Genetics Flashcards
Genotype
All of the alleles of an organism
Homozygous or heterozygous
Phenotype
measurable trait an organism has (the trait exhibited)
Chromosome
structure composed of genes located in nucleus of a cell (humans have 46)
Locus
specific location of a gene on a chromosome
Allele
Different versions of a gene (humans have 2 on each autosomal gene, one from each parent)
Mutation
a change in some part of the DNA code
Spontaneous or induced
Mitosis
Division of somatic cells
One exact copy of each chromosome made and distributed into 2 daughter cells
Meiosis
Process which gamete cells are produced (egg/sperm)
Only occurs in germ cells of gonads
2 consecutive divisions>4 sperm cells, 1 egg
Sex chromosomes vs Autosomes
Humans have 22 autosomes, 1 allosome (sex pair-determines gender, X and Y)
autosomes are any chromosome that isn’t a sex chromosome
Autosomal vs X-linked
Autosomal affect males and females equally, x-linked are more common in males
Translocation
rupture of a chromosome resulting in pieces restocking in wrong combinations
Deletion
genetic material removed from chromosome
Insertion
genetic material added to a chromosome
Penetrance
probability that people in a population who have a particular gene combination will show the condition
Expression
components of the phenotype that are exhibited in a person
Genetic Marker
Sequence of DNA with a known location on a chromosome
Dominant vs Recessive
Phenotype of dominant seen in heterosexual and homo
Phenotype of recessive only seen when homozygous recessive
Autosomal Recessive
25% chance of infection, 50% chance of carrying gene
2 copies of allele required to express phenotype
males and females equally affected
X-linked
5% of disorders
males more likely to develop mutant phenotype, females are recessive
no male to male, but all daughters of affected male are carriers
Trisomy 21
Down syndrome
most common chromosomal abnormality in live births/non-lethal
Michael translucency
intellectual disability, characteristic facial appearance, cardiac/hearing/visual/GI problems
Trisomy 18
Edward’s Syndrome
2nd most common
kidney/heart defects, delayed development, club foot, low ears, small jaw, clenched hand
many die before birth or in first month
Intra-uterine growth restriction is hallmark of pregnancy
Increased risk with maternal age
Trisomy 13
Patau syndrome
severe intellectual disability, cleft lip/palate, seizures, small jaw, polydactyly, heart/brain defects
many die within first days/weeks
Cri-du-Chat Syndrome
deletion of part of short arm of chromosome 5
Partial monosomy
cat-like cry (larynx development), wide set eyes, low ears, intellectual disability
Klinefelter’s Syndrome
Only affects males
extra X chromosome
accounts for many first trimester losses
hypogonadism, infertility, gynecomastia, reduced hair
Turner Syndrome
Only affects females
Monosomy (only one x, 45 chromosomes)
Gonadal dysgenesis, short, broad chest, webbed neck, infertility, amenorrhea, CV abnormalities
Huntington’s Disease
Neurodegenerative disorder uncontrolled movements/chorea, emotional problems, loss of thinking ability, changes in personality, adult onset HD gene on chromosome 4 (CAG), dominant Microscopic protein deposits in neurons Autosomal dominant
Alzheimer’s
Neurodegenerative
most common form of dementia (65%), usually late onset (after 60 years)
Loss of acetylcholine
Familial-early onset (<5%)
Sporadic-late onset (more common), APOE chromosome 19
Autosomal dominant
Breast and Ovarian Cancer Syndrome
BRCA1 and 2
early onset of breast cancer (<50), FH of breast and ovarian cancer, increased bilateral/development of both cancers
Colorectal Cancer
Results from genetic and environmental factors
can happen sporadically or from familial inheritance
Diet, exercise, smoking &obesity strong risk factors
Familial adenomatous polyposis (FAP)
<1% of colorectal cancers
develops in 20’s, risk of colorectal cancer near 100% usually before 50 years
polyp>cancer development 10+ years
Mutation in adenomatous polyposis coli gene (APC)
Colectomy recommended before 20 years
Autosomal dominant
Hereditary Nonpolyposis Colorectal Cancer (HNPCC)
AKA Lynch Syndrome
2-3% of colorectal cancers
rapid transition from adenoma>cancer, occurs in 30’s and 40’s
can occur with or without polyps
50% chance of cancer in women, 70% in men
associated with other cancers (uterus, ovaries, stomach, urinary tract, bowel, bile ducts)
HNPCC gene mutation
Autosomal dominant
Chronic Myelogenous Leukemia
excess WBC in bone marrow more common in men 55years caused by chromosome 22 Hallmark symptoms-fever, night sweats, fatigue; infections, anemia, bleeding slow progression Bone marrow aspiration for diagnosis
Hemophilia
Bleeding disorder on F8 (more common, Hemo A) or F9 (Christmas disease, Hemo B)
bleeding into muscles/tissues
X-linked recessive
Sickle Cell
Atypical hemoglobin molecules, crescent shaped RBC, premature breakdown of RBC, anemia, SOB, fatigue, renal failure
Mutation of HBB gene
common in Greece, Africa, turkey, Italy…
Most common bleeding disorder in US
Autosomal recessive
Cystic Fibrosis
Disruption in water and chloride transport/water balance
causes thick, sticky mucous obstructing airways and pancreatic ducts
difficulty breathing, lung infections, poor growth rate, Meconium ileus (newborn intestinal obstruction)
Mutation in CFTR gene
Sweat chloride test for diagnosis
Autosomal recessive
Marfan Syndrome
Mutation of FBN1
Defect in connective tissue (bone, ligaments, muscles, blood vessels, heart valves)
Tall, long arms, thin, long face, scoliosis, hyper flexible, chest deformities
aortic aneurysms/dissection and dislocated lens of eye common
Autosomal dominant
Neurofibromatosis Type I
AKA Recklinghausen disease
most common type of mutation NF1 (tumor suppressor)
subcutaneous tumors, cafe-au-lait spots, freckles in axilla/groin
Autosomal dominant
Polycystic Kidney Disease
clusters of fluid-filled sacs in kidneys, kidney failure, inability to filter blood properly
hypertension, back pain, hematuria, UTI, kidney stones, aortic/brain aneurysm
recessive rare but lethal
Dominant: PKD1 and PKD2 genes (90%), late onset
Recessive: PKDH1 gene, early onset, lethal
Bigest cause of birth defects?
Unknown
“inborn errors of metabolism”
autosomal recessive errors present at birth
inherited defect of one or more enzymes
Baby tested at 24-36 hours and 5-10days
Aneuploidy
Abnormal number of chromosomes
Balanced Translocation
Rupture of chromosome resulting in pieces restocking in wrong combinations
Inversion
A chromosome piece is lifted out, flipped around and reinserted
Teratology
Study of abnormal development
Teratogens
Anything capable of disrupting embryonic or fatal development and producing malformations
Eg: alcohol, tobacco, excess vitamin A
Critical period 3-16weeks
Pedigrees
Make-square
Female-circle
Has condition-shaded
Carrier-half shaded
