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2.  Around 1857, Mendel began breeding garden peas to study inheritance. Because they are available in many varieties with distinct heritable characters with different traits (genes). 2 Each pea plant has male (stamens) and female (carpal) sexual organs.Each pea plant has male (stamens) and female (carpal) sexual organs. In nature, pea plants typically self-fertilize, fertilizing ova with their own pollens.In nature, pea plants typically self-fertilize, fertilizing ova with their own pollens. However, Mendel could also move pollens from one plant to another to cross-pollinate plants.However, Mendel could also move pollens from one plant to another to cross-pollinate plants.

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16. 16 PpPpPpPp PpPpPpPp P p P p PPPP PpPpPpPp PpPpPpPp PpPpPpPp PpPpPpPp pp PP p p 100% Purple F 2 generation 3 Purple : 1 White F 1 generation Recessive allele Dominant allele PPPP pp X PpPpPpPp PpPpPpPp PpPpPpPp PpPpPpPpX Pea plant Homozygous Heterozygous

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19. 19 Genotype (Genetic make up) PPPhenotype(Colour) PPPPpppp Homozygous PpPpPpPp PpPpPpPp Heterozygous An organism having a pair of identical alleles An organism having a pair of two different alleles Phenotype: Is t he organism’s appearance المظهر. Genotype: Is t he organism’s genetic makeup الطرز الـﭽينى.

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25.  The two pairs of alleles segregate independently of each other.  The presence of one specific allele for one trait has no impact تأثير on the presence of a specific allele for the second trait. 25 When sperm and ova each with four classes of alleles combine, there would be 16 equally probable ways in which the alleles can combine in the F 2 generation.When sperm and ova each with four classes of alleles combine, there would be 16 equally probable ways in which the alleles can combine in the F 2 generation. These combinations produce four distinct phenotypes in a 9:3:3:1 ratio.These combinations produce four distinct phenotypes in a 9:3:3:1 ratio. This was consistent with Mendel’s results.This was consistent with Mendel’s results. Each character appeared to be inherited independently.Each character appeared to be inherited independently. Fig. 14.7b, Page 253

26. 26 It is a mating between two parent plants differing in two characters. Y R y r YR yr RY y r F 1 Yellow Round YYRR rryyX

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28. 28 R Y y r X R Y y r yyrr yyRR YYrr YYRRYR YrYrYrYr yRyRyRyR yrYR YrYrYrYr yRyRyRyR yr Yellow Round Yellow Wrinkled Green Round Green Wrinkled F 2: % of Phenotype ? Page 253, Fig. 14.7

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31.  It is not possible to predict the genotype of an organism with a dominant phenotype.  The organism must have one dominant allele, but it could be homozygous dominant or heterozygous.  Test cross, is breeding a homozygous recessive with dominant phenotype, but unknown genotype, can determine the identity of the unknown allele. is breeding a homozygous recessive with dominant phenotype, but unknown genotype, can determine the identity of the unknown allele. 31 Fig. 14.6 Q: What is the result of Cross hybridization of purple X white colored flowers ?

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41.  Dominant character (allele)  Dominant character (allele) الصفة السائدة Is fully expressed in the organism’s appearance. Is fully expressed in the organism’s appearance.  Recessive character (allele)  Recessive character (allele) الصفة المُتنحية Has no noticeable effect تأثير غير ملحوظ on the organism’s appearance. Has no noticeable effect تأثير غير ملحوظ on the organism’s appearance.  Homozygous مُتماثل الجينات An organism with two identical alleles for a character. An organism with two identical alleles for a character.  Heterozygous مُختلف الجينات An organism with two different alleles for a character. An organism with two different alleles for a character.  Karyotype الطرز الكروموسومى The display of an organism’s chromosomal pattern  Phenotype الطرز المظهرى A description of an organism’s traits (feature مظهر ). A description of an organism’s traits (feature مظهر ).  Genotype الطرز الجينى A description of an organism’s genetic makeup. A description of an organism’s genetic makeup. 41

42.  Thousands of genetic disorders, including disabling or deadly hereditary diseases, are inherited as simple recessive traits.  These range from the relatively mild (albinism ) to life-threatening (cystic fibrosis).  These range from the relatively mild (albinism الألبينو، البُهاق ) to life-threatening (cystic fibrosis).  Heterozygotes have a normal phenotype because one “normal” allele produces enough of the required factors ().  Heterozygotes have a normal phenotype because one “normal” allele produces enough of the required factors ( for normal trait ).  A recessively inherited disorder shows up only in the individuals who inherit homozygous recessive allele from parents.  Thus, individuals who lack the disorder are either homozgyous dominant or heterozygous.  Heterozygous member may have no clear phenotypic effects, but is a carrier who may transmit a recessive allele to their offspring.  Most people with recessive disorders are born from carrier parents with normal phenotypes.  Two carriers have a 1/4 chance of having a child with the disorder, 1/2 chance of a carrier, and 1/4 free. 42

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44. 44 1. Cystic fibrosis: a lethal recessive disorder  One in 25 person is a carrier.  The normal allele codes for a membrane protein that transports Cl - between cells and the environment.  If these channels are absent, there are abnormally high extracellular levels of chloride that causes the mucus coats of certain cells to become thicker and stickier than normal.  This mucus build-up in the pancreas, lungs, digestive tract, and elsewhere favors bacterial infections.  Without treatment, affected children die before five, but with treatment can live past their late 20’s. 2.Tay-Sachs disease a lethal recessive disorder. –It is caused by a dysfunctional enzyme that fails to break down specific brain lipids. –The symptoms begin with seizures, blindness, and degeneration of motor and mental performance a few months after birth. –Inevitably, the child dies after a few years. A- Recessively inherited disorders

45. 45 3. Sickle-cell disease.  It is caused by the substitution of a single amino acid in hemoglobin.  When oxygen levels in the blood of an affected individual are low, sickle-cell hemoglobin crystallizes into long rods.  This deforms red blood cells into a sickle shape.  Doctors can use regular blood transfusions to prevent brain damage and new drugs to prevent or treat other problems. The two alleles are codominant as both normal and abnormal hemoglobins are synthesized.The two alleles are codominant as both normal and abnormal hemoglobins are synthesized.

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47. 47 Many other disorders have a multifactorial basis.  These have a genetic component plus a significant environmental influence.  Multifactorial disorders include:  heart disease, diabetes, cancer, alcoholism, and certain mental illnesses, such a schizophrenia and manic-depressive disorder.  The genetic component is typically polygenic.  At present, little is understood about the genetic contribution to most multifactorial diseases

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49. 49 Section B: Sex Chromosomes CHAPTER 15 THE CHROMOSOMAL BASIS OF INHERITANCE 1.The chromosomal basis of sex varies with the organism 2.Sex-linked genes have unique patterns of inheritance

50. 50  In human and other mammals, there are two varieties of sex chromosomes, X & Y.  An individual who inherits two X chromosomes usually develops as a female.  An individual who inherits an X and a Y chromosome usually develops as a male. This X-Y system of mammals is not the only chromosomal mechanism of determining sex.This X-Y system of mammals is not the only chromosomal mechanism of determining sex. Other options include the X-0 (in locust) system, the Z-W system (in birds), and the haplo-diploid system (in bees).Other options include the X-0 (in locust) system, the Z-W system (in birds), and the haplo-diploid system (in bees). In Human, the SRY gene (Sex-determining Region of the Y chromosome) modifies embryonic gonads into testes.In Human, the SRY gene (Sex-determining Region of the Y chromosome) modifies embryonic gonads into testes. Females lack the SRY gene, thus, the embryonic gonads develop into ovaries.Females lack the SRY gene, thus, the embryonic gonads develop into ovaries. Fig. 15.8, Page 276

51. 51  In the X-Y system, Y and X chromosomes behave as homologous chromosomes during meiosis.  In reality, they are only partially homologous and rarely undergo crossing over  In both testes (XY) and ovaries (XX), the two sex chromosomes segregate during meiosis and each gamete receives one.  Each egg receives an X chromosome.  Half the sperm receive an X chromosome and half receive a Y chromosome.  Because of this, each conception has about a fifty-fifty chance of producing a particular sex.

52. 52  The sex chromosomes, especially the X chromosome, have genes for many characters unrelated to sex.  These sex-linked genes follow the same pattern of inheritance as the white-eye locus in Drosophila.  If a sex-linked trait is due to a recessive allele, a female have this phenotype only if homozygous.  Heterozygous females will be carriers. Fig. 15.9, Page 277

53. 53 Because males have only one X chromosome (hemizygous), any male receiving the recessive allele from his mother will express the trait.Because males have only one X chromosome (hemizygous), any male receiving the recessive allele from his mother will express the trait. Therefore, males are far more likely to inherit sex- linked recessive disorders than are females.Therefore, males are far more likely to inherit sex- linked recessive disorders than are females.

54. 54 Sex-linked disorders in human. 1.Duchenne muscular dystrophy: affects one in 3,500 males born in the United States. –Affected individuals rarely live past their early 20s. –This disorder is due to the absence of an X-linked gene for a key muscle protein, called dystrophin. –The disease is characterized by a weakening ضعف of the muscles and loss of coordination فـقـْد التوازن. 2.Hemophilia: is a sex-linked recessive trait defined by the absence of one or more clotting factors. 2.Hemophilia: is a sex-linked recessive trait defined by the absence of one or more clotting factors عوامل تجلط. –These proteins normally slow and then stop bleeding. –Individuals with hemophilia have prolonged bleeding because a firm clot forms slowly. –Individuals with hemophilia have prolonged bleeding because a firm clot تجلط forms slowly. –Individuals can be treated with intravenous injections of the missing protein. –This gene is transmitted to offspring via the mothers. –Thus, Sons borne from hemophilic woman should be exempted from circumcision.

55. 55 3. Color blindness: is a disorder inherited as a recessive sex- linked character and affect both males and females. 3. Color blindness: عمى الألوان is a disorder inherited as a recessive sex- linked character and affect both males and females.  A color blind female ( X a X a ) may be born to a color blind father ( X a Y ) and a carrier mother ( X A X a )

56. 56 It is common in meiosis and includes:It is common شائع in meiosis and includes: a)Chromosomal deletions/translocations  Homologous chromatids may break and rejoin at incorrect places, thus, one chromatid will loose more genes than it receives.  Homologous chromatids may break تـَنكسر and rejoin at incorrect places, thus, one chromatid will loose more genes than it receives. b)Chromosomal duplications (Polyploidy).  result from nondisjunction during gamete production in one parent. A diploid embryo that is homozygous for a large deletion or male with a large deletion to its single X chromosome is usually missingmany essential genes and this leads to a lethal outcome.A diploid embryo that is homozygous for a large deletion or male with a large deletion to its single X chromosome is usually missing many essential genes and this leads to a lethal outcome. –Duplications and translocations are very harmful. Translocation or inversion can alter phenotype because a gene’s expression is influenced by its location.Translocation or inversion can alter phenotype because a gene’s expression is influenced by its location. Chromosomal aberration.

57. 57 A)- Aneuploidy ( Chromosomal duplication) 1- Down syndrome [ : Is due to three copies of chromosome 21 ( Trisomies ). 1- Down syndrome [ Polyploidy (2n + 1 ), trisomy in autosomes ]: Is due to three copies of chromosome 21 ( Trisomies ). Although chromosome 21 is the smallest human chromosome, it severely alters an individual’s phenotype in specific ways. Although chromosome 21 is the smallest human chromosome, it severely alters يُغير an individual’s phenotype in specific ways. Fig. 15.14

58. 58  Most cases of Down syndrome result from nondisjunction during gamete production in one parent.  The frequency of Down syndrome correlates with the age of the mother.  This may be linked to some age-dependent abnormality in the spindle checkpoint during meiosis I, leading to nondisjunction. 2- Klinefelter’s syndrome, (a)- An XXY male, occurs once in every 2000 live births. 2- Klinefelter’s syndrome [ Polyploidy (2n + 1), trisomy in sex chromosomes ], (a)- An XXY male, occurs once in every 2000 live births. These individuals have male sex organs, but are sterile.These individuals have male sex organs, but are sterile. There may be feminine characteristics, but their intelligence is normal.There may be feminine characteristics له صفات أنثوية, but their intelligence is normal. (b)- An XYY male, tend to somewhat taller than average. (b)- An XYY male, tend to somewhat taller than average. (c)- A trisomy female ( XXX ), which occurs once in every 2000 live births, produces healthy females. (c)- A trisomy female ( XXX ), which occurs once in every 2000 live births, produces healthy females. 3- Turner’s syndrome, a monosomy female ( X0 ), or, which occurs once in every 5000 births, produces phenotypic, but immature females غير ناضجة جنسيا.

59. 59 B)- Chromosomal structure-alterations: It can also cause human disorders. It can also cause human disorders.  Deletions, even in a heterozygous state, cause severe physical and mental problems. 1. Cri-du-chat, results from a specific deletion in chromosome 5. 1. Cri-du-chat عارض مواء القط, results from a specific deletion in chromosome 5.  These individuals are mentally retarded, have a small head with unusual facial features, and a cry like the mewing of a distressed cat.  This syndrome is fatal in infancy or early childhood. 2.Myelogenous, [leukemia (CML)]. Caused by chromosomal translocations since a fragment of chromosome 22 switches places with a small fragment from the tip of chromosome 9.

60. 60 www.youtube.com/watch?v=prbAy_2gKR Biology - Laws of Heredity - Genetics Plz open the video

61. 61 www.youtube.com/watch?v=- mRphwIVEcM Gregor Mendel working with Punnett Squares. Plz open the video

62. 62 Plz open the video www.youtube.com/watch?v=- 2YPAt8hOmE Mendelian Genetics

63. 63 ► 3:34► 3:34► 3:34► 3:34 www.youtube.com/w Mendel and Genetics atch?v=rU3CDi08-Hk Plz open the video

64. 64 www.youtube.com/watch?v=ZnoxLqnb_Q g Mendel study genes and inherited traits using peas Plz open the video

65. 65 www.youtube.com/watch?v=ioMhw85wI18 Mendel's Law of Heredity Plz open the video

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68. 68 Q1: Write whether each of the following statements is True (T) or False (F): 1-( ) Sickle-cell disease is a dominantly inherited disorder. 2-( ) The 3 : 1 phenotypic ratio is characteristic of the F1 generation of a monohybrid cross. 3-( )A mating between parents differing in two characters is called;Monohybrid 4-( )The separation of alleles into separate gametes is known as Mendel’s law of independent assortment. 5-( ) An organism’s expressed traits is known as genotype.

69. 69 Q 2: Choose the correct answer (one answer only): 1-Which of the following is a genetic disorder that caused by genes and environmental factors (multi-factorial disorder): a)- colour blindness b)- Tay-Sachs disease c)- cancer d)- cystic fibrosis 2-Which of the following is a dominant genetic disease? a)- sickle-cell anaemia. b)- cystic fibrosis c)- Tay Sachs disease d)- none of the above 3-Huntington's disease is an example of a genetic disorder caused by: a)- lethal dominant allele b)- non-lethal dominant allele c)- recessive allele d)- multiple alleles 4- An organism with two identical alleles for a character (trait) is: a)- homozygous b)- heterozygous c)- semizygous d)- multizygous

70. 70 5-The self-cross of dihybrid (RrYy) will result in which of the following phenotypic ratio: a)- 1: 1: 1: 1 b)- 9: 3: 3: 1 c)- 1: 2: 2: 1 d)- 3: 3: 3: 1 6-Mendel's law of segregation means that the two members of an allelic pair are: a)- distributed to separate gametes. b)- distributed to the same gamete. c)- assorted dependently. d)- segregated pairwise. 7-Which of the following is represented by the appearance (such as colour) a)- phenotype b)- genotype c)- kariotype d)- none of them 8-Different alleles are --------------------- -Alternative version of genes (different molecular forms of a gene).a b-Different phenotypes. c-Self-fertilizing,true breeding homozygotes. d-Organism’s genotype. 9-Crosses between F1 individuals resulting from the cross AABB X aabb lead to F2 phenotypic ratios close to------------- a-1:2:1 b-1:1:1:1 c-3:1 d-9:3:3:1 10-A heterozygote has a---------------for the trait being studied. a-Pair of identical alleles. b-Pair of nonidentical alleles. c-Haploid condition,in genetic terms. d- a and c.