2155 #2 Newborn Complications: Heredity and Environmental Influences

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What is a gene?

A peice of DNA that codes a single process

Humans have 100,000

What is a chromosome?

Organized sections of genes

Humans have 23 pairs

What is DNA?

The specific building block of both genes and chromosomes

What is DNA made of?

A sugar, a phosphate group and a nitrogen base

Human Chromosomes

23 pairs of chromosomes in each cell

22 pairs of Autosomes

1 pair of sex chromosomes

XX= female

XY= male

Normal sperm carries

either an X or a Y sex chromosome

Normal Ovum carries

an X chromosome

Cell Reproduction: Mitosis (3)

Same cell reproduces itself

Starts with one cell with 23 pairs of chromosomes

Ends with 2 cells that have the same 23 pairs of chromosomes
(diploid)

Cell Reproduction: Meiosis (4)

Same cell reproduces to form a new type of cell

This new cell has 1/2 the chromosomes (23 single units)
(Haploid)

Done by ova and sperm

Zygote (4)

One celled human formed from the union of a sperm and ovum

The sex of the new human is determined

The chromosome now has 23 pairs (diploid)

Dizygotic (2 eggs & sperm/different genetic code) /Monozygotic twins (1 egg & sperm then splits/same genetic code)

1st wk of development Zygote (3)

Divides in the 1st 30 hrs

Progresses into a solid ball of cells= Morula (12-16cells) after 3 days

Stem cell research is done at the 8 cell stage

As the Morula enters the uterus

it differentiates into a Blastocyst (Baby) and Trophoblast (preplacenta and membranes)

Induced pluripotent cell

Scientists have discovered ways to take an ordinary cell, such as a skin cell, and reprogram it by introducing several genes that convert it into a pluripotent cell

True embryonic stem cell

Derived from embryos" made from unused embryos that are donated by couples who have undergone in vitro fertilization

Embryonic stem cells

made by somatic cell nuclear transfer: transferring the nucleus from a somatic cell- any cell of the body- to another cell, in this case an egg cell

Embryonic stem cells from unfertilized eggs:

(parthenogenesis embryonic stem cells):
Through chemical tx, unfertilized eggs can be tricked into developing into embryos without being fertilized by sperm, a process called parthenogenesis- in research stage

All blood in the umbilical cord belongs to the

fetus

Cord blood (3)

contains multiple populations of ES (Embryonic stem) like and other pluripotential stem cells

Capable of giving rise to hematopoietic, epithelial, endothelial, and neural tissues both in vitro and in vivo.

Umbilical cord blood: a unique source of pluripotent stem cells for regenerative medicine

Cord blood for future use (3)

Positive ID
-DNA never changes

If cord blood is obtained at birth, then it can be used in many situations

Cord blood contains (2)

stem cells which can replace disease cells in that person or perhaps others

useful in the tx of leukemia, immune disorders, other cancers, and blood system disorders

Cord blood is superior to what and why (5)?

to bone marrow.

Collection poses no risk
Less chance of fatal rejection rx
Works with less than perfect match
Available for use more rapidly
Large scale cord blood banking would promote better availability

Private cord blood bank

Families pay

Public cord blood bank

public are registered with the FDA

Karyotype (4)

Genes too small to see with microscope

Chromosomes can be seen during replications, and in a lab arranged in order of largest to smallest (autosomal) and sex chromosomes last

Noted 46- XX normal female
Noted 46 XY normal male

Monozygotic twin

One egg= Identical

Dizygotic twin (5)

2 eggs= Fraternal

Healthiest situation= each baby has their own amnion/chorion and placenta

The closer they are inutero the more danger exists.

Increased mortality up to 60% in a shared amniotic sac

Separate amnion? Separate chorion?

Moms w/ multi gestation pg (5)

are High Risk
6x more likely to be hospitalized
-PTL, PPROM, abruption, pyelonephritis, pp hemorrhage
-Increased incidence of GDM
-Increased risk of other rare complications

Alleles (4)

pairs of genes
1 set from mom
1 set from dad

In chromosomes there are 2 possible gene sets- alleles, for what we see

If the alleles are the same (2)

Homozygous

Always see this genetic code expressed

If the alleles are different (3)

Heterozygous
The dominant gene will be expressed (phenotype=you can see it)
and at the same time the recessive gene will be carried (genotype=hidden non-expressed)

What eye color is dominant? (2)

Brown
1 of the alleles is all it takes for expression

Which eye color is recessive? (2)

Blue
Both alleles much match to be expressed

Which blood types are dominant?

A and B

Which blood type is recessive? (3)

O
Their genotype is O
Their phenotype is O

Type A could be

AA or AO genotype

Type B could be

BB or BO genotype

Which Rh factor is dominant?

Positive

Which Rh factor is recessive?

Negative
Genotype = Neg. Neg
Phenotype = Neg. Neg

5 Autosomal Dominant Diseases (7)

Huntingtons Disease
Marfan's Syndrome
Noonan Syndrome
Dwarfism/Achondroplasia
Neurofibromatosis

Only need to have 1 gene to have
Because there is often a "normal" gene in the genotype the severiity of expression varies greatly

4 Autosomal Recessive Diseases (5)

PKU (Phenylketonuria)
Sickle cell anemia (African)
Tay-Sachs (Jewish)
Cystic Fibrosis (White, European)

If both parents are carriers (of the allele: one gene is wnl, the other is not) for each pg 50% carriers, 25% affected, 25% no abnormal gene- not affected or carriers

Sex linked Dominant & 4 types (5)

Located on the X chromosome:

Vit D resistant Rickets
Polydactly
Polycystic Renal Disease
Focal Dermal Hypoplasia

3 Sex linked Recessive & how it works (4)

Carried on the X

The X chromosome is physically longer than the Y (contains more DNA).
So- On the affected X there is no corresponding wnl Y to "dominate" the affected X therefore the affected X is expressed
So... Male offspring are primarily affected
-Color Blindness
-Duchenne's muscular dystrophy
-Hemophilia A & B

Sex linked recessive for female offspring

Xx- recessive
There for the abnormal allele not expressed
Phenotype=wnl

Sex linked recessive for male offspring

If he gets any (x) that is abnormal, it must be expressed
Phenotype not wnl

Multifactoral Disorders (2)

Most common type of genetic disorders

Many congenital conditions are caused by the interaction of many genes and environmental factors

Environmental factors include (4)

Age and health status of parents
Exposure to Pollutants and/or Infectious agents

Malformations can be mild to severe (2)

The more severe the defect, the greater the number of genes involved

In the presence of environmental influences it may take fewer genes to manifest the disease/disorder

5 Specific Multifactoral Disorders

Many heart defects

Neural Tube defects (ancephaly, spina bifida)

Cleft lip/palate

Pyloric stenosis

Congenital hip dysplasia (new name "developmental dysplasia of the hip")

Chromosomal Abnormalities & 2 examples (5)

Cause of 50% of spontaneous abortions

This differs from single gene defects and multifactoral disorders in that entire chromosomes (MANY genes) are involved

Defects can be structural or numerical

Trisomy- 47 (extra chromosome)
Monosomy- 45 (missing a gene)

Trisomy (5)

Each chromosome is wnl, but there are too many of them: 47 is each cell

Most common is Trisomy 21= Downs Syndrome

Increased risk if mom over 35

Also Trisomy 13 or 18- more severe

XXY, XYY Kleinfelters Syndrome (aggressive behavior)

Monosomy (4)

Each body cell has a missing chromosome

Most incompatible with life

Turners Syndrome: XO, ALWAYS female, most of these are spont ab's

Cystic Hygromas (Large cystic mass on neck)- may be dx with US, short stature

Structural Chromosomal Abnormalities (4)

Part of one or more chromosomes may be missing or added
Or DNA rearranged within the chromosome

Some of these abnormalities are harmless

Some are not-
Fragile X Syndrome- most common form of male mental retardation

Translocation- all or part of a chromosome is attached to another

Potential Nursing Dx (7)

Knowledge Deficit

HR for Ineffective Family Coping

HR for alteration in the family process

HR for alteration in parenting

Grief

HR for social isolation of the family

HR for alteration in parent infant attachment

Nursing Interventions (4)

Emotional Support

Provide Counselling

Providing referrals to support services in the community
-March of Dimes, Cystic Fibrosis Foundation

Referral to a genetic counselor- preconception or post event for the future

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