Lecture 36 How do mutations affect health and crainofacial development? Flashcards
how many mutations is the average child born with that were not present in parents?
100-200
How many infants are born with a diagnosable genetic condition that can be attributed to a single major mutation?
- 1 in 50
What are some examples of chromosome disorders?
- aneuploidy
- rearrangements/translocations
- deletions
- insertions
- duplications
What is aneuploidy?
- an abberation in chromosome number caused by segregation of chromosomes during mitosis or meiosis
how many infants are born with aneuploidy?
- 1 in 400
Where do most cases of aneuploidy originate in?
- female meiosis I and risk rises with maternal age
Examples of aneuploidy
- 9p trisomy
- down syndrome
- edwards syndrome
key characteristics of down syndrome?
- upslanting palpebral fissure
- low set small folded ears
- short neck
- flattened nasal bridge
- brushfield spots
- epicanthal fold
What is the most common chromosomal condition?
- down syndrome
What is down syndrome?
- full or partial extra copy of chromosome 21
- 1 in 700 babies in the US
(6000 babies a year)
Most of the down syndrome cases can be classified as?
- nondisjunction (95% of cases)
What is the least common form of down syndrome?
- Mosaicism (1%)
What form of down snydrome is classified as a full or partial copy of chromosome 21 attaching to another chromosome (usually chromosome 14)
- Translocation (4%)
What is the main risk factor that has been linked to having a baby with down syndrome?
- Maternal age
results from nondisjunction or mosaicism
T/F most of the children with down syndrome come from mothers over the age of 35?
- False
- due to higher birth rates in younger women 80% of children with down syndrome are born to women under 35 years of age
What percentage of cases of down syndrome are traced to the father?
- 5%
Is heredity a factor in trisomy 21 (nondisjunction) and mosaicism?
- no
non craniofacial features of individuals with down syndrome
- low muscle tone
- small stature
- cognitive delay (very mild to severe)
- transverse palmar crease
(these traits vary)
What is a transverse palmar crease?
- a single deep crease across the center of the palm
How many adults with down syndrome reach age 60?
- 80%
What is the main thing to be concerned about with down syndrome patients?
- heart defects
- spinal problems
(always ask about heart problems)
What percent of children with down syndrome are born with some type of congenital heart defect?
- 50%
Spinal problems in down syndrome patients
- some people with down syndrome may have a misalignment of the top tow vertebrae in the neck
What is atlantoaxial instablility?
- misalignment of the top two vertebrae in the neck
- this condition puts them at risk of serious injury to the spinal cord from over extension of the neck (need extra support in chair)