GENETICS-LECTURE Flashcards
Chromosome?
An organized package of DNA found in the nucleus of the cell
Come in pairs
Humans have how many pairs of chromosomes?
23
Genes?
Small segment of a chromosome that can be identified with a specific function
A gene is a segment of DNA that determines a trait
Genes?
- Come in pairs on each autosome (1-22)
- Each copy of the gene is called an allele
- 2 identical alleles: homozygous
- If they are different: heterozygous
Each copy of the gene is called an?
allele
2 identical alleles=?
homozygous
if they are different alleles= ?
heterozygous
Aneuploidy?
error in cell division resulting in an increased number or a decreased number of chromosomes
Nondisjunction?
paired homologous chromosomes do not separate before migrating into the egg or sperm. Creates a gamete with either two copies or no copies of a particular chromosome.
Phenotype?
expression of the altered gene in the physical appearance or signs of disease process
Genotype?
an individual’s particular set of genes
Multifactorial inheritance: multiple gene alterations along with environmental factors
True or False?
Most conditions where there is a monosomy (one chromosome) are incompatible with life
Translocation?
occurs when 2 (usually nonhomologous) chromosomes exchange segments of DNA. If it results in the correct amount of material it is called a balanced
Mosaicism?
Have separate cell lines with some having the appropriate # of chromosomes and some having altered chromosomes
- Child of parent with this may have a genetic disorder
Translocation
Penetrance?
probability that a gene will be expressed phenotypically
New mutation?
no family history of the disease
- Is a translocation involved?
- Difficult to calculate future risks
Deletions and duplications?
occurs when an unequal crossing over or abnormal segregation causes a chromosome to have a missing segment (deletion) or an additional segment (duplication)
- Cri du chat syndrome (large deletion on chromosome 5)
Deformation?
anomalies that represent the normal response of a tissue to an unusual mechanical force
- i.e clubfoot
Disruption: breakdown of previous normal tissue example?
Amniotic band syndrome
Homozygous?
identical pair of chromosomes
Heterozygous?
different chromosomes in a pair
Karyotype? (genetic testing)
picture of an individual’s chromosomes, takes about 3 days for results
Chromosome Microarray (CMA) (genetic testing)
- Test for individuals with multiple abnormalities not specific to a well delineated genetic syndrome
- Determines size, precise breakpoints, gene content
- Takes about 3-5 weeks to obtain results
FISH? (genetic testing)
Fluorescence in situ hybridization: used to detect deletions and duplications of specific genes not visible to the microscope
What does FISH (genetic testing) stand for?
F- Fluorescence
I- in
S- situ
H- hybridization
How long does FISH testing take?
2 weeks for the results
Normal female karyotype?
46XX (females)
Females= XX
Normal male karyotype?
or 46XY (males)
Males= XY
What karyotype is Klinefelter’s syndrome?
47XXY
46+ 1= 47
& 2 XX+ Y (female= 2 X’s)
Is Klinefelters syndrome?
Monosomy
Trisomy
Normal
Deletion
Trisomy: 47XX
47XXY (Klinefelter’s syndrome)
What karyotype is turner syndrome?
Monosomy
What karyotype is turner syndrome?
45X0
Deletion: 22q-
(deletion on the q arm of the 22 chromosome)
Ring Chromosome ?
Type of genetic alteration depends on which chromosome develops a ring
Who is Gregor Mendel?
Father of Genetics
Autosomal Dominant? *** KNOW
The gene is passed on from only 1 parent
The paired gene from the 1 parent would be normal
The parent that passes on the gene mutation does have the disorder
Autosomal chromosomes- chromosomes 1-22
The offspring ?
- 50% will be passed on to the child
examples:
- Huntingtons disease
- Neurofibromatosis
- Marfans
- Dwarfism
Autosomal Recessive (AR)? KNOW!!
- Occurs when both copies of an altered gene are present
- AR conditions are usually more severe & have earlier onset of symptoms
- Called recessive b/c 2 copies of the gene are necessary to produce the disease (homozygous)
- One altered gene is inherited from each parent
Parents are carriers (heterozygous
Autosomal Recessive (AR)? KNOW!
- Inheritance of 2 copies of the mutated gene
- 1 copy from each parent - It is located on 1 of the autosomal chromosomes
Offspring who inherit 1 abnormal gene in the pair are considered to be carriers:
- They can pass the gene to their children BUT they themselves are NOT AFFECTED
What are some examples of autosomal recessive?
- cystic fibrosis
- albinism
- PKU thalasemmia
- sickle cell anemia
Sex Chromosome of a female?
XX
Sex Chromosome of a male?
XY
Early in embryonic development what happens to sex chromosomes?
one of the two X chromosomes is randomly and permanently deactivated.
This causes the gamete has?
- one chromosome to contribute to the embryo
X- Linked Conditions: KNOW!!
- Conditions that are the result of an altered gene on the X chromosome
- Females who are carriers have a 50% chance of passing on the altered gene
- A daughter who receives an altered gene from her mother and an unaltered gene from her father is a carrier, like her mother
- Sons of mothers with the altered gene have no backup X chromosome so they will develop the disease
- A male cannot transmit the condition to his sons (because he contributes a Y chromosome
X- Linked Conditions
So if the father is affected it has an abnormal X AND the mother is not
all the female offspring will inherit the disease
BUT
none of the sons
Because daughters always inherit their father’s X chromosome!!
X- Linked Recessive usually occurs in?
Males
X- Linked Conditions:
If the mother is affected & she has 1 abnormal X & the father is not there is only a ___ % chance that each daughter or son will inherit the disorder
50%
BECAUSE mothers have the 2 X chromosomes that they can pass on
Sons inherit their fathers ___ chromosome?
Y chromosome
X- Linked Recessive this pattern is seen in males because males only have 1 X chromosome
(x-linked recessive disorder)
A single recessive gene on that X chromosome will the disease
The Y chromosome does not contain most of the genetics of the X chromosome which results in
(X- linked recessive disorder)
the male not being protected in the X- Linked recessive
If the father is affected and has an abnormal X none of his sons will be affected
BUT
all the daughters will be carriers
& if the mother is a carrier there is a 50% chance their son will be affected
Daughters have a 50% chance of being a carrier
Females can have X- Linked recessive disorders it is more RARE!
What are some examples of X- Linked recessive disorders?
1- color blindness
2- hemophilia
3.Duchenne muscular dystrophy
4. night blindness
X- Linked Conditions?
Y chromosome: has very few genes & alterations of the genes rarely cause health problems, except for infertility because genes contain material that affects spermatogenesis
Sex Chromosome abnormalities?
48XXYY: extra X chromosome interferes with male sexual development, reducing levels of testosterone
47XXY: Klinefelter’s syndrome
47XXX: tall stature, learning disabilities, birth defects, intellectual disabilities
45X or 45XO: Turner’s syndrome
48XXYY (sex chromosome abnormality)
extra X chromosome interferes with male sexual development, reducing levels of testosterone
47XXY (sex chromosome abnormality)
:Klinefelter’s syndrome
47XXX (sex chromosome abnormality)
tall stature, learning disabilities, birth defects, intellectual disabilities
45X or 45XO (sex chromosome abnormality)
Turner’s syndrome
Genetic Counseling?
- Family to bring detailed medical history and family history for pedigree
- Appointment may last several hours
- Multidisciplinary
- Exam of child & possibly the parents
- Tests
- In-depth discussion of condition
Genetic Testing?
- Help parents & child understand the implications & limitations of genetic tests
- Keep in mind that genetic testing affects families
-Not all family members want to know the results
- Respect each family member’s wishes
- Inform them that genetic testing is voluntary
- Some genetic testing may not be covered under insurance & is very expensive
- Inform parents there may be incidental findings
Genetic Testing?
- Anticipate stress and anxiety while awaiting test results
- Child may harbor resentment against a carrier or affected parent
- Parental guilt may exist because of inheritance
- Parents may lower expectations of the child as a result of known genetic disorder
- They may blame any problem on the disorder
- Make sure parents understand that the risk of having an affected child occurs with each pregnancy
- Support parents as they grieve for the “perfect child”
- Provide written information, support groups
Cri du Chat Syndrome?
random mutation & random event that occurs
5
(large deletion on chromosome 5)
- High-pitched cry – sounds like a cat
- Intellectual disability
- Delayed development
- Small head size (microcephaly)
- Low birth weight
- Weak muscle tone (hypotonia)
- Distinctive facial features
- Widely set eyes (hypertelorism)
- Low set ears
- Small jaw
- Rounded face
- Possible heart defect
Trisomy 21 (Down Syndrome) KNOW!!
Most common genetic disorder for genetic disability
**Protocols are now available to detect this genetic disorder
Down Syndrome Physical Features?
General - short stature, hypotonia, obesity
Head - midface hypoplasia, flattened occiput, microcephaly, fine sparse
hair, alopecia
Eyes – up-slanted palpebral fissures, inner epicanthal folds, Brushfield spots (iris speckling), lens opacity (59%), visual/ocular defects (15-45%)
Ears – small, prominent, low set, overfolding upper helix, small canals, hearing loss (66-75%)
Nose – small with flat nasal bridge
Mouth - open mouth, large protruding fissured tongue, small
hypoplastic teeth with irregular
Down syndrome Physical Features?
Neck - excess skin at nape, short neck, occasional webbing
Cardiac –Congenital (40-50%) AV canal, VSD, PDA, ASD, tetralogy of Fallot, aberrant subclavian artery
G/I – celiac disease, GI atresia, tracheoesophageal fistula, diverticula
G/U – small penis, chryptorchidism (5-50%)
Extremities - broad hands, short fingers, 5th finger midphalanx hypoplasia (60%)
Simian crease (50%), wide gap between 1st and 2nd toes (96%), joint hyperflexibility
Skin – dry hyperkeratotic skin (75%), cutis marmorata (43%)
Other – seizures, hyperthyroidism, hypothyroidism, Mild-to-moderate mental retardation
What are the risks for Down syndrome? Trisomy 21?
Maternal age:
Age 30 < 1 in 1,000 chance
Age 35 1 in 400
Age 42 ~ 1 in 60.
http://www.babymed.com/tools/other/down_syndrome/default.aspx
50% of trisomy 21 fetuses spontaneously abort in early pregnancy
What are some nursing conditions for trisomy 21?
What are the newborns at risk for? (KNOW)!!
Hypotonic, hyperextensibile, poor feeding, mouth breather- large protruding tongue at risk for mouth breathing & causes problems with feeding + provide education***
Atresia of duodenum- at risk for malformation in their gut (blind pouch)
Annular pancreas- pancreas can wrap around the gut & can cause obstruction
Hirschsprung’s Disease- can present with severe constipation or obstruction
Developmental Delay- can use specific growth curves for children to plot - the weight, height & head circumference
- Developmental delays can also include intellectual delays
Thyroid Disease- common & need to be monitored- newborn screening checked for congenital hypothyroidism - checked several times first year then yearly
Immune Dysfunction- risk for pneumonia is high
Ear Infections- common due to their anatomy @ risk for conductive & sensorineural hearing loss
Musculoskeletal Concerns- these children are smaller & shorter & can have smaller heads BUT also have increased risk for obesity in their teenage years.
- Joint flaccid- they have hypotonic but very-neck can be hyperflexible- between their 1st & 2nd cervical vertebrae - make sure you protect the spinal cord & avoid high risk sports
Malignancies- motor development can take 2 X’s as long - 90% of these children are able to walk by the age of 3 y/o. Leukemia is about 18% > the general population.
Sleep Problems- OSA related to their narrow posterior throat & hypotonia BUT also their large tongue size & enlarged tonsils
Skin/Hair- dry skin, atopic dermatitis, allergic - hair loss & thin hair
ALL DELAYS NEED TO BE REFERRED TO LOCAL INTERVENTIONS SERVICES!
Dx for down syndrome?
Physical appearance & specific tests
Down syndrome
- parents should be informed asap of the diagnosis
- provide support groups & community supports
Trisomy 18 Edwards Syndrome
- can cause spontaneous abortions or stillbirths
characterized by:
- prenatal growth deficiency
- characteristics hand gestures with overriding fingers
- nail hypoplasia
-short sternum
-severe heart defects - internal heart anomalies
Trisomy 13- Patau Syndrome
- least common & most severe
- average survival <3 days
Plan for min intervention:
at the time of delivery
due to length of average survival
end of life care & support
+ education
central apnea common- can cause death few weeks
severe heart defects- can contribute
chance viable past few weeks- severe developmental delay
live to later childhood years rare that this occurs
also true with trisomy 18- difficult to live past 1 year of life
Turner Syndrome
Affects only females
results when a sex chromosome
(the X chromosome) is missing or
partially missing.
occurs in about 1 in 2,500 newborn girls worldwide
can cause a variety of medical and developmental problems
Short stature (evident by about age 5), lack of pubertal development, amenorrhea, infertility, heart defects, learning disabilities and social adjustment problems.
Treatment: growth hormone therapy, sex hormone replacement therapy.
Turner Syndrome (KNOW)
- normal growth 1st 2-3 years of life
BUT children’s growth is affected.
- These children are not able to menstruate or conceive. They are small in their stature.
*coarctation of the aorta
*hearing loss
*opthalmic issues
*hip dysplasia
* scoliosis
You want to watch their growth- this is a result of an entire X chromosome
Turner syndrome is the only disorder?
That a child can survive without an entire X
This condition ONLY AFFECTS GIRLS
abnormal meiotic air In the sperm causes this- the girls receive no sex chromosome from the sperm
What would be some symptoms of turner syndrome that you would see?
- prematurity
-feeding difficulty
-reflux
-failure to thrive
-neck webbing
-shield chest
-coarctation of the aorta
-edema of the hands & feet
Will women with turner syndrome still remain infertile even after estrogen therapy?
Yes, they still will remain infertile
What are some nursing interventions for turner syndrome?
- Be patient when child is feeding
-educate the parents - in teens there is a lack of sexual characteristics this can be difficult for teens.
-assess for hypothyroidism - assess for cardiovascular disorders
*** You want to get a baseline echocardiogram - monitor this on a regular basis
The lack of puberty can be treated with estrogen supplements so that the girls can develop secondary sexual characteristics
Should you refer patients that have turner syndrome to endocrinology?
Yes, so they can be started on hormonal therapy
What also do you want to provide for someone that has turner syndrome?
anticipatory guidance b/c these people are at risk for obesity
height & weight WNL at birth BUT then their height will decelerate after that time
Klinefelter Syndrome: KNOW!
- Boys are born with an extra X chromosome
- 1 in 700 male births
-large spectrum of involvement- some people are affected A LOT & others are minimally affected. - identified by parental amniocentesis - can be associated with AMA
10% dx in infancy & childhood due to speech & language delays
- mild hypotonic motor delays
- academic & behavioral problems
- 10% are dx in adolescents & young adulthood by physical features & pubertal delays
-incomplete puberty caused by testosterone deficiencies
-5% for infertility issues later on in life
- hypogonadism later on in adulthood
Klinefelters syndrome
dx- in small areas throughout life
-delayed puberty
-tall
-infertility issues
-speech & reading delays
**these children can be on testosterone maintenance - through endocrine specialists
Marfan’s Syndrom: KNOW!
-connective tissue disorder
1. cardiovascular
2. skeletal
3. eye mutations
- skin, lungs
dilation or dissection in the aorta
myopia
sciolosis
spontaneous pneumothorax
stretch marks or striae of the skin
disproportionate stature
long narrow face
high arched pallet
crowded teeth
- majority have a normal intelligence, ADD or seizures
visual problems & fine motor skills due to their joint laxity
Marfan syndrome
recommendation of cardiac in all people with this condition
- early treatment with beta blockers can be life saving
- early prophylactic surgeries can be life saving
- cardiac referral can be important
- monitoring their opthalmic complications - refer them to an opthalmologist to make sure they are being closely monitored
- monitor them closely with sports & stimulants like coffee, cold meds etc.
