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BIOD 210 GENETICS FINAL EXAM COMPLETE
STUDY REFERENCE
©What nitrogenous bases are purines - Adenine and Guanine ©What nitrogenous bases are pyrimidines? - cytosine, thymine, uracil ©How can you differentiate between purines and pyrimidines? - purines are double-ringed while pyrimidines are single-ringed ©What are the differences between DNA and RNA? - 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 ©Nucleoside vs Nucleotide - nucleoside: pentose sugar + nitrogenous base nucleotide: pentose sugar + nitrogenous base + phosphate group ©What type of bonds bind nucleotide chains? - Phosphodiester bonds ©What are the 4 requirements for a molecule to be genetic material? - 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 ©Where are chromosomes located? - cell's nucleus ©what is a centrosome? - location in the cell that contains centrioles ©What are centrioles? - microtubules that produce mitotic spindle fibers, aids in cell division, and make up the cytoskeleton of the cell ©How many centrioles are there for every centrosome? - 2 centrioles/ centrosome ©How many copies of each type of chromosome does each eukaryotic cell typically have? - 2 copies ©what are homologous chromosomes? - copies of the same type of DNA ©What are non-homologous chromosomes? - copies of different chromosomes with different DNA
©What happens during mitosis prometaphase? - centrioles have reached polar regions and mitotic spindle fibers have connected to the kinetochore ©What happens during mitosis metaphase - all chromosomes are lined up on the metaphase plate ©What happens during mitosis Anaphase? - mitotic spindle fibers pull chromosomes apart into chromatids (4n) ©What happens during mitosis telophase? - nuclear envelope reforms plasmo-membrane is pinched; sister chromatids are still condensed at this point ©What happens during cytokinesis? - cells split off; genetic material becomes uncondensed ©What happens during Meiosis? - Division of one diploid cell to yield 4 haploid cells that are completely different ©What happens during Meiosis 1? - 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. (1 diploids becomes 2 haploid) ©What happens during Meiosis 2? - 1. Independent segregation of sister chromatids.
- Each cell divides again, producing 4 haploid cells. ©What are the three theories of DNA Replication? - 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 ©What did the Meselson-Stahl experiment suggest was the correct theory of DNA Replication? - semi-conservative ©Describe the Meselson-Stahl experiment - 1. Bacteria were grown in a medium containing heavy isotope 15N for many generations.
- Some bacteria were moved to a medium containing light isotope 14N. Samples were extracted after 1 & 2 cycles of DNA replication.
- Centrifugation formed a pellet. Heavier DNA (bases made from 15N) settled closer to bottom of tube.
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) ©What are Okazaki fragments? - Relatively short fragment of DNA synthesized on the lagging strand during DNA replication ©What enzyme relieves the tension caused by the discontinuous synthesis of the lagging strand? - Topoisomerase ©What happens during the termination stage of DNA replication in prokaryotes? - 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 ©What is the difference between prokaryotic and eukaryotic DNA - prokaryotic DNA is small and circular eukaryotic DNA is long and linear ©What enables DNA Replication to occur as quickly as it does in eukaryotes (the entire human genome can be replicated in 8 hours)? - Eukaryotes have multiple replicons (replication forks)
©What are the names and functions of the additional DNA Polymerases used during eukaryotic DNA replication? - 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 ©What happens during the initiation stage of DNA replication in eukaryotes? - ©Explain what Griffith's Transformation experiment is and the results of the experiment. - Griffith experimented with virulent and antivirulent strains of pneumonia. He observed that when heat-killed virulent strains were placed in close proximity to live anti-virulent strains, the antivirulent strains would become virulent. This led him to propose the existence of some material being able to be passed between organism that would genetically alter the organism. ©Explain what the Avery and McLeod experiment was and how it expanded on what Griffith discovered with the transforming principle. - This experiment began by running preliminary tests on the physical
©What is the purpose of Mitosis? - cell regeneration, growth, and asexual reproduction ©What is the purpose of Meiosis? - produce gametes for sexual reproduction ©How does meiosis differ between males and females? - 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. ©What are histones? - Proteins that pack DNA into condensed formed; Because eukaryotic DNA is so long, histones help provide structural support by compacting the DNA ©How does acetylation/deacetylation help package and unpackage DNA along nucleosomes? - 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) ©Why are heterochromatin inaccessible for transcription? - 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
©What is the Central Dogma? - DNA (replication) - > RNA (transcription) - > Protein (translation) ©What are the names and function of the three basic elements of a gene?
- promoter- where initiation begins; the sigma factor binds to a strand of DNA and clips and untwists to make a transcription bubble) RNA-coding sequence- the sequence that actually gets transcribed; 3'-5' strand terminator- marks the end of a gene ©What ingredients are necessary for RNA transcription in prokaryotes?
- RNA Polymerase (A holoenzyme the binds and unwinds DNA via its sigma factor), initiation factors, ©Where does transcription occur? - the endoplasmic reticulum via ribosomes ©What direction is RNA polymerized? - RNA is polymerized in a 5' to 3' direction ©Describe the differences between the template strand and the non- coding strand in transcription for prokaryotes (including the 5' and 3' orientation of both) - The non-coding template strand is in a 5'-3' direction and is ignored during transcription
Enhancer: Activators bind to enhancers to increase transcription ©How does transcription termination differ between prokaryotes and eukaryotes? - Eukaryotic transcription requires additional promoters/proteins, a polyadenylation site, and must undergo additional post-transcriptional processing ©What is the termination sequence used by eukaryotes? - Poly A tail at T site ©What 3 ways are pre-mRNAs modified? - 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 ©How do intronic sequences (introns) differ from exonic sequences (exons)? Which are more important for making a mature mRNA in Eukaryotes? - 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
©What three things must a mature mRNA possess? - 5'- 7 - methylguanine cap, exons spliced together, and polyadenylation tail ©What are the characteristics of the genetic code? - 1. Linear mRNA sequence derived from the template DNA strand
- Triplet Code = Tree ribonucleotides --> One amino acid
- Unambiguous - Each triplet specifies only a single amino acid
- Degenerate - A single amino acid can be coded for by multiple triplet codes (18/20 amino acids
- No internal punctuation; therefore, comma less
- Non-overlapping - A single ribonucleotide can only be in one triplet code
- Universal with only minor exceptions ©What is the triplet representing the START codon? - AUG (met) ©Describe the structure and function of tRNA - 1. Transfer RNA- a single polynucleotide strand that's folded into a clover shape.
- H bonds between specific base pairs hold the molecule in this shape.
- Every tRNA molecule has a specific sequence of 3 bases at one end called an anticodon.
- They also have an amino acid binding site at the other end.
- It is found in the cytoplasm and carries amino acids that are used to make proteins (translation) to the ribosome.
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. ©What are the 4 types of R groups for Amino Acids? - Acidic, basic, polar, and non-polar ©What is the role of the anticodon site? - 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 ©What is the role of the acceptor site? - Located on the ribosome, the acceptor site accepts the tRNA and binds to anticodon site ©What are the small and large subunits within translation? - Small subunit decoded the genetic message Large subunit catalyzes polypeptide formation ©What occurs at the A-site in translation? - accepts a tRNA w/ amino acid
©What occurs at the P site of the ribosome during translation? - holds the tRNA which is linked to the growing polypeptide chain. When a stop codon is reached, the peptidyl-tRNA bond of the tRNA located in the P- site is cleaved releasing the newly synthesized protein ©What occurs at the E-site during translation? - tRNA that has released their amino acid is released from the ribosome ©In what direction is the mRNA read by the ribosome? - 5'-3' direction ©In what direction is protein sequence synthesized during translation? - Synthesized from N-terminal to C-terminal ©What happens during the initiation stage of translation? - 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)
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 3:1 (dom: rec) ©How are dominant vs. recessive traits defined in terms of the F generation? - In the F1 progeny, whichever phenotype is observed is the dominant phenotype ©What is a test cross? - crossing an organism with a dominant phenotype with one that has a recessive phenotype ©How do you interpret the results of a test cross? - If the test cross results in any recessive offspring, then the parent organism is heterozygous for the allele in question. If the test cross results in only phenotypically dominant offspring, then the parent organism is homozygous dominant for the allele in question. ©What genotypic ratios will the P1, F1, and F2 generations have if a dihybrid/trihybrid cross is performed? - For a dihybrid cross, we anticipate a 1/16:2/16:1/16:2/16:4/16:2/16:1/16:2/16:1/16 genotypic ratio For a tri-hybrid cross, we anticipate a 27:9:9:9:3:3:3:1 genotypic ratio
©What phenotypic ratios will the P1, F1, and F2 generations have if a dihybrid/trihybrid cross is performed? - For a dihybrid cross, we anticipate a 9:3:3:1 phenotypic ratio For a trihybrid cross, we anticipate a 27:9:9:9:3:3:3:1 phenotypic ratio ©What is Mendel's principle of segregation? - The members of each pair of genes (alleles) separate (segregate) during gamete formation. ©What is Mendel's principle of independent assortment? - genes/alleles assort independently from one another when forming gametes; these alleles combine at random in hybrids to form new combinations ©What phase of meiosis is responsible for the principle of segregation? - Anaphase- 1 ©Which phase of meiosis is responsible for the principle of independent assortment? - Metaphase 1 bc tetrads don't have to line up identically ©What is the product law in Mendelian genetics? - The product law states that the product of the ratios derived from the monohybrid cross of parents will yield offspring of the genotypic ratio 9:3:3: ©What is the sum law as it applies to independent assortment - The sum law is used whenever two events are independent of one another but
