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Karyotypes and Pedigrees

Karyotypes and Pedigrees. Chapter 14. Chromosome Review. All of an organism’s DNA can be packaged into chromosomes Humans - 23 pairs or 46 total chromosomes Each pair of chromosomes contain genes with 2 alleles (1 from each parent ). Chromosome Review.

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Karyotypes and Pedigrees

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  1. Karyotypes and Pedigrees Chapter 14

  2. Chromosome Review • All of an organism’s DNA can be packaged into chromosomes • Humans - 23 pairs or 46 total chromosomes • Each pair of chromosomes contain genes with 2 alleles (1 from each parent)

  3. Chromosome Review • All of an organism’s DNA can be packaged into chromosomes • Humans - 23 pairs or 46 total chromosomes • Each pair of chromosomes contain genes with 2 alleles (1 from each parent) • Chromosome Numbers • 1-22 autosomes • Sex chromosomes “#23” • XX – Female • XY - Male

  4. Pedigree • A pedigree is a chart for tracing genes in a family • Phenotypes are used to infer genotypes on a pedigree

  5. Pedigree Basics Circle – Female Square – Male Horizontal Line – Mating Vertical Line – Offspring Shaded – Has trait Unshaded – No trait

  6. Human Genome • Human Genes- human genome contains 20,000 to 30,000 genes. • 99.9% of all nucleotide bases are exactly the same in all people • Less than 2% of genome actually codes for proteins

  7. Karyotypes • Karyotypes- picture of all chromosomes in a cell for one organism

  8. Creating a Karyotype

  9. Karyotype Uses • Used to identify certain genetic disorders in which there are extra or too few chromosomes (i.e. Down syndrome 

  10. Identifying Gender by Karyotype Male Female

  11. Autosome Disorders

  12. Trisomy 21 (Down’s Syndrome) • Extra 21st chromosome • Male or female (47XX or 47XY) • 1/700 births • characteristic facial features, short stature; heart defects • susceptibility to respiratory disease, shorter lifespan • prone to developing early Alzheimer's and leukemia • often sexually underdeveloped and sterile, usually some degree of mental retardation.

  13. Patau Syndrome (trisomy 13) • Extra 13th chromosome • Male or female (47XX or 47XY) • serious eye, brain, circulatory defects as well as cleft palate. • 1:5000 live births. • Children rarely live more than a few months.

  14. Edward’s Syndrome • Extra 18th chromosome • Male or female (47XX or 47XY) • almost every organ system affected • 1:10,000 live births. • Most are stillborn or miscarried • Children with full Trisomy 18 generally do not live more than a few months.

  15. Alterations in Chromosome Structure • Sometimes, chromosomes break, leading to 3 types of changes in chromosome structure: 1. Deletion: a portion of one chromosome is lost during cell division. That chromosome is now missing certain genes. When this chromosome is passed on to offspring the result is usually lethal due to missing genes.

  16. Alterations in Chromosome Structure - Example: Cri du chat (cry of the cat): A specific deletion of a small portion of chromosome 5; these children have severe mental retardation, a small head with unusual facial features, and a cry that sounds like a distressed cat.

  17. Alterations in Chromosome Structure 2. Duplication: if the fragment joins the homologous chromosome, then that region is repeated Example - Fragile X: the most common form of mental retardation. The X chromosome of some people is unusually fragile at one tip - seen "hanging by a thread" under a microscope. Most people have 29 "repeats" at this end of their X-chromosome, those with Fragile X have over 700 repeats due to duplications. Affects 1:1500 males, 1:2500 females.

  18. Alterations in Chromosome Structure 3. Translocation: a fragment of a chromosome is moved ("trans-located") from one chromosome to another - joins a non-homologous chromosome. • The balance of genes is still normal (nothing has been gained or lost) but can alter phenotype as it places genes in a new environment. • Can also cause difficulties in egg or sperm development and normal development of a zygote.

  19. Sex Chromosome Disorders

  20. Turner’s Syndrome • In females,(45XO) sex organs fail to develop at puberty • Occurs 1/ 2,000 births • http://www.youtube.com/watch?v=ldjb-FR-PKo Only 1 X chromosome

  21. Triple X Syndrome • In females (47XXX) • Have normal development • Usually taller for their age • Occurs 1/ 1,00 births

  22. Klinefelter’s Syndrome • In males (47XXY) • Sterile, feminine qualities (higher voice, breast development) • Little facial hair • Taller than average • Occurs 1/ 1,000 male births

  23. Jacob’s Syndrome • Male (47XYY) • Lead normal lives (most don’t even know they have this) • Produce more testosterone  more facial hair, taller • Occurs 1/ 1,500 births?

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