Human Genetic Disorders

Transcription

1 Human Genetic Disorders

2 HOMOLOGOUS CHROMOSOMES Human somatic cells have 23 pairs of homologous chromosomes 23 are inherited from the mother and 23 from the father

3 HOMOLOGOUS CHROMOSOMES Autosomes o Are the first 22 pairs of homologous chromosomes that do not influence the sex of an individual Sex Chromosomes o Pair # 23 of chromosomes that determine the sex of an individual o Female (XX) ; Male (XY)

4 HOMOLOGOUS CHROMOSOMES

5 Mutations Are changes in the DNA nucleotide sequence of a gene that may result in a defective protein or no protein made

6 Point mutations affect one nucleotide on the gene sequence oit can be a substitution, deletion, or insertion of a nucleotide

7 Example : A C on DNA gets changed to a T

8 Autosomal Recessive Traits In order to express the trait, two recessive alleles must be inherited o aa = homozygous recessive A heterozygous individual is called a carrier because they carry the defective recessive allele but they do not express the trait o Aa genotype

9 Albinism Mutation results in inability to make the protein melanin that provides pigment to skin, hair, and eyes

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11 Cystic Fibrosis (CF) Mutation causes a deletion of 3 nucleotides on the CFTR gene, as a result the protein is missing in the cell membrane The CFTR protein is a channel protein that transports Cl ions Accumulation of thick mucus in lungs and respiratory passages, potential respiratory failure

12 Cystic Fibrosis (CF)

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14 Sickle Cell Anemia Point mutation results in the substitution of the amino acid valine for glutamic acid in the β- Hemoglobin protein The β-hemoglobin protein does not fold properly inside the red blood cells giving them an elongated sickle shape The sickle RBC cannot carry oxygen

15 Normal and Sickled Red Blood Cells

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17 Autosomal Dominant Traits If dominant allele is present on the autosome, the individuals that have homozygous dominant or heterozygous genotypes will have the disorder o AA or Aa genotypes Individuals with recessive genotype will not have the disorder o aa individual is normal

18 Achondroplasia

19 Achondroplasia

20 Achondroplasia A form of dwarfism Homozygous dominant (AA) and Heterozygous (Aa) individuals have the dwarf phenotype Homozygous recessive (aa) have normal height

21 Sex-Linked Traits Sex-linked traits are produced by mutations of genes located on the X chromosome Most sex-linked traits are recessive The mother passes the defective allele on her X chromosome to her sons and since they only have 1 X chromosome, they will show the disorder

22 Sex-Linked Pedigree

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24 Hemophilia Protein necessary for normal blood clotting is missing People can bleed to death from small cuts or have internal bleeding from bumps or bruises

25 Hemophilia

26 Hemophilia

27 Color Blindness Red-green Individuals are unable to distinguish certain colors Red-green The most common ins red-green color blindness

28 Color Blindness

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30 Nondisjunction Results from errors in Meiosis Homologous pairs of chromosomes do not separate in anaphase of Meiosis I or sister chromatids do not separate in anaphase of Meiosis II

31 Nondisjunction It results in extra chromosomes (n+1) or missing chromosomes (n- 1) in the gametes When a gamete with an abnormal number of chromosomes joins a normal one, the child will have an abnormal number of chromosomes

32 Nondisjunction

33 Non-disjunction

34 Down s Syndrome Caused by nondisjunction of autosome #21 The individual has an extra chromosome 21 or trisomy chromosomes (45 autosomes instead 44)

35 Down Syndrome Phenotype Upward slant to eyes Small, flattened nose Short webbed neck Small hands with short fingers In addition, down syndrome always involves some degree of mental retardation, from mild to

36 Down s Syndrome

37 Down s Syndrome or Trisomy 21 Karyotype

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40 Klinefelter s Syndrome Non-disjunction of the X chromosome Results in an extra X chromosome genotype XXY (47 XXY) The individual is a male

41 Klinefelter s Syndrome Phenotype Males with some development of breast tissue normally seen in females Little body hair is present, and such person are typically tall, have small testes Infertility results from absent sperm No evidence of mental retardation

42 Klinefelter s Syndrome Karyotype

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45 Turner s Syndrome Non-disjunction of X chromosome Female inherits only one X chromosome, genotype XO (45X) Underdeveloped ovaries and lack of secondary sexual characteristics Sterile No evidence of mental retardation

46 Turner s Syndrome

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48 Turner s Syndrome Karyotype

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