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Portage Genetics Module 6

HEAL100 Health Care — exam and revision material · Other

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Health Care exam material, 5 pages. Originally published on StudyMerit.

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5
Academic year
2025/2026
Language
English

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6.1: Chromosomal Mutations  Chromosome Mutations or Aberrations  changes in total chromosome number, additions or deletions of chromosome segments, or complete rearrangement of chromosome section  Aneuploidy  addition or deletion of a single AUTOSOMAL chromosome Not sex chromosomes Not entire set o Monosomy = deletion of a single chromosome  Lethal in mammals  For X-chromosome, if either incomplete or missing, developmental delays or health problems  Baffles scientist because there is still another copy of every gene present  Tolerated in plants  Less viable, less fertile; NO EVOLUTIONARY ADVANTAGE o Trisomy = addition of a single chromosome  More tolerable, but can be lethal  Small chromosome = greater chance of survival  Large chromosome = lesser chance of survival  In plants, creates different phenotypes  Less viable  Less fertile  Grow slower  Types of Trisomy o Trisomy 21 = Down Syndrome  Discovery and history  Langdon Down (1866)  1/700 babies, over 6,000 afflicted  MATERNAL AGE linked o Speculation???  Eggs are much older, even though they are arrested in meiosis I, but more time is given for them to develop abnormalities and have difficulties during cell division o

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 Lifespan ~50 years (dementia)  Genetics  14-16 phenotypes, but most exhibit half of them  NONDISJUNCTION DURING MEIOSIS 1 OF ANAPHASE 1 OR 2 IN THE OVUM  Down Syndrome Critical Region (DSCR) o Used mouse model  Did not always display phenotype characteristics o 3 copies of chromosome 21 present on 95% of afflicted individuals o 2% have mosaic of trisomy  Some have 2 copies, some have 3 o Small percentage have translocation of extra piece, but it is attached to another chromosome  Higher incidence of LEUKEMIA o Lower chance of cancers w/tumor due to DSCR1 gene  Blocks vascular epithelial growth factor (VEGF)  Means that vasculature cannot develop to support solid tumor growth  Testing for Genetic Disorders o Use prenatal genetic screenings  10 weeks  Mother’s blood + cell-free fetal DNA  Non-invasive  Determine risk estimate of developing aneuploidy  Is there abnormal amount of chromosomes 21, 18, 13, or sex chromosomes?  15-22 weeks  CVS = Chorionic villus sampling  Cells from placental biopsy  More invasive, higher risk to mother and baby  Calls analyzed via PCR or FISH (fluorescent in situ hybridization)  22 weeks  Amniocentesis o Remove amniotic fluid from placenta o Contains fetal cells  Karyotyping done to detect aneuploidy, deletions, duplications,

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