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HUMAN GENETICS

HUMAN GENETICS. HUMAN GENETICS. 1. WHAT ARE SOME EXAMPLES IN HUMANS OF CHROMOSOMAL EFFECTS? 2. WHAT ARE SOME EXAMPLES IN HUMANS OF AUTOSOMAL DOMINANT AND RECESSIVE TRAITS?. HUMAN GENETICS. 3. WHAT ARE SOME OTHER FORMS OF INHERITANCE IN HUMANS? 4. WHAT IS A PEDIGREE?

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HUMAN GENETICS

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  1. HUMAN GENETICS

  2. HUMAN GENETICS • 1. WHAT ARE SOME EXAMPLES IN HUMANS OF CHROMOSOMAL EFFECTS? • 2. WHAT ARE SOME EXAMPLES IN HUMANS OF AUTOSOMAL DOMINANT AND RECESSIVE TRAITS?

  3. HUMAN GENETICS • 3. WHAT ARE SOME OTHER FORMS OF INHERITANCE IN HUMANS? • 4. WHAT IS A PEDIGREE? • 5. HOW CAN GENETIC DISORDERS BE DETECTED?

  4. 1. WHAT ARE SOME EXAMPLES IN HUMANS OF CHROMOSOMAL EFFECTS?

  5. Chromosomal Inheritance • All but one pair of chromosomes in males and females are the same. • Autosomes - Nonsex chromosomes • The different pair, sex chromosomes, determines the sex of an individual. • X-linked (sex-linked) is the term used for genes carried on the X chromosome.

  6. X-Linked Alleles • X-linked alleles have a different pattern of inheritance than alleles on autosomes because the Y chromosome is blank for these alleles. • Inheritance of a Y chromosome cannot offset the inheritance of an X-linked recessive allele.

  7. Human X-Linked Disorders • Color Blindness • In humans, color vision receptors in the retina are three different classes of cone cells. • Only one type of pigment is present in each class of cone cell. • The allele for blue-sensitive is autosomal, but the red- and green-sensitive proteins are on the X chromosome.

  8. Human X-Linked Disorders • Muscular Dystrophy • Absence of protein dystrophin allows calcium to leak into muscle cells. • Hemophilia • Hemophilia A due to lack of clotting factor IX and hemophilia B due to lack of clotting factor VIII.

  9. Changes in Chromosome Number • Monosomy and Trisomy • Monosomy (2n - 1) occurs when an individual has only one of a particular type of chromosome. • Trisomy (2n + 1) occurs when an individual has three of a particular type of chromosome.

  10. Changes in Sex Chromosome Number • An abnormal sex chromosome number is the result of inheriting too many or too few X or Y chromosomes. • Nondisjunction during oogenesis or spermatogenesis.

  11. TURNER SYNDROME XO KLINEFELTER XXY TURNER SYNDROME X0

  12. Sex Chromosome Syndromes • Poly-X Females • More than two X chromosomes and extra Barr bodies in the nucleus. • Range from tall and thin to tall and severely retarded depending on number of X chromosomes. • Jacobs Syndrome • XXY due to nondisjunction during spermatogenesis. • Taller than average

  13. Changes in Chromosome Structure • Deletion • End of a chromosome breaks off, or two simultaneous breaks lead to loss of an internal segment. • Translocation • Movement of a chromosome segment from one chromosome to another, non-homologous chromosome.

  14. WILLIAMS SYNDROME

  15. ALAGILLE SYNDROME

  16. Changes in Chromosome Structure • Duplication • Presence of chromosomal segment more than once in the same chromosome. • Known to occur as a result of an inversion in which segment is turned 180o.

  17. 2. WHAT ARE SOME EXAMPLES IN HUMANS OF AUTOSOMAL DOMINANT AND RECESSIVE TRAITS?

  18. Human Genetic Disorders • Autosome - Any chromosome other than a sex chromosome. • When a genetic disorder is autosomal dominant, an individual with AA or Aa has the disorder. • When a genetic disorder is autosomal recessive, only aa individuals have the disorder. • Carriers - Individuals unaffected by a disorder but can have an affected child.

  19. Human Genetic Disorders • Autosome - Any chromosome other than a sex chromosome. • When a genetic disorder is autosomal dominant, an individual with AA or Aa has the disorder. • When a genetic disorder is autosomal recessive, only aa individuals have the disorder. • Carriers - Individuals unaffected by a disorder but can have an affected child.

  20. Autosomal Recessive Disorders • Tay-Sachs Disease • Progressive deterioration of psychomotor functions. • Cystic Fibrosis • Mucus in bronchial tubes and pancreatic ducts is particularly thick and viscous. • Phenylketonuria • Lack enzyme for normal metabolism of phenylalanine.

  21. Autosomal Dominant Disorders • Neurofibromatosis • Tan or dark spots develop on skin and darken. Small, benign tumors may arise from fibrous nerve coverings. • Huntington Disease • Neurological disorder leading to progressive degeneration of brain cells, in turn causing severe muscle spasms and personality disorders.

  22. 3. WHAT ARE SOME OTHER FORMS OF INHERITANCE IN HUMANS?

  23. Multiple Allelic Traits • When a trait is controlled by multiple alleles, the gene exists in several allelic forms. • ABO blood types Phenotype Genotype A IAIA,IAi B IBIB,IBi AB IAIB O ii

  24. LARGE NUMBER OF TRIPLET REPEATS OF CGG AT FRAGILE SITE ON X CHROMOSOME

  25. 4. WHAT IS A PEDIGREE?

  26. 5. HOW CAN GENETIC DISORDERS BE DETECTED?

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