GENETIC DISORDERS IN HUMAN REPRODUCTION Turner Syndrome

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GENETIC DISORDERS IN HUMAN REPRODUCTIONTurner
Syndrome

• Khalid Esmail
• Leslie Newcombe
• Nicola Yang

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Introduction

• Also Gonadal Dysgenesis
• Most common sex chromosome abnormality in females
• Occurs in 1 per 2,500 girls
• Described by Dr. Henry Turner in 1938
  chromosomal abnormality discovered in 1960
• Normal has two X chromosomes 46 in all
• Turner syndrome has a missing or damaged X
  chromosome in some/all cells only 45 in all

Images courtesy of North Central Regional
Technology in Education Consortium
(http//www.ncrtec.org/tl/camp/gene/female.gif)
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Causes

• X-Chromosome Monosomy
• Male gamete ? 22 autosomes (regular
  chromosomes) and one
• sex chromosome.
• (Monosomy X-chromosome lost during meiosis of
  sperm)

Normal cell division during meiosis

• X-Chromosome Defects
• - Missing / damaged portion of X-chromosome
• -Results in small, large or no effects
• - Some genes ? absent
• - Activate usually silent genes

Monosomy sex chromosome lost during sperm
meiosis
All images courtesy of National Institute of
Child Health and Human Development
Source http//turners.nichd.nih.gov/ClinFrIn
tro.html
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Causes
X-chromosome lost during embryonic development

• X-Chromosome Mosaicism
• Lost during the early stages of embryonic
  development
• Some cells still have two, some only one
• Effects not as evident

All images courtesy of National Institute of
Child Health and Human Development
Source http//turners.nichd.nih.gov/ClinFrIn
tro.html
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Diagnosis

• Karyotyping
• Chromosomal pattern
• Only way to confirm diagnosis
• It is done
• Before birth amniocentesis or chorionic villous
  sampling
• After birth blood test

Chorionic villous sampling sample of placental
tissue.
Image courtesy of http//www.nlm.nih.gov/medlinepl
us/ency/imagepages/9181.htm
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Identifying features Symptoms

• Problems with body development and body systems

• Primary Features
• Ovarian Failure
• Medical Problems
• Short Stature

Growth curve comparing the average heights of
girls without TS, the average heights of girls
with TS and the average heights of girls with TS
that are not treated
Growth chart for children with Turner syndrome.
Source Rieser P, Davenport M. Turner Syndrome A
Guide for Families. Houston, TX Turner Syndrome
Society of the United States 2002. Data derived
from Lyon et al.
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Identifying FeaturesSecondary Features
Images courtesy of www.medscape.com/
viewarticle/445555_1, http//health.families.com/t
urner-syndrome-3417-3419-gem and
http//www.nlm.nih.gov/medlineplus/ency/imagepages
/1111.htm
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Treatment

• No known cure for chromosome abnormality
• However,
• Injections of human growth hormones (HGH),
  estrogen, and progesterone
• Trigger further development

HGH injection
Image courtesy of http//www.hghforheight.com/inje
ction.gif
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Summary --- Conclusion

• TS Having damaged or missing portion of X-
  chromosome
• Three causes
• X- Chromosome Defects
• X- Chromosome Monosomy
• X- Chromosome Mosaicism
• Diagnosed with Karyotyping
• Many features/symptoms ovarian failure, short
  stature etc.
• Not prone to mental retardation
• No cure for TS
• Injections of hormones may stimulate development
  

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Works Cited
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