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GENETICS FINAL EXAM 2026 COMPLETE
STUDY GUIDE A+
โ What nitrogenous bases are purines Answer: Adenine and Guanine โ What nitrogenous bases are pyrimidines? Answer: cytosine, thymine, uracil โ How can you differentiate between purines and pyrimidines? Answer: purines are double-ringed while pyrimidines are single- ringed โ What are the differences between DNA and RNA? Answer: DNA: double stranded, has deoxyribose sugar(hydroxyl group at 2' carbon), bases: A, T, G, C RNA: single stranded, has ribose sugar(one oxygen is removed from the 2' Carbon), bases: A, U, G, C โ Nucleoside vs Nucleotide Answer: nucleoside: pentose sugar + nitrogenous base nucleotide: pentose sugar + nitrogenous base + phosphate group
โ What type of bonds bind nucleotide chains? Answer: Phosphodiester bonds โ What are the 4 requirements for a molecule to be genetic material? Answer: 1.) Must contain important info to encode hereditary traits 2.) Must be capable of replication 3.) Must be capable of variation by mutation 4.) Must be able to express information โ Where are chromosomes located? Answer: cell's nucleus โ what is a centrosome? Answer: location in the cell that contains centrioles โ What are centrioles? Answer: microtubules that produce mitotic spindle fibers, aids in cell division, and make up the cytoskeleton of the cell โ How many centrioles are there for every centrosome? Answer: 2 centrioles/1 centrosome โ How many copies of each type of chromosome does each eukaryotic cell typically have? Answer: 2 copies
โ What happens during mitosis prophase? Answer: centrioles move to opposite ends of the cell using spindle fibers nuclear membrane breaks down chromatin (DNA) condenses into chromosomes (the "x"'s); bound by a kinetochore that attracts mitotic spindle fibers โ What happens during mitosis prometaphase? Answer: centrioles have reached polar regions and mitotic spindle fibers have connected to the kinetochore โ What happens during mitosis metaphase Answer: all chromosomes are lined up on the metaphase plate โ What happens during mitosis Anaphase? Answer: mitotic spindle fibers pull chromosomes apart into chromatids (4n) โ What happens during mitosis telophase? Answer: nuclear envelope reforms plasmo-membrane is pinched; sister chromatids are still condensed at this point
โ What happens during cytokinesis? Answer: cells split off; genetic material becomes uncondensed โ What happens during Meiosis? Answer: Division of one diploid cell to yield 4 haploid cells that are completely different โ What happens during Meiosis 1? Answer: 1. Homologous chromosomes pair to form tetrads.
- Crossing over (exchange of sections of genetic material) occurs at chiasmata.
- Cell divides into two. Homologous chromosomes separate randomly. Each cell contains either maternal or paternal copy. ( diploids becomes 2 haploid) โ What happens during Meiosis 2? Answer: 1. Independent segregation of sister chromatids.
- Each cell divides again, producing 4 haploid cells. โ What are the three theories of DNA Replication? Answer: semi- conservative(parent strands split and are used as templates for new DNA + it binds to the new DNA), conservative(parents split to make new strands and then rejoin with each other), dispersive(old and new DNA strands randomly join together
โ What happens during the initiation stage of DNA replication in prokaryotes? Answer: initiator proteins are added, helicase attaches to the strand, helicase unwinds DNA strand to form replication fork, DNA primase adds RNA primers, Single-stranded binding proteins bind onto the unwound strands to prevent the strands from rejoining โ What happens during the elongation stage of DNA replication in prokaryotes? Answer: DNA Polymerase 3 adds new nucleotides (DNTPs) to the 3' end of both strands โ What are the differences between the leading and lagging strands during DNA replication in prokaryotes? Answer: The leading strand undergoes continuous synthesis while the lagging strand undergoes discontinuous synthesis (Synthesis of the lagging strand has to be discontinuous because DNA polymerase cannot make a new strand in the 3' to 5' direction. Therefore, a series of Okazaki fragments, each with their own RNA primer, must be made as to the fork advances) โ What are Okazaki fragments? Answer: Relatively short fragment of DNA synthesized on the lagging strand during DNA replication โ What enzyme relieves the tension caused by the discontinuous synthesis of the lagging strand? Answer: Topoisomerase
โ What happens during the termination stage of DNA replication in prokaryotes? Answer: DNA Polymerase 3 dissociates, DNA Polymerase 1 removes RNA primers in a 5'-3' direction and replace the primers with DNA, DNA Ligase seals the strand and repairs any nicks left by the RNA primers โ What is the difference between prokaryotic and eukaryotic DNA Answer: prokaryotic DNA is small and circular eukaryotic DNA is long and linear โ What enables DNA Replication to occur as quickly as it does in eukaryotes (the entire human genome can be replicated in 8 hours)? Answer: Eukaryotes have multiple replicons (replication forks) โ What are the names and functions of the additional DNA Polymerases used during eukaryotic DNA replication? Answer: Polymerase Alpha- synthesizes RNA primers on leading and lagging strands (low processivity so it dissociates quickly) Polymerase epsilon- greater processivity than alpha; 3'-5' exonuclease activity( deletes mistakes and synthesizes RNA primers on the leading strand) Polymerase Delta- greater processivity; 3'-5' exonuclease activity; synthesizes RNA primers on the lagging strand
radioactive phosphorus (to test nucleotides) to see, after infection, whether the infected cells would be radioactive. They used a centrifuge to isolate the protein shells from the nucleic acids. The pellet at the bottom for the test ran with radioactive sulfure showed the supernatant the pellet was in to be more radioactive and the test with the phosphorus showed the pellet to be more radioactive. This suggested that DNA was the transforming principle โ Identify this part of the chromosome Answer: p-arm โ Identify this part of the chromosome Answer: q-arm โ What are chromatids? Answer: one of two identical "sister" parts of a duplicated chromosome โ What are the 4 phases of the cell cycle? Answer: G1, S, G2, Mitosis โ What is the purpose of Mitosis? Answer: cell regeneration, growth, and asexual reproduction โ What is the purpose of Meiosis? Answer: produce gametes for sexual reproduction
โ How does meiosis differ between males and females? Answer: Meiosis in males makes four sperm, while meiosis in females makes one egg and three polar bodies. This is so the extra chromosomes have a place to go. Polar bodies eventually disenegrate. โ What are histones? Answer: Proteins that pack DNA into condensed formed; Because eukaryotic DNA is so long, histones help provide structural support by compacting the DNA โ How does acetylation/deacetylation help package and unpackage DNA along nucleosomes? Answer: When acetyl groups are added to cytosine, this makes the chromatin more compact (heterochromatin) When deacetylase removes these acetyl groups, this makes the chromatin less compact (euchromatin) โ Why are heterochromatin inaccessible for transcription? Answer: heterochromatin are densely packed so they are too compact for DNA Polymerase 3 to access the DNA. Thus, the template strand can not be accessed for transcription โ What is the Central Dogma? Answer: DNA (replication) - > RNA (transcription) - > Protein (translation)
โ What are the two types of terminators used in prokaryotic transcription? Answer: Rho-dependent : Rho helicase gets added to the transcript and clips the RNA Rho-independent : no helicase added; C-G regions loop such that the RNA polymerase can no longer fit on the strand, causing it to dissociate โ What are the differences between prokaryotic replication and transcription? Answer: Replication yields DNA strand while Transcription yields an RNA molecule transcription uses RNA polymerase in the initation stage, whereas replication uses DNA polymerase Transcription only needs Rho helicase (if that) to terminate, whereas Replication used DNA Polymerase 1 and DNA Ligase to terminate โ What are activators and enhancers in eukaryotic transcription? Answer: Activators : Chemical/agent that regulates gene expression by increasing transcription Enhancer: Activators bind to enhancers to increase transcription
โ How does transcription termination differ between prokaryotes and eukaryotes? Answer: Eukaryotic transcription requires additional promoters/proteins, a polyadenylation site, and must undergo additional post-transcriptional processing โ What is the termination sequence used by eukaryotes? Answer: Poly A tail at T site โ What 3 ways are pre-mRNAs modified? Answer: Splicing : Introns are removed and exons are joined to make mature mRNA Capping: 5' methylguanine cap is added to the 5' end to prevent degradation Addition of polyadenylation site โ How do intronic sequences (introns) differ from exonic sequences (exons)? Which are more important for making a mature mRNA in Eukaryotes? Answer: Introns are removed because they do not code for the proteins the mature mRNA will yield after undergoing translation. Exons, however, do code for these proteins. Thus, exons are more important for making a mature mRNA
- It is found in the cytoplasm and carries amino acids that are used to make proteins (translation) to the ribosome. โ What is an anticodon? Answer: An anticodon is the three unpaired bases on a tRNA that is complementary to one mRNA. โ What is the orientation of the codon to the anticodon? Answer: They are antiparallel to one another โ What is the difference between degeneracy and wobble in the genetic code? Answer: Wobbly says that the codon's third nucleotide can be changed while still yielding the same amino acid (the same tRNA can bind to different codons) Degeneracy says that different codons can code for the same amino acid โ What are the 3 codons that represent STOP? Answer: UAA, UAG, UGA โ What is the chemical composition of an amino acid? Answer: Amino group, carboxyl group, central carbon, and a variable R-group
โ How are amino acids linked in chains to form a protein? Answer: Peptide bond caused by peptidyl transferase โ Describe the structure and function of rRNA Answer: Ribosomal RNA- forms the two subunits in a ribosome along with proteins. The ribosome moves along the mRNA strand during proteins synthesis. rRNA in the ribosome helps to catalyse the formation of peptide bonds between the amino acids. โ What are the 4 types of R groups for Amino Acids? Answer: Acidic, basic, polar, and non-polar โ What is the role of the anticodon site? Answer: Located on the tRNA, the anticodon site is where complementary codon is bound to the anticodon connected to the tRNA. When the codon and anticodon bind, the amino acid is "dropped" and joined to the polypeptide chain โ What is the role of the acceptor site? Answer: Located on the ribosome, the acceptor site accepts the tRNA and binds to anticodon site
โ What happens during the initiation stage of translation? Answer: Initiation factors bind to small subunit; causes small subunit to bind to mRNA Start codon for MET moved into P-site; a charged tRNA comes into the ribosome to bind to MET Initiation factors dissociate and the Large subunit binds (forms the translation complex) โ What happens during the elongation stage of translation? Answer: polypeptide chain is synthesized; 1 codon progression until stop codon is reached โ What happens during the termination stage of translation? Answer: The Release factor binds to the A-site, hydrolizing the ribosome and causing the translation complex to dissociate โ How does prokaryotic translation differ from eukaryotic translation? Answer: Eukaryotic translation utilizes a larger ribosome, IFs bind to the Kozak sequence rather than the Shine- Dalgarno sequence, and eukaryotic IFs bind to cap and poly-A tail to create a closed-loop structure (more effective translation)
โ What is the genotypic ratio of the P1, F1, and F2 generations before/after a monohybrid cross? Answer: P1: 1:1 (parental genotype: parental genotype) F1: If one parent is homozygous dominant and the other is homozygous recessive (like in a test cross), the genotypic ratio would be 0:1:0 (homo dom: heterozygous: homo rec) F2: If a test cross is performed, the genotypic ratio would be 1:2: (homo dom: heterozygous: homo rec) โ What are the phenotypic ratios of the P1, F1, and F2 generations before/after a monohybrid cross? Answer: P1: 1:1 (parental genotype: parental genotype) F1: If one parent is homozygous dominant and the other is homozygous recessive (like in a test cross), the genotypic ratio would be 1:0 (dom: rec) F2: If a test cross is performed, the genotypic ratio would be 3: (dom: rec) โ How are dominant vs. recessive traits defined in terms of the F generation? Answer: In the F1 progeny, whichever phenotype is observed is the dominant phenotype โ What is a test cross? Answer: crossing an organism with a dominant phenotype with one that has a recessive phenotype
