chpt 7.6-7.7 test Flashcards
genome organization refers to…
the sequential structure of a genome
the human genome is composed of…
coding and non coding regions
what % of the human genome codes for proteins? what is the remaining genome composed of?
2%. The remaining genome is composed of introns within genes and repeating sequences between genes.
the eukaryotic genome contains…
-transposons (transposable elements of DNA)
-pseudogenes (non-coding sequences, similar to existing genes).
The discipline of comparative genomics seeks to understand…
the genetic relationship between all forms of life on Earth
the declining cost and increasing efficiency of genomic technologies raises…
numerous ethical questions about the use of genomic information
HUMAN GENOME PROJECT
the joint government and private actor research project that sequences the human genome
VARIABLE NUMBER TANDEM REPEATS (VNTRs)
non-coding, repeating sequences of DNA that vary in length between homologous chromosomes and between individuals
LINEs (LONG INTERSPERSED NUCLEAR ELEMENTS)
repetitive DNA sequences, approx. 6500 bp in length on average, interspersed throughout the genome
SIGNs (SHORT INTERSPERSED NUCLEAR ELEMENTS)
repetitive DNA sequences, approx. 500 bp in length on average, interspersed throughout the genome
TRANSPOSON
a small segment of DNA that can move to a different position in the genome and insert themselves into different chromosomes.
PSEUDOGENE
a sequence of DNA that is similar to an existing gene but does not code for proteins
COMPARATIVE GENOMICS
study of the organization, functions, and relationships of the genomes of different species
Human DNA is found in…
the nucleus of human cells in duplicate.
Each human nucleus contains…
two copies of the 22 autosomal chromosomes and one pair of sex chromosomes.
each autosomal chromosome is numbered by size from…
1 to 22 (+each gene has two copies, known as alleles, that may be identical or different)
each allele of a given gene resides at…
the same locus on both homologous chromosomes.
how many scientists from around the world collaborated to sequence the genetic code?
over 200
genome organization refers to…
the sequential organization of the genome
introns are non-coding regions in genes and occupy what % of genome?
24%
what % of genome occupies spaces between genes?
almost 75%
what % of the total genome consists of repeated sequences that are non-functional
more than 50%
in eukaryotes, non coding regions are filled with
variable number tandem repeats (VNTRs), also known as microsatellites. (sequences of base pairs that repeat over and over again. lengths and positions of VNTRs vary. # of these non-coding regions in an organism’s genome is proportional to the complexity of the organism)
long repetitive non-coding DNA sequences are used as a…
defense mechanism against the shortfalls of DNA replication
telomeres are…
non-coding regions at the ends of chromosomes that preserve coding DNA from being lost during replication
repetitive DNA sequences are also found near the — and play a role during —
centromeres, cell division
two more types of repetitive DNA sequences that are found in the genome:
LINEs (long interspersed nuclear elements) and SINEs (short interspersed nuclear elements)
Pseudogenes are thought to be — of older genes and remain in the genome but —.
mutated versions, serve no function
With the human genome sequenced, scientists have begun to compare it with the genomes of other…
species to determine the molecular basis of differences in anatomy, physiology, and developmental patterns between species.
Species comparisons may reveal…
the mutational changes that have driven the evolution of our species and many others.
Comparative genomics the study of…
the organization, functions, and relationships of the genomes of different species
-% of sea urchin genes have a human gene counterpart
70%
-% of fruit fly genes have a human gene counterpart.
40%
Sea urchin’s genome that codes for its immune system is — — than the immune system section of the human genome
more complex
Comparative genomics also includes the study of individual sequences of DNA. The differences in genes and gene fragments in different species can be analyzed to understand…
how cell functions vary from one organism to another
Viruses have small genomes that consist of only…
RNA or DNA
viruses rely on their host’s genetic machinery to…
replicate themselves
Many errors are made by a virus’s polymerase enzymes, especially those of the influenza A virus. As a result, there is a…
very high mutation rate
Retrovirus: A retrovirus what enzyme to do what?
-reverse transcriptase to transcribe its RNA genome into DNA
Retrovirus: The viral DNA is then incorporated into the host’s genome by an enzyme called —, then transcribed and translated to produce —-. These proteins and RNA are used to assemble —-.
integrase, virus proteins and viral RNA, new virus particles
Viruses have what types of applications?
research and therapeutic
TRANSDUCTION is the
use of viral vectors to introduce new genetic material into an existing cell
REVERSE TRANSCRIPTASE is
a viral enzyme that uses RNA as a template strand to synthesize complementary DNA
RETROVIRUS is
a virus that uses reverse transcriptase for replication (related to HIV)
Virology is the branch of biology that studies…
viruses
Viruses contain a protective protein coat surrounding a core of nucleic acid (strands of DNA or RNA) that stores the…
hereditary information needed for the virus to reproduce inside a living cell.
The amount of hereditary information stored in a virus is —. The type of nucleic acid may be a ….
incredibly small, single strand of DNA or a single strand of RNA or a double strand of DNA or a double strand of RNA
T/F: Viruses exist that can infect virtually any type of cell: animal, plant or bacteria
True
Viruses are not capable of living independently outside of cells. They must —— for survival and reproduction.
invade cells and use the host cell’s machinery
outside a cell, viruses are…
dormant
T/F: Viruses differ structurally from prokaryotic and eukaryotic cells
True
Viruses are not cellular, so they have no…
cytoplasm, membrane-bound organelles, or cell membranes
Viruses cause disease in plants and animals, which can affect…
populations, species, and ecosystems
In bacteriophages and most other viruses, the nucleic acid is…
DNA, the molecule found in human and bacterial chromosomes. DNA (deoxyribonucleic acid) is composed of adenine, thymine, guanine and cytosine. The 5-carbon sugar is deoxyribose.
Some viruses contain — instead of DNA
RNA. RNA (ribonucleic acid) contains adenine, uracil, guanine and cytosine. The 5-carbon sugar is ribose.
The RNA virus contains a few molecules of a specialized enzyme. The difference between the two types of viruses is small but significant:
RNA viruses are generally much more serious than those carried by DNA viruses
Scientists develop vaccines and new treatments to fight…
viral infections
Viruses are also used in biotechnology to..
clone copies of genes
One of the methods used by scientists to classify viruses is the size and shape
of the…
capsid
A capsid is a…
protein covering around the central core of a virus particle and provides protection to the nucleic acid. In some viruses, the capsid is enclosed in a membrane.
Virus particles contain the genetic information needed to make copies of itself but they lack the…
metabolic machinery to put the information to work. The host cell supplies this machinery
Viruses that infect humans are currently classified into how many groups. These groups differ ion what?
21, their genomes, or sets of genes, and their method of replication
Replication is a fundamental process of all cells, in which…
the genetic material is copied before the cell reproduces
Lytic cycle is the replication process in viruses in which…
the virus’s genetic material uses the copying machinery of the host cell to make new viruses
Lysogenic cycle is the replication process in viruses in which…
the viral DNA enters the host cell’s chromosome; it may remain dormant and later activate and instruct the host cell to produce more viruses
(in lysogenic) The viral DNA that has become part of the host chromosome is then referred to as a…
provirus. A provirus can invade a cell, but does not kill it.
One of the most efficient ways to kill bacteria is to…
infect them with viruses. Viruses that destroy bacteria are called bacteriophages.
Life Cycle of a Bacteriophage
1- bacteriophage locks onto the bacterium’s cell wall + deposits their DNA inside the cytoplasm.
2- The viral DNA then controls the functioning of the bacterium’s cell parts.
3- Even though the number of genes of a phage virus is small, the DNA they contain is enough to prevent the host bacterial cell from performing its normal life functions.
Viral genes redirect the host cell from producing the materials it needs to perform only three functions:
- Manufacturing hundreds of copies of viral DNA
- Producing new proteins for viral protein coats
- Producing a powerful enzyme that dissolves the bacterium’s cell wall.
When the DNA and the protein coats have been assembled, the newly formed phage viruses burst, infecting…
nearby cells and repeating the cycle.
The Lytic Cycle Steps
- Attachment: A phage virus attaches itself to a host bacterial cell.
- Entry: The phage’s DNA is injected inside the bacterium.
- Replication: The host cell replicates the phage DNA and produces phage protein coats.
- Assembly: The phage cells are assembled inside the bacterium cell.
- Lysis and Release: The host cell is destroyed and the phage cells are released.
The Lysogenic Cycle Steps
- Attachment: A phage virus attaches itself to a host bacterial cell.
- Entry: The phage’s DNA is injected inside the bacterium.
- Provirus Formation: viral DNA becomes part of the host cell’s chromosome for many generations.
Comparisons: fate of host DNA after infection of virus
Lytic Cycle- Takes over host DNA
Lysogenic Cycle- Becomes part of DNA
Comparisons: Incubation time in host
Lytic Cycle- Release of new viruses after one generation of host activity
Lysogenic Cycle- Release of new viruses after several generations of host activity
Comparisons: Onset of viral disease symptoms
Lytic Cycle- Immediate
Lysogenic Cycle- Delayed
three fundamental classes of viruses:
DNA viruses, retroviruses, and RNA viruses.
DNA viruses- store genetic material as —- and replicate their — in a manner similar to — cells
DNA, DNA, human
Retroviruses and RNA viruses- store their genetic material as —.
RNA
Retroviruses reproduce by first…
converting their RNA into DNA in infected cells, and then converting this DNA back into RNA.
RNA viruses have the unique ability to…
directly reproduce their RNA to create new RNA virus offspring through a process known as RNA replication. (This ability to directly duplicate RNA distinguishes RNA viruses from DNA viruses and retroviruses and, importantly, from human cells. )
—- are by far the most abundant viruses in nature
RNA viruses
Viral DNA interrupts this sequence by…
deactivating the host’s cell mRNA and forcing the host ribosomes to produce viral proteins instead of those needed by itself.
Interruption of the Production of a Host’s Protein Synthesis by DNA Virus
- Viral DNA released into host celL
- Replication of viral DNA
- Deactivates mRNA of host cell
- Makes viral mRNA using host cell materials
- Host ribosomes “read” viral mRNA code
- Ribosomes produce viral protein
For RNA viruses, the transcription step is unnecessary but most encode a special enzyme, —- to catalyze replication of the RNA
RNA replicase
Some RNA viruses lyse their hosts but many…
escape from their hosts without lysing them
Interruption of the Production of a Host’s Protein Synthesis by RNA Virus:
- Viral RNA released into host cell
- Replication of viral RNA
- Deactivates mRNA of host cell
- RNA serves as mRNA
- Host ribosomes “read” viral mRNA code
-Ribosomes produce viral protein
Before certain RNA viruses can take over a host’s machinery, the viral RNA must be converted into… + What enzyme carries out this process
- a form that the cell’s ribosomes can recognize.
- reverse transcriptase carries out this process (catalyzes formation of a cDNA copy of the viral RNA. Therefore –> reversing the usual DNA-to-RNA sequence)
This ability makes RNA retroviruses is especially lethal since…
the retroviral DNA produced by the enzyme often splice itself into the host’s DNA
The host’s chromosomes will contain DNA copies of the retroviral genes, which may lay dormant/latent for…
months or years before becoming active.
The absence of a protein coat allows…
foreign genes to go unrecognized; so no antibody production occurs..
what occurs during the latency period?
-the retroviral DNA remains dormant and the individual looks and feels healthy.
-nothing can remove the spliced genes and every time the host undergoes mitosis, the retroviral DNA divides too. (number of infected cells increases, reproduce)
When the dormant genes become active again, the infected cell will produce and release…
retroviruses with protein coats
Generally, retroviruses do not lyse their hosts but instead leave by —-, a process similar to budding. (virus is enveloped in a segment of the cell membrane as it emerges from the cell. The immune system is stimulated since the protein coats are foreign + production of antibodies begins.
extrusion
The number of infected cells and the number of retroviruses may be very large at the time of release causing…
- an overload on the immune system. - host organism may become very sick or die before enough antibodies can be made to counteract the retroviruses
