5.1/2 APPLIED LEC Flashcards
Human Life Cycle
Gametes are produced, formation of gametes is called meiosis. Gametes are haploid
Fertilization describes the fusion of the gametes to create the diploid zygote.
cell divisions to produce the multicellular diploid adults
nondisjunction
abnormal disjunctional segregation of chromosomes
chromosomes don’t move to their proper poles
can occur in Meiosis I or/and Meiosis II
Meiosis I – two homologous chromosomes dont pass to separate cells
Meiosis II – failure of the two chromatids of a chromosome to pass to separate cells
What is Aneuploidy?
An organism that displays an aneuploid condition, has abnormal number of certain chromosomes
What is a Karyotype?
orderly display of the chromosomes
autosomes (non-sex chromosomes) ordered 1-22
sex chromosomes : 23rd pair (either to x or one x and one y chromosome
alternate organization: chromosomes arranged from largest in size to progressively shorter in size.
Amniocentesis
assessing a karyotype
Take (draw) some of the amniotic fluid that surrounds the developing fetus.
Biochemical tests may be conducted
Karyotypes are made from the chromosomes of the cultured cells
Babies are 14th to 16th week of pregnancy
CVS (chorionic villus sampling)
take sample of chorionic villus tissue
Conducted earlier 8 to 10th week of pregnancy, so you can get the results much earlier
Biochemical tests may be conducted
Karyotypes are made from the chromosomes of the cultured cells
Results can be collected earlier, within a day or two.
How do you make a Karyotype?
- blood taken
- add phytohemagglutin, stimulate mitosis
- incubate for 2-3 days at 37 degrees C
- add celcemid to culture for 1-2 hours (stops mitosis in metaphase (chromosomes will be condensed, better visualization))
- transfer to tube with fixative, centrifuge cells, add low salt solution or hypotonic solution (gets rid of RBC and swells lymphocytes)
- drop cells onto microscope slide, stain with giesma, examine under microscope, digitize images, process, arrange photos (using computer) for karyotype
What are Karyotypes Useful?
They are useful for genetic screening to identify specific chromosomal defects in their number, size, & type
Klinefelter syndrome
47, XXY
- Males have an extra X number of sex chromosomes, for example XXY.
- Have very small testes and are sterile.
- Display feminine body contours
- Have enlargement of breast tissue
Trisomu
Another type of aneuploidy, describes a condition when an individual has 3 copies of a certain chromosome
Alterations in autosomes (non sex chromosomes) - Down Syndrome
trisomic aneuploid condition
trisomy chromosome 21
Mild to moderate intellectual disabilities
Delayed development
Impulsive behavior
Poor judgment
Short attention span
Slow learning
A short neck with excess skin at the back
A flat face and nose
Small ears, hands, and feet
Poor muscle tone or loose joints
A single crease in the palm of the hand
Upward slanting eyes, sometimes with a skin fold covering the inner corner of the eye
Patau syndrome
Trisomy Chromosome 13 karyotype
- Severely mentally challenged
- Cleft palate
- Deaf
- Malformed organs
47, 13+
Edwards syndrome
Trisomy Chromosome 18 karyotype
47, 18+
Trisomy of Chromosome 18
- Small newborns
- low set ears, webbed neck, receding chin
- organ malformations
- big back part of skull: occiput
- small mouth and jaw
- sheild chest
- wideset nipples
- flexed big toes
- clenched hands
turner syndrome
female with only one X chromosome
only viable human monosomy
0X
- short in stature
- webbed neck
- shield like chest
- internal sex organs do not mature, females are sterile
- constriction of aorta
- wide spread nipples
- poor breast development
Triple X syndrome
usually normal phenotype and fertile, others have variable expression
Jacobs syndrome (alteration of sex chromosomes
xYY
- normal male
- much taller than average
- normal fertility & intelligence
Why do Meiotic Mistakes Occur
accidental in their occurrence. Generally mistakes occur without any genetic predisposition.
the larger percentage of trisomic conditions are due to maternal errors (from 71-100% maternal error
The older the mother is, there seems to be greater incidences of Down Syndrome (1/100 children at age 40, 1/36 at 44, 1/180 at 38, 1/300 age 36)
karyotypes of normal vs cancer cells
cancer cell’s karyotype has several mutations, extra chromosomes, and missing chromosomes
Mitotic chromosome instability in cancer cells
relationship between aneuploidy and tumour formation, may lead to aneuploidy and activation of oncogenes & inactivation of tumour suppressors.
Dr. Ghulam Mufti
Genome chip and explains that the patterns displayed on the computer output indicates the different gene expressions for individuals with varying conditions
offer the hope of more customized treatments (personalized treatments) for those living with cancer and other health-related challenges
