Ch 10 - Genetics Flashcards
the study of individual genes and their effect on seemingly rare, single gene disorders
Genetics
the study of all genes in the human genome together. This includes their interactions with each other and the environment
- genetic material across ethnic, culture, etc
genomics
What are the implications of shifting to a genomics focus?
cancer research → target drug and tx measurements to know how to they respond across humanity
Human genome project findings
Human beings are 99.9% equal on the DNA level
Humans do not have more genes than other species. The use of different proteins enables higher functioning at a more differentiated level than in other species.
What is the most efficient, cost effective way to be able to predict genetic disorders?
What does it include?
Accurate family history
Should include history of diseases, as well as ethnic and cultural background of all blood related relatives for 3 generations
Tests for down syndrome & spina bifuda
Tested at 16 weeks
Has a high false positive rate.
MSAFP 4
US test for downs syndrome, tests fat fold in the back of the neck.
noninvasive.
Nuchal translucency
What are some tests you might consider for someone who is black or jewish?
sickle cell - blacks
Tay Sachs - jews
What are some tests you might consider for disorders that are specific to family history? (hint: genetic disorders)
trisomy’s
cystic fibrosis (autosomal recessive gene - both parents must have for children to be affected)
Huntington’s
The different ways a test can be done
- Blood
- US
- IVF
- CVS - chorionic villus sampling - sample of amniotic tissue
- Amniotic fluid (toward end of 2nd trimester, but w/in enough time to terminate before viability)
Screening for genetic disorders and other inborn errors of metabolism while in the hospital
Usually done between 24-48 hrs of birth.
~30 disorders per screening
PKU - phenylketonuria
If you have too much phenolyline, it may result in neurologic/cognitive delays, but is manageable if caught early
BRCA1 & BRCA2
breast cancer screen
How many chromosomes do both sperm & egg contribute each?
23
22 autosomes + 1 sex chromosome
contributes most of the traits & characteristics
autosomes
Which sex chromosome determines the sex of the baby?
father’s
chromosomal disorder caused by missing/incomplete X chromosome.
happens in females
causes short stature, delayed puberty, infertility, …. etc
many will miscarry spontaneously
turners (X-linked) - also called gonadal dysgenesis
Most will lead normal lives
chromosomal disorder caused by a male w/ an extra X chromosome
causes infertility, small testicles, mild intellectual disability, gynecomastia
Klinefelter syndrome (Y linked)
Most will lead normal lives
What is the major cause of reproductive loss?
chromosomal anomalies
What % of pregnancies w/ chromosomal anomalies result in spontaneous abortion?
When do they generally occur?
60%
Generally before the first 12 weeks of pregnancy
an abnormal number of chromosomes within a cell
is a type of chromosomes abnormality
An extra or missing chromosome is a common cause of genetic disorders.
Aneuploidy
the condition in which a normally diploid cell or organism acquires one or more additional sets of chromosomes.
has 3 or more times the haploid chromosome number
polyploidy
Most common type of chromosomal abnormality, responsible for most genetic cases of mental retardation
Aneuploidy
the result of a union between normal gamete and one with an EXTRA chromosome
trisomy
the result of a union between normal gamete and one MISSING a chromosome
monosomy
The most common autosomal aneuploid conditions involve …
trisomies
When do most trisomies occur?
oogenesis
What factor in the woman will increase the risk of trisomies?
advanced maternal age. More risk the older the mom is.
trisomy 21
down syndrome
trisomy 13
patau syndrome
trisomy 18
edward’s syndrome
what percentage of newborns w/ trisomy 13 & 18 are born stillborn?
50%
What is this describing: wide spaced eyes low nasal bridge no neck low set ears simian crease in hand
Down syndrome
ways in which abnormalities of chromosome structure occur:
Translocation - EXCHANGE of chromosomal material between two chromosomes
Deletion - loss of chromosomal material and partial monosomy for the chromosome involved. Often associated with retardation (both cognitive and psychomotor) and organ malformation
Inversions - portion of the chromosome has been REARRANGED in reverse order.
Combination of genetic and environmental factors
Examples would be neural tube defects and cleft lip/palate
multifactorial
- tends to run in families, but not as easily inheritable
One gene controls a particular disease or disorder.
Much more common than chromosomal abnormalities. Include things like autosomal dominant, autosomal recessive, and X linked dominant and recessive modes of inheritance
Unifactorial
risk and recurrence are HIGH
Only one copy of a variant allele needed for phenotypic expression- only one parent needs to pass the gene on for expression of the trait.
Autosomal Dominant Inheritance
Need a gene from each parent in order to have the disorder show up
People who only have one gene passed on are known as carriers
May skip generations
If affected individual reproduces, all children will at least be carriers
Autosomal Recessive Inheritance
A mode of genetic inheritance by which a dominant gene is carried on the X chromosome.
No male to male transmission (XX/XY)
X Linked Dominant Inheritance
Abnormal genes carried on X chromosome
Females can be hetero or homozygous because they have two X chromosomes
Males said to be hemizygous because they only have one X chromosome
X Linked Recessive Inheritance
PKU
Cystic fibrosis
sickle cell dz
Autosomal Recessive Inheritance
huntington dz
Marfan syndrome
Achondroplasia
Factor V Leiden
Autosomal Dominant Inheritance
Hemophelia
Color blindness
Duchenne muscular dystrophy
Fragile X syndrome
X Linked Recessive Inheritance
Hypophosphatmic Rickets
X Linked Dominant Inheritance
Helps individuals and families to understand the medical facts surrounding a diagnosis, including probable course of the disorder and the available management
Choosing a course of action that seems to them appropriate in view of their risk, family goals, and ethical and religious standards and act in accordance with that decision
Make the best possible adjustment to the disorder in an affected family member or to the risk of recurrence of the disorder
genetic counseling
Ethical, legal, and social implications of genetic testing
not 100% accurate
costly & not always covered by insurance
patient confidentiality - obligation to pass on info about genetic disorders to other family members
cultural values (IVF)
