Lecture 21: Chromosomal Aneuploidy and X Inactivation Flashcards
1
Q
What is a karyotype? How is this made?
A
- An ordered visual representation of the chromosomes in the cell
- Take blood sample, treat cells with mitogen, then colchicine, then stain
2
Q
What’re the different -centric types of chromosomes? (Karyotypes)
A
- Metacentric chromosomes (A) (central centromere)
- Submetacentric chromosomes (B) (slightly towards one pole centromeres)
- Acrocentric chromosomes (C, D, E) (severely towards one pole)
3
Q
The Y chromosome has ______ genes than X chromosomes
A
- Fewer
4
Q
What is Trisomy 21? What happens when it occurs?
A
- Three 21 chromosomes
- Down Syndrome
5
Q
What are some dysfunctions that down syndrome causes?
A
- Enlarged colon
- Intestinal blockage
- Degree of mental retardation
6
Q
What can increase the likeliness of giving birth to down syndrome children?
A
- Having a child over the age of 45
7
Q
What other animals can develop down syndrome?
A
- Reesus monkeys
8
Q
What is Amniocentesis? What is the risk?
A
- Where you take a sample of amniotic fluid and take some foetal cells
- Spin cells in centrifuge
- Carry out karyotyping
- To test for Down-Syndrome
- 0.1% risk of miscarriage
9
Q
What is a variation of Amniocentesis?
A
- Chrionic Villus Sampling, taken at 10-13 weeks, less accurate (90%, higher risk (1%)
10
Q
What’s one reason for Down Syndrome?
A
- Nondisjunction
- 95% of down syndrome babies have two maternal chromosome 21
- Homologous chromosomes fail to separate properly
- Daughter cells have two copies of chromosome 21, two cells
11
Q
What is Klinefelter Syndrome?
A
- XXY
12
Q
What effects does Klinefelter Syndrome have?
A
- Tall
- Mild degree of mental retardation
- Feminine physique
- Female type pubic hair
- Testicular atrophy
13
Q
What is Turner Syndrome?
A
- X0 (1 X)
14
Q
What does Turner Syndrome cause?
A
- Shortness
- Problems with internal organs (Heart)
- Poor breast development
- Widely spaced nipples
- No menstruation
- Skin has brown spots
15
Q
What is the Barr Body-Lyon Hypothesis?
A
- Males have XY
- Females have XX
- Inactivate one of the x chromosomes (condenses)
- Dark body where the chromosome has been condensed is called a Barr-Body
