESULTS IN A NEW COMBINATION
OF TRAITS IN 2 OF THE 4 GAMETES
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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
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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
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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)
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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
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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
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PUNNETT SQUARE
S= smooth
s= 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
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CYSTIC FIBROSIS- 1/20 CAUCASIANS IS A
CARRIERTHICK MUCUS IS PRODUCED IN THE
LUNGS AND PANCREAS = DIFFICULTY
BREATHING AND DIGESTING FOODAVERAGE 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
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MULTIPLE ALLELIC TRAITS
HUMAN BLOOD TYPE
 A, B, O, AB
 USED IN PATERNITY SUITS TO
DISPROVE FATHERHOOD
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INCOMPLETE DOMINANCE
THE INDIVIDUALS WITH ONE OF
EACH TYPE OF ALLELE HAVE A
MIXTURE OF THE TWO TRAITS
 Red x White = Pink
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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
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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
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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