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Human Heredity Pages 341-348 Objectives:
Identify the types of human chromosomes Explain how sex is determined Explain how pedigrees are used to study human traits Describe examples of the inheritance of human traits Explain how small changes in DNA cause genetic disorders Updated April 2006 Created by C. Ippolito April 2006
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Human Heredity Karyotype Sex Chromosomes Autosomes
Is a picture of chromosomes arranged in pairs based on their size and shape Sex Chromosomes Pair that determines sex Females – have pair formed of two identical “X” chromosomes Males – have an unmatched pair composed of an “X” chromosome like the females and a smaller “Y” chromosome Autosomes The 22 other pairs of chromosomes that do not determine sex Updated April 2006 Created by C. Ippolito April 2006
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Normal Female Karyotype
Updated April 2006 Created by C. Ippolito April 2006 3
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Normal Male Karyotype Updated April 2006 Created by C. Ippolito
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Sex Determination Sex of a child is determined by the male parent.
Sex cells of parents contain one member of each pair. The egg cell will always have an X The sperm can have an X or Y. Female - egg is fertilized by a sperm bearing an X chromosome. Male - egg is fertilized by a sperm bearing an Y chromosome. Updated April 2006 Created by C. Ippolito April 2006 5
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Human Traits Pedigree Chart
a diagram that shows the relationships within a family a circle represents a female a square represents a male horizontal line connecting a circle to a square represents a marriage a filled-in circle or square shows that the individual has the trait vertical line(s) and brackets below that line show their child(ren) Updated April 2006 Created by C. Ippolito April 2006
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Gene and Allele Gene Allele determines a trait in a human.
alternate form of gene interaction of 2 alleles on chromosome pair determine a person’s trait. Updated April 2006 Created by C. Ippolito April 2006 7
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Recessive Autosomal Disorders
Recessive Allele both chromosomes must possess this factor for it’s trait Albinism Cystic Fibrosis Galactosemia Phenylketonuria Tay Sach’s Disease Sickle Cell Anemia Updated April 2006 Created by C. Ippolito April 2006 8
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Albinism Missing pigments Treatment Type I Type II
in skin, hair, and eyes low vision due to abnormal retina Treatment sunscreen protection and opaque clothing vision aids Type I missing enzyme to form pigment Type II some pigment formed “P” gene defective Updated April 2006 Created by C. Ippolito April 2006
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Cystic Fibrosis bronchial mucus becomes very thick and viscous
Mucus sits in alveoli and bronchi Daily manual message known as “cupping and clapping” used to loosen mucus. Regular visits to hospital needed to “suction” lungs usually die before their 18th birthday current treatment may extend life into 28 No cure but gene has been identified Genetic screening possible 1:20 Caucasians are carriers occurs in 1:2,500 births Updated April 2006 Created by C. Ippolito April 2006 10
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Galactosemia Diagnosis - blood test at birth
no enzyme to break down galactose enlarged liver, kidney failure, cataracts, brain damage Diagnosis - blood test at birth Prenatal test - amniocentesis Treatment – dietary restriction Updated April 2006 Created by C. Ippolito April 2006
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Phenylketonuria (PKU)
No enzyme – to break down phenylalanine. phenylketone build up which can harm developing brain cells. mental retardation. Diagnosis - blood test at birth. Treatment special diet low in phenylalanine until age 7. Adults excess phenylalanine causes headaches 1:5000 births Updated April 2006 Created by C. Ippolito April 2006 12
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Tay Sachs Disease Lipid buildup around nerve cells.
Normal until 4 months of age. 5th month - lethargy 8th month reactions and movements not normal child becomes blind, deaf, has seizures, paralysis, and dies before 5th year. No cure, no treatment, no definite test for presence of gene Genetic Counseling - Carriers should not marry high occurrence in American Jews - 1:1,000 births higher occurrence in Ashkenazy Jews - 1:40 births Updated April 2006 Created by C. Ippolito April 2006 13
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Dominant Autosomal Disorders
Dominant Allele presence forces trait to appear Achondroplasia Huntington’s Chorea Hypercholesterolemia Updated April 2006 Created by C. Ippolito April 2006 14
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Achondroplasia Gene controlling fibroblast function Diagnosis
short stature, legs and arms short compared to trunk (body), prominent forehead, a protruding jaw, bowed legs Diagnosis X-ray and clinical interview Molecular testing can identify mutated gene (FGFR3) Treatment monitor growth, check for apnea, surgical correction if walking difficult Genetic Counseling Updated April 2006 Created by C. Ippolito April 2006
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Huntington’s Chorea Chronic neurological disease No Cure; No treatment
slow destruction of brain cells. uncontrolled motions appears in middle age (40’s) death within 10 to 20 years of onset Woody Guthrie - hobo poet and folk singer - “This Land is Your Land” No Cure; No treatment Gene has been identified and presence can be determined by blood test 1:20,000 births Updated April 2006 Created by C. Ippolito April 2006 16
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Polygenic Inheritance
Single trait controlled by two or more sets of alleles. Traits show continuous variation “bell curve” The greater the number of alleles the more perfect the bell curve will be. Known polygenic traits: Skin Color Height Possible polygenic traits Cleft Palate Club Foot Hypertension Diabetes Schizophrenia Allergies Updated April 2006 Created by C. Ippolito April 2006 17
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Multiple Alleles Trait controlled one gene pair with more than two distinct alleles. Human Blood types IA - codominant -causes A blood IB - codominant -causes B blood i - recessive -cause O blood Incomplete Dominance Alleles for A and B do not dominate so the heterozygote IAIB has what is known as Type AB blood Updated April 2006 Created by C. Ippolito April 2006 18
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Blood Types Type A Type AB IAi - heterozygous for A
Protein marker (antigen) on membrane of the RBC. Type A IAi - heterozygous for A IAIA - homozygous for A produces anti-B can be given A or O blood Type B IBi - heterozygous for B IBIB - homozygous for B produces anti-A can be given B or O blood Type AB IAIB - heterozygous for AB produces no antibody Universal Receiver can be given any blood Type O ii - homozygous for O produces anti-A and anti-B Universal Donor can be given only O blood Updated April 2006 Created by C. Ippolito April 2006 19
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Sickle Cell Anemia abnormal hemoglobin
changes shape during oxygen deprivation block the flow of blood through vessels lung tissue damage (acute chest syndrome), pain episodes (arms, legs, chest and abdomen), stroke, damages the spleen, kidneys and liver. Damage to the spleen makes sickle cell disease patients, especially young children, easily overwhelmed by certain bacterial infections. originated in areas where malaria was endemic hybrids protected from malaria Diagnosis blood test followed by hemoglobin electrophoresis Treatment vaccinations, pain management, intravenous fluids, hydroxyurea (lessens sickling) Updated April 2006 Created by C. Ippolito April 2006
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Human Chromosomes pp. 349-354 Objectives:
Identify the characteristics of human chromosomes Describe some sex-linked disorders and explain why they are more common in males than in females Explain the process of X-chromosome inactivation Summarize nondisjunction and the problems it causes Updated April 2006 Created by C. Ippolito April 2006
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Sex-Linked Genes genes on the “X” with no equivalent part on the “Y”
appear more often in males - inherit only one allele hemophilia Duchenne Muscular Dystrophy Updated April 2006 Created by C. Ippolito April 2006
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Chromosome Abnormalities
chromosome pairs do not separate properly Nondisjunction is the failure of chromosome pairs to separate properly. Updated April 2006 Created by C. Ippolito April 2006
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Nondisjunction The failure to separate results in:
sex cells extra chromosome or sex cells missing chromosome Updated April 2006 Created by C. Ippolito April 2006
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Down Syndrome Trisomy 21 1:800 < 40 1:90 > 40
1:800 < :90 > 40 short stature; enlarged tongue rounded head; eyefold mental retardation Updated April 2006 Created by C. Ippolito April 2006
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Down Syndrome Karyotype
Updated April 2006 Created by C. Ippolito April 2006
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Cri du Chat Syndrome Monosomy 5 (piece deleted) moon face as infant
malformed larynx eyefold misshapen, low ears severe mental retardation Updated April 2006 Created by C. Ippolito April 2006
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Fragile X Syndrome 1:1000 ♂ 1:2500♀ children adults:
1:1000 ♂ :2500♀ children normal but hyperactive or autistic adults: short stature; long face prominent jaw; large ears stubby hands ♂’s more likely to be mentally deficient Updated April 2006 Created by C. Ippolito April 2006
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Turner Syndrome 45, XO 1:6000 ♀ short with broad chest webbed neck
ovaries, oviduct, uterus small no puberty; no menstruation most normal mentally Updated April 2006 Created by C. Ippolito April 2006
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Turner Syndrome Karyotype
Updated April 2006 Created by C. Ippolito April 2006
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Klinefelter Syndrome 47, XXY 1:1500 ♂
genitalia, testes, prostate small no 2o sex characteristics some breast development large hands, feet; long limbs slow but no deficiency (XXXY) Updated April 2006 Created by C. Ippolito April 2006
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Klinefelter Karyotype
Updated April 2006 Created by C. Ippolito April 2006
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Triple X Syndrome 47, XXX 1:1500 ♀ outwardly normal
tendency to learning disability menstrual irregularity early onset menopause Updated April 2006 Created by C. Ippolito April 2006
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Jacob Syndrome 47, XYY 1:1000 ♂ taller than normal persistent acne
speech & reading problems more aggressive due to size “criminal” syndrome Updated April 2006 Created by C. Ippolito April 2006
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