Basic genetics Flashcards
what are chromosomes made of?
Chromosomes are thread
-like structures located
inside the nucleus of animal and plant cells. * Each chromosome is made of protein and a single
molecule of deoxyribonucleic acid (DNA)
Karyotype - what is this?
(kary has chromosomes)
we don’t usually order these - it is a specific test. If there is an issue, you need to test both partners.
- Cytogenetic test (examines chromosomes)
- identification of numerical and structural chromosomal
abnormalities.
Euploid (correct # of chromosomes) or ANEUPLOID (missing or additional chromosome)
- An individual with a normal number of chromosomes would
be considered EUPLOID. (46 XX or 46 XY). - If there is an abnormality regarding the chromosomes,
this would be considered ANEUPLOIDY (image).
Karyotype…
Limitations
cost, TAT (turn around time) 3+ weeks to result, lab quality/resolution, pt history (bone marrow transplant) - instead of blood cells, need check or skin cells to interpret
Genetic Carrier Screening
- Determines the risk for passing an inherited genetic condition.
- Done preconception, can allow the couple to decide how to best grow their family.
- Genetic conditions are dominant (affected individual) or recessive (carrier) & x-linked
- Screening offered preconception focuses on recessive (carrier) & x-linked genetic conditions.
- Examples of recessive diseases:
- Cystic Fibrosis, Spinal Muscular Atrophy (SMA), Hemoglobinopathies, etc…
- Examples of X-linked disease:
- Fragile X
autosomal recessive conditions
Two copies of an abnormal gene must be present in order for
the disease or trait to develop - 25% unaffected 50% carriers (usually not symptomatic), 25% affected
Horizon - what are sperm providers tested for?
- SPRING works with Natera (this is the lab that runs the screening)
- Natera’s carrier screening test is named Horizon.
- Expanded Carrier screening that SPRING utilizes:
- Horizon-up to 421 Carrier Screening panel
- Egg provider: includes X-linked conditions
- Sperm provider: Not screened for X-linked conditions
- Offered to all patients by Provider
- PN reviews option and helps to schedule/follow up
how to inform patients of this option
- Everyone is expected to be a carrier of at least one genetic condition, most are healthy (60% screen positive)
- Both partner positive for recessive condition : ~1 in 4 chance of an affected pregnancy
- X-linked condition:
- Boys: 1 out of 2 chance for boys to be affected
- Girls: 1 out of 2 chance for girls to be carriers
- Appropriate for all patients of any and all ethnicities (pan-ethnic)
- Many conditions being tested for may not be life altering
- Family history is important to determine what other genetic testing could be relevant
- Encourage discussion of results with family members
- Genetics counselors can advise patient on results and options
carrier screening completed at an outside facility
- Some comparable panels will be accepted per ethnicity screening of the couple – see chart CN11
- Report must be uploaded to the patient documents
- Utilize the test name “Genetic Carrier Screening” that are not Horizon.
- Add details under remarks on the lab panel –panel name & number of conditions tested.
- GC must be tasked to review results, inc. document title and page number of CR result, if applicable.
- The GC will review report/input and sign off in Blood/Lab tests.
- If acceptable expanded carrier screening (ECS) panel completed (as per Table 1 in CN11) it is NOT recommended that they repeat screening.
- Checklist item cannot be checked as completed unless waiver signed and review/sign-off completed by APP (NP/PA).
- For patients selecting a sperm donor, the carrier screening results of IP/donor MUST be cross checked by an APP/GC.
- CA—task APP, NP or PA for your site, to review CR-results prior to patient purchasing.
- NYC- formal counseling by Spring GC or GeneScreen is required prior to purchase. This must be uploaded to chart.
- PDX- TBD
we don’t really want ppl to repeat screening if they’ve had it already bc it leads to confusion
what is PGT testing?
(embryo pagent)
- Preimplantation genetic testing (PGT) can be done to evaluate an embryo prior to transfer.
GC calls patient with:
- Embryo testing,(PGT), POC(Anora) and
Panorama (NIPT) results. - Can provide risk assessment/education
- PGT options
- Donor results, etc
formal apt.
- $300, full consult ~ 1hr, insurance not currently
accepted unless Progyny - $100, for 15min call, if indicated per ECS, etc..
- Send order to Finance to obtain auth for
Progyny or to provide CL (cost letter) to pt. prior to appt.
Genetics Consult Types - formal
Paid Consult
* Spring Genetics Counselor
* Outside Genetics Counselor
* Genescreen (NYC)
* Per Insurance or patient preference
Genetics Consult Types -Genetics Information Session (GIS)
- Free Consult (~15 min or less)
- Testing Lab’s GC (Natera)
PGT-A : Aneuploidy testing ** Most common**
(A line)
This only tells if the chromosomes are lined up accurately -
Identify/transfer only Euploid embryos (46 XY or XX)
