sex aberrations
Post on 13-Jul-2015
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Each person is made in God’s image
(Gen. 1:27).
50% of spontaneous abortion are chromosomal abnormal Mostly triploidy. 45 XO, trisomy 16 98% of fetus with turner abort Generally 6/1000 the incidence of chromosomal
abnormalities
Unexplained infertility
Multiple abortion >2
Prior case of defective baby
Presence of congenital
anomalies
› 45% have minor single
anomalies
› 9% 3 minor anomalies
› 1.5% have major anomaly
2 or more major anomalies
may represent genetic
syndrome or chromosomal
abnormalities(10%).
1. Klinefelter syndrome- XXY
male in spite of having 2 X chromosomes or with a 44-XXY
chromosomes.
The Sperm containing both X and Y combines with an egg containing the X, results in a male child.
The egg may contribute the extra X chromosome.
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 results from absent sperm.
Evidence of mental retardation may or may not be present.
2. Turner syndrome –XO
have only 45 chromosomes ( 2n-1)
-externally female in spite of the presence of only one X
chromosomes which are short and flat chested like those with XXX
syndrome
3. Jacob’s Syndrome- XYY (Criminal syndrome)
XYY syndrome is an aneuploidy (abnormal number) of the sex chromosomes in which a human male receives an extra Y-chromosome
causes no unusual physical
features or medical problems.
may be slightly taller than
average
May have more severe acne
than normal.
Skeletal malformations may
also accompany
includes large hands and
feet,
have normal sexual
development and are able to
conceive children.
4. Triple-X- superfemale, metafemale, XXX
-individual has 47 chromosomes (2n +n)
affects about 1 in 1,000 females.
usually results from an error in the formation of a mother's egg cell or a father's sperm cell.
Sometimes, it occurs as a result of an error early in the embryo's development.
physically and mentally normal
May include hypertelorism, epicanthal folds, depressed nasal bridge
Delay in growth and mental development, when present, is usually mild.
Occasionally associated with Prader-Willi syndrome.
5.YO
-a condition which is lethal because x chromosome is necessary for life
Deletions (deficiencies)
Duplications
Inversions
Translocations
Deletions (deficiencies)
- Loss of a (generally small) segment of chromosome
A B C D E F G A B D E F G
C
Arise through spontaneous breakage some
chromosomes have fragile spots, radiation, UV,
chemicals, and viruses .
Ionizing radiation acts like little atomic "cannon balls",
blasting through strands of DNA or chromosomes.
Break points of chromosomes are highly reactive ("sticky"),whereas normal ends of chromosomes are capped bytelomeres, which do not readily bond to other molecules.
Why do they rejoin?
Deletion disorder in human:
1. Cri- du -chat, or cat-cry syndrome.
- Individuals with this syndrome have high pitched, plaintive cry, very similar to that of a kitten in distress.
represent a loss in chromosomal material.
Mental retardation
Slow motor skill development
Low birth weight and slow growth
Small head (microcephaly)
Partial webbing of fingers or toes
Wide-set eyes (hypertelorism)
Fragile Sites
are weak points at specific locations in chromatids
is a place where part of a chromosome attached to the rest of the chromosome. They have been identified in sex chromosomes as well as on autosomes.
EX.
2. Fragile X syndrome (FXS), Martin–Bell syndrome, or Escalante's syndrome (more commonly used in South American countries), is a genetic syndrome that is the most common known single-gene cause of autism and the most common inherited cause of intellectual disability
May arise
through unequal
crossing over
A B C D E F G
A B C D E F G
x
A B C D E F F GA B C D E G
Deletion Duplication
Changes in the numbers of genes
Cri-du-chat syndrome - Micro deletion of chromosome 5
DiGeorge syndrome - Micro deletion of chromosome 22
Schizophrenia & Obsessive Compulsive Disorder
-Micro deletion of chromosome 22 associated
Angelman syndrome- Micro deletion of chromosome 15
Prader-Willi syndrome- Micro deletion of chromosome 15
Large deletions will most probably be lethal
Smaller deletions may allow survival
Prader-Willi lack of muscle tone in newborn
poor swallowing reflex
as adult - gross obesity
mean I.Q. ~ 50
microdeletion of 15
developmentally delayed
jerky movements
stiff, fixed smile
uncontrolled laughter
abnormal E.E.G., epilepsy
microdeletion of 15
Deletions (deficiencies)
Duplications
Inversions
Translocations
Redundant segment of a chromosome
A B C D E F G A B C D E F F G
inherited neurological disorder that affects the peripheral nerves. individuals experience weakness and wasting (atrophy) of the muscles
of the lower legs beginning in adolescence; later they experience hand weakness and sensory loss.
caused by having an extra copy (a duplication) of the PMP22 gene. It is inherited in an autosomal dominant manner. Treatment : physical therapy; occupational therapy; braces and other
orthopedic devices; orthopedic surgery; and pain medications.
Deletions (deficiencies)
Duplications
Inversions
Translocations
A B C D E F G H I J K
A B C H G F E D I J K
180O
A portion of the chromosome has
broken off
A B
C
D
E
F G
turned upside down and reattached,
therefore the genetic material is
inverted.
• 180o reversal of chromosome segment
• Produced through breakage and
reassociation of chromosome
A B
C
D
E
F G
Inversions cause complicated synapsis at meiosis for heterozygotes
Those not containing the centromere
are called paracentric.
Chromatids involved in crossing over do not allow development of
functional gametes
Inversions containing the centromere
are called pericentric.
May change phenotype through “position effects”
move active genes to sites generally inactive;
lose gene function
move inactive genes to sites generally active;
gain gene function
May act to preserve blocks of genes (specific alleles) which
function well together
No gain or loss of information; just rearrangement of genome.
Deletions (deficiencies)
Duplications
Inversions
Translocations
Reciprocal Translocation: Exchange of segments between non-homologous chromosomes
F
A
B
C
D
E
L M NO
P
Q
A B C
D E F
O N M L
Q P
segment from one chromosome is exchanged with a segment from another nonhomologous one, so two translocationchromosomes are generated simultaneously.
A portion of one chromosome is transferred to
another chromosome.
Lead to impaired fertility
› complications to synapsis and segregation
May lead to changes in phenotype
› position effects
› human cancers and translocations
A B C
D E F
O N M L
Q P
A B C D E F
L M N O P Q
Only 1/3 of the segregations will lead to
usable gametes
Fertility is reduced by 2/3
Chronic myelocytic leukemia, is a slowly progressing blood
and bone marrow disease that usually occurs during or after
middle age, and rarely occurs in children.
Several human cancers are associated with reciprocal
translocations
Normally, the bone marrow makes blood stemcells (immature cells) that become mature blood cells over time.
A blood stem cell may become a myeloid stem cell ora lymphoid stem cell.
A lymphoid stem cell becomes a white blood cell.
A myeloid stem cell becomes one of three types of mature bloodcells: RBC, platelets and Granulocytes.
Reciprocal translocation between chr. 22 and chr. 9
9 9 22 22
Reciprocal translocation between chr. 22 and chr. 9
9 9 22 22
Chr. 9 segment
has an oncogene;
when moved, it
becomes active
Translocations between chr. 8 and one of three others:› 8 & 2 or 8 & 14 or 8 & 22
Chr. 8 has an oncogene ( genes involved in cell proliferation)
Chr. 2, 14, 22 have genes coding for antibody production and their enhancer genes
Oncogene becomes highly active under control of enhancers!
Fusions
› two chromosomes join to form one
Fissions
• one chromosome splits to form two
Polydyspondylie
› mental retardation and spinal malformations
› fusion of two chromosomes w/ loss of short
arms
Familial Down Syndrome› fusion of chromosomes 14 and 21
14 21 14+21
synapsis
Three possible disjunctions
X
X
X
X
X
X
MYTH: Down syndrome is hereditary and runs in families.
TRUTH:
• Down syndrome is hereditary in approximately 1% of all instances.
• In the other 99% of cases Down syndrome is completely random and the
only known factor that increases the risk is the age of the mother (over
35).
• Translocation is the only type of Down syndrome known to have
hereditary link.
Myths and Truths about Down
Syndrome
Maternal Age:
Women are born with all the eggs they will ever have.
Therefore, when a woman is 30 years old, so are her eggs.
Errors can crop up in the eggs' genetic material as they age over time.
Therefore, older women are more at risk of giving birth to babies with
chromosome abnormalities than younger women.
Since men produce new sperm throughout their life, paternal age does not increase risk of chromosome abnormalities.
MYTH: Children with Down syndrome must be placed in segregated special
education programs.
TRUTH: Children with Down syndrome have been included in regular academic
classrooms in schools across the country.
The current trend in education is for full inclusion in the social and educational
life of the community.
Inclusion is a right, not a privilege for a select few
It is possible to treat diseases by altering our very genes‚giving us new ones if ours are non-functional, changing badgenes for good ones.
Human Genome Project
The primary goal is to determine the sequence of chemical base pairs
which make up human DNA, and to identify and map the total genes of
the human genome from both a physical and functional standpoint.
We need to understand that the “genome” ofindividual is unique. Mapping the human genomeinvolves sequencing multiple variations of eachgene. There is a need to get ready , to facecourageously and to appreciate the truth that mostchromosome abnormalities can occur.
This study is about embracing all, making acommitment to do whatever it takes to provide eachone in the community- an inalienable right to belong,not to be excluded. Assume then, that living andlearning together is a better way that benefitseveryone, not just children who are labeled ashaving a difference.
Thank you for listening…
Enjoy Being Normal!
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