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Dragonfly Chapter 14 The Human Genome. Section 14-1: Human Heredity Key Concepts: How is sex determined? How do small changes in DNA Cause genetic disorders?

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Presentation on theme: "Dragonfly Chapter 14 The Human Genome. Section 14-1: Human Heredity Key Concepts: How is sex determined? How do small changes in DNA Cause genetic disorders?"— Presentation transcript:

1 Dragonfly Chapter 14 The Human Genome

2 Section 14-1: Human Heredity Key Concepts: How is sex determined? How do small changes in DNA Cause genetic disorders? I.Human Chromosomes A. Karyotype: A picture of chromosomes taken during mitosis and cut out and arranged into homologous pairs.

3 Diploid Cell: ________ of homologous chromosomes Human diploid cell has ____ chromosomes arranged in ____ pairs The 46 chromosomes contain Two sets billion nucleotide pairs Mendelian genetics requires that organisms of gene from each parent inherit a single copy In humans, _______________ (reproductive cells of egg and sperm) contain a single copy of each gene (one set of genetic information). the gametes

4 Gametes are formed in the __________ (sperm) and __________(egg) by meiosis. Each gamete contains 23 chromosomes (one set) or __________________ (N) of chromosomes. ________________ requires the egg and the sperm to join and produce a ______________ (fertilized egg) that contains 46 chromosomes (two sets) or _____________________ (2N). testes ovaries haploid number zygote diploid number Fertilization

5 Humans have 46 total chromosomes 44 _____________ follow regular Mendelian genetics 2 _________________ (X and Y) are sex-linked autosomes sex chromosomes A.Pedigree Chart: A pedigree chart shows the _________________ within a family and can be useful to help with __________________________ within families. It is another __________________ _________ of a particular cross and the genotype of the family members. relationship genetic inheritance problems outcome way to predict the

6 A circle represents a female. A square represents a male. A horizontal line connecting a male and female represents a marriage. A vertical line and a bracket connect the parents to their children. A half-shaded circle or square indicates that a person is a carrier of the trait. A completely shaded circle or square indicates that a person expresses the trait. A circle or square that is not shaded indicates that a person neither expresses the trait nor is a carrier of the trait. Section 14-1 Figure 14-3 A Pedigree Pedigree

7 Human Traits Phenotypes are determined by genotype as well as ________________________________. ________________________________ on gene expression are not inherited, but genes are. environmentally influenced Environmental influences

8 III. Human Genes The __________________: Complete set of genetic information Composed of about 30,000 genes Blood Group Genes Human Blood comes in a variety of genetically determined blood groups There are many different types of blood groups but the ones associated with the ABO blood group and the Rh blood groups are best known.. human genome

9 Rh blood groups is controlled by single gene with ________________. It is another antigen in blood, first discovered in Rhesus monkeys. The arrangement of the alleles determines only _______ possible types _____________ (+) contains the antigen, or ___________ (-) doesn’t contain the antigen. Positive is ______________ over negative. Rh-positive is identified with two genotypes: Rh+/Rh+ or Rh+/Rh- Rh-negative is identified with one genotype: Rh-/Rh- Two alleles two positive negative dominant

10 ABO Blood Groups: Discovered in 1900 by Karl Landsteiner. He realized that all blood is classified into four types: ____, ____, ____, and _____ due to the presence of or absence of specific __________ in the blood. Alleles I A and I B are __________________ and i o is ________________ to both I A and I B O ABB A codominant recessive Antigens are ______________________ used by the immune system. When an unrecognized antigen is present an immune response takes place and the cells ____________________________. chemical markers antigens _ clump or agglutinate

11 Phenotype (Blood Type Genotype Antigen on Red Blood Cell Safe Transfusions To From Section 14-1 Figure 14-4 Blood Groups Go to Section: Blood Type and Antigen Interactions

12 B. Recessive Alleles: Trait controlled by a recessive allele. This results in the disorder being present ___________________________. Examples include: PKU (Phenylketonuria), Tay Sachs disease and Cystic Fibrosis, Albinism, and Galactosemia (See chart on page 345) only if both alleles are recessive

13 C. Dominant Alleles: Traits controlled by a dominant allele. This results in the disorder being present when __________________________. Examples include: Achondroplasia (dwarfism), Hypercholesterolemia, and Huntington’s Disease only one allele is present

14 caused by Section 14-1 include Autosomol Disorders Recessive alleles Dominant alleles Codominant alleles Albinism Galactosemia Tay-Sachs disease Huntington’s disease Sickle cell disease Cystic fibrosis PhenylketonuriaAchondroplasia Hypercholes- terolemia Autosomal Disorders

15 Huntington Disease: It is controlled by a _________________________. The gene is located on Chromosome #4. single dominant allele Genetic degenerative disease that shows no symptoms until a person is in their ____________________. It progresses with gradual degeneration of their nervous system leading to loss of muscle control and mental function until death occurs. thirties or forties

16 Question? Would you want to know now if you could potentially get Huntington’s disease when you are older? Would you want to know if you could pass the gene on to your offspring before you have children? A. Codominant Alleles: controlled by _______________________________________. Sickle Cell Anemia is such a disorder. (This will be discussed in detail later) two alleles that share dominance

17 IV. From Gene to Molecule The link between ______________________ is not easily determined but for several diseases we have been able to make the connection. For both _____________ and ________________ a small change in the DNA of a _____________ affects the ______________________, causing a serious genetic disorder. genetics and phenotype Cystic fibrosisSickle cell disease single gene structure of a protein

18 A. Cystic Fibrosis: (See figure 14-8 p. 347) Cystic Fibrosis a.k.a. “CF” is a common genetic disease. It is most common in people of Northern European decent. It is a _______________________ of a gene found on the # 7 chromosome and affects the______________________________ Recessive disease digestive and respiratory systems

19 It is caused by the____________________ in the middle of a sequence for a protein and causes the protein to be ______________ and doesn’t allow Chloride ions to transport across the membrane, as they should. This causes the cells in a person’s airways to be unable to transport chloride ions and become __________________. deletion of 3 bases abnormal clogged with mucus

20 Chromosome # 7 CFTR gene The most common allele that causes cystic fibrosis is missing 3 DNA bases. As a result, the amino acid phenylalanine is missing from the CFTR protein. Normal CFTR is a chloride ion channel in cell membranes. Abnormal CFTR cannot be transported to the cell membrane. The cells in the person’s airways are unable to transport chloride ions. As a result, the airways become clogged with a thick mucus. Section 14-1 Figure 14-8 The Cause of Cystic Fibrosis

21 B. Sickle Cell Anemia The patient’s blood cells were found to be irregularly shaped, ____________________, and this is how the disease got its name. In normal red blood cells the ____________________ carries ___________ and distributes it around the body. In sickle cell disease, the red blood cells are sickle–shaped, causing the blood hemoglobin to no longer carry oxygen as well and _____________________ like a sickle hemoglobin molecule oxygen disrupts the normal functioning of the bodies cells, tissues and organs

22 This person is deprived of oxygen and the result is physical weakness, and damage to the brain, heart, spleen. It may be fatal. The cause: A _________________ in the DNA that codes for Hemoglobin polypeptides is changed. This substitutes Valine for glutamic acid. This change makes the hemoglobin less soluble in blood. This will cause the hemoglobin to come out of the blood and _______________. This crystallization causes the ________________ of the blood cells and the medical consequences. single base crystallize sickle shape

23 The genetics: The allele for sickle cell (H S ) is ___________ with the allele for normal hemoglobin (H A ). codominant Heterozygotes (H S H A ) are said to be ____ ____ __________ and have some effects of the disorder because they have both normal and sickle cell blood hemoglobin. Sickle cell carriers

24 DNA normal hemoglobin CAC GTG GAC TGA GGA CTC CTC Messenger RNA sequence GUG CAC CUG ACU CCU GAG GAG Normal hemoglobin amino acid sequence Val – His – Leu – Thr – Pro – Glu – Glu… …146 DNA Sickle Cell Anemia CAC GTG GAC TGA GGA CAC CTC Messenger RNA sequence GUG CAC CUG ACU CCU GAG Val – His – Leu – Thr – Pro – – Glu… …146

25 The distribution: Sickle Cell anemia is most prevalent in people of __________________. 10% of African Americans and 40% of populations in Africa and Asia carry the gene for Sickle cell anemia. Why? The carriers for the disease have a ___________________, a dangerous disease caused by a blood parasite found in tropical areas of the world. African descent resistance to Malaria

26 Sickle Cell Anemia is a __________ that has provided an ____________ in Malaria prone areas and in these areas it is _______________________ and therefore Sickle Cell Anemia persists. favored by natural selection H S H A HS HAHS HA H S H S H A H A advantage mutation

27 Section 14-2: Human Chromosomes Key concepts: Why are sex-linked disorders more common in males than in females? What is nondisjunction, and what problems does it cause?

28 I. Human Genes and Chromosomes Human diploid cell contains ______________________ of DNA. All neatly packed into the 46 chromosomes. __________________ of the DNA actually functions as genes. Genes are located on the chromosomes and each gene occupies a ______________________ on a chromosome. Genes may exist in ____________________ (alleles) Each chromosome contains ______ of the alleles for each of its genes Chromosome #21 and 22 are the ____________ of the human autosomes. These were the first two chromosomes whose sequences had been determined. 6 billion base pairs Small part specific place several forms one smallest

29 Both also contain genes for some genetic disorders like ________________________ ___________________________ We also discovered that there are many _________________________ segments of DNA Human chromosomes also have ________________ that can cross over just as we saw in the fruit fly. Leukemia and Amyotrophic Lateral Sclerosis (ALS) non-coding, repeating Linked genes

30 II. Sex-linked Genes 1. _______________________ are the ones that __________ in males and females 2. Chromosomes that are the ________ in male and females = _______________ 3. In humans: females = ____ and Males = ____ 4. The Y chromosome is smaller than the X Sex Chromosomes differ same autosomes XX XY

31 A. Sex Determination 1. Female _________ carry an X chromosome 2. _________ gametes can carry either an X or Y (meiosis segregates the chromosomes; _______ of the sperm carry X and ______ of the sperm carry Y) 3. In humans, _____________________________ of an offspring Female: XX male: XY gametes Male 50% X males determine the sex X Y X XXXY XXXY 50%

32 In some animals such as birds, butterflies, and some fish, the female determines the sex because she has the __________ chromosomes. Sex-linked Genes 1. In addition to determining the sex of an individual, the sex chromosomes carry genes that ____________________ differing affect other traits.

33 Sex-linked Genetic Disorders May be on the X or Y chromosome, but Most often expressed in ____________because they only have one X chromosome and thus all the alleles are expressed even if they are recessive. usually on the X because the Y has very few genes. males Colorblindness is a recessive disorder in which people can’t distinguish between certain colors. ____________________ colorblindness is most common. X C and X c are ________________ for normal and colorblind vision. Red-green the alleles

34 X C X C and X C X c are X C X c is a _______________________ and can pass the gene on to her sons. X c X c is a X C Y is a X c Y is a both normal vision females. carrier for colorblindness colorblind female. normal male and colorblind male.

35 Father (normal vision) Colorblind Normal vision Mother (carrier) Daughter (normal vision) Son (normal vision) Daughter (carrier) Son (colorblind) Section 14-2 Male Female Figure Colorblindness Go to Section: Colorblindness

36 Father (normal vision) Colorblind Normal vision Mother (carrier) Daughter (normal vision) Son (normal vision) Daughter (carrier) Son (colorblind) Section 14-2 Male Female Figure Colorblindness Go to Section: Colorblindness

37 Hemophilia is a __________________________ in which one is unable to clot their blood. Also known as Hemophilia is caused by a defect in a gene and the protein for normal blood clotting is missing. recessive sex-linked disorder “bleeders disease”.


39 Royal Family and Hemophilia

40 Muscular Dystrophy is another Here the affected individual inherits a degenerative __________disorder. The gene that codes for a _____________ is defective. They rarely live past early adulthood. Treatments are being explored that ___________ the defective gene. sex-linked recessive disease. muscle muscle protein replace

41 III. X-Chromosomes Inactivation Males survive with only one X chromosome so, what do females do with 2? They ___________; it becomes inactive. This creates a dense region in the nucleus known as a ______________. This is seen in coat color in cats. The cells will randomly shut off the coat color allele in one X chromosome and turn them off in the other X chromosome in other cells and this leads to some areas that are spotted orange and some spotted black, creating a tricolor cat, ________. This only happens in __________ because males only have one X chromosome. shut one off Barr body calico females

42 IV. Chromosomal Disorders Whole/sets of chromosome mutations 1._______________ = failure of homologous chromosomes to separate normally during meiosis This results in a disorder of __________________ 2. Examples of disorders include Down’s Syndrome, Klinefelter’s, and Turner’s Syndrome Nondisjunction chromosome number

43 Homologous chromosomes fail to separate Meiosis I: Nondisjunction Meiosis II Section 14-2 Nondisjunction Go to Section:

44 Homologous chromosomes fail to separate Meiosis I: Nondisjunction Meiosis II Section 14-2 Nondisjunction Go to Section:

45 Homologous chromosomes fail to separate Meiosis I: Nondisjunction Meiosis II Section 14-2 Go to Section: Nondisjunction


47 2. Examples of disorders include Down’s Syndrome, Klinefelter’s, and Turner’s Syndrome Nondisjunction disorders: Disorders in which the failure of _____________________ during one of the stages of meiosis causes a gamete to have _______________________________. Nondisjunction can occur in ___________________________. chromosome separation too few or too many chromosomes autosomes or sex chromosomes

48 Down’s Syndrome: Down’s syndrome is an example of ____________________________, specifically chromosome 21. In Down’s syndrome there is an ___________ of chromosome 21 (trisomy 21). Doing a _____________ (display of all the chromosomes in a cell nucleus) and looking at the chromosomes under a microscope detect the extra chromosome. Characteristics of Down’s syndrome include _________________, physically challenged, facial irregularities, and often heart defects. nondisjunction of an autosome extra copy karyotype mental retardation

49 Incidence of Down’s Syndrome and mother’s age

50 Turners Syndrome: Nondisjunction of the sex chromosomes in which They have the chromosome makeup of _________ where “O” represents the missing chromosome. 45 XO a chromosome is missing. This individual is female in appearance but does not develop the female sex organs during puberty and is ________. sterile.

51 Klinefelter’s Syndrome: Nondisjunction of the sex chromosomes in which an _____________________ is present. They have the chromosome makeup of ________. They are ___________ in appearance and are also sterile. May also be 48 XXXY or 49 XXXXY extra X chromosome 47XXY male No nondisjunctions of the sex chromosomes have ever produced and survived without an ______________. This is because the X chromosome carries many genes X chromosome essential for life.

52 XXY condition Results mainly from nondisjunction in mother (67%) Phenotype is tall males –Sterile or nearly so –Feminized traits (sparse facial hair, somewhat enlarged breasts) –Treated with testosterone injections

53 Nondisjunction of Sex Chromosomes

54 The impact of the sex chromosome nondisjunction has led us to understand the importance of the _____________________ in determination of sex of an individual. This has recently been determined to be true because the Y chromosome has been found to have a gene that turns on ______________________ in the embryo even if many X chromosomes are present. Y chromosome male sexual development

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