Developmental Malformations Flashcards
Every individual is said to be unique in every aspect and this is determined by the?
genes in the chromosomes
is hereditary when the defect of one parent is transmitted in the gametes through the generations
defect
simply imply that the individual is born with the defect and has no reference
to it being hereditary or no
congenital defects
not all defects are hereditary
True or False
True
all congenital defects have a genetic
origin
True or False?
False, Not All.
not all hereditary defects are congenital, for some are made
manifest later in life of the individual
such as those inborn errors of
metabolism
True or false?
True
showed that although some traits are transmitted to generation of offspring in an unchanged state, the physical expression of a trait differed
from genetic constitution
Mendel
a unit of genetic information (gene) is transmitted unchanged from generation to generation
first law
alternate forms of the gene must segregate during gamete formation and recombine independently in the offspring to provide a 1:2:1ratio
second law
This alternate form of gene was later called? and its transmission outlined
the concepts of dominance and
recessivity
allele
non-allelic traits do not segregate but assort randomly and recombine with a probability representing the product of their independent probabilities
Third law
There are three modes of genetic defect transmission in animals and these includes;
✓ mutant genes of large effect
✓ change in number or morphological state
✓ additive effects of many genes of small effects but influenced by environmental factors
is the most commonly reported genetic defects in domestic animal species, compared to humans where autosomal dominant inheritance was reported to account for most cases
autosomal recessive inheritance
individual contains a pair of identical alleles of a given gene
homozygous
if a heterozygote affected animal mates with a homozygote animal; each offspring has 50% risk of being
affected
Assuming that both parents
are heterozygote affected, the risk
that the offspring produced are
affected increases to how many percent?
75%
Cases reported in farm animals that are expressed by autosomal dominant inheritance include?
idiopathic epilepsy and familial convulsion in cattle
male of the species carries the?
XY chromosomes
the female of the species carry the
XX chromosomes
If
the defect is X-linked, an affected
female (XX) is mated to anormal
male (XY), there is 50% chances that
the female offspring will carry the
defect, and 50% of the male will inherit the maternal X chromosomes
containingthe defect.
an individual with possessing only one allele
hemizygous
However, if the allele is recessive
to the normal allele, the affected female carrying the allele will not express the defect, but the male who has only one X chromosome been hemizygous for the trait and will not carry any normal allele and would express the defect
diploid number of chromosomes in
somatic cells, e.g., in human the
diploid number is
46
In gametes however, the haploid number is
23
The karyotype for a species is writtenas the diploid number of chromosome and the sex
chromosome, for instance 46,XY to
denote a human male
chromosomal abnormalities, there
occur two types:
✓ numerical abnormality
✓ structural abnormality
Abnormalities in the number of
chromosomes are called?
heteroploidy
When an individual is born and carries with its multiples of the haploid number of its chromosomes,
the condition is called?
Polyploidy
involves either an increase or decrease in the normal number of chromosomes without regard to completion of full haploid set
aneuploidy
If there are three sex chromosomes instead of two (e.g.,XXY, or XYY), the condition is called
trisomy
if only one sex chromosome occur (e.g., OX, OY), the condition is called
monosomy
occur as a result of non disjunction of chromosomes during the anaphase stage in meiosis of germ cells or in mitosis at the zygote, and result to
heteroploidy
the presence of two or more population of cells with different genotypes.
mosaicism
In animals, particularly in fraternal twinning (male and female twin) in cattle, sheep and goats, there are chances that fetal sharing of circulation result to population of cells between twins, resulting to the presence of different genotypes in cell population of one twin. This condition is called?
chimerism
example of chimerism
freemartin
defects in sex chromosome number are called?
gonadal dysgenesis
example of gonadal dysgenesis
✓ Turner’s syndrome (45, 0X)
✓ Klinefelter’s syndrome (47, XXY)
parts of the chromosome exchange places with another and is called?
reciprocal
translocation
heteroploidy involves either?
polyploidy or aneuploidy
For instance, in humans, the diploid number are ________ and in polyploidy, the number may be ______ or ______.
23N
69 (triploidy) and 92 (tetraploidy)
in what phase in meiosis heteroploidy occur as a result of nondisjunction of chromosomes?
anaphase stage
occur at the chromosome and be expressed in the individual
number of structural abnormalities
a typical example of translocation was that observed is?
down syndrome in humans
where a piece of the chromosome is missing
chromosomal deletion
where two breaks occurs and a realignment result to a reversal of the order of the chromosome
inversion of chromosome
one of the best-studied diseases due to polygenic inheritance
diabetes in humans
is a defect where there is a deficiency of insulin
diabetes mellitus
increased blood sugar levels
hyperglycemia
although some malformations are clearly associated with abnormal genes, many are required in?
utero
differentiating cells are destroyed or altered by agents
teratogens
cells become committed to specific developmental pathways
early in embryogenesis
can be acquired not only by deletion of critical primordial cells
congenital malformations
agents that affect developing cells and tissue altering its structure, genetic constitution, or botj
teratogens
teratogens causing a defect in DNA result to malformations, and may be heritable.
susceptibility to teratogenesis depends on the genotype of the developing fetus and the way they interact with teratogens
the cells in the developing fetus are most susceptible to the adverse effects of teratogens during the stage of cellular differentiation, and organogenesis.
susceptibility to teratogenesis varies with the developmental stage of the fetus at the time of exposure
some teratogens cause cell death, some cause excessive cell growth, and other cause specific gene damage that leads to the expression of the defect
teratogens act on specific ways on developing cells and tissues to initiate a sequence of abnormal developmental events
the dose and the period of exposure .
may determine the magnitude of the effect as malformation, death, or no effect at all
teratogenesis is dose dependent and cumulative
Teratogen may be grouped under the following categories;
- physical agents
- chemical agents
- biological agents
physical agents includes;
✓ trauma
✓ ionizing radiation
✓ heat
✓ cold
✓ pressure
chemical agents includes;
✓ drugs
✓ chemicals
✓ hormones
✓ vaccines
✓ toxins
✓ toxicants
biological events includes;
✓ metazoan
✓ bacteria
✓ fungi
✓ protozoan including viruses
are the agents often implicated in cases of congenital malformation
drugs, viruses and plant toxins
plant toxins proven to cause malformations include?
✓ coniine and gamma coniceine from conium maculatum
✓ nicotine from nicotiana tabacum
✓ undefined alkaloid from veratrum californicum
a drug released in the 60’s to relieve nausea during pregnancy.
thalidomide
a twin joined at some portions of the body, with both twins presenting complete parts
symmetrical conjoined twin
symmetrical conjoined twins are also called what?
siamese twins
two blastoderm developing from a single ovum joined at the thorax called?
thoracopagus
two blastoderm developing from a single ovum joined at the ilium of pelvis
ileopagus
two blastoderm developing from a single ovum joined at ischium of pelvis
ischiopagus
twins joined in some portions of the body, but one twin may be incompletely developed
asymmetrical conjoined twins
this malformation is a result of problems in placental circulation with compression of umbilical vessels of one the twins
asymmetrical conjoined twins
the attached malformed part of the twin is called?
parasite
a twin presented without body form and heart
acardius amorphous
a conjoined twin presenting two distinct bodies, united to a common point, but one of the twins is incompletely developed
duplication of parts
mechanical constriction of the BLASTULA and GASTRULA causes this malformation. Examples include;
✓ dicephalus monster
✓ dipygus monster
malformation with two heads
dicephalus monster
malformation with two hind parts
dipygus monster
the basic defect is arrest in development of cells in the neural tube resulting;
✓ defect in neural tube formation
✓ incomplete closure and formation of the vertebral column
✓ abnormalities in the ventricular system of the brain
Example of defects in neural tube and axial skeleton
✓ spina bifida
✓ anencephaly
✓ cranioschisis
✓ cephalocele
✓ hydrocephalus
✓ amyelia
✓ hydromyelia
✓ syringomyelia
imperfect closure of vertebra
spina bifida
failure of the brain to develop
anencephaly
imperfect closure of the cranium
cranioschisis
