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Genetics OLA 2
| Question | Answer |
|---|---|
| Where does protein synthesis occur? | cytoplasm |
| An organism's ___ is determined by the sequence of bases in its DNA | genotype |
| An organism's ___ is a product of the proteins it produces | phenotype |
| Ribosome moves ___ on the mRNA and builds protein from its N- to C-terminus | 5' > 3' |
| What are the stages in translation | 1. tRNA charging 2. Initiation 3. Elongation 4. Termination |
| During the tRNA charging stage of translation, ___ "charge/attach" a specific amino acid to its corresponding tRNA 3' end | aminoacyl-tRNA synthetases |
| What would occur if the ShineDalgarno sequence in a prokaryotic mRNA was mutated? | the ribosome would not select the proper initation codon, resulting in a failure to initiate translation |
| The formation of the peptide bond in the second step of elongation is catalyzed by which part of the ribosome? | rRNA in the large subunit of the ribosome |
| the adapter molecule between nucleotide language and amino acid language | tRNA |
| what is the ribosonal subunit that binds mRNA with initation factors in BACTERIA/PROKARYOTES | shine dalgarno |
| what is the ribosonal subunit that binds mRNA with initation factors in EUKARYOTES | kozak sequence and 5' cap |
| What is the P site for EUKARYOTES during the initiation stage of translation | Met |
| What is the P site for PROKARYOTES during the initiation stage of translation | fMet |
| the process of chemically linking a specific amino acid to its corresponding tRNA molecule | tRNA charging |
| What happens if tRNA charging fails | wrong AA is inserted |
| a stretch of DNA containing a cluster of genes that are transcribed together from a single promoter | operon |
| Anatomy of an operon: DNA sequence required for transcription to initiate via binding of RNA Polymerase | promoter |
| Anatomy of an operon: Genes that encode proteins involved in a common process, and that are important for cell function | structural genes |
| Anatomy of an operon: *DNA* sequence downstream of promoter, to which a regulator protein can bind and prevent movement of the RNA polymerase from the promoter to transcribe the structural genes | Operator |
| Anatomy of an operon: A *protein* encoded by a regulator gene, that binds the operator and controls transcription of the structural genes | Regulator |
| a section of DNA or RNA that codes for a specific protein | cistron |
| an mRNA that encodes for more than one protein | polycistron |
| A _______ operon is one in which transcription is normally on, and it needs to be turned off | repressible |
| The regulator protein that acts on a negative repressible operon is synthesized as _____________ | an inactive repressor |
| In a positively controlled repressible operon, the regulatory protein is synthesized as a(n) ___ | active activator |
| chromatin that condenses and decondenses during the cell cycle | euchromatin |
| chromatin that is highly condensed throughout the cell cycle | heterochromatin |
| what does chromatin consist of? | chromosomal DNA + proteins |
| specifies the translational initiation site in eukaryotic mRNAs | Kozak sequence |
| identical copies of a chromosome connected at the centromere, formed during DNA replication | sister chromatids |
| an insertion or deletion that changes the reading frame of a gene | frameshift mutation |
| transcriptional activator regulated by glucose. | catabolite activator protein (CAP) |
| specifies the translational initiation site in prokaryotic mRNAs | shine-dalgarno sequence |
| nucleotide triplet coding for an amino acid. | codon |
| repair pathway that removes bulky DNA damage such as thymine dimers. | nucleotide excision repair (NER) |
| a cell with only one set of chromosomes, such as gametes. | haploid |
| prokaryotic genes regulated by a common promoter. | operon |
| a disorder appearing earlier or more severe in successive generations, often due to repeat expansion. | genetic anticipation |
| exchange of genetic material between nonsister chromatids during prophase I. | crossing over |
| a gene that promotes cell division and can cause cancer when overactive. | oncogene |
| a base substitution in which a purine replaces a purine, or a pyrimidine replaces a pyrimidine. | transition mutation |
| How many codons would be possible in a triplet genetic code if only three nucleotide bases (A, C, and U) were used? | 27 (3^3) |
| How do nonsense codons differ from sense codons | nonsense codons do not encode an amino acid |
| Why is translation a good target for antibiotics | translation differs significantly between bacterial and eukaryotic cells |
| What is the biochemical consequence of histone acetylation on chromatin structure and gene expression | It weakens the interaction between histone tails and DNA, promoting an open chromatin structure and increasing transcription |
| How do lacI⁻ mutations lead to constitutive expression of the lac operon genes? | the repressor fails to bind the operator in the absence of lactose and in the presence of lactose |
| The lactose operon is a negative inducible operon, the repressor protein is synthesized as | An active repressor |
| The tryptophan operon in trp operon is an example of a negative repressible operon. When there are high levels of tryptophan available to the organism, which of the following is most likely? | Transcriptional termination is likely |
| Histone methylation is associated with: | Epigenetic mark that can be found in chromatin of expressed or repressed genes |
| A mutation changes a G:C base pair into an A:T base pair. This mutation is best classified as | Transition (purine>purine and pyrimidine>pyrimidine : same-base-type sub) |
| A coding sequence undergoes a single base substitution. The resulting protein is shorter than normal. Which type of mutation most likely occurred? | nonsense mutation |
| A missense mutation in TP53 prevents the protein from binding DNA. Which cellular process would most directly fail? | activation of DNA repair genes |
| If DNA polymerase proofreading activity (3’→5’ exonuclease) is lost but mismatch repair remains functional, what would you predict? | large increase in mutation rate |
| A parent carries 38 CAG repeats in a gene associated with Huntington’s disease. Their child develops symptoms earlier and has 50 repeats. This phenomenon is best explained by | genetic anticipation |
| Which type of radiation is more likely to cause double-strand DNA breaks? | ionizing radiation (x-rays) |
| During which stage of meiosis do homologous chromosomes pair up and crossing over occur? | prophase I |
| If a parent cell has 16 chromosomes, how many chromosomes will each daughter cell have after meiosis? | 8 |
| What is the key difference between meiosis I and meiosis II? | Meiosis I reduces the chromosome number (reductional), while meiosis II separates sister chromatids (equational). |
| During which stage of meiosis do sister chromatids separate? | anaphase II |
| What is the primary purpose of meiosis in sexually reproducing organisms? | to halve the number of chromosomes and create genetic diversity |
| During which phase of the cell cycle is DNA replicated? | S phase (interphase) |
| What structure is responsible for pulling chromatids apart during anaphase | spindle fibers |
| A 30s subunit is scanning mRNA for the initiation codon. What sequence will the 30s subunit recognize? | shine-dalgarno sequence (30s subunit is the bacterial small ribosomal subunit) |
| Human hemoglobin consists of four subunits, 2 α and 2 β. What level of protein structural organization does this represent? | quaternary |
| Which nucleotide in the tRNA anticodon is subject to wobble pairing? | The 5' end |
| What molecule is hydrolyzed by RF-3 in prokaryotes to induce translational termination? | GTP |
| What is not a function regulated by p53? a) Arrest the cell cycle at G1/S b) Initiate DNA repair c) Degrade mutant transcripts d) Initiate apoptosis | c) degrade mutant transcripts |
| The DNA sequence GGA CAT GAC experiences a mutation, changing to GGA CTT GAC. What type of sequence mutation does this represent? a) Transition substitution b) Deletion c) Transversion substitution d) Insertion | transversion substitution (exchanges purine A with pyrimidine T) |
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