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Genetics Chapter 13-16
Terms in this set (140)
What does the term peptidytransferase relates to?
a peptide bond formation during protein synthesis
Where is the valine alteration found ?
in β chain of sickle cell hemoglobin
Where is the glutamic acid found
in β-chains of normal cell in the sixth positon
What determines the primary structure of a protein?
the sequence of amino acids
What protein class directly controls many of the metabolic reactions within a cell?
What does the secondary structure of a protein includes?
α-helix and β-pleated sheet
what are the side groups of a amino acids typically grouped under?
Polar (hydrophilic) and Nonpolar (hydrophobic)
What are Two functional domains and how do they related to the structure of tRNA
they are amino acids attachment sites and are the anticodon for tRNA
What is the Wobble hypothesis and how does it relate to the structure of tRNA
the woblbe hypothesis states that the first two positions of the codon are precise in their complementary relationships
What are the two forms of posttranslational modification of proteins?
phosphorylation and glycosylation of side chains
How does electrophoteric separates HbA form HbS
based on the difference of their charges
What does the term protein domain mean (HINT: Folded shape)
proteins domains are regions of proteins that impart a specific and usually limited function of the protein.
What regions are located in the protein domain?
DNA binding, ATP binding, and regions that undergo regulation
What causes there to be more alteration in amino acids ?
a base addition occurring at the beginning of a coding region of a gene. the protein will experience more altered amino acids compared with the original gene with a base addition near the end of the coding region
Amino Acid Sequence
Where is the C and N Terminus sites ?
A is located at the C terminus site
L is located at the N terminus site
Amino Acid Sequence
a substitution of adenine for cytosine in the seventh base in the coding region of the mRNA (counting from the 5`end)
Amino Acid Sequence
a frameshift mutation (adds or deletes single bases in DNA) resulting in an insertion of a base between the ninth and tenth positions of the coding region of the mRNA (counting from the 5' end of the coding region of the mRNA)
Amino Acid Sequence
a nonsense mutation (fails to code for an amino acid) involving bases 4, 5, and 6 in the coding region of the mRNA (counting from the 5' end of the coding region of the mRNA)
T/F Proteins are composed of strings of nucleotides connected together by 5'-3' phosphodiester
T/F Prokaryotic and eukaryotic ribosomes are structurally and chemically identical.
T/F rDNA is the portion of a genome (the cell's DNA) that is involved in the production of ribosomal RNA
T/F The primary structure of a protein is composed of the sequence of amino acids in that protein
T/F Sickle-cell anemia is caused by the absence of the alpha chain of hemoglobin
WHat are ribozymes?
RNAs that demonstrate autonomous (on their own) catalytic properties such as self splicing
How was RNA self-splicing discovered?
in Tetralymena by T. Cech in 1982
How does hydrophobic interaction influence protein structure?
Hydrophobic interactions: Nonpolar side chains of amino acids tend to associate to form hydrophobic clusters usually away from the protein surface.
How does hydrogen bonds influence protein structure?
such bonds may occur between the components of the peptide bond the side chain or a combination of the two. They are responsible for helical and pleated sheet structures of proteins
How does disulfide bridges influence protein structure?
Such bonds are formed between two cysteine side chains and, because of their covalent nature, represent relatively strong attractive forces between different regions (sometimes distant) of proteins.
In what ways do the amino acid side chains of a polypeptide interact to influence protein shape and thus function
Higher level folding of proteins is dependent on a variety of interactions (ionic, covalent, hydrogen,hydrophobic, hydrophilic)
Regarding the protein structure, how are β-pleated sheets arranged and stabilized?
Several chains run in parallel or antiparallel fashion stabilized by hydrogen bonds formed between components of the peptide linkage
Considering the types of side chains on amino acids and their relationship to protein structure, where are the amino acids with hydrophobic side chains most likely to be located?
away from the water environment and in the interior portion of the molecule
what are spontaneous mutations?
Mutations that arise in nature, from no particular external agent
what is 5-bromouracil classified as?
a base analogue
where a class of mutations that results in multiple tandem amino acid changes in proteins is called a
what causes xeroderma pigmentosum?
Ultraviolet light causes pyrimidine dimers to form in DNA. Some individuals are genetically incapable of repairing some dimers at "normal" rates
Describe the mutagenic action of 5-bromouracil.
5- bromouracil is an analogue of thymine, which anomalously pairs with guanine and can result in a substituation.
Under what condition(s) might one have an amino acid substitution in a protein that does not result in an altered phenotype
The possibility of a change in protein function, therefore phenotype, depends on the location and chemical properties of the involved amino acid(s).
What is the Ames test and how does it work?
Four tester strains of Salmonela typimurium are used to test for sensitivity and specificity of mutagenesis. The rate of mutation in the presence of a suspected mutagen is compared to the rate of spontaneous mutation
What is the effect of ultraviolet light on DNA
generation of pyrimidine dimers
is the process of error correction of mismatched bases carried out by DNA polymerases
T/F Of the two cell lines that can contain a mutation in an organism, somatic and germline (reproductive cells), the latter is most consequential to subsequent generations
T/F 5-bromouracil causes mutations by chemically altering the structure of a nitrogenous bases.
T/F A missense mutation causes premature chain (protein) termination.
is a contiguous genetic complex that is under coordinated control
In prokaryotes what level is genetic regulation considered to be located?
T/F Genetic regulation in eukaryotes can take place at a variety of levels from transcriptional to posttranslational
When is negative control applied?
to regulatory condition that occurs when protein is associated with a particular section of DNA and greatly reduces transcription?
DNA binding protein also refers to what type of protein?
a transcriptional regulartory protein
In the lac operon, the product of structural gene lacZ is capable o
splitting the β-linkage of lactose.
where does the elements TATA and CAAT. appear
appear as consensus sequences upstream from transcription start sites
Regarding eukaryotic and prokaryotic genetic regulation, what process seems to be the most similar between the two?
DNA methylation may be a significant mode of genetic regulation in eukaryotes. Methylation refers to
addition of methyl groups to the cytosine of CG doublets.
Present a detailed description of the actions of the enhancer regulatory proteins in inducible systems (activation) in eukaryotes.
Inducible system: the repressor is normally active, but the inducer inactivates the repressor.
What is the function of the lacY gene in the lac operon?
The lacY gene codes for permease, a membrane-bound protein that transport lactose into the bacterial cell
Enhancers are said to be cis-acting. What is meant by cis-acting and what are enhancers?
Cis-acting means that the genes under control must be in the same chromosome as the cis-acting element. Enhancers are sections of DNA that regulate transcription of other sections of DNA.
What is alternative splicing?
Alternative splicing is a process that allows through differential splicing of premRNA, a variety of different forms of mRNA
In eukaryotes describe the function of transcription factors that bind to proximal regions and those that bind to distal regions
One class assembles at promoter regions adjacent to the site of transcription. The other class binds at more distant regions (enhancers and silencers).
Describe the function and general structure of promoters in eukaryotes.
Promoter regions are necessary for the initiation of transcription. Promoters that interact with RNA polymerase II are usually located within 100 bp upstream of a gene and usually contain a TATA box and a CAAT box.
What is the function of RNA interference (siRNA)?
RNA interference appears to be a sequence-specific posttranscriptional regulatory mechanism that employs short RNA sequences.
Describe the general structure of a transcription factor including DNA binding- and activation- domains
Transcription factors are modular proteins with at least two functional domains: one binds to DNA in promoters and enhancers and another activates transcription.
Approximately 5 percent of the cytosine residues are methylated in the genome of any given eukaryote. In what way is DNA methylation related to genetic regulation?
There is an inverse relationship between the degree of methylation of eukaryotic DNA and the degree of gene expression.
T/F Alternative RNA splicing is a method that apparently allows for the production of many different polypeptides from the same pre-mRNA.
Provide an example of alternative splicing.
Various splicing schemes occur in the CT/CGRP gene in different tissues. In thyroid tissue, only the first four exons remain, while in the brain, exons 5 and 6 are included, but not exon 4.
Name the different levels of regulation in eukaryotes.
In what way is chromosomal organization within the nucleus of an interphase cell thought to be related to gene activity?
In general, gene-poor chromosomes are located at the nuclear periphery, while gene-dense chromosomes are located internally.
what causes a decrease in transcription when looking at mutagenic studies
Mutagenic studies of the promoter region of the β-globin gene indicate that some areas are more likely to affect transcription rates than mutations in other areas. When mutations occur in consensus sequences (modular elements such as GC box, CAAT box, TATA box),
What is the location of an enhancer in relation to the gene it affects?
The position of an enhancer need not be fixed; it can be upstream, downstream, or within the gene it regulates.
Describe how nucleosomes may influence gene transcription.
The binding of transcription factors requires accessing nucleosomal DNA, and such factors may displace nucleosomes. The removal of a nucleosome from a stretch of DNA exposes it to binding by transcription factors and RNA polymerase, allowing transcription to proceed.
T/F The lac operon consists of three structural genes as well as the adjacent region of DNA known as the regulator.
T/F The enzyme permease cleaves the linkage between glucose and galactose residues in lactose.
T/F Transcription factors are proteins with at least two functional domains, one that binds to DNA and one that binds to RNA polymerase or to other transcription factors.
T/F Transcription in eukaryotes is influenced by enhancers, just as in prokaryotes.
T/F In general, one could say that there are fewer levels of regulation possible in prokaryotes than in eukaryotes.
T/F Alternative RNA processing can result in different mRNAs that start with different exons.
T/F Alternative RNA processing generates different mRNAs that can direct the synthesis of different polypeptides.
T/F Regulation of RNA transport through the nuclear membrane is as common in prokaryotes as in eukaryotes.
T/FIn the eukaryotic promoters that have it, the CAAT box appears to be critical to the promoter's ability to facilitate transcription.
are mutant versions of genes that are normally involved in promoting the cell cycle
cyclin-dependent kinase combines with what?
combines with cyclins to exert local control of the cell cycle
p53 is also known as?
"guardian of the genome, "
What is is responsible for arresting cell progression if DNA is damaged and initiating apoptosis if DNA cannot be repaired
What protein functions as a cell-cycle regulator by causing cell death (apoptosis) after the cell has been exposed to ultraviolet light or other forms of radiation that cause massive DNA damage?
What are three general mechanisms that appear to result in the conversion of proto-oncogenes to oncogenes?
point mutations, deletions, overexpression
Provide a definition of cancer at the genetic level (DNA)
Cancer is a genetic disorder that can result from mutation of a given gene or genes, which may produce a defective gene product or a change in the timing or amount of gene expression. Such mutations alter cell-cycle control.
Provide a definition of cancer at the anatomical level (think about cells and tissues).
Cancer is the uncontrolled proliferation of cells and the ability of cells to metastasize or migrate to other sites to form secondary growths.
Describe the cellular and molecular function of the ras gene family and the consequences of mutations in ras.
The ras gene family encodes a protein of 189 amino acids, which is involved with signal transduction in the cell membrane. Point mutations may cause changes in function that promote abnormal signaling, thus stimulating uncontrolled cell growth.
Describe three separate genetic mechanisms whereby proto-oncogenes can become overexpressed.
They may acquire a new promoter or upstream regulatory signals, additional copies (amplification), or a particular gene.
What is a tumor suppressor gene? What are oncogenes? What is the normal (nonmutant) cellular version of an oncogene called?
A tumor suppressor gene is a gene whose normal function is to suppress cell division. When mutant, cell division control is lost and a cancer may form. Oncogenes are genes that induce or maintain uncontrolled cellular proliferation associated with cancer. The normal cellular version of an oncogene is called a proto-oncogene.
Chronic myelogenous leukemia appears to be associated with a chromosomal rearrangement. How could a chromosomal rearrangement cause cancer?
By joining chromosomes 9 and 22 through translocation, a hybrid gene,
bcr/c-abl, produces a 200-kDa protein, which is inappropriately overactive and causes the disease.
What is the name for a normal gene that serves to promote cellular division?
What three places in the cell cycle seem to serve as points of control (checkpoints)?
G1/S, G2/M, M
When someone is said to have a predisposition to cancer for reasons of heredity, what may be the cause of their cancer
A person has inherited a mutation in a proto-oncogene or tumor suppressor gene.
What is the difference between tumor suppressor genes and proto-oncogenes?
Tumor suppressor genes act to restrict cell division, while proto-oncogenes act to stimulate cell division.
What is the significance of the CDKs?
CDK symbolizes a class of protein kinases that, when activated, selectively phosphorylate target proteins. Many of these phosphorylated proteins are involved in cell-cycle control.
Much has been written lately about p53 in terms of cancer biology. What is p53 and what is its significance?
It is a tumor suppressor gene that normally functions to control the transition from late G1 to S phase. Mutations in the p53 gene are important in the development of a number of cancers. The product of p53 has DNA-binding properties.
Why do cancer researchers study molecular events associated with mitosis?
While mitosis is a basic process related to genetic and general biological studies, it is also a significant event in the cell cycle. The cell cycle is regulated by a variety of gene products that, when altered by mutation, may lead to cancer.
Describe the difference between a proto-oncogene and an oncogene.
An oncogene is a mutant form of a proto-oncogene.
How do most carcinogens cause cancer
causes transformation by binding to or changing DNA
T/FAs more is learned about cancer, it has become clear that cancer, with few exceptions, has no genetic (DNA) basis.
List several classes of environmental agents that are known to cause cancer.
radiation, chemicals, sunlight, dietary compounds, tobacco
Name two proteins that combine or interact to directly control progression through the cell cycle.
protein kinases, cyclins
T/F The gene p53 is called the "guardian of the genome" because it corrects mutations in the spindle apparatus before nondisjunction can occur.
T/F There are several checkpoints in the mitotic cell cycle. All occur in the S phase.
T/F A tumor suppressor gene normally functions to suppress cell division.
T/F Any agent that causes damage to DNA is a potential carcinogen.
T/F When the normal retinoblastoma protein is phosphorylated, it acts to stimulate cell division.
List and describe the role of all molecular constituents present in a functional polyribosome.
A functional polyribosome will contain the following components: mRNA, charged tRNA, large and small ribosomal subunits, elongation and perhaps initiation factors, peptidyl transferase, GTP, Mg2+, nascent proteins, and possibly GTP-dependent release factors.
During translation, what molecule bears the anticodon? The codon?
Anticodon = tRNA
Codon = mRNA
The alpha chain of eukaryotic hemoglobin hemoglobin is composed of 141 amino acids. What is the minimum number of nucleotides in an mRNA coding for the polypeptide chain?
141 amino acids = 3 nucleotides per amino acid = at least 423 nucleotides (426 including termination codon).
Assuming that 5' cap, poly-A tail, and UTR are omitted
Protein Function: Enzyme
lower activation energy
Protein Structural Function: Keratin, Collagen, Tubulin
Collagen- connective tissue
Protein Transport Function:
hemoglobin membrane transporters
Protein Function: Hormones and receptors
Protein Function: Transcription factors
Protein Function: COntraction
what is a example of intracellular protein
FKBP12 and hemoglobin
What is a example of a membrane ion channel?
What ion is known to finger transcription factor
What are the translation steps
sequence of recognition
synthesis using a template
guided by sequence
Steps for initiation of Translation
Step 1 :mRNA binds to small subunit
Step 2: Initaitor tRNA(fmet) binds to mRNA codon
Step 3: Large subunit binds to complex
Steps for Elongation during Translation
Step 1: Second charged tRNA has entered A site
Step 2: Peptide bond forms uncharged tRNA moves to the E site and subsequently out of the ribosome the mRNA has been translocated three bases to the left
Step 3: the 1st elongated site is complete
Step 4 : A third charged tRNA enters A site
Step 5 : Tripeptide formed
Step : Polypeptide chain synthesized and exiting ribosome
What is a process through which specific amino acids are attached to individual tRNA
What happens to the amino acid during Charging
the amino acids reacts with ATP with the 5` phosphate group with the carboxyl end of the amino acid
THEN they encounter with specific tRNA molecule and the amino acid is transferred to the 3` end forming a covalent bond
This charged tRNA molecule containing specific anti-codon and amino acid can participate in the translation process.
What is the arrangement of multiple folded proteins that are composed of more than one polypeptide chains
a Quaternary structure of a protein
Give a example of a Quaternary level of protein structure
Hemoglobin has two alpha and two beta chains
What are the four levels of protein organization
Primary, secondary, tertiary, quaternary
What is the function of the primary level for protein organization
The amino acids linked through the peptide bonds
What is the function of the secondary and tertiary level for protein organization
are a result of the hydrogen bonds and cystine bonds occurring between amino acids in a polypeptide chain
What is the function of the quaternary level for protein organization
contains more than one amnio acid being apart of it depended mainly on the type and structure of the proteins that are involved
what are two non-enzymatic proteins that are involved int he exchange of gaseous molecues
Hemoglobin and myoglobin
what are structures that are used in acting against infectious organisms
How does an enzyme function?
Enzymes are protein molecules that Aid in converting a reaction to a product this process is basically done by reducing the activation energy required by the reactants and getting transferred as product
Why are enzymes essential for living?
The energy of activation is the increased kinetic energy that the reactant has to attain in order for them to be converted to products. this process of increasing the kinetic energy of the reactants could be obtained at elevated temperatures human systems has to be contained with a specific temperature range in such elevated temperature or just can not allowed inside the human system for the such circumstances reactions do not take place in other words the physicalogical temperatures within a living organism we organism we do process and enzymes
Discuss the importance of mutations in genetic studies
Before the utilization of molecular techniques it is only through mutation that it was said to be the tool they gave me a clear picture of gene positions and other important factors regarding a particular Gene to the geneticist
Why would a mutation in a somatic cell of a multicellular organism Escape detection
Mutation likely occurred in a somatic cell are not supposed to be transferred to its next-generation likewise the presence of a autosomal cell with recessive mutation would be masked by the presence of the wild-type gene present in the same cell
Why is a random mutation more likely to be deleterious than beneficial?
Random mutations are more likely to be involved in an active Gene and would render it inactive when situation occurred a gene that decides the fate of an organism in such random mutations are more deleterious than it is supposed to be beneficial also there is a chance that could change product work in combination with another one in a common environment
Describe a tautomeric shift and how it may lead to a mutation
Tautomers are molecules that different only in a single proton shift. During replication a purine will be replaced by pyrimidine for the Next Generation leading to a frame mutation
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