Question | Answer |
Allele | a specific function at a specific location on a chromosome |
Genotype | actual genetic information carried by the individual |
Heterozygous | having two different alleles aa corresponding points on a chromosome pair |
Homozygous | having two identical alleles at corresponding points on a chromosome pair |
Karyotype | visual representation of chromosomes arranged in order of size |
mutation/mutagen | a change in the genetic makeup (DNA) of a cell which will be inherited |
Phenotype | expression of genes, appearance of the individuals characteristics |
Translocation | abnormal placement of part of the chromosome |
Teratogenic | agents that cause damage during embryonic or fetal development |
non-disjunction | |
Singe-Gene Disorders | classified by inheritance patterns - recessive, dominant, x-linked recessive
Single gene controls a specific function- e.g. color blindness
May have system effects - e.g. cystic fibrosis, Tay-sachs, phenylketonuria (PKU) |
Autosomal Recessive Disorders | Both parents must pass on the allele for this disorder
-parents may be heterozygous and unaffected; termed carries (Cc)
-parents may be homozygous and affected (cc)
-Normal parent (CC) |
Autosomal Recessive Disorder affect on children | -male and female children affected equally
-homozygous recessive child has the disorder (cc)
-heterozygous child- no clinical signs of disease; child is a carrier (Cc) |
What are examples of autosomal recessive disorders? | Cystic fibrous, PKU, Tay-Sachs, Sickle cell anemia |
Autosomal Dominant Disorders | inheritance of one bad allele causes disorder; only one parents needs to carry allele
-no carriers; either affected or unaffected-unaffected persons do not transmit disorder
Hh-affected
hh-normal
HH-dont live long |
Autosomal Dominant Disorders conditions | some conditions become evident later in life
-allele disorder may have been passed on to next generation before diagnosis of disease in parent
-termed "delayed lethal" genotype |
Examples of autosomal dominant disorders | Adult polycystic kidney disease, huntington disease, familial hypercholedsterolemia, marfan syndrome |
X-linked dominant disorder | Rare!
heterozygous males and females affected
-reduced penetrance in females
EX: fragile X syndrome
-most common genetic cause of cognitive deficits
-effects are variable and related to the extent of mutation of the allele |
X-linked recessive disorder | allele carried on the X chromosome
-manifested in heterozygous males lacking the matching unaffected gene on the Y chromosome
-heterozygous females are carriers
-homozygous recessive females may be affected
-inheritance seems to "skip generations" |
X-linked recessive disorder examples | duchenne muscular dystrophy and classic hemophilia |
Multifactorial disorders | are those involving a number of genes or genetic influences combined with environmental factors |
examples of multifactoral disorders | cleft palate, congenital hip dislocation, congenital heart disease, type 2 diabetes mellitus, anencephaly, hydrocephalus, myelomeningocele, club foot |
Chromosomal disorders | results from chromosomal abnormalities such as atypical number of chromosomes or structural abnormality |
Chromosomal disorder vs. single-gene disorders | single gene disorders are caused by a mutation in one or more genes in a chromosome while chromosomal disorders are caused by structural or numerical abnormalities |
Examples of chromosomal disorders | down syndrome, turner syndrome, and klinefelter syndrome |
Down syndrome | trisomy 21 (gathering of 3 pieces of chromosome at one point), may be due to non-disjunction or translocation |
Turner Syndrome | XO
-high risk of uterine and cervical cancer
-affects females
-infertility
-short stature (first indicator of syndrome)
-cardiac and kidney issues
-lack ovaries |
Klinefelter syndrome | XXY
-extra x chromosome is present
-infertility
-male genitalia (sperm not produced and testes small) but female characteristics (breasts), possible female organs internally |
Down syndrome (more) | -affects physical and mental development
-risk w/ maternal age (30 if no previous children, 35 if previous children) |
Characteristics of Down Syndrome | -small head, round face, flat facial profile
-slanted eyes and epicanthic fold
-large tongue, high-arched palate
-small hands, single palmar crease
-short stature
-muscles tend to be hypotonic, loose joints
-delayed developmental stages |
Characteristics of Down Syndrome continued | -cognitive impairment ranges from mild to major
-delayed or incomplete sexual development; males infertile and females have low rate of conception |
Germline mutations | autosomal dominant, autosomal recessive, x-linked dominant and x-linked recessive
-single genes passing on of the trait |
Pharmacogenomics | study of how a person's genetic inheritance affects the body's response to drugs
-uses DNA and amino acid sequencing to create new drugs that work at molecular level to prevent and treat disease |
Nutrogenomics | studying the relationship between human genome, nutrition and health |
Gene therapy | available for some diseases, insertions of genes into individuals cells and biological tissues to treat diseases (cancer), mutant alleles are replaced with functional ones |
PM | poor metabolizer-absent or greatly decreased ability to clear or activate drug
-dont get a lot of benefit from drug; build up=side effects |
IM | intermediate metabolizer-heterozygous for both normal and reduced activity genes
-decent results from drug |
EM | extensive metabolizer-the norm
-use the drug, get the benefit, clear it effectively, w/ little to no side effects |
RM | rapid metabolizer-greatly increased activity that accelerate clearance or increases activation
-increased effectiveness, OD easily, leave system so fast benefits negligible |
Diagnostic testing | used to confirm or rule out a known or suspected genetic disorder in a symptomatic individual.
EX: DMD, congenital myotonic dystrophy, hemochromatosis, fragile x, cystic fibrosis |
Predicitive testing | offered to asymptomatic individuals (usually adults) with a family history of a genetic disorder.
EX: FAP and Huntingtons disease |
Carrier testing | is performed to identify individuals who have a gene mutation for a disorder inherited in an autosomal recessive or X-linked recessive manner. Carriers usually do not themselves have symptoms related to the gene mutation.
EX: hemophilia A and Tay-sachs |
Prenatal testing | performed during a pregnancy to assess health status of a fetus; offered when there is an increased risk of having a child with a genetic condition due to maternal age, family history, ethnicity, or suggestive fetal ultrasound
EX: beta-thalassemia |
Preimplantation genetic screening | used to decrease the chance of a particular genetic condition for which the fetus is specifically at risk; |
Preimplantation genetic screening continued | test one cell removed from early embryos conceived by in vitro fertilization; then transfer only those embryos determined not to have mutation to mother’s uterus
EX: spinal muscular atrophy |
Newborn Screening (NBS) | identifies individuals who have increased chance of having a specific genetic disorder so that further testing and treatment can be started as soon as possible.
EX: PKU, hypothyroidism, and sickle cell |