Higher Order Genetics Flashcards
What is anaphase?
(1) stage of mitosis during which sister chromatids separate and move away from each other. (2) Anaphase I and II: stages of meiosis during which chromosome homolog pairs separate (I), and then sister chromatids separate (II)
What is an apicoplast?
a derived non-photosynthetic plastid found in most Apicomplexa
What are bacteriocins?
a protein produced by bacteria of one strain and active against those of a closely related strain
what is a bacteriophage?
a virus that infects bacteria
What are centromeres?
constricted region of a mitotic chromosome that holds sister chromatids together. This is also the site on the DNA where the kinetochore forms so as to capture microtubules from the mitotic spindle
What is chromatin?
complex of DNA, histones, and non-histone proteins found in the nucleus of a eukaryotic cell. The material of which chromosomes are made.
What does competent mean when referring to bacteria?
A bacteria that can take up DNA
What are composite transposons?
similar in function to simpletransposonsand Insertion Sequence (IS) elements in that it has protein coding DNA segments flanked by inverted, repeated sequences that can be recognized bytransposaseenzymes
What is conjugation?
in prokaryotes, the direct transfer of DNA between two cells that are temporarily joined. When the two cells are members of different species, conjugation results in horizontal gene transfer
What is conservative movement?
a type of DNA movement where the element is excised from one piece of DNA and inserted in another. Insertion sequences and some transposons use this method.
What is copy number variation?
a phenomenon in which sections of the genome are repeated and thenumberof repeats in the genome varies between individuals in the human population.
What are DNA-only transposons?
transposable element that exists as DNA throughout its life cycle. Many move by cut-and-paste transposition
What is epigenetic inheritance?
inheritance of phenotypuc changes in a cell or organism that do not result from changes in the nucleotide sequence of DNA. Can be due to positive feedback loops of transcriptions regulators or to heritable modifications in chromatin such as DNA methylation or histone modifications
What is euchromatin?
region of an interphase chromosome that stains diffusely; “normal” chromatin, as opposed to the more condensed heterochromatin
What is heterochromatin?
Chromatin that is highly condensed even in interphase; generally transcriptionally inactive
What are histones?
one of a group of small abundant proteins, rich in arginine and lysine, that combine to form the nucleosome cores around which DNA is wrapped in eukaryotic chromosomes
What is histone H1?
“linker” (as opposed to “core”) histone protein that binds to DNA where it exists from a nucleosome and helps package nucleosomes into the 30-nm chromatin fiber
What is horizontal transfer?
gene transfer between bacteria via natural transformation by released naked DNA, transduction by bacteriophages, or sexual exchange by conjugation
What are insertion sequences?
Any of several discrete DNAsequencesthat repeat at various sites on a bacterial chromosome, on certain plasmids, and on bacteriophages and that can move from one site to another on the chromosome, to another plasmid in the same bacterium, or to a bacteriophage
What are LINEs?
Long interspersed nuclear elements: a group of non-LTR (long terminal repeat)retrotransposonswhich are widespread in the genome of manyeukaryotes. They make up around 21.1% of the human genome. LINEs are transcribed into mRNA and translated into protein that acts as a reverse transcriptase. The reverse transcriptase makes a DNA copy of the LINE RNA that can be integrated into the genome at a new site.
What is the lysogenic cycle?
a type of phage replicative cycle in which the viral genome becomes incorporated into the bacterial host chromosome as a prophage, is replicated along with the chromosome, and does not kill the host
What is the lytic cycle?
a type of phage replicative cycle resulting in the release of new phages by lysis of the host cell
What is metaphase?
the third stage of mitosis, in which the spindle is complete and the chromosomes, attached to microtubules at their kinetochores, are all aligned at the metaphase plate
What is microsatellite DNA?
a tract of repetitiveDNAin which certain DNAmotifs (ranging in length from 2–13 base pairs) are repeated, typically 5–50 times.
Microsatellites occur at thousands of locations within an organism’sgenome; additionally, they have a highermutationrate than other areas of DNA leading to highgenetic diversity.
What is minisatellite DNA?
a tract of repetitiveDNAin which certainDNAmotifs (ranging in length from 10–60 base pairs) are typically repeated 5-50 times.Minisatellites occur at more than 1,000 locations in the human genome and they are notable for their high mutation rate and high diversity in the population.
What is mitosis?
a process of nuclear division in eukaryotic cells conventionally divided into five stages: prophase, prometaphase, metaphase, anaphase and telophase. Mitosis conserves chromosome number by allocating replicated chromosomes equally to each of the daughter nuclei
What is mobile DNA?
a type of DNA that can move around within the genome. They include: transposons, plasmids, bacteriophage elements and introns
What are nonretroviral transposons?
type of transposable element that moves by being first transcribed into an RNA copy that is converted to DNA by reverse transcriptase then inserted elsewhere in the genome. The mechanism of insertion differs from that of the retroviral-like transposons
What is a nucleoprotein?
a complex consisting of a nucleic acid bonded to a protein
What are nucleosomes?
beadlike structure in eukaryotic chromatin, composed of a short length of DNA wrapped around an octameric core of histone proteins. The fundamental structural unit of chromatin
What is a pandoravirus?
a genus of giant virus with the largest genome size and second largest physical size of any known viral genus.
What is phase variation?
the random switching of phenotype and expression of proteins involved in infection at frequencies much higher than mutation rates
What is position effect variegation?
alteration in gene expression resulting from change in the position of the gene in relation to other chromosomal domains, especially heterochromatic domains. When an active gene is placed next to heterochromatin, the inactivating influence of the heterochromatin can spread to affect the gene to a variable degree, giving rise to position effect variegation
What is prometaphase?
the second stage of mitosis, in which the nuclear envelope fragments and the spindle microtubules attach to the kinetochores of the chromosomes
What is prophase?
the first stage of mitosis, in which the chromatin condenses into discrete chromosomes visible with a light microscope, the mitotic spindle begins to form, and the nucleolus disappears by the nucleus remains intact
What are pseudogenes?
nucleotide sequence of DNA that has accumulated multiple mutations that have rendered an ancestral gene inactive and nonfunctional
What is replicative movement?
a type of DNA movement where the element is duplicated as it moves so that a copy stays in the donor DNA as well as in the recipient DNA molecule. Replicative transposition involves the formation and resolution of a cointegrate molecule
What is a replicon?
a nucleic acid molecule, or part of one, which replicates as a unit, beginning at a specific site within it.
What are retrotransposons?
a transposable element that moves within a genome by means of an RNA intermediate, a transcript of the retrotransposon DNA
What are retroviral-like retrotransposons
a large family of transposons that move themselves in and out of chromosomes by a mechanism similar to that used by retroviruses, being first transcribed into an RNA copy that is converted to DNA by reverse transcriptase then inserted elsewhere in the genome
What are retroviruses?
RNA-containing virus that replicates in a cell by first making an RNA-DNA intermediate and then a double-strand DNA molecule that becomes integrated into the cell’s DNA
What is reverse transcriptase?
enzyme first discovered in retroviruses that makes a double-strand DNA copy from a single-strand RNA template molecule
What is satellite DNA?
a fraction of a eukaryotic organism’sDNAthat differs in density from most of itsDNAas determined by centrifugation, that consists of short repetitive nucleotide sequences, that does not undergo transcription, and that is often found in centromeric regions.
What is a sex pilus?
a hair-like appendage found on the surface of many bacteria. Conjugative pili allow for the transfer of DNA between bacteria, in the process of bacterial conjugation
What are simple transposons?
Mobile DNA segments that consist ofgenesneeded forinsertion, particularly the gene coding for transposases, which are enzymes that catalyze their insertion
What are SINEs?
short interspersed nuclear elements: sequences ofnon-coding DNApresent at high frequencies in various eukaryotic genomes. They are a class ofretrotransposons, DNA elements that amplify themselves throughouteukaryoticgenomes, often throughRNAintermediates. Short-interspersed nuclear elements are characterized by their size and method of retrotransposition
What are site-specific recombinases?
Site-specific recombinases (SSRs) perform rearrangements (during recombination) of DNA segments by recognizing and binding to short DNA sequences (sites), at which they cleave the DNA backbone, exchange the two DNA helices involved and rejoin the DNA strands
What is site-specific recombination?
a type ofgenetic recombinationin whichDNAstrand exchange takes place between segments possessing at least a certain degree ofsequence homology
What are telomeres?
end of a chromosome, associated with a characteristic DNA sequence that is replicated in a special way. Counteracts the tendency of the chromosome to otherwise shorten with each round of replication
What is telophase?
final stage of mitosis in which the two sets on separated chromosomes decondense and become enclosed by nuclear envelopes
What is transduction?
the process by which foreign DNA is introduced into a cell by a virus or viral vector
What is transfection?
the process of deliberately introducing naked or purified nucleic acids into eukaryotic cells
What is transformation?
a change in genotype and phenotype due to the assimilation of external DNA by a cell. When the external DNA is from a member of a different species transformation results in horizontal gene transfer
What are transposable elements?
segment of DNA that can move from one genome position to another by transposition. Also known as transposons
What are transposases?
an enzyme that binds to the end of a transposon and catalyzes the movement of the transposon to another part of the genome by a cut and paste mechanism or a replicative transposition mechanism
What is transposition?
movement of a DNA sequence from one genome site to another
What is vertical transfer?
The transmission of genetic material from a parent organism or organisms to offspring
What is virulence?
the degree of damage caused by a microbe to its host.
How is genetic material arranged in bacteria?
Can have:
- single circular chromosome
- two circular chromosomes
- linear chromosome
- both circular and linear DNA
What are examples of transposable elements in bacteria?
- Insertion sequences
- Composite transposons
- Bacteriophage
True or False: bacterial plasmids replicate independently of the chromosome
True
How is microbial DNA transferred between bacteria?
- Vertical transfer (parent to daughter)
- Transformation
- Conjugation
- Transduction
What determines whether transferred DNA will survive?
Whether it’s self-replicating or integrated into the chromosome
How can DNA be integrated into the host chromosome?
The DNA molecule may encode its own proteins for integration (integrases, recombinases) or the DNA may recombine into the chromosome by homologous recombination
What is required for transformation to occur?
Free DNA
Competent cell
What techniques make cells competent?
Chemical
Electroporation
What is required for conjugation to occur?
F+ donor bacteria with conjugative plasmid
F- recipient bacteria
Why should the F+ donor bacteria be in its log phase?
So there is enough protein for the construction of the sex pilus
What is required for transduction to occur?
A bacteriophage with bacterial DNA and a normal cell
What changes a virus from a lysogenic cycle to a lytic cycle?
UV irradiation
What are the two types of transfection?
Stable (integration into the chromosome) and Transient (expressed from a replicating vector/plasmid)
How many DNA molecules make up a chromosome?
One
True or False: Prokaryotes are haploid
True
What do histones do?
neutralises the charge of the DNA and allows the DNA to be compacted
Where is heterochromatin usually found?
Centromeres
Which is denser, heterochromatin or euchromatin?
Heterochromatin
What is a nucleosome composed of?
- A core region comprising of two copies of the histone proteins H2A, H2B, H3 and H4
- DNA wound around the core
- One associated histone H1 protein
Which amino acids are histones rich in?
Lysine and Arginine
How does chromatin remodelling repress transcription?
When the gene promoter and activator regions are wound in the nucleosome, enzymes cannot access the DNA in order to transcribe it
How do nucleosomes bind to neighbouring nucleosomes?
Histone proteins have amino acid “tails” which stick out of the nucleosome and can react and form bonds with neighbouring nucleosomes
How do you prevent bonding between nucleosomes? What does this cause?
Acetylation of histone tails stops interaction with neighbouring nucleosomes. This prevents condensation of the DNA and promotes transcription
What is responsible for moving nucleosomes to expose a gene promoter/activator?
SWI-SNF
What type of DNA is found in centromeres?
Satellite DNA - short, highly repetitive DNA sequences
What is the name of a unit of DNA in which an individual act of replication occurs
Replicon
How many replicons do prokaryotes have?
One
How many replicons do eukaryotes have?
Many
What are the components of a eukaryotic genome?
Coding DNA
Pseudogenes
Non-coding DNA
True or False: There is only one rRNA gene
False - eukaryotes contain 100+ copies of the rRNA genes in order to keep up with the transcription demand
What are inactive variants of normal genes called?
Pseudogenes
How do pseudogenes arise?
Mutations that prevent functional expression of the gene product
What are the two types of satellite DNA?
Microsatellite DNA
Minisatellite DNA
How many proteins does the genetic material in mitochondria encode for?
13
What types of transposable elements are found in prokaryotes?
Insertion sequences
Transposons
Bacteriphage
What types of transposable elements are found in eukaryotes?
Transposons
Retro-viruses
Retro-transposones
True or False: All prokaryote transposable elements are DNA intermediates
True
What is the simplest transposable element?
Insertion sequences
True or False: Composite transposons have insertion sequences at either end of the coding sequence
True
What are the two mechanisms of movement for elements with a DNA intermediate?
Conservative
Replicative
What mechanism of movement do insertion sequences and some transposons use?
Conservative
What did LINEs originate from?
Retroviruses
What mechanism of movement do LINEs use?
Replicative
What did retrotransposons originate from?
Retroviruses
What does integration of retrotransposons require?
Reverse transcriptase and an integrase/transposase enzyme
