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N398 Exam 2 > Genetics > Flashcards

Genetics Flashcards

1
Q

What is the nurse’s role in genetics and genomics?

A
  • Assessment
  • Identification
  • Referral activities
  • Education, care, support
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2
Q

What are the 4 broad types of genetic disorders and diseases?

A
  1. Chromosomal anomalies (mutations)
  2. Mendelian single-gene disorders
  3. Polygenic/multifactorial disorders
  4. Other
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3
Q

What are the 2 types of chromosomal anomalies?

A
  1. Abnormal number (genome mutation)

2. Abnormal structure (chromosome mutation)

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4
Q

Euploidy

A

46 chromosomes

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5
Q

Aneuploidy

A

Any # other than 46 chromosomes

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6
Q

Monosomy

A

Deficiency of a chromosome

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7
Q

Polysomy

A

Too many chromosomes

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8
Q

Characteristics of abnormal number

A
  • Disorders involving sex chromosomes are more common and less debilitating
  • Loss of chromosome material is more serious than excess of material
  • Nondisjunction during meiosis is usually the cause of abnormal number (can be meiosis I or II)
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9
Q

What are 4 causes of abnormal structure?

A
  • Deletion
  • Duplication
  • Inversion
  • Translocation
  • These alter the structure of individual chromosomes
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10
Q

What are 2 types of mutations?

A
  1. Point mutation: substitution of a single base pair (may or may not change an amino acid)
  2. Frameshift mutation: addition of deletion of 1 or 2 nucleotides (changes reading frame so all codons after mutation are incorrect)
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11
Q

What are 3 Mendelian single-gene disorder patterns of inheritance?

A
  1. Autosomal dominant
  2. Autosomal recessive
  3. X-linked
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12
Q

Characteristics of autosomal recessive disorders

A
  • Due to mutation of a recessive gene on an autosome
  • Males and females are equally affected
  • Unaffected individuals may transmit disease to offspring (carrier)
  • May see delay of onset, incomplete penetrance, variable expressivity
  • Examples: cystic fibrosis, sickle cell
  • AA = normal, Aa = carrier, aa = affected
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13
Q

Autosomal recessive: homozygous dominant and heterozygous parents

A

Offspring genotypes

  • AA = 50% (normal)
  • Aa = 50% (carrier)
  • aa = 0% (affected)
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14
Q

Autosomal recessive: heterozygous parents

A

Offspring genotypes

  • AA = 25% (normal)
  • Aa = 50% (carrier)
  • aa = 25% (affected)
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15
Q

Autosomal recessive: homozygous recessive and heterozygous parents

A

Offspring genotypes

  • AA = 0% (normal)
  • Aa = 50% (carrier)
  • aa = 50% (affected)
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16
Q

Characteristics of autosomal dominant disorders

A
  • Due to mutation of dominant gene on an autosome
  • Males and females equally affected
  • Does NOT skip generations, affected individuals have an affected parent
  • Unaffected individuals do not transmit disease (no carriers)
  • Example: Huntington’s disease
  • AA = affected, Aa = affected, aa = normal
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17
Q

Autosomal dominant: homozygous dominant and heterozygous parents

A

Offspring genotypes

  • AA = 50% (affected)
  • Aa = 50% (affected)
  • aa = 0% (normal)
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18
Q

Autosomal dominant: heterozygous parents

A

Offspring genotypes

  • AA = 25% (affected)
  • Aa = 50% (affected)
  • aa = 25% (normal)
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19
Q

Autosomal dominant: homozygous recessive and heterozygous parents

A

Offspring genotypes

  • AA = 0% (affected)
  • Aa = 50% (affected)
  • aa = 50% (normal)
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20
Q

Autosomal dominant: homozygous recessive and homozygous dominant parents

A

Offspring genotypes

  • AA = 0% (affected)
  • Aa = 100% (affected)
  • aa = 0% (normal)
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21
Q

Characteristics of X-linked recessive disorders

A
  • Seen more often in males (only have one X)
  • Can skip generations via carrier female
  • Never passed from father to son (because father passes Y to son)
  • Passed from father to all daughters (daughters are affected or carrier)
  • Example: Duchenne Muscular Dystrophy, Hemophilia A
22
Q

Polygenic traits

A
  • Result from several genes acting together

- Example: height, weight, IQ

23
Q

Multifactorial traits

A
  • Genes make individual susceptible
  • Environmental factors may trigger susceptibility or influence expression of a trait
  • Difficult to predict risk of occurrence but “runs in families”
  • Example: Type 2 Diabetes, HTN
24
Q

Penetrance and Expressivity

A

Both terms quantify modification of gene expression by varying environmental and genetic background

25
Q

Penetrance

A
  • % in which gene is expressed
  • % of individuals with a given genotype who exhibit the associated phenotype
  • How something skips a generation
26
Q

Expressivity

A
  • Level of expression
  • Extent of variation in phenotype associated with a particular genotype
  • How environment and other genes are influential
  • Differences among individuals with same disorder
27
Q

Congenital

A
  • Present at birth
  • May or may not be hereditary
  • De novo = from new, not hereditary
  • Could be result of deviation in utero development
28
Q

Hereditary

A
  • Inherited genetically
29
Q

Down Syndrome

A
  • Individuals have an extra copy of chromosome 21 (trisomy 21)
  • Most common chromosomal disorder
  • Risk increases with maternal age
30
Q

Down Syndrome Pathophysiology

A
  • Nondisjunction (95%): pair of 21st chromosome fails to separate in meiosis
  • Translocation (4%): full or partial copy of chromosome 21 attaches to another chromosome
  • Mosaicism (1%): some cells have 46 chromosomes and some have 47
31
Q

Down Syndrome Assessment

A
  • Cognitive disability
  • Low set ears
  • Wide nasal bridge
  • Protruding tongue (hypotonic)
  • Upward slant to eyes, epicanthal folds
  • Single palmar crease
  • Small stature
  • Nuchal changes (back of neck)
  • Hypotonia
  • Increased risk for: congenital heart disease, leukemia, respiratory
32
Q

Down Syndrome Diagnosis

A
  • Prenatal testing: screening, ultrasound (CHD and nuchal change), amniocentesis and chorionic villus sampling
  • After birth: physical examination, karyotype
33
Q

Down Syndrome Management

A
  • Trends point toward longer life span
  • Early developmental intervention
  • Surgeries as needed
  • Supportive interventions
34
Q

Duchenne Muscular Dystrophy

A
  • X-linked recessive
  • Affecting only males
  • Apparent by age of 3
35
Q

Duchenne Muscular Dystrophy Pathophysiology

A
  • Muscle cells are deficient in protein dystrophin (weak cell membrane)
  • Leak creatinine kinase and take in calcium
  • Proteases and inflammatory process are activated
  • Leads to muscle fiber necrosis and muscle degeneration
36
Q

DMD Clinical Manifestations

A
  • Present with muscle weakness, difficulty walking
  • Large calves (normal fiber replaced with fat and connective tissue)
  • Gradual loss of ability to ambulate by 8-13 years
  • Gower’s sign: how they stand up
  • Scoliosis
  • Osteoporosis, fractures
  • Muscle weakness progresses to respiratory weakness and premature death
37
Q

DMD Diagnosis

A
  • History and physical
  • Elevated creatinine kinase initially
  • Muscle biopsy
  • Genetic testing
38
Q

DMD Management

A
  • Life expectancy: 20 years
  • Goal is to maintain function and independence: surgery, bracing, physical therapy, prevent obesity, prompt attention to infection, steroid use
  • Psychosocial support
39
Q

Sickle Cell

A
  • Autosomal recessive: aa = affected, Aa = carrier
  • Chromosome 11
  • Sickle cell disease: homozygous inheritance
  • Sickle cell trait: heterozygous inheritance
  • More common in African Americans or Mediterranean descent
  • More common in parts of world where malaria is present and offers malaria protection
  • Point mutation: changes hemoglobin stability and solubility
40
Q

Sickle Cell Pathophysiology

A
  • Genetic mutation causes defective hemoglobin molecule (Hb S)
  • When O2 is low, Hb S undergoes polymerization and changes into sickled shape (RBCs don’t travel well in bloodstream)
  • Step 1: Sickling = occlusion of small arteries, tissue damage, pain
  • Step 2: Anemia = shorter lifespan due to hemolysis, hyperbilirubinemia
41
Q

Triggers for cells to sickle

A
  • Dehydration
  • Infection
  • Fever
  • Acidosis
  • Hypoxia
  • Exposure to cold
42
Q

Sickle Cell Clinical Manifestations

A
  • Symptoms typically don’t present until 4-6 months of life bc fetal Hb is higher in O2
  • Chronic anemia
  • Pallor
  • Jaundice
  • Fatigue
  • Delayed growth and puberty
  • Infections: most common cause of death
43
Q

3 types of sickle cell crisis

A
  1. Vaso-occlusive
  2. Acute sequestration
  3. Aplastic anemia
44
Q

Vaso-occlusive sickle cell crisis

A
  • Sickled cells and vasospasm block blood flow
  • Thrombosis and infarction
  • Extremely painful
  • Lasts days or weeks
  • Potential locations: joint or bone pain, acute chest syndrome, dactylics, priapism, cerebrovascular
45
Q

Acute sequestration sickle cell crisis

A
  • Usually children 6 months - 4 years
  • Blood pools cause enlargement
  • Hypovolemic shock
  • Emergency
  • Potential locations: spleen (may remove), liver, lungs
46
Q

Aplastic anemia sickle cell crisis

A
  • Increased destruction or decreased production of hemoglobin
  • Profound anemia
  • Associated with viral infections, fever
47
Q

Sickle Cell diagnosis

A
  • Newborn screening
  • History and physical
  • Lab: anemia, sickled and target cells
48
Q

Sickle Cell treatment

A
  • Stem cell transplant
  • Education to prevent sickling crisis (risk factors)
  • Vaccinations
  • Penicillin prophylaxis (even when not sick)
  • Transfusions
  • Splenectomy
  • Pain management, hydration, oxygenation
49
Q

Sickle Cell complications

A 
Strokes, swelling, spleen
Infection, infarction
Crisis, chest syndrome, cardiac problems
Kidney disease
Liver and lung problems
Eyes/erection
50
Q

Cystic Fibrosis

A
  • Most common single-gene disorder
  • Autosomal recessive: aa = affected, Aa = carrier
  • Chromosome 7, 1300 different mutations
  • Caucasian Americans
  • Defect in membrane transporter for chloride ions in epithelial cells
  • Production of abnormally thick secretions in glandular tissues

N398 Exam 2 (6 decks)

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