Molecular Genetics — Flashcards

Flashcard 371: 5α-reductase deficiency = _____

Answer: 46XY

Flashcard 372: What serum marker is characteristically elevated in choriocarcinoma? _____

Answer: β-hCG

Extra: β-hCG is characteristically elevated in choriocarcinoma, hydatidiform moles, and gestational trophoblastic disease. It is also used to monitor treatment response and screen for recurrence.

Flashcard 373: Chronic myeloproliferative disorders (except CML) are associated with _____ mutations - the mutation is in a gene encoding a(n) tyrosine kinase, which causes tyrosine hyperphosphorylation and hypersensitivity of progenitor cells to cytokines, prolonging cellular growth

Answer: V617F JAK2

Flashcard 374: HbH and Hgb Barts = _____ thalassemia ↑ HbA2 and ↑ HbF = _____ thalassemia

Answer: alpha

Flashcard 375: 24 y/o woman is diagnosed with gestational diabetes mellitus during her 1st pregnancy. -Mother & younger sister had high blood surgars during pregnancy. -If this patient's gestational hyperglycemia is genetically predisposed, she is most likely to have decreased activity in what enzyme?

Answer: Glucokinase Glucokinase need to phosphorylate glucose to breakdown in glycolysis in order to release ATP to close down the K channel, which lead to influx of Ca that causes release of insulin. due to Maturity Onset Diabetes of the Young (MODY) (hereditary mutation of glucokinase gene) Key: Her mother & her younger sister had diabetes too during their pregnancy, very young.

Flashcard 376: What are the following markers? -Ras -c-Jun -B1 - adrenoreceptor -S- 100 -Adenylate cyclase -C-fos

Answer: Ras: Protooncogene activates MAP kinase pathway, affect transcription, has GTPase gene product. (associated with colon, pancreatic, and lung cancer.) -c-Jun: The protein that binds to DNA in southwestern blot (double stranded DNA probe). -B1-adrenoreceptor: Gs protein couple receptor. -Adenylate cyclase: cleaves ATP to form cAMP. -S-100: calcium binding proteins. -c-Fos: Proteins that bind to DNA to form double stranded DNA probe in Southwestern blot.

Flashcard 377: In an experiment, individual bacterial colonies lack a specific enzyme involved in DNA replication. - This enzyme is responsible for removing short fragments of RNA that are base-paired to the DNA template. - Which enzyme is most likely deficient in this strain of E. coli?

Answer: DNA polymerase I It removes RNA primers (5' to 3' exonuclease activity) and replaces them with DNA nucleotides. **Note:** Do not confuse with **Primase**, which synthesizes the RNA primers.

Flashcard 378: 65 y/o woman with chronic obstructive pulmonary disease & type 2 DM. -She's hospitalized with septicemia. -Cultures shows rapidly dividing gram-negative bacteria. -Replication of theses microbial cells requires synthesis of two daughter strands of DNA using the parents strands as templates. -Which processes will differ the most between the 2 dauther strands formed at each replication fork?

Answer: Joining of DNA fragments by ligase which is specific for lagging strands.

Flashcard 379: What kind of mutation exists in the following base changes? - CUU (Leucine) → AUU (Isoleucine) - UUU (Phenylalanine) → UUC (Phenylalanine) - CAG CCC ACT → CAG TCC CAC T - CAG CAG UAA → CAG CAG CAA - UCA → UGA (Silent, Missense, Nonsense, Nonstop, Frameshift)

Answer: - **CUU (Leucine) → AUU (Isoleucine)**: Missense mutation - **UUU (Phenylalanine) → UUC (Phenylalanine)**: Silent mutation - **CAG CCC ACT → CAG TCC CAC T**: Frameshift mutation - **CAG CAG UAA → CAG CAG CAA**: Nonstop mutation (Stop codon → Amino acid) - **UCA → UGA**: Nonsense mutation (Amino acid → Stop codon)

Extra: - **Silent**: Same amino acid (often 3rd position/wobble). - **Missense**: Different amino acid. - **Nonsense**: Changes to a Stop codon (UAA, UAG, UGA). - **Nonstop**: Stop codon changes to an amino acid. - **Frameshift**: Insertion or deletion not in a multiple of 3, shifting the reading frame.

Flashcard 380: Describe the characteristics or mutations associated with the following Hemoglobins: - Hemoglobin C - Hemoglobin F - Hemoglobin H - Hemoglobin S

Answer: - **HbC**: Glutamate → **Lysine** mutation at position 6 of the β-globin chain. - **HbF**: Fetal hemoglobin (α2γ2); has higher O2 affinity than HbA. - **HbH**: β4 tetramers; occurs in **3-gene deletion** α-thalassemia. - **HbS**: Glutamate → **Valine** mutation at position 6 of the β-globin chain.

Extra: Note: **Hb Barts** (γ4) occurs in **4-gene deletion** α-thalassemia (Hydrops fetalis). Both HbH and Hb Barts have very high oxygen affinity and are poor at oxygen delivery. Mnemonic for β6 mutations: - Hb**S**: **V**aline (**S**ickle) - Hb**C**: **L**ysine (Ly-**C**-ine)