Congenital and Genetic abnormalities

 

Congenital abnormalities

 

  1. due to developmental error during fetal development

  2. almost always detected at birth

 Developmental processes are occur at a rapid rate therefore errors have devastating implications

Stem cells differentiate into their specialized cell types, move to area of organ or tissue placement then divide.

 

Errors in embryogenesis – if they occur at the particular organs critical period in development that organ will be severely development

 

Different structures devel @ different times

 

Organogensis – begins at day 15 post conception therefore this is the most vulnerable time for mutations.

 

  • each organ has its own critical period within fetal development – different organs develop at different times

  • The CNS has an extensive critical period therefore most congenital abnormalities will also affect the CNS

 

Tatatogens: Mutagenic agents

  • drugs

  • microbes

  • vitamin,mineral or nutrient deficiency

 

Taratogens: – agents that affect the fetal development environment

  • the maternal body

  • the environment outside the maternal body

 

  1. Falitamide:a taratogen causing limb reduction defects

  2. Alcohol: causes Fetal alcohol Syndrome

  3. Deficiency: Vitamin, mineral or nutrients eg folic acid

  4. Viral infections: eg Rubella virus causing german measles

 

Fig. gestational development

 

Genetic Abnormalities

 

  • Not always present at birth

  • genetic code mutations

eg diabetes

 

autosomal dominant and recessive

 

Homozygous for a particular gene when identical alleles of the gene are present on both homologous chromosomes.

 

Heterozygous for a particular gene when two different alleles occupy the gene’s position on the homologous chromosomes.

 

Types of Chromosomes

  1. autosomal chromosomes 22 pairs

  2. sex chromosomes –1 pair, 2 chromosomes the X and Y

 

3 primary types of abnormalities

     

  1. Chromosomal Abnormalities

  • reflects an atypical number of chromosomes or a structural abnormality in one or more chromosomes.

  • Trisomy 21 – Downs Syndrome

 

  1. Single gene (monogenic) Chromosomal Abnormalities

2a. autosomal recessive

  • 25% chance of the individual being affected

  • 50% of individuals will be carriers for the gene

  • 25% of individuals will be unaffected

  • Cystic Fibrosis

 

    2b. autosomal dominant

  • 25% of individuals will be carriers for the gene

  • 50% chance of inheritance

  • 25% will be lethals (noncompatoible with life)

  • Dwarfism

 

    2c.X-linked recessive

  • the mutated affected gene is linked to the X chromosome

  • hemophilia

 

  1. Complex trait (polygenic and environmental) Chromosomal Abnormalities

  • type 2 diabetes

  • more than one gene is affected

  • lifestyle (enviro factors)

 

 

  1. Chromosomal abnormalities

Numeric abnormalities:

 

  • Aneuploidy – extra or missing Chromosome

  • Trisomy – additional Chromosome to the pair eg trisomy 21

  • Monosomy – only one chromosome, one missing from the pair (lethal)

  • named for the Chromosome # involved

  • Karyotype is the characteristic chromosome complement of a eukaryote species

     

  1. Trisomy 21

  2. Turners Syndrome

  • female XO (1 in 3000 live births)

  1. Klinfelters syndrome

  • male XXY (1 in 500)

  • fig 7-11

 

Structural defects:

  1. Chromosomal deletion: The loss of a segment of the genetic material from a chromosome.

 

  1. Chromosomal Inversion: a chromosome rearrangement in which a segment of a chromosome is reversed end to end.

  2. Chromosome translocation: is a chromosome abnormalitycaused by rearrangement of parts between nonhomologous chromosomes.

Martin, Glenn and Porth, Carol, Mattson. 2009. Pathophysiology Concepts of Altered Health States. 8th ed. Lippincott Williams and Wilkins. Philadelphia

About these ads

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

Follow

Get every new post delivered to your Inbox.

%d bloggers like this: