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REPRO FINAL
| Question | Answer |
|---|---|
| WHAT DOES PGD STAND FOR? | Pre-implantation Genetic Diagnosis |
| What is the purpose of PGD? | -To identify genetic abnormalities in embryos created through IVF before implantation. -One or both parents has known genetic abnormality -Embryos are screened for specific mutation |
| What do embryos get screened for in PGD? | Specific mutations |
| What does PGS stand for? | Pre-implantation Genetic Screening |
| What is the purpose of PGS? | To screen embryos from genetically NORMAL parents for chromosomal disorders. |
| What does PGT stand for? | Pre-implantation Genetic Testing |
| What are the two major categories of PGT? | PGT-A = Aneuploidy testing (formerly PGS) PGT-M = Monosomic/single-gene defect testing (formerly PGD) |
| What does PGT-A test for? | Aneuploidy (abnormal chromosome number). |
| Which older term is associated with PGT-A? | PGS |
| What does PGT-M test for? | Monosomic/single-gene defects. |
| Which older term is associated with PGT-M? | PGD |
| What are the 6 steps in the PGT process? | 1. Genetic counseling 2. IVF 3. Trophectoderm (blastocyst) biopsy 4. Freeze blastocyst 5. Genetic testing of biopsied sample 6. FET of “unaffected” embryos |
| Define step 1 of the PGT process? | 1. Genetic Counseling: Genetic counseling allow parents to review family history, inherited disease risks, and determine appropriate testing. |
| Define step 2 of the PGT process? | IVF: 1.Eggs are collected from ovaries 2. Sperm fertilizes eggs in a lab 3. Embryos begin developing Why: PGT can only be performed on embryos created through IVF. Goal: Create embryos that can later be genetically tested. |
| Define step 3 of the PGT process? | Trophectoderm (Blastocyst) Biopsy: A few cells are removed from the blastocyst (day 5–6 embryo). Cells come from the trophectoderm (future placenta), NOT the inner cell mass that becomes the baby (harmful). |
| Define step 4 of the PGT process? | Freeze Blastocyst: The embryo is frozen (cryopreserved). WHY? Genetic testing takes time, so the embryo is stored safely while results are processed. |
| Define step 5 of the PGT process? | Genetic Testing of Biopsied Sample: Removed cells are analyzed in the lab. Doctors look for: Chromosomal abnormalities (PGT-A) Single-gene disorders (PGT-M) Structural chromosome abnormalities |
| Define step 6 of the PGT process? | FET of “Unaffected” Embryos: FROZEN EMBRYO TRANSFER (FET): A healthy/unaffected embryo is thawed and transferred into the uterus. Only embryos without the targeted disorder are selected. |
| WHAT SAMPLE CAN BE USED FOR KARYOTYPING? | Lymphocytes from blood sample → common in adults Cheek swab → collects cells from inside the mouth Chorionic villus sampling (CVS) → placental cells during pregnancy Amniocentesis → fetal cells from amniotic fluid |
| What are the basic steps of karyotyping? | Collect cells Culture cells Add phytohemagglutinin → stimulate mitosis Add colcemid → stop at metaphase Centrifuge and fix cells Stain chromosomes on slide Photograph and arrange chromosomes into a karyotype |
| Why is mitosis stopped at metaphase in karyotyping? | Because chromosomes are most condensed and visible. |
| CHROMOSOME TERMINOLOGY: What is euploidy? | Normal chromosome number; exact multiple of the haploid number (2n = 46 in humans). |
| CHROMOSOME TERMINOLOGY: What is Aneuploidy? | An abnormal number of chromosomes. |
| CHROMOSOME TERMINOLOGY: What is trisomy? | Presence of an extra chromosome (2n + 1); example: Down syndrome (+21). |
| CHROMOSOME TERMINOLOGY: What is triploidy? | Three complete sets of chromosomes (3n = 69 in humans). |
| WHAT ARE THE LETTERS REPRESENTING FEMALE KARYOTYPE? | XX |
| WHAT ARE THE LETTERS REPRESENTING MALE KARYOTYPE? | XY |
| What are Heritable vs non-heritable disorders? | Heritable = inherited from parents; runs in families Non-heritable = random mutation/chromosome error; not inherited |
| What is multifactorial inheritance? | A condition caused by multiple genes + environmental factors. Unlike single-gene disorders, there is not one single mutation responsible. Examples: Height Type 1 diabetes Type 2 diabetes |
| What role do environmental factors play in multifactorial inheritance? | Environment interacts with genes to influence disease risk. Examples: Fetal alcohol syndrome → alcohol exposure FROM MOM Type 1 diabetes --> viral infection/ immunocompromise Type 2 diabetes → diet/lifestyle |
| What causes non-heritable chromosomal disorders? | NOT inherited from parents Result from random mutations or chromosome errors during gamete formation or early embryonic development Examples: Down syndrome (nondisjunction) Turner syndrome Some cases of achondroplasia |
| What is nondisjunction? (NON HERITABLE DISORDERS) | (MITOSIS DNA SEPERATION) Failure of chromosomes to separate properly during cell division, causing extra or missing chromosomes. |
| What is de novo mutation? (NON HERITABLE DISORDERS) | (DNA OR GAMETE SPECIFIC) A new mutation appearing for the first time in a family due to mutation in sperm, egg, or zygote. |
| What is the Main idea of multifactorial inheritance? | Genes may increase susceptibility, but environmental factors influence whether the condition develops. |
| What happens if nondisjunction occurs during meiosis? | The sperm or egg is abnormal before fertilization, so the zygote starts abnormal and ALL cells are affected. |
| What happens if nondisjunction occurs during mitosis? | The zygote starts normal, but an error after fertilization causes only SOME cells to become abnormal → mosaicism. (MEIOSIS HAPPENS FIRST THEN MITOSIS HAPPENS TO BUILD BABY INTO LITERAL HUMAN) |
| What is mosaicism? | Presence of two genetically different cell populations in one individual due to a mitotic error after fertilization. |
| What's the Difference between meiotic and mitotic errors? | Meiotic error → whole embryo affected Mitotic error → mosaicism (mixed normal + abnormal cells) |
| Why does mosaicism occur? | A chromosome separation error occurs during mitosis after the zygote has already formed. |
| TRUE OR FALSE: Trisomies of maternal origin (most frequently in Meiosis 1) are 10X more common than those of paternal origin | TRUE |
| What is trisomy rescue (anaphase lag)? | An embryo starts trisomic (47 chromosomes) but loses the extra chromosome in some cells during mitosis, resulting in mosaicism. |
| Why does timing matter in mosaicism? | A biopsy may sample abnormal cells or normal cells that do not perfectly represent the entire embryo. |
Created by:
bythedeli