1 / 53

Chromosomes and Genes

Chromosomes and Genes. CHROMOSOMES AND GENES. 1. WHAT ARE THE DEGREES OF DOMINANCE? 2. IN WHAT WAYS DO GENES BEHAVE? 3.WHAT IS THE CHROMOSOMAL THEORY AND WHAT HAPPENS WHEN THE NUMBER CHANGES?. CHROMOSOMES AND GENES. 1. WHAT ARE THE DEGREES OF DOMINANCE? SIMPLE OR COMPLETE DOMINANCE.

loring
Download Presentation

Chromosomes and Genes

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chromosomes and Genes Mader: Biology 8th Ed.

  2. CHROMOSOMES AND GENES • 1. WHAT ARE THE DEGREES OF DOMINANCE? • 2. IN WHAT WAYS DO GENES BEHAVE? • 3.WHAT IS THE CHROMOSOMAL THEORY AND WHAT HAPPENS WHEN THE NUMBER CHANGES? Mader: Biology 8th Ed.

  3. CHROMOSOMES AND GENES • 1. WHAT ARE THE DEGREES OF DOMINANCE? • SIMPLE OR COMPLETE DOMINANCE Mader: Biology 8th Ed.

  4. SIMPLE OR COMPLETE DOMINANCE • EXAMPLE: • Rh FACTOR IN BLOOD TYPING OF HUMANS • Rh+ INDIVIDUALS ARE DOMINANT TO Rh- INDIVIDUALS . Mader: Biology 8th Ed.

  5. GENOTYPE Rh+Rh+ Rh+Rh- Rh-RH- PHENOTYPE HAS Rh+ BLOOD TYPE HAS Rh+ BLOOD TYPE HAS Rh- BLOOD TYPE Rh FACTOR IS SIMPLE DOMINANT TRAIT Mader: Biology 8th Ed.

  6. CHROMOSOMES AND GENES • 1. WHAT ARE THE DEGREES OF DOMINANCE? • INCOMPLETE DOMINANCE Mader: Biology 8th Ed.

  7. Incomplete Dominance • Exhibited when the heterozygote has an intermediate phenotype between that of either homozygote. Mader: Biology 8th Ed.

  8. Incomplete Dominance Mader: Biology 8th Ed.

  9. CHROMOSOMES AND GENES • 1. WHAT ARE THE DEGREES OF DOMINANCE? • CODOMINANCE Mader: Biology 8th Ed.

  10. CODOMINANCE • SICKLE CELL ANEMIA • THE SICKLING GENE “s” CAUSES PRODUCTION OF AN ABNORMAL HEMOGLOBIN THAT CRYSTALIZES AT LOW OXYGEN CONCENTRATIONS • THE NORMAL GENE “S” CAUSES PRODUCTION OF NORMAL HEMOGLOBIN Mader: Biology 8th Ed.

  11. GENOTYPE SS Ss ss PHENOTYPE NORMAL HEMOGLOBIN EXTREMELY LOW OXYGEN CONDITIONS RESULT IN SICKLING IN THE EXTREMITIES SICKLING EPISODES CAN BE FREQUENT AND INCLUDE MAJOR ORGANS SICKLE CELL ANEMIA Mader: Biology 8th Ed.

  12. SICKLE CELL ANEMIA Mader: Biology 8th Ed.

  13. CHROMOSOMES AND GENES • 2. IN WHAT WAYS DO GENES BEHAVE? Mader: Biology 8th Ed.

  14. 2. IN WHAT WAYS DO GENES BEHAVE? • PLEIOTROPISM – ONE GENE HAS MANY EFFECTS • EXAMPLE MARFAN SYNDROME (A COLLECTIONS OF SYMPTOMS ASSOCIATED WITH A CONDITIONS IS CALLED A SYNDROME) Mader: Biology 8th Ed.

  15. PLEIOTROPISM • MARFAN SYNDROME SYMPTOMS: TALL AND THIN WITH LONG LEGS, ARMS AND FINGERS NEARSIGHTEDNESS WALL OF AORTA IS WEAK, ENLARGES AND OFTEN SPLITS RESULTING IN DEATH Mader: Biology 8th Ed.

  16. PLEIOTROPISM • MARFAN SYNDROME ALL THESE SYMPTOMS ARE TRACED TO ONE DEFECTIVE DOMINANT GENE THAT CAUSES AN INABILITY TO PRODUCE NORMAL FIBRILLIN. FIBRILLIN IS A PROTEIN THAT STRENTHENS ELASTIC FIBERS MANY BELIEVE THAT ABRAHAM LINCOLN HAD MARFAN SYNDROME Mader: Biology 8th Ed.

  17. 2. IN WHAT WAYS DO GENES BEHAVE? • EPISTASIS IN MULTIGENIC TRAITS • ONE ABNORMAL GENE INTERFERES WITH THE ACTION OF ANOTHER NORMAL GENE. Mader: Biology 8th Ed.

  18. EPISTATSIS • PARENTS ARE TWO WHITE FLOWERING PLANTS THAT PRODUCE ONLY PURPLE OFFSPRING. WHEN AN F2 IS PRODUCED FROM THE PURPLE OFFSPRING OF THE F1 THEY PRODUCE A PHENOTYPIC RATIO OF 9 PURPLE TO 7 WHITE. THIS CAN’T BE EXPLAINED BY ANY MODE OF INHERITANCE DISCUSSED SO FAR. Mader: Biology 8th Ed.

  19. EPISTATSIS IN WHITE-PURPLE FLOWERS • P1 AAbb(WHITE FLOWER) X aaBB(WHITE FLOWER) • F1 AaBb (PURPLE FLOWER) • F2 AABB, AABb,AaBB,AaBb,AABb, (PURPLE FLOWERS) AAbb, Aabb,aaBB,aaBb,aabb (WHITE FLOWERS) Mader: Biology 8th Ed.

  20. AA OR Aa ACTIVE ENZYME A BB OR Bb ACTIVE ENZYME B INTERMEDIATE PRODUCT PURPLE PRODUCT PRECURSOR IF EITHER GENE A OR B IS HOMOZYGOUS RECESSIVE IT BLOCKS PRODUCTION OF THE FINAL PURPLE PRODUCT Mader: Biology 8th Ed.

  21. 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 Mader: Biology 8th Ed.

  22. Inheritance of Blood Type Mader: Biology 8th Ed.

  23. Polygenic Inheritance • Occurs when a trait is governed by two or more sets of alleles. • Each dominant allele has a quantitative effect on the phenotype, and these effects are additive. • Result in continuous variation of phenotypes. Mader: Biology 8th Ed.

  24. Height in Human Beings Mader: Biology 8th Ed.

  25. Mader: Biology 8th Ed.

  26. Mader: Biology 8th Ed.

  27. Environment and Phenotype • GENE EXPRESSION MAY BE ALTERED BY THE ENVIRONMENT Mader: Biology 8th Ed.

  28. Himalayan Rabbits - Enzyme coding for black fur is active only at low temperatures. • Black fur only occurs on extremities. Where body temperature is low. Mader: Biology 8th Ed.

  29. DARK FUR DEVELOPS UNDER THE ICE PACK DUE TO LOW TEMPERATURE INTERACTION WITH THE GENE Mader: Biology 8th Ed.

  30. 3.WHAT IS THE CHROMOSOMAL THEORY AND WHAT HAPPENS WHEN THE NUMBER CHANGES? Mader: Biology 8th Ed.

  31. CHROMOSOMAL THEORY OF INHERITANCE • GENES “RIDE” ON THE CHROMOSOMES THEREFORE WHAT HAPPENS TO THE CHROMOSOME AFFECTS THE GENES LOCATED ON IT Mader: Biology 8th Ed.

  32. 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. Mader: Biology 8th Ed.

  33. 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. Mader: Biology 8th Ed.

  34. Drosophila Mader: Biology 8th Ed.

  35. 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. Mader: Biology 8th Ed.

  36. 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. Mader: Biology 8th Ed.

  37. Hemophilia Pedigree Mader: Biology 8th Ed.

  38. Gene Linkage • The existence of several GENES on the same chromosome. • GENES on the same chromosome form a linkage group because they tend to be inherited together. • Can be used to build a linkage map. Mader: Biology 8th Ed.

  39. Constructing a Chromosome Map • A linkage map can also be called a chromosome map because it tells the order of gene loci on chromosomes. • If crossing-over occurs between two linked alleles of interest, a dihybrid produces four types of gametes instead of two. Mader: Biology 8th Ed.

  40. Crossing-Over Mader: Biology 8th Ed.

  41. Linkage Data • The percentage of recombinant phenotypes can be used to map chromosomes because there is a direct relationship between the frequency of crossing-over and the distance between alleles. • Assumed 1% crossing-over equals 1 map unit. Mader: Biology 8th Ed.

  42. Changes in Chromosome Number • Polyploidy • Occurs when eukaryotes have more than 2n number of chromosomes. • Named according to number of sets of chromosomes. • Major evolutionary force in plants. • Some estimate 47% of flowering plants are polyploids. Mader: Biology 8th Ed.

  43. 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. Mader: Biology 8th Ed.

  44. Down Syndrome • Down syndrome (Trisomy 21) is caused by three copies of chromosome 21. Mader: Biology 8th Ed.

  45. 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. Mader: Biology 8th Ed.

  46. Sex Chromosome Syndromes • Turner Klinefelter (XO) (XXY) Mader: Biology 8th Ed.

  47. 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 Mader: Biology 8th Ed.

  48. 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. Mader: Biology 8th Ed.

  49. Changes in Chromosome Structure Mader: Biology 8th Ed.

  50. 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. Mader: Biology 8th Ed.

More Related