Human Genetics Ch 12

Chromosomal Mutations Genetic Diseases….

Ultrasound Sonic picture of fetus Boy or girl?

Amniocentesis

Amniocentesis Remove amniotic fluid with baby’s cells Observe karyotype 1% risk to fetus

Amniocentesis

Nondisjunction Failure of homologous chromosomes to separate properly during meiosis Karyotype will show extra or missing chromosomes

Diseases from Nondisjunction Down’s syndrome extra 21 Trisomy 13 (Patau Syndrome) Klinefelter’s syndrome 47 XXY Turner Syndrome 45X Edwards Syndrome Trisomy 18 Cri-du-Chat Syndrome missing part of Chromosome #5 Link

Downs Syndrome Karyotype

Downs Syndrome 1/700 live births Extra chromosome #21 Mental retardation Short Heart defects Same facial features More frequent in mothers over 40

Downs Syndrome

Down’s Syndrome

Down’s Syndrome

Down’s Syndrome

Down’s syndrome

Trisomy 13

Trisomy 13 Patau syndrome rare 1/20,000 Extra #13 Not alert Deaf Harelip Cleft palate Polydactyly Live ~6 months

Trisomy 13 (Patau)

Trisomy 13

Trisomy 13

Klinefelters Syndrome

Klinefelters 47 XXY 2/1000 male births Male but sterile

Turner’s Syndrome

Turners 45X_ Female, usually sterile and sexually immature Short, webbed neck

Turners 47

Turners 17

Edward’s Syndrome(Trisomy 18)

Edwards Extra #18 Smaller Ears low and malformed Webbed neck Receding chin Usually die of pneumonia or heart failure

Cri-du-chat (missing part of chromosome #5)

Cri-du-chat (missing part of chromosome #5) Heart problems Mental retardation Abnormality in larynx - cries like a cat

Simple Recessive Heredity

1. Cystic Fibrosis (CF) Defective protein in plasma membrane Mucus clogs lungs, liver, pancreas 1/20 white am. are carriers 1/2000 white americans born with CF Physical therapy, special diet, drug therapy, gene therapy raised life exp to adulthood

2. Tay Sachs Disease Missing enzyme that breaks down a lipid produced and stored in tissues of the central nervous system Newborns appear normal for 5 months Blind, paralyzed, mentally retarded, die before age 5 1/1600 Amish and Jews of Eastern European descent

Baby with Tay Sachs Video link

Children age 3-5 with Tay Sachs

3. Phenylketonuria (PKU) Failure of brain to develop Absence of enzyme that converts phenylalanine to tyrosine, so amino acid builds up in the body Most common in people with ancestors from Norway or Sweden

Testing Can detect in newborns, appear normal at first, but milk is high in phenylalanine

Special diet Avoid foods with phenylalanine PKU warnings on diet foods

Mom with PKU Can have high phenylalanine in blood and can damage the fetus even if the fetus is normal Control diet

Simple Dominant Heredity Six fingers Widow’s Peak Free earlobes Tongue rolling Usually lethal genetic disorders result in death before they can be passed on

Hapsburg Lip The above portrait is of Charles II, who was King of Spain from 1665 to 1700, and who displays this characteristic trait, a trait that was passed down through the Austro-Hungarian monarchy through successive inbreeding.ﾊ The Hapsburg lip deformity 
affected poor Charles II so badly that he could not chew his food.ﾊ Years of inbreeding had also taken its toll on his 
intelligence (he was retarded) and his powers of procreation (he was impotent). http://www.msu.edu/course/lbs/333/fall/hapsburglip.html

1. Huntington’s Disease Causes the breakdown of the brain, mental deterioration and loss of muscle control Onset after age 30-50 (after had kids!) Can test to see if carrier and can pass to kids and will develop the disease

Brain Deterioration

Huntington’s Disease 30,000 currently suffer in US Over 150,000 have 50% risk of developing it

When Heredity Follows Different Patterns 1. Incomplete Dominance Neither allele is dominant, but combine to make a blended phenotype Ex: Red, white, pink carnations R = red pigment R’ = defective gene

Incomplete Dominance cont. RR = Red RR’ = Pink R’R’ = White What would the offspring look like if you crossed Red and White? What would the offspring look like if you crossed Pink and Pink?

2. Codominance Both alleles are expressed in heterozygous offspring No dominant or recessive No blending Ex: Chickens B = Black feathers W = white

2. Codominance What would a cross of a black chicken and a white chicken look like? BB x WW

BW = checkered chickens!

Codominance - Sickle Cell Anemia Affects African Americans and (white Americans with Mediterranean Sea ancestors) 1/12 African Americans are heterozygous carriers

Codominance-Sickle Cell Anemia

SS = sickle cell anemia AS = sickle and normal cells and protection from Malaria

3. Sex-linked Inheritance Genes on the sex chromosomes are passed on differently in men and women XX = female XY = male

3. Sex-linked Inheritance

3. Sex-linked Inheritance Y doesn’t have the same alleles as X Ex: Color blindness, Duchenne’s Muscular Dystrophy, Hemophilia

Colorblindness

Colorblindness

Colorblindness

3. Sex-linked Inheritance Color blindness: XN = Normal Xc = colorblind recessive No gene on Y XNXc x XNY? XNXc x XcY?

4. Polygenic Inheritance Trait controlled by many genes Phenotypes have a continuous range of variability Ex: skin color, height Homozygous recessive = aabbcc Homozygous dominant = AABBCC Heterozygous = AaBbCc

Eye Color

Height

5. Multiple Phenotypes Trait controlled by multiple alleles in a population Each individual gets only 2 alleles Ex: Blood Types 3 Alleles: IA, IB, i

5. Multiple Phenotypes IA IA or IAi = A Blood IB IB or IBi = B Blood IA IB =AB Blood i i = O Blood

Donating Blood Immune system destroys foreign proteins Type AB can accept all blood types Type A can accept ? Type B? Type O?

Mother and Child Reunion Beth Sarah Baby 1 Baby 2 Baby 3 Anti-A Anti-B Blood Type Possible Genotypes Actual Genotype

Questions 1. Which two babies are Beth’s twins? 2. Which baby is Sarah’s? 3. Now that you know the mother of each baby, can you narrow down each baby’s genotype? 4. What blood type is the twin’s father? 5. What are the possible blood types of the father of Sarah’s baby? Explain!

Environment Temp, light, nutrition, chemicals, and infections can all influence if a gene is actually expressed. Internal Environment changes with age or different hormones. Sex-Influenced trait: expressed differently in males and females

Sex-influenced Ex: Male Pattern Baldness Genotype Male Female BB Bald Bald Bb Bald Not bald bb not not Ex: Horn size in mountain sheep, feather color in birds

Sex-Influenced trait BB or Bb Only BB