CHROMOSOMAL ABNORMALITIES Flashcards
are either numerical or structural.
• They are a very common cause of early spontaneous miscarriage.
• Usually, but not always, cause multiple congenital anomalies and learning difficulties.
Chromosomal abnormalities
Variations in Chromosome Number
⚪– the usual number and sets of chromosomes
⚪ – the presence of three or more complete sets of chromosomes
⚪ – the presence of additional chromosomes or missing individual chromosomes
Euploidy
Polyploidy
Aneuploidy
NONDISJUNCTION
______ of the chromosomes during division
● Meiotic - too many/few chromosomes in all cells
● Mitotic - group of cells/patch of tissue with altered chromosome number
Malsegregation
Types of Polyploidy
⚪ – three sets of chromosomes
23 x 3 = 69
⚪ – four sets of chromosomes
23 x 4 = 92
Triploidy
Tetraploidy
Types of Aneuploidy
⚪ – one less chromosome
(23 x 2) – 1 = 45
⚪ – one additional chromosome
(23 x 2) + 1 = 47
Monosomy
Trisomy
Aneuploidy
⚪ When aneuploidy occurs in humans, syndromes can result. Examples include the following:
- Trisomy 13 - Patau Syndrome
- Trisomy 18 - Edwards Syndrome
- Trisomy 21 - Down Syndrome
- Turner Syndrome
- Klinefelter (XXY) Syndrome
- Jacob’s (XYY) Syndrome
Mental and physical deficiencies, wide variety of defects in organs, large
triangular nose, early death
Patau
Trisomy 13
Mental and physical deficiencies, facial
abnormalities, extreme muscle
tone, early death
Trisomy 18
Mental deficiencies, abnormal
pattern of palm creases, slanted eyes, flattened face, short stature
Down syndrome
Trisomy 21
Sexual immaturity (no sperm),
breast swelling (males)
Klinefelter
XXY
Tall and thin (males)
Jacobs
XYY
Tall and thin, menstrual
irregularity (females)
Triple X
XXX
Short stature, webbed
neck, sexually undeveloped
(females)
TURNER
X0
Survival rate is very high for this non-disjunction!
Down’s Syndrome
a.k.a-
trisomy 21
- Incidence is only 1 in 6000-11, 000 live births.
- It is uncommon for fetuses with this condition to survive
Edward Syndrome
⚪ This karyotype demonstrates trisomy 18
⚪ Shorthand: (47, XX or XY, +18).
⚪ 30% of these children die within the and only 10% survive one year.
⚪ There is severe mental retardation. ⚪ Other characteristics:
● elongated skull, a very feet.
narrow pelvis, rocker bottom
● the ears are often low set and the mouth and teeth are small.
● nearly all babies born with this condition die in early infancy.
Edward Syndrome
⚪ This karyotype demonstrates trisomy 18
⚪ Shorthand: (47, XX or XY, +18).
⚪ Characteristics:
● Ave life span = 2-4 months
● Small at birth
● Clenched fists with overlapping fingers
● Rocker bottom feet with protruding heels
● Elongated skull
● Low set ears
● Congenital heart problems
● Mental retardation
Trisomy 18
Only 1 in 15,000 live births. (most aborted naturally)
⚪ Survival:
Forty five percent die within the first month 90% by six months Less than 5% reach 3 years.
Trisomy 13: Patau Syndrome
⚪ Characteristics:
● Ave life span = 6 months
● Cleft lip and palate
● Small eyes
● Polydactyly
● Congenital heart defects
● Severe CNS disorders
Patau’s Trisomy 13
⚪ Trisomy 13
- having one fewer chromosome in each body cell
Monosomy
1 in 2,500 births 45, X karyotype 23rd Chromosome Monosomy Nondisjunction hypogonadism in phenotypic females
No menstruation No breast development Narrow hips Broad shoulders and neck
Turner Syndrome
Women with Turner’s syndrome can live relatively normal lives, though they are unable to bear children.
The phenotype of this female includes short stature, short broad neck, and a broad chest. Intelligence does not seem to be affected.
Turner’s Syndrome
The Sex-linked Trisomies!
⚪_______
Shorthand: 47, XXY
⚪______
Shorthand: 47, XYY “Supermale”
Klinefelter Syndrome
Jacob Syndrome
⚪ Nondisjunction of the X chromosome.
⚪ 47, XXY karyotype
⚪ The Sperm containing both X and Y combines with an egg containing the X, results in a male child.
⚪ The oocyte may contribute the extra X chromosome
● “extra inactivated X”
Kleinfelter syndrome
⚪ Males with some development of breast tissue normally seen in females.
⚪ Little body hair is present, and such person are typically tall, have small testes.
⚪ Infertility from Azoospermia.
⚪ Mental retardation may or may not be present.
Klinefelter Syndrome
⚪ The cause of this condition is a deletion of about half of the short arm of chromosome 5.
⚪________ babies are severely mentally retarded, round face, low set ears, heart disease, and have a small cranium.
⚪ Occurrence:
● 1/1,000,000 live births.
● Karyotype:
46XX or 46 XY with chromosome #5 upper arm deletion.
Cri-du-chat
1/10,000 – 1/25,000 Deletion in 15q1.11 - .13 Compulsive eating Obesity Poor sexual development in males
Prader Willi
