Author Notes

hellooo and thank you for visiting! i hope this study guide helps you prep for the EOC or the unit 2 test! :)

• use the test feature to test yourself on this knowledge

  • like this guide? check out the ones i made for the other units!!

﹙✦﹚﹒﹒abbreviations are used throughout this guide!

﹙Overview﹚

unit 2 will discuss the technology that scientists and medical professionals use in the word of genetics and DNA

╭ Other Resources :

:: unit 2 terms ﹒﹒ a knowt deck transferred over from my friend’s quizlet of the key terms in this unit !

﹙2.1 - Genetic Testing and Screening﹚

✦﹒genetic disorders are diseases caused by the abnormalities in an individual’s genetic material ; they can be screened/tested to help determine if someone has it, will develop one, or is a carrier for that disorder

• genetic disorders can be developed by environmental and genetic factors

• genetic disorders have different types—

  • single gene disorder - caused by changes or mutations tht occur in the DNA sequence of one gene

    • inheritance patterns include autosomal recessive + dominant, and sex-linked

    • it will result when a gene is mutated, which causes a nonfunctional protein

  • multifactorial disorder - caused by a combination of environmental factors and mutations in multiple genes

    • many common chronic illnesses r multifactorial

    • ex: chromosomes 6, 11, 14, etc. r diff genes tht can influence breast cancer development

  • chromosomal disorder - caused when there are issues in chromosomes (ex: missing/extra copies of genes or breaks, deletions/rejoinings of chromosomes )

    • karyotypes r important in diagnosing this

  • mitochondrial disorder - mutations in nonchromosomal DNA of the mitochondria, passed on from the mother

• types of genetic testing and screening include—

  • carrier screening - determines if the individual carries a copy of an altered gene for a recessive disease, often used if disease is common in a couple’s ethnic bg or family history

    • examples include tay-sachs + sickle cell

  • preimplantation genetic diagnosis (PGD) - used following in vitro fertilization to diagnose a genetic disease/condition before the embryo is implanted in the uterus

    • a single cell is removed frm the embryo to be tested

    • patient + doctor choose which embryo to implant

  • fetal screening/prenatal diagnosis allows parents to diagnose a genetic condition in their developing fetus

    • tests such as amniocentesis, chronic villi sampling (CVS), and regular scheduled ultrasound to allow parents to monitor the health of the growing fetus

  • newborn screening - used to detect genetic/metabolic conditions for early diagnosis + to provide quick treatment for disease

    • state tests for newborns typically screen anywhere frm 4-20+ disorders

    • most widespread type of screening

✦﹒polymerase chain reaction (PCR) allows scientists to explore our genome by amplifying (copying) a tiny specific piece of our DNA

flowchart of the steps of PCR

✦﹒testing DNA can be done by looking at the sequence of nucleotides

• a single-nucleotide polymorphism is one base pair in the genome’s sequence

• the gene of interest is tracked by these steps—

  1. extract and isolate DNA from cells

  2. amplify DNA using PCR

  3. restriction digest PCR products using restriction enzymes

  4. separate DNA fragments using gel electrophoresis

  5. determine genotype by results

✦﹒pregnant patients tend to have genetic testing and screening to monitor the growth of the fetus

• a screening test looks at the overall risk with how likely the child would have a particular condition/disorder

• a diagnostic test provides a more definitive answer to if the child will be born with that particular condition/disorder

  ”poster” of the main four genetic tests + screenings by me!!

﹙✦﹚﹒distinguish between the types of genetic disorders, know the process of PCR, ESPECIALLY know the genetic tests and screenings— it showed up A LOT in the unit 2 test for me

→ not included : 2.1.4, which is just determining the phenotype to compare to genotype frm 2.1.3

﹙2.2 - Our Genetic Future﹚

✦﹒gene therapy is a molecular treatment that alters the genes of a person afflicted with a genetic disease

• gene therapy uses different mechanics—

  • insert - a functional gene is given to a patient, providing their body w/the needs to make the functional protein; defective gene is still present but its effects are masked by functional gene

  • disable - dysfunctional gene is disabled, eliminating the impact of the protein

  • repair - dysfunctional gene is repaired to produce a functional protein

• a genetic disorder that is a good candidate for gene therapy applies with the following—

  • no current effective treatments

  • single-gene disorder

  • affected gene is known

  • adding a functional copy of the gene will resolve the issue

  • functional genes can be delivered to affected tissue

• gene therapy uses vectors to deliver the treatment, usually being a virus (see table)

  • no cell integration = temporary effects

    • cell integration = long lasting effects

  vector	max gene size + nucleic acid type	cell specificity	triggers immune response?	host cell integration?	efficiency
  plasmid	any size + DNA	n/a	no	no	not efficient
  liposome	any size + DNA	n/a	no	no	not efficient
  herpes virus	20k bp (20 kb) + DNA	cells of the nervous system	yes	no; remains active in cell for long time	not efficient
  adeno-associated virus	5k bp (5 kb) + DNA	dividing + non-dividing cells + variety of cell types	no	yes	efficient
  adenovirus	7.5k bp + DNA	dividing + non-dividing cells + variety of cell types	yes	no	efficient
  retrovirus	8k bp + RNA	dividing cells	yes	yes; but at random, can disrupt other genes	not efficient
  lentivirus	8.5k bp + RNA	dividing + non-dividing cells + variety of cell types	no	yes; but at random, can disrupt other genes	efficient

• gene therapy can either be in vivo (takes place in living organism) or in vitro (takes place outside of living organism, performed in lab)—

  • ex vivo

    • pros - less likely to cause immune response, target can be harvested, ensuring vector to enter correct cells + can be tested prior to reintroducing them back into the patient to make sure the vector properly integrated the gene into the cells

    • cons - wait time for benefits of gene therapy to be received

  • in vivo

    • pros - receives benefits of gene therapy readily

    • cons - more chance of immune response, vector enters cells other than those needing functional gene, + cell cannot easily be tested to ensure its working

• genome editing uses tools in the cell to cut DNA and replace mutated genes by altering the DNA in stem cells

  • recall that stem cells can develop into many diff types of cells

  • somatic (non heritable) and germline cells are targeted and used in this process

• Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) is a genome editing technique that has short palindromic repeated DNA sequences found in the genome of bacteria

  • has spacers + repeaters which store fragments of foreign DNA

    • spacer DNA is not identical, but a unique seq of DNA; matches perfectly w/viral DNA

    • gene is formatted like this: repeater-spacer-repeater-spacer…

  • cas9 - a restriction enzyme tht cuts + unwinds DNA, shutting off the target gene

    • can be tailored to target diff genes by changing the guide RNA to match the target DNA

  • guide RNA - specific RNA sequence that recognizes the target DNA region of interest + directs the cas nucleotide there for editingimage that demonstrates how CRISPR works!

my concept map of gene therapy overall with fragile X syndrome

✦﹒reproductive technology allows parents to decide on the child they hope to have based on the traits in an embryo’s DNA

• in vitro fertilization (IVF) is a reproductive technology where the eggs are removed from the woman and joined with a sperm cell (from partner) in a test tube (in vitro) to form a single-celled zygote tht becomes an embryo

  

• pre-implantation genetic testing (PGT) is a technique that helps reduce the chance of the embryo possessing a genetic defect by analyzing the chromosomes and implanting the chosen one in

﹙✦﹚﹒DEFINITELY understand how to know what vector works best for a scenario, mechanics of gene therapy + what is CRISPR and how it works