LN 08 (Developmental Malformation) Flashcards
simply imply that the individual is born with the defect and has no reference to it being hereditary or not
congenital defects
How is hereditary defects not always congenital?
some are made manifest later in life of the individual
physical expression of a trait
phenotype
genetic constitution of an organism
genotype
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 1:2:1 ratio
second law
alternate form of gene
alelle
non-allelic traits do not segregate but assort randomly and recombine with a probability representing the product of their independent probabilities
third law
Three modes of genetic defect transmission
- Mutant genes of large effect
- Change in number or morphological state of chromosomes
- Additive effects of many genes of small effects but influenced by environmental factors
are expressed according to the foregoing laws of inheritance
mutant genes of large effect
most commonly reported
genetic defects in domestic animal species
autosomal recessive inheritance
most commonly reported
genetic defects in humans
autosomal dominant inheritance
individual contains a pair
of identical alleles of a given gene
homozygous
individual contains different alleles for a given gene
heterozygous
ratio between those affected and not affected in any given mating is
three phenotypic normal to one affected individual, or 25% chances
congenital tremor
pig
cerebellar atrophy
sheep
cerebellar hypoplasia
cattle
cranium bifidum
pig
congenital hydrocephalus
cattle
atresia ani
pig
chediak-higashi syndrome
cattle, horse
combined immunodefiecency
horse
inherited goiter
sheep
familial polycythemia
cattle
congenital porphyria
cattle, pig
Cases reported in farm animals that are expressed by autosomal dominant
inheritance include
- idiopathic epilepsy
- familial convulsion in cattle
heterozygote affected animal mates with a homozygote animal, each offspring has ___ risk of being affected
50%
both parents are heterozygote affected, the risk that the offspring produced are affected increases to
75%
Breeding patterns that result to a defect observed to occur in the males
only tend to suggest that the defect is
Y linked
Two types of chromosomal abnormalities
- numerical abnormality
- structural abnormality
Abnormalities in the number of chromosomes are called
heteroploidy
individual is born and carries with its multiples of the haploid number of its chromosomes
polyploidy
involves either an increase or decrease in the normal number of chromosomes without regard to completion of full haploid set
aneuploidy
there are three sex chromosomes instead of two
trisomy
f only one sex chromosome
occur (e.g., OX, OY)
monosomy
result of nondisjunction of chromosomes during
the anaphase stage in meiosis of germ cells or in mitosis at the zygote
heteroploidy
heteroploidy results to, ____, which is the presence of two or more population of cells with different
genotypes
mosaicism
In ruminants, fraternal twinning results to the presence of different
genotypes in cell population of one twin in a condition known as
chimerism (due to fetal sharing of circulation)
example of chimerism
freemartin
In humans, defects in sex chromosome number are called
gonadal dysgenesis
gonadal dysgenesis examples
- Turner’s syndrome (45, 0X)
- Klinefelter’s syndrome (47, XXY)
fragment of chromosomes becomes attached to another chromosome
translocation
parts of the chromosome exchange places with another
reciprocal translocation
example of translocation in humans
Down syndrome
two breaks occurs and a realignment result to a reversal of the order of
the chromosome
inversion of chromosome
defect is governed by the additive effect of two or more genes of small effect but is conditioned by non-genetic environmental influences and is expressed
polygenic inheritance
One of the best-studied diseases due to polygenic inheritance
diabetes
defect where there is a deficiency of insulin, and therefore there occur persistent hyperglycemia
diabetes mellitus
study of congenital malformations
teratology
malformation acquired in utero when differentiating cells are destroyed or altered by agents known as
teratogens
agents that affect developing cells and tissue altering its structure, genetic constitution, or both
teratogens
includes trauma, ionizing radiation, heat, cold and
pressure
physical agents
includes drugs, chemicals, hormones, vaccines,
toxins and toxicant
chemical agents
metazoan, bacteria, fungi, protozoan, including
viruses
biological agents
teratogenic agent that causes Amelia (absence of limbs) in affected humans
thalidomide
twin joined at some portions of the body, with both twins presenting complete parts
symmetrical conjoined twin
named by the anatomic location of union, and carry the suffix “pagus”
Symmetrical conjoined twins (also called
Siamese twins)
basic mechanism for symmetrical conjoined twin formation
splitting of the zygote
resulting to two blastoderms developing from a single ovum
joined at the thorax
thoracopagus
joined at the ilium of pelvis
Ileopagus
joined at ischium of pelvis
ischiopagus
Examples of symmetrical conjoined twin
- Thoracopagus
- Ileopagus
- Ischiopagus
twins joined in some portions of the body, but one twin may be incompletely developed
asymmetrical conjoined twins
malformation is a result of
problems in placental circulation with compression of umbilical vessels of one of the twins
Asymmetrical conjoined twins
attached malformed part of the twin is called
parasite
a twin presented without body form and heart
acardius amorphous
acardius amorphous is an example of
Asymmetrical conjoined twins
a conjoined twin presenting two distinct bodies, united to a common point, but one of the twins is incompletely developed
duplication of parts
What causes duplication of parts?
Mechanical constriction of the blastula or gastrula
Examples of duplication of parts
- Dicephalus monster (2 heads)
- Dipygus monster (2 hind parts)
imperfect closure of vertebra
spina bifida
failure of the brain to develop
anencephaly
imperfect closure of the cranium
cranioschisis
brain tissue protrudes in a hole of the skull
cephalocele
cerebrospinal fluid is produced but not drained
hydrocephalus
complete failure of the spinal cord development
amyelia
dilatation of the central spinal canal
hydromyelia
cavitations of the spinal cord
syringomyelia
palatoschisis
open palate
chieloschisis
slit upper lip
nasoschisis
split nose
a developmental defect of
frontal and nasal bones with two eyes developing in one socket
cyclopia or cebocephalia
failure of the facial structures to develop
aprosopus
absence of lower jaw
agnathia
very small jaw
micrognathia
strangulation of the developing limb with umbilical vessels leading to amputation or fusion
abnormalities in hind limb
failure of limb development
sympodia
fused hindlimbs
symelia
thorachoschisis
sternal fissure
omphaloschisis
opening at umbilicus
gastroschisis
opened walls of stomach
incomplete development of ventral body walls where affected animals show exposed visceral organs
schistosomus reflexus
a female born co-twin to
a male that have altered gonadal development due to blood exchanges in utero
intersex or hermaphroditism
failure of cartilage formation and subsequent improper ossification
resulting to short limbs
achondrodysplasia
skeleton is missing or failed to develop
chondrodystrophia
abnormal mixtures of tissues indigenous to their location
hamartomas
consist of tissues that are foreign to the area
teratoma
disease in which an animal is born with flexed, absolutely rigid limbs but this is a primary problem not with bones or joints but rather with innervation of muscles because of dysraphism in the spinal cord
arthrogryposis
Defects in Skeletogenesis
- achondrodysplasia
- chondrodystrophia
Abnormalities in Tissues or Organs
- foramen ovale in the heart
- atresia ani (no anal opening)
- intersex or hermaphroditism
Defects in Ventral Body Walls
- thoracoschisis
- omphaloschisis
- gastroschisis
- schistosomus
Abnormalities in Hind Limbs
- sympodia
- symelia
Some structures fail to fuse at median plane:
- palatoschisis
- chieloschisis
- nasoschisis
defects in the development of the jaws
- agnathia
- micrognathia
often implicated in cases of
congenital malformation
- Drugs
- Viruses
- Plant toxins
cells in the developing fetus
are most susceptible to the adverse effects of teratogens during
Cellular differentiation and organogenesis
Plant toxins proven to cause malformations
- Coniine and gamma coniceine
- Nicotine
- Undefined alkaloid of Veratrum Californicum