Genetics part 1 Flashcards
What is genetics?
Study of individual genes and their effects on relatively rare, single-gene disorders
What is genomics?
Study of all the genes in the human genome together, including their interactions with each other, the environment, and the influence of other psychosocial factors and cultural factors
What do these studies [genetics and genomics] allow us to do?
Allows us to predict susceptibility, onset, progression, and response to treatment for many hereditary diseases
How many genes are in the human genome?
20,500
What does gene therapy do?
- corrects defective genes that are responsible for disease development.
- Involves inserting a healthy copy of the defective gene into the somatic cells of the affected individual.
- Diseases that could be treated with this range from hemophilia and other single-gene disorders to complex disorders such as cancer
What are the reasons patients decide either to be tested or not tested?
-Seldom autonomous
-Based on feelings of and commitment to others
-Socioeconomic factors
-Cultural and ethnic differences
-Gap in ability to diagnose and ability to
treat
How should genetic history be obtained for genetic counseling in pregnancy?
Questionare or checklist
What is the goal of genetic counseling?
The goal is to identify a risk.
What is an occurrence risk?
Parents are known to be at risk for producing a child with disease; what’s the risk of their child having the disease?
What is a recurrence risk?
Once they have produced a child with disease, what’s the chance their next child will also have the disease?
Interpretation of risks?
very personal decision-making process for parents
What kind of screenings fall under population based screening?
Newborn screening for phenylketonuria [PKU]
What is predictive testing/screening?
it is used to clarify the genetic status of asymptomatic family members
What are the two types of predictive testing?
Presymptomatic testing
Predispositional testing
What is presymptomatic testing?
if the gene mutation is present, symptoms of the disease are certain to appear if the individual lives long enough. (i.e Huntington’s Disease)
What is predispositional testing?
BRCA 1 gene, a positive does not indicate a 100% risk for developing the condition (breast cancer)
What are prenatal tests used for?
used to identify the genetic status of a fetus at risk for a genetic condition (done in 1st trimester)
What is maternal serum screening?
Maternal serum screening: a blood test used to see if a pregnant woman is at increased risk for carrying a fetus with a neural tube defect (NTD) or chromosomal abnormalities (Down syndrome, Trisomy 18 or Trisomy
What is a fetal ultrasound?
Imaging of the fetus inside the uterus obtained by using high-frequency sound waves. Can screen for physical features associated with genetic abnormalities
What is amniocentesis and when is it done?
Invasive procedure that obtains fetal DNA from amniotic fluid; after 15 weeks gestation
What is chorionic villus sampling and when is it done?
invasive procedure obtaining fetal DNA from chorionic villi; before 15 weeks gestation
What are alleles?
genes that code for variations of the same trait…hair color, eye color, etc
What is a karyotype?
A pictorial analysis of the number and size of an individual’s chromosomes
What is a pedigree chart?
Way to show the inheritance pattern of a trait or illness
What are chromosomal abnormalities?
A major cause of reproductive loss, congenital problems, and gynecologic disorders
Can occur during mitosis (somatic cell-autosomal disorders) or meiosis (sex cells-sex-linked disorders)
Type of autosomal chromosomal abnormality
Downs syndrome (trisomy 21)
What is trisomy 18?
Edwards’ Syndrome
Severe to profound intellectual disability
Most don’t survive to their 1st birthday
What are the types of chromosomal abnormalities in regards to sex chromosomes?
Turner syndrome
Klinefelter syndrome
What is Turner syndrome?
Monosomy x
Most common deviation in females
Short in stature and webbing of neck,
low hairline; intelligence may be impaired
What Klinefelter syndrome?
Trisomy xxy
Most common deviation in males
Affected males have poorly developed secondary sexual characteristics and small testes. Usually infertile, usually tall and may be slow to learn
What are autosomal dominant inheritance disorders and give examples.
An affected parent who is heterozygous for the trait has a 50% chance of passing the variant allele to each offspring. No skipping of generations.
Huntingtons disease, Marfan syndrome
What are autosomal recessive inheritance disorders and give examples.
Both genes of a pair associated with the disorder must be abnormal for the disorder to be expressed. The chance of the train occurring in each child is 25%
Examples: Cystic fibrosis, sickle cell
When do inborn errors of metabolism occur?
Occur when a gene mutation reduces the efficiency of encoded enzymes to a level at which normal metabolism cannot occur.
Defective enzyme action interrupts the normal series of chemical reactions from the affected point onward (PKU
Type of x-linked dominant disorders?
fragile x syndrome
rett syndrome
multifactorial genetic malfunction?
Combination of environmental and genetic factors
Cleft lip and palate
Congenital heart disease
Neural tube defects
Pyloric stenosis
