Sex linked genes genetic disorders
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Sex-linked Genes & Genetic Disorders. Unit 5: Genetics Ch. 11-3 & Parts of Ch. 14. Learning Goals. 1. Describe where sex-linked traits are located and and why these traits generally affect men more than women. Give an example of a sex-linked trait.

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Sex-linked Genes & Genetic Disorders

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Sex linked genes genetic disorders

Sex-linked Genes & Genetic Disorders

Unit 5: Genetics

Ch. 11-3 & Parts of Ch. 14


Learning goals

Learning Goals

  • 1. Describe where sex-linked traits are located and and why these traits generally affect men more than women. Give an example of a sex-linked trait.

  • 2. Describe dominant and recessive disorders and give an example of each.

  • 3. Explain nondisjunction and how it leads to trisomy and monosomy.


Sex linked genes

Sex-Linked Genes

X Chromosome

  • Some genes are carried on the sex chromosomes (X & Y)

    • XX = female, XY = male

  • Several disorders are carried on the X chromosome

Y Chromosome


Sex linked genes genetic disorders

  • Because men have only 1 X, they don’t have a “backup” X like women

  • If the X is bad, men have the disease

    • EX: Colorblindness, hemophilia, muscular dystrophy


Color blindness

Color-Blindness

  • Three genes for color vision are located on the X chromosome.

  • In males, a defective version of any one of these genes produces colorblindness.


Sex linked genes genetic disorders

  • Sex-linked Crosses

    • 1) Must show sex chromosomes for each parent & alleles for each X chromosome

    • 2) Answer must include male or female


Predict gender phenotypes

Predict Gender & Phenotypes

  • Colorblindness is a recessive trait

  • Geno: Pheno:

    • XCXC

    • XcXc

    • XCXc

    • XCY

    • XcY

Normal Female

Colorblind Female

Normal / Carrier Female

Normal Male

Colorblind Male


Pedigree charts

Pedigree Charts

  • A chart used to examine the appearance of traits, especially diseases, over several generations.


Genetic disorders

Genetic Disorders

  • Some genes code for nonfunctional proteins.

  • These cause hereditary diseases.


Dominant disorders

Dominant Disorders

  • If you have the gene, you have the disease

    • May not show up until later in life, after you’ve had kids and passed it on

    • Huntington disease, Dwarfism


Huntington s disease

Huntington’s Disease

  • Results in the early death of some neurons in the brain. People loose the ability to control their movements.

  • Symptoms usually don’t start until the 20s to early 30s.

  • The disease is fatal, usually by the late 30s or early 40s.


Recessive disorders

Recessive Disorders

  • Can remain hidden and skip generations

  • Heterozygous individuals (Rr) are called “carriers”

    • Albinism, cystic fibrosis, Tay-Sachs, phenylketonuria


Sex linked genes genetic disorders

  • Cystic Fibrosis- Protein does not fold properly. Causes a build up of mucus in the lungs


Chromosomal disorders

Chromosomal Disorders

  • 1) Nondisjunction: chromosomes do not separate properly during meiosis

  • The results are cells with abnormal numbers of chromosomes.

    • Cells end up with extra chromosomes (47) or fewer chromosomes (45).


During meiosis

During Meiosis


Sex linked genes genetic disorders

  • Trisomy: If there are three homologous chromosomes instead of two

    • Down syndrome is caused by trisomy of chromosome 21


Sex linked genes genetic disorders

Where is the mutation?


Sex linked genes genetic disorders

Where is the mutation?


Sex linked genes genetic disorders

  • Monosomy: the cell is missing one chromosome

    • Turner’s syndrome is a female with one “X” chromosome not 2 “X” chromosomes.


Sex linked genes genetic disorders

  • 2) Alterations in Chromosome Structure

    • Deletion: portion of chromosome is deleted

      • EX: Cri du chat (Cry of the cat)

    • Duplication: piece of chromosome is repeated

      • Ex: Fragile X Syndrome

    • Translocation: piece of chromosome is deleted from one homologous pair and reattached to another homologous pair


Deletion cri du chat

Deletion: Cri du chat


Duplication fragile x

Duplication: Fragile X


Translocation

Translocation


Learning goals1

Learning Goals

  • 1. Describe where sex-linked traits are located and why these traits generally affect men more than women. Give an example of a sex-linked trait.

  • 2. Describe dominant and recessive disorders and give an example of each.

  • 3. Explain nondisjunction and how it leads to trisomy and monosomy.


Whiteboard practice

Whiteboard Practice

  • Legend & Parents

  • Punnett Square & Answers


Sex linked genes genetic disorders

  • Queen Victoria was a carrier of hemophilia (h), a recessive, sex-linked disease. King Edward was normal (H).

    • 1. Make a legend

    • 2. Genotypes of parents?

    • 3 & 4. Show the cross.

    • 5. Give probabilities for both sons and daughters


Sex linked genes genetic disorders

  • Muscular Dystrophy (d), is a recessive, sex-linked disease. A man who has muscular dystrophy marries a woman who is homozygous normal

    • 1. Make a legend

    • 2. Genotypes of parents?

    • 3 & 4. Show the cross.

    • 5. Give probabilities for both sons and daughters


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