Genetics Flashcards
How many chromosomes in human cells and how many pairs?
46 chromosomes
23 pairs
Define autosome
any chromosome that is not a sex chromosome - 22 pairs
Describe haploid number
the number of chromosomes in sex cells/gametes n=23
Describe diploid number
the total number of chromosomes in somatic cells 2n=46
What arm is the short and what arm is the long in a chromosome?
p=short arm
q=long arm
For every one male diploid cell how many spermatozoa do we get?
4 spermatozoa - each is haploid (n)
For every one female diploid cell how many ovum do we get?
1 haploid ovum (n)
Describe codominance
when two alleles for a trait are equally expressed ex: checkered chickens
Describe incomplete dominance
heterozygotes have phenotypes that have both alleles visible as a blend - makes a third phenotype (one allele isn’t expressed over the other) ex red and white flowers -> pink flower
Describe penetrance
the probability that individuals in a population who have a particular gene combination will show the condition
Describe expression
the components of the phenotype that are exhibited in an individual ex: myotonic muscular dystrophy
Describe anticipation
genetic diseases that increase in severity or have earlier onset with each successive generation ex: huntington disease
Describe balance translocation
rupture of a chromosome resulting in the pieces “re-sticking” in the wrong combinations
Describe inversion
a chromosome piece is lifted out, turned around, and reinserted
Describe Robertsonian translocation
tends to arise as an offspring of a balanced carrier
involve any 2 out of chromosomes
results in formation of a “new” chromosome which the bigger chromosome can produce an unbalanced gamete
can produce trisomy 21
What kind of disease is Huntington’s Disease?
Autosomal dominant
Describe Autosomal dominant
vertical pattern multiple generations affected variable expressivity reduced penetrance males and females affected equally
What kind of disease is cystic fibrosis?
Autosomal recessive
Describe autosomal recessive
25% of human monogenic disorders rare horizontal inheritance consanguinity single generation affected males and females affected equally
Describe x-linked
5% of human monogenic disorders
no male to male transmission is possible
all daughters of an affected male are heterozygous carries
What kind of disease is Fragile X syndrome?
x-linked dominant
What kind of disease is Duchenne muscular dystrophy?
X-linked recessive
What is the most common chromosomal abnormality in live births?
Trisomy 21
What is included in the Quad screen? What is other common prenatal test?
maternal serum AFP, estriol, hCG, inhibin-alpha
Nuchal translucency
What is Edwards Syndrome?
Trisomy 18
2nd most common autosomal trisomy
club foot (Rocker bottom feet)
lethal mutation
What is Patau syndrome?
Trisomy 13
severe intellectural disability
polydactyly
lethal mutation
Describe Cri-du-Chat syndrome
deletion of part of short arm of chromosome 5
cat-like cry due to abnormal larynx development
can be detected in utero with CVS
Describe Klinefelter’s syndrome
extra X chromosome, 47XXY affects males hypogonadism infertility gynecomastia reduced hair
What is the most common sex chromosome aneuploidy in males?
Klinefelter’s syndrome
47 XXY
Describe Turner syndrome
45X Monosomy Affects development in females gonadal dysgenesis (non-functional ovaries) short stature broad chest webbed neck amenorrhea infertility cardiovascular abnormalities
Describe Huntington’s disease
neurodegenerative disease autosomal dominant CAG trinucleotide repeat uncontrolled jerky movements (chorea) emotional problems loss of thinking ability changes in personality no treatment from symptom onset to death is 15 years
Describe Alzheimer’s disease
neurodegenerative disease loss of acetylcholine formation of plaques and tangles several gene mutations cause predisposition to AD 2 forms: familial and sporadic
What is the only human disorder of complete dominance?
Huntington’s diseasse
Describe Familial Alzheimer’s Disease
early onset AD
rare -<5%
autosomal dominant
Describe Sporadic Alzheimer’s Disease
late onset AD
accounts for most cases of AD
one gene - Chromosome 19 apolipoprotein E (APOE) gene shown to increase risk
What are the 2 major breast and ovarian cancer genes?
BRCA1 - chromosome 17 and BRCA2 - chromosome 13
autosomal dominant
What is the strongest risk factor for colorectal cancer in most people?
diet, exercise, smoking, obesity
in small portion of people it is genetic predisposition
Describe Familial Adenomatous Polyposis (FAP)
<1% of all colorectal cancers
mutation in APC = tumor suppressor gene on chromosome 5
develops in 20’s
near 100% of getting cancer before age 50
total colectomy is recommended b4 age 20
Describe Hereditary Nonpolyposis Colorectal Cancer (HNPCC)
Lynch syndrome
2-3% of all colorectal cancers
mutation in one of many genes for DNA repair
more rapid transition to cancer than FAP - 30’s + 40’s
50% in women, 70% in men
regular colonoscopy starting age 25 for relatives, upper endoscopy, endometrial/ovarian screening
Describe Chronic Myelogenous Leukemia
myeloproliferative disorder
translocation bet/w chromosomes 9 & 22 (Philadelphia chromosome) -> enzyme that causes too many stem cells -> WBCs
nonfunctional WBC
insidious onset, fever, night sweats, fatigue
Describe Hemophilia
mutation on F8 or F9 genes
X-linked recessive pattern
hemarthroses (sponataneous bleeding into a joint), bleeding into muscles, prolonged bleeding
What does a mutation in F8 gene cause?
Factor VIII deficiency -> hemophilia A (classic hemophilia)
What does a mutation in F9 gene cause?
Factor IX deficiency -> hemophilia B (Christmas Disease)
Describe Sickle Cell Disease
mutation on HBB gene
autosomal recessive
atypical hemoglobin molecules (hemoglobin S)
anemia, infections, episodic pain, SOB, fatigue, delayed growth
Describe Cystic Fibrosis
autosomal recessive
mutation in CFTR gene -cystic fibrosis transmembrane conductance regulator- regulates cl channels in epithelial cells
thick sticky mucous in airways and pancreatic ducts
failure to thrive
meconium ileus - newborn intestinal obstruction
What is the most common cause of morbidity associated with CF?
pulmonary disease
What are the 3 most common organisms in CF pulmonary system?
S. aureus, P. aeruginosa, Aspergillus
