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Genetics Exam 1 Review

Terms in this set (57)

In the Avery Experiment, DNase ____ the transforming factor
eliminated
In the Avery experiment, RNase ____ the transforming factor.
did nothing to
If protein were the genetic material, then protease would ____ the transforming factor in the Avery Experiment.
Eliminate
a nucleoside is composed of
a pentose sugar and a nitrogenous base.
Which of the following bases is not found in DNA?
Uracil
A double stranded molecule of DNA is known to 22% cytosine. It must have ____% adenine.
28
Experiments by ________ led to the rejection of the Tetranucleotide Hypothesis.
Chargaff
Two strands of DNA are
- twisted around each other in a helix
- held together by hydrogen bonds
- antiparallel
Chromatin structure
- is fluid and capable of changing
- is most highly organized and compacted in heterochromatin regions of the chromosome
-can influence the expressions of genes
Chromosomes are always X shaped structures of DNA and protein.
False
Complete media
- contains everything that a prototrophic organism needs to grow.
- contains everything that an auxotrophic organism needs to grow.
- contains a multitude of preassembled biomolecules.
Given the following biochemical pathway, in which the letters represent chemical substances in the pathway and numbers represent enzymes that catalyze the reactions represented by the arrows. Additionally, substance D is required for the proper growth of a cell:A -- 1 --> B -- 2 --> C -- 3 --> DIf a cell has a mutation that prevents enzyme #2 from functioning then you would expect
- the addition of C to result in growth
- the addition of D to result in growth
- the addition of large amounts of A to result in the accumulation of large amounts of B
What is the function of peptidyl transferase activity?
- It cleaves the polypeptide from the last tRNA during termination
- it forms peptide bonds
Which of the following does NOT enhance the binding of the ribosome to the 5' end of the eukaryotic mRNA?
Kozak sequence
Termination of translation requires
- peptidyl transferase
- a stop codon in the A site
- release factor
Translation
- is influenced by the methyl guanosine cap and poly A tail of eukaryotic mRNA
- begins at the start codon and ends at the stop codon
- consumes a lot of energy
What is the minimum number of different aminoacyl-tRNA synthetases required by a cell?
20, one for each amino acid
Which of the following is NOT require during the process o tRNA charging?
GTP
If a base substitution in one codon changed multiple amino acids in the resulting protein, this would provide evidence that the genetic code was not
nonoverlapping
A ____ bond is used to link together amino acids in a protein.
peptide
Prokaryotic a d eukaryotic tRNA
- have a specific three dimensional shape recognized by the enzyme responsible for attaching a specific amino acid to their acceptor stem
- are able to pair with other strands of RNA
- contain many chemically modified nitrogenous bases such as pseudouridine and inosine
- are composed of at least three stem loops
Which of the following statement about the formation of the peptide bond between amino acids is incorrect?
the amino group of the first amino acid and the carboxyl group of the second amino group are involved in forming a peptide bond.
stability
traits usually dont change mid lifespan
accurate replication
characteristics tend to be passed on
mutable
change is possible
Mendels law of segregation and law of independent
traits follow regular inheritance patterns
Nucleic acids
- chains of nucleotides
- four types of nucleotides (A,T, C, G)
- pentose sugar, phosphate, nitrogenous base (purine and pyrimidine)
Protein
- chains of amino acids
- 20 types of amino acids
-more complex
- life is complex. Proteins are likely to be the genetic material
transformation:
the ability of a molecule to enter a cell and alter its phenotypic characteristics
Purine
adenine and guanine
Pyrimidine
thymine (DNA), cytosine, uracil (DNA).
Tetranucleotide Hypothesis:
- DNA is a repeated chain of ATCG. Assume equal quantiles for all four nucleotides
- Chargaff: a=t(u) c=g
- purines= pyrimidines
Wilkins and Franklin
- helical
- two repeating structures
- phosphate backbone
- bases towards the center
RNA structure
- Ribose
-uracil
-phosphodiester bonds
- single stranded (internal base pairing)
- stem loop
Watson- Crick- Franklin Model:
- DNA helical
- two strands of antiparallel nucleotides
-phosphodiester bonds form sugar- phosphate- outside
- hydrogen bonds form between complementary bases (holds strains together)
- base pairs 0.34 nm apart
- major and minor groves
Gene
- segment chromosomes with specific functions
- initially defined by defective function
Mutagens
- substance that can alter the sequence of bases in genes.
- chemical, xrays
Which of the following statements about somatic mutations is FALSE?
They may be inherited in the offspring of mutated individuals
Which of the following correctly describes nonsense mutations?
They cover a codon for a particular amino acid within a gene into a stop codon.
Which of the following types of mutations does NOT lead to a change in the amino acid sequence of the gene product?
silent
Loss of function mutations tend to be _____ because half the normal enzyme activity usually_____.
recessive; is sufficient to produce the wild type phenotype.
Spontaneous causes of mutation would include
- segments of DNA that randomly insert themselves at various places along the chromosome
- reactions of nitrogenous bases with water that alter the base pairing rules for the moleucle.
- strand slippage that occurs when a repeated sequence of nucleotides gets replicated
- mistakes that occur during replication due to wobble pairing between nitrogenous bases
substances that are mutagenic
- may alter the ability of a base to pair with another base in the opposite DNA strand.
- would generate more his+ revertant growing on minimal media in an Ames Test
- are more like to cause cancer
Assume that you have discovered a new chemical mutagen that modifies guanine so that is mispairs with adenine when adenine is in the template DNA strand during DNA replication. However, this mispairing is limited to when the modified guanine is being added to the newly replicating DNA strand. When the modified guanine is in the template DNA strand it always pairs normally with cytosine being added to the growing newly synthesized strand. What type of mutation would you predict would be caused by the new chemical mutagen?
A- to- C base substitutions
In double stranded DNA molecule a G is paired with a T. Which of the following statements are true?
- this could be corrected by Mismatch Repair if the DNA is hemimethylated
- this could be due to DNA polymerase making a mistake during replication
- This oould be due to the deamination of a methylated cytosine.
- this could be corrected by DNA polymerase proofreading.
Mutations may be prevented by
- breaking the covalent bond that has formed bw adjacent thymine's
- cutting out chemically damaged bases like uracil and resynthesizing that segment of DNA
- relying upon the ability of DNA polymerase to proofread during the process of replication
What is the function of DNA glycosylase?
recognize and remove modified bases from the sugar component of DNA
Our modern understanding of the "gene" includes:
- a gene may code for an enzyme
- a gene may code for a single RNA
- a gene may code for multiple RNA
- a gene may code for a protein
All mature mRNA produced in eukaryotes are the same length as the gene that coded for them.
False
Beadle and Tatum's idea of one gene = one protein is not exactly correct because
- some genes for rRNA or tRNA which are never converted into proteins
-some eukaryotic genes can have their exons spliced together in different ways, producing different RNA's which code for different proteins
-Some eukaryotic mRNA are cleaved at different spots, changing the ORF of the mRNA.
Eukaryotic promoters
- may include sequences more than 1000 nucleotides upstream from the transcriptional start site.
- are composed of a core promoter and regulatory promoter
- may include sequences downstream of the transcriptional start site.
Eukaryotic RNA polymerase I is responsible for synthesizing
large rRNA
Which of the following features s primarily responsible for rho protein to cause termination of transcription.
Helicase activity
Termination of transcription in prokaryotes
- involves the formation of a stem loop terminator structure
- relies upon internal base pairing within a RNA strand
Which of the following statements are TRUE regarding transcription in most organisms?
Different genes may be transcribed from different strands of DNA
RNA polymerase
- is composed of more than one protein
- can be nonspecific in its initiation
- synthesizes new strands of RNA beginning at its 5' end
- pairs RNA nucleotides with complementary DNA nucleotides in the template strand
-synthesizes RNA molecules
Transfer RNA
- carry amino acids to the ribosome
- are less than 100 nucleotides long
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