slide1 n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Genetic Disorders PowerPoint Presentation
Download Presentation
Genetic Disorders

Loading in 2 Seconds...

play fullscreen
1 / 13

Genetic Disorders - PowerPoint PPT Presentation


  • 90 Views
  • Uploaded on

Genetic Disorders. Things Can Go Wrong With DNA and Chromosomes. I. Overview of DNA Structure. A. Review 1. A gene is a segment of DNA that codes for a particular protein 2. Proteins determine the physical traits of an organism

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Genetic Disorders' - marek


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

Genetic Disorders

Things Can Go Wrong With DNA and Chromosomes

slide2

I. Overview of DNA Structure

A. Review

1. A gene is a segment of DNA that codes for a particular protein

2. Proteins determine the physical traits of an organism

3. In humans, DNA is organized into 23 pairs of homologous chromosomes

B. DNA Structure

1. The basic building block of DNA is a nucleotide

2. Nucleotide chains are held together to form a double helix

3. Nucleotides are represented using the letters A,T,C,G

slide4

II. DNA Based Disorders

A. Dysfunctional Genes

1. A gene can be missing some of its nucleotides or some of the nucleotides present may be in the wrong order

  • The protein made from that gene may not work properly

B. Missing Genes

1. A person can be born missing most or all of a gene

  • No protein is produced and the trait cannot be expressed properly
slide5

C. Examples of DNA Based Disorders

1. Sickle-cell anemia

  • Caused by a substitution of one nucleotide in the allele for normal hemoglobin
  • Red blood cells become sickle-shaped
  • These tend to become stuck in capillaries, leading to tissue death
  • Most common among individuals with African decent, because it provides a resistance to Malaria

Normal Red Blood Cell

Sickle Cell

slide6

Huntington’s Disease

    • Produced by a single dominant allele
    • A gradual change of the nervous system occurs around the age of 30 or 40
    • Marked by a painful, progressive loss of muscle control and mental function until death occurs
slide7

III. Chromosomal Based Disorders

  • Causes

1. Nondisjunction

    • during meiosis I, homologous chromosomes do not separate properly
    • Results in an extra copy of a chromosome in one cell, and a loss of that chromosome from another
  • Results
    • After fertilization, the resulting person will have an abnormal number of chromosomes
      • A monosomic cell is missing one chromosome
      • A trisomic cell has one extra chromosome
slide8

C. Nondisjunction of Sex Chromosomes

  • Genes critical to all embryonic development are on the X chromosome
    • absence of an X chromosome is lethal
    • absence of a Y chromosome is not lethal
  • Individuals can survive if they have an extra sex chromosome
  • Affects approximately 1 birth in every 1000
slide9

D. Disorders involving Sex Chromosomes

1. Klinefelter Syndrome

 males with extra X-chromosomes

  •  can be XXY, XXXY, OR XXXXY
    • Affects 1/500 births
    • phenotypically male with some female characteristics
    • enlarged breasts, low body hair count, small testes, long legs, thin, sterile
    • mental retardation occurs when there are more than 2 X-chromosomes
slide10

2. Triple X and Quad X Syndrome

  •  females with extra X-chromosomes (XXX, or XXXX)
    • Affects 1/700 female births
    • sometimes no visible difference from XX females
    • limited fertility
    • XXXX females are always mentally retarded
  • 3. Turner Syndrome
  •  females with only one X-chromosome
    • Affects 1/2500 live female births
    • more than 90% self abort
    • no ovaries, short, shield-like chestlow set ears, webbed neck
    • no mental deficiencies
slide11

E. Nondisjunction of Autosomal Chromosomes

  • Can affect chromosomes #1 - #22
  • There only 3 trisomies that result in a baby that can survive for a time after birth
  • Most frequently, the baby dies in utero.

F. Disorders Involving Autosomal Chromosomes

1. Down Syndrome

 one extra chromosome 21 -written as

(47,+21)

  • 1/6 die within the first year
  • average life expectancy is 16 years
  • lower than average mentality
  • shorter than average height, broad forehead, round head, open mouth, etc.
slide12

IV. Diagnosing Gene Disorders

A. Karyotype - a display of all the chromosomes in the nucleus

1. The process:

  • Harvested cells in metaphase are treated and stained
  • Chromosomes are observed under the microscope
  • A photograph is taken and enlarged
  • Chromosomes are arranged in homologous pairs
  • Abnormalities are identified
slide13

B. Prenatal Diagnosis

1. Amniocentesis

  • Fluid is removed from the sac surrounding the embryo
  • Cells are grown in the laboratory and treated with a chemical that prevents cell division
  • A karyotype is prepared and analyzed for abnormalities

2. Chorionic villus biopsy

  • Cells are removed directly from the membrane surrounding the embryo and analyzed for abnormalities
  • Recent studies have linked limb defects in babies to CVB tests done before the 10th week of pregnancy.

What ethical considerations are parents facing with regards to prenatal diagnosis of DNA based disorders?