Genetis Week 11 and 12 Flashcards
What is Autosomal Aneuploidy
It is Aneuploid cells that have missing or additional chromosomes not in multiple of 23.
- typically one chromosome is affected, but multiple can be involved
Name the types of Aneuploidy
-Monosomy
-Trismoy
Explain the types of Aneuploidy
Monosomy: There is one copy of a chromosome in a diploid cell, almost always lethal
Trisomy: When there are three copies of a chromosome, Some are compatible with life
What Causes Aneuploidy
It results from no disjunction, where chromosome fail to separate during meiosis.
- This leads to gametes lacking a chromosome or having an extra chromosome , forming monosomic or trisomic zygotes.
What is Trisomy 21 also known as
Down syndrome
What is the prevelance of Trisomy 21
- The most common autosomal aneuploidy compatible w life
What is Trisomy 21 caused by
Mostly Extra copy of chromosome 21( non disjunction) and also remainder is caused by Chromosome translocation
What is the common cause of mosaicism in Trisomy 21
- A Trisomic conception followed by the loss of the extra chromosome during ,mitosis in some embryonic cells
Name the 2 key genes on chromosome 21
- DYRK1A
-APP
What are some of the associated medical conditions once somone has Trisomy 21( Down syndrome)
- Respiratory infections
-Heat defects
-Intellectual Disability
-Hearing loss
What is the function of the 2 genes on chromosome21
DYRK1A: Assoicated with intellectual disability
APP: Linked to Alzheimer like features
What are some clinical features of down syndrome
- small ears
-Round cheecks
-Short neck
-Short hands and feet
-Hypotonia(Decreased muscle tone)
Are males Trisomy 21 sterile or non sterile
nearly alwways sterile
What does mosaicism in Trisomy 21 result in
- Milder clinical expression of the phenotype
What is Trisomy 18 also known as
- Edward sydrome
What is the prevelance of Trisomy 18
- Second most common autosomal trisomy
When is trisomy 18 more common to occur
At conception
What are the clinical features of Trisomy 18(Edward Syndrome)
-Facial and hand abnormalities
-Small ears
- Small mouth
-Heat defects
What are the causes of Mortality in Edward syndrome
- Infections
-Heart defects
What are the outcomes of patients who survive to infancy with Trisomy 18(ES)
- Psycholotor delay which is greater than in down syndrome
-Slow progression in milestone
-Most do not walk independently
What are the 2 karyotypes of Trisomy 21
- 47,XY,+21 or 47,XX, +21
What is the karyotype of Trisomy 18
- 47,XY,+18
What is the prevealnce of Trisomy 13
rare/less common compared to T21 and T18
What is Trisomy 13 also known as
- Patau Syndrome
What is the karyotype of Trisomy 13
- 47,XY,+13
When does the risk of Trisomy 13 increase
- with advanced maternal age
What are the clinical features of Trisomy 13
- Small malformed eyes
-Extra fingers and toes
-Skin defects on the posterior scalp
Name the malformations that occur in Trisomy 13
- Malformation of the CNS which is seen as Heart defects and Renal abnormalities
What happens for the patients with Trisomy 13 that survive
They have severe development disabilites
What is Turner syndrome caused by
Single x chromosome
What is the karyotype for Turner syndrome
45,X
What are characteristics of Turner syndrome
- Short stature
-Webbed neck
-Triangular shaped face
When is Turner syndrome often diagnosed
At birth
What is Klinefelter Syndrome caused by
- 47,XXY Karyotype
What are the features of Klinefelter Syndrome
- Tall stature
-Small testes
-Low testosterone levels
What is the cognitive impact of Klinefelter syndrome
- Low verbal IQ
-Increased risk of learning disabilities
What treatemtn is used for Klinefelter syndrome
- Testosterone therapy
What is the karyotype for Triple X female
- 47 XXX
What are the characteristics of Triple X female
- Tall
-Menstral irregularities
What are the characteristics of 47 XYY syndrome
-Tall
-Reduced IQ
