Chapter 14: Human Genetics

Chapter 14: Human Genetics • Mr. and Mrs. Smith are both heterozygous for a cleft chin. All three children have cleft chins. The are SURE that their 4th child will also have a cleft chin. Are they right?

14-1 Human Heredity • Vocabulary • Karyotype —Autosome • Sex Chromosome — Pedigree • Karyotype • During Mitosis, scientists take pictures of chromosomes and look at them under a microscope

14-1PROCESS BOX 14-1Human • What types of information do you think you could figure out from a karyotype? 2 LINE MINIMUM

14-1 Human Heredity • What can a karyotype tell us? • Gender • XX = female XY = male • Total # of chromosomes in a cell • 46 in a body cell • 2 sets of 23 • 46 = diploid (2n) • 23 = haploid (n)

14-1 Human Heredity • Autosomes v. Sex chromosomes • Autosomes are the first 22 pairs • Code relates to non-gender issues • Sex chromosomes are the last pair • Determine gender

14-1PROCESS BOX 14-2Human • A karyotype sow 46 total chromosomes with the last pair having 1 X and 1 Y chromosome. What gender is this person? What evidence do you have? 2 LINE MINIMUM

14-1 Human Heredity • Pedigrees • Show family relationships and how a trait is passed down • Notes • O = female  = male  = shows trait • I, II, III = mark generations • 1,2,3 = each person in generation • O— marriage | O = baby

14-1PROCESS BOX 14-3Human • How would a pedigree look if all family members were recessive for a trait? How could the dominant trait be introduced? 3 LINE MINIMUM

14-1 Human Heredity • How will I know… • If it is a recessive or dominant trait? • If dominant, one parent HAS to have it (seen EVERY generation) • If recessive, neither parent HAS to have it (seems to “skip” generations) • If it is an autosomal or sex-linked trait? • If sex-linked, more males will show the trait than females • If autosomal, males and females with show the trait evenly

14-1PROCESS BOX 14-4Human • Is the following pedigree sex-linked or autosomal? Dominant or recessive? How do you know? 3 LINE MINIMUM

14-2 Human Chromosomes • Vocabulary • Sex-linked —Nondisjunction • Sex-linked genes • Special pattern of inheritance for genes on the X or Y chromosome • Called sex-linked genes because these chromosomes determine gender 50-50 ratio of having a boy or a girl…MALES determine gender!

14-2 Human Chromosomes • Males v. females: sex chromosomes • Males only have 1 X; cannot be heterozygous • Males tend to show these traits more often • Females have 2 XX; can be heterozygous • Females have two chances to show dominant allele

14-1PROCESS BOX 14-5Human • Male-patterned baldness is a sex-linked trait. If it happens in females too, then why do we call it MALE-patterned baldness? 3 LINE MINIMUM

14-2 Human Chromosomes EXAMPLES OF SEX-LINKED TRAITS DUCHENNE’SMUSCULARDYSROPHY HEMOPHILIA COLOR-BLINDNESS

14-2 Human Chromosomes • How to set up sex-linked Punnett Squares • Read problem-decide it’s sex-linked • Write XX for mom & XY for dad • Determine parent genotypes • Carrier = XAXa • Set up • Fill in • Solve • Out of all children? Out of 4 • Out of only boys/only girls? Out of 2

14-1PROCESS BOX 14-6Human • How do sex-linked Punnett Squares compare to Punnett Squares that are not sex-linked? 2 LINE MINIMUM

14-2 Human Chromosomes • Nondisjunction • When chromosomes fail to separate properly during either Meiosis I or Meiosis II • Gametes (sex cells/sperm and egg) have the wrong number of chromosomes

14-1PROCESS BOX 14-7Human • How many chromosomes would a cell have if it was fertilized by a normal sperm but the egg had NO chromosomes separated during meiosis? 2 LINE MINIMUM

14-2 Human Chromosomes • Nondisjunction Diseases • Autosomes • Trisomy 21 – Down’s syndrome • Extra #21 chromosome • Mild to serious mental deficiency • 1/800 births • Trisomy 18—Edward’s Syndrome • Extra #18 chromosome • Heart and kidney defects, mental deficiency • 1/5000 births; only 1% live to be 10

14-2 Human Chromosomes • Nondisjunction Diseases • Autosomes • Trisomy 13 –Patau Syndrome • Extra #13 Chromosome • Malformed fingers and feet; eye defects • Severe mental deficiency • 1/16000 births; 80% die within 1st year • Cri du Chat • Partial delection of #5 chromosome • Malformed larynx makes cries sound like cat • Characteristic facial features, mental deficiency • 1/35000 births

14-2 Human Chromosomes • Nondisjunction Diseases • Sex chromosomes—Monosomies • Turner’s Syndrome - 45 XO • Sterile, underdeveloped, short, webbed neck • 1/2000 births • 45YO – Dead – need X chromosome to survive

14-2 Human Chromosomes • Nondisjunction Diseases • Sex chromosomes—Trisomies • Klinefelter’s syndrome – 47 XXY • Underdeveloped, sterile, increased breast tissue but male • 1/1000 births • 47XXX – Triple female • Fertile; Normal in appearance; more fragile • 1/1000 births • 47 XXY—Triple Males (Jacob’s Syndrome) • Fertile; taller; higher rate in criminals? • 1/1000 births

14-2 Human Chromosomes SEX CHROMOSOMENONDISJUNCTION AUTOSOMALNONDISJUNCTION

14-2 Human Chromosomes • Recognizing Nondisjunction on a Karyotype • Count chromosomes • 46 = “Normal” • More or less? • Look for extra or missing chromosome and determine disease • Note Gender • Write out as Total Number, Sex combination, description 46 XX-Normal female

14-2 Human Chromosomes

14-2 Human Chromosomes • X-inactivation and Barr Bodies

14-2 Human Chromosomes • X-inactivation and Barr Bodies • Too little genetic information—BAD • Too much genetic information—BAD • So…how do females “deal” with extra X-chromosome? • Randomly switch off one of the X chromosomes • Does not happen in normal males…DEAD X chromosome with black allele switched off...orange color X chromosome with orange allele switched off...black color

14-2 Human Chromosomes • Calico cats show sex-linkage and codominance for color spots • XBXO = calico female • XBXB = black female  XBY = black male • XOXO = orange female  XOY = orange male • A litter of cats was birthed to a black femal cat. In the litter of 6 cats, there are 2 black males and 4 calico females. What color is the father cat?

14-1PROCESS BOX 14-7Human • How could a calico cat be a male? (It IS possible?) Explain. 3 LINE MINIMUM

Chapter 14: Human Genetics