ch. 14 Developmental Genetics and Birth Defects

Flashcards about genetics in medicine, chapter 14, developmental genetics and birth defects

What is Dysmorphology?

The study of birth defects and abnormal development.

T/F: Gene expression occurs throughout a lifetime

true

1. Malformations Definition

2. What is meant by “genetic program”?

1. Result from intrinsic abnormalities in genetic programs operating in development.

   • ex: extra or fused fingers

2. they specify a series of developmental steps used repeatedly in different parts of the embryo at different stages

Deformations Definition

When does it occur?

Dysmorphology

Caused by extrinsic (environmental factor) factors physically impinging on the fetus during development.

• common in 2nd trimester

• ex: arthrogryposes - contractions of the joints of the extremities, associated with twins or decreased amniotic fluid

Disruptions Definition

What are some causes?

Destructions of irreplaceable fetal tissue, resulting from vascular insufficiency, trauma, or teratogens.

• difficult to treat

• ex: amnion disruption - partial amputation of a fetal limb with strands of amniotic tissue

due to vascular insufficiency, trauma, or teratogens

Define Pleiotropy syndrome

What is Pleiotropic sequence?

1. Pleiotrophy syndrome - Multiple abnormalities in parallel- A single underlying causative agent may result in abnormalities in multiple organ systems

2. Pleiotropic Sequence - mutation affects only 1 organ system at 1 point in time, and the disruption of that system causes the rest of the pleiotropic symptoms

   1. Ex: Robin Sequence - restriction of mandibular growth and the tongue lies posteriorly so the palatal shelves don’t close properly creating a cleft palate

Environmental factors include mutagens and teratgon. Define both

1. Mutagen - cause damage by creating mutations

2. Teratogen - act directly and transiently on developing embryonic tissue

   1. ex: fetal retinoid syndrome*

Examples of environmental teratogens

Fetal retinoid syndrome, thalidomide syndrome, fetal alcohol syndrome

List categories of teratogens:

Industrial agents

• lead, mercury, pesticides/herbicides

Recreational substances

pharmacological agents

Infectious agents

Factors influencing teratogenic effects include:

Dosage, acute vs. chronic exposure

time of exposure

stage of development

genotype of embryo

Thalidomide was developed in the 1950s to treat what?

What were the side effects?

Pregnancy-associated morning sickness

Side effects:

• stunted limb growth

• deafness, blindness, cleft palate, etc

What are the components of TORCH?

Toxoplasma (parasite in cat feces)

Others

Rubella (German measles)

Cytomegalovirus (in herpes fam)

Herpes simplex

Fetal Alcohol Syndrome Symptoms - depend on the stage of development and amount can dictate the severity of symptoms

• Behavioral disturbances

• brain defects

• cardiac defects

• spinal defects

• craniofacial abnormalities

• Broad upper lip

• flattened nasal bridge

• hypoplastic upper lip

• Microophthalmia

• Short nose

Tobacco use in mothers leads to which birth defect?

low birth weight

Define

1. Proliferation

2. Differentiation

3. Migration

4. Apoptosis

1. Cell division

2. Cells acquire novel functions or structures - related to mitosis

3. Cell movement within the embryo

4. Programmed cell death (important in some cases for development)

*these processes allow for growth and morphogenesis

Where in the human body is cell migration most important? Name 3 diseases associated with cell migration.

1. Cell migration is most important in the central nervous system

2. Associated diseases

   • Lissencephaly

   • Hirschsprung Disease

   • Waardenburn syndrom

Three stages of embryonic development:

Pre-embryonic, embryonic, fetal

*Provide examples of complications in cell migration

1. Lissencephaly

2. Hirschsprung Disease

3. Waardenburn syndrome

Which cell migration condition is a mutation causing reduced speeds of migration that causes intellectual disability?

Lissencephaly

Which cell migration condition is due to a failure of migration leading to aganglionic colon (colon is not innervated and food is unable to be processed properly).

Hirschsprung Disease

Which cell migration condition causes a defect in the skin and hair pigmentation color of the iris and effects colon innervation?

Waardenburg syndrome

1. When does apoptosis generally occur?

2. Describe the process

3. Which diseases underlie suspected defects in apoptosis?

1. when tissues need to be remodeled during morphogenesis (ex: separation of fingers)

2. immune system will eliminate lymphocyte lineages that react to self

3. DiGeorge Syndrome

Describe the 3 stages of the embryonic development

Pre-embryonic (conception to about 15 days)

• zygote (egg+sperm) to blastocyte to implantantion

• inner cell mass = embryo

• trophoblast = placenta

Embryonic (2 to 8 weeks)

• endometrial development

• placenta forms

• amnion forms (extra embryonic membrane)

• ectoderm, mesoderm, endoderm formgrowth and maturation of organs and systems

Fetal ( 8 weeks to birth)

• ongoing organogenesis

• increased mass

*all occurs through mitosis

What are the three primary germ layers?

Ectoderm, mesoderm, endoderm

Why are the Hox genes important in development?

Regulates segmentation - where the head form, the trunk, and other body structures in the embryo. Hox genes help to establish the body plan by determining the identity of segments.

T/F: the longer differentiation a stem cells takes, the less options it will have to develop into said options

true

Describe two conditions related to neural tube defects

• Ancencephaly - forebrain, meninges, vault of the skull, and skin are absent

• Spina bifida - failure of fusion of the vertebral arches, lumbar area

_____ is the leading cause of still birth in early infants, and handicap in surviving children

neural tube defect

What is the single greatest casual factor in neural tube defects?

Folate deficiency