chapter 7- dna structure and gene function
transcription
a cell rewrites a gene's DNA sequence to a complimentary RNA molecule
prion (PrP)
a normal membrane protein that can exist in multiple 3D shapes, at least one of which is abnormal and can cause disease
semi-conservative replication
every new DNA molecule made by a cell is composed of half old and half new DNA
all viruses contain
genetic info and a protein coat
viroid
highly would circle of RNA that lacks a protein coat
synthesis stage of viral replication
host cell produces multiple copies of the viral genome; mutations during this stage are the raw material for viral evolution
why are viruses considered not alive during synthesis?
host cell provides all resources
how would a virus infect a plant cell?
penetrate waxy outer leaf layers and thick cell walls
ribosomes
physical location where translation occurs, contain large and small subunits
introns
portions of the mRNA that are removed before translation
repressor
prevents transcription of genes if binded to a protein
what does the misfiling of prions do?
stimulates others normal proteins to misfold resulting in cell death
genetic code
the set of rules by which a cell uses the codons in RNA to assemble amino acids in a protein
attachment stage of viral replication
virus attaches to a host cell by adhering to a receptor molecule
bacteriophage
virus that infects bacteria
termination 2 of translation
a release factor binds to the stop codon
initiation 2 of translation
a tRNA carrying the first amino acid binds the first codon on the mRNA
elongation 1 of translation
a tRNA carrying the second amino acid binds to the second codon on the mRNA
elongation 4 of translation
a tRNA carrying the third amino acid binds to the third codon
insertion mutation
adds one or more nucleotides to a gene
purines (double ring structure)
adenine and guanine
genome
all of the genetic material in an organism's cell
initiation 1 of translation
an mRNA strand attaches to the small ribosomal subunit
penetration stage of viral replication
animal cells engulf virus (endocytosis), viruses hitch a ride, bacteriophages inject genetic info through cell wall holes
mutation
any change in a cell's DNA sequence
mutagen
any external agent that induces mutations
termination stage of transcription
at the terminator sequence, RNA polymerase detaches from the DNA and releases the RNA strand
what is the correct order of viral replication?
attachment, penetration, synthesis, assembly, release
gene expression
conversion of the information encoded in a gene first into mRNA and then to a protein
where does translation occur?
cytoplasm and ribosome
chromosome
discrete package of DNA coiled around proteins
start codon
AUG (methionine)
operator
DNA sequence located between the promoter and the protein-encoding regions
initiation stage of transcription
RNA polymerase binds to and unzips DNA
elongation stage of transcription
RNA polymerase reads the DNA strand and adds complimentary nucleotides to an RNA strand
lytic infection
an infection by a bacteriophage that causes the host bacterium to burst immediately after assembling new viruses
removing certain introns/ exons
can make nonfunctional proteins
messenger RNA
carries info that specifies a protein
transfer RNA
carry each amino acid to the correct spot along mRNA molecule
silent mutations
change in genetic code that doesn't change the amino acid
epigenetics
changes in gene expression that do not involve changes to the DNA sequence itself
which is the most dense structure of DNA?
chromosomes
operon genes
code specific proteins
ribosomal RNA
combines with proteins to form ribosomes
template strand
contains the DNA sequence that is actually transcribed to RNA
cells controlling gene expression
contributes to different cell types
alleles
encode same RNA or protein products, but may represent different forms
homeotic genes
encode transcription factors that are expressed during the development of an embryo
XX
female
supportive therapy
fluids and other forms of medication to build up a natural immune response (2 weeks)
operon
group of related genes plus a promoter and an operator that control the transcription of the entire group at once
codon
group of three consecutive mRNA bases that corresponds to one amino acid
karyotype
image showing all of an individual organism's chromosomes
lac operon
in E. coli, three lactose-degrading genes plus the promoter and operator that control their transcription
when are lac operons expressed?
in the presence of lactose sugar
post-translational modifications
increase functional outcomes of proteins in an organism
benefit of polysomes
increases and maximizes protein production
lysogenic infection
infection by a bacteriophage where genetic material replicates along with host genome, but infected cells do not immediately produce new viruses; the infection may become lytic at any time
XY
male
characteristics of viruses
much smaller than a cell, lack organelles, nucleus, membrane, cytoplasm, and ribosomes
RNA
multifunctional nucleic acid that differs from DNA
do antibiotics work against viruses?
no
what happens if mRNA is not physically out of the nucleus?
no proteins are produced
frameshift mutation
nucleotides are added or deleted by a number other than a multiple of three
where does transcription occur?
nucleus
release stage of viral replication
once the virus particles are assembled, they are ready to leave the cell
transcription factors
protein that attract RNA polymerase to proper location
promoter
recognized by RNA polymerase, DNA sequence that not only signals a gene's start but also indicates which of the two strands isn the templates
central dogma
relationship between nucleic acids and proteins as a flow of information
deletion mutation
removes nucleotides
splicing
removing intron and connecting externs from pre mRNA to mature mRNA
substitution mutation
replacement of one DNA base with another
gene
segment of DNA that contains instructions to make a specific protein or DNA molecule
complementary
sequence of each strand determines the sequence of the other
polysomes
single mRNA is read multiple times for more proteins
is RNA single or double stranded?
single stranded
virus
small infectious agent that is simply genetic info enclosed in a protein coat
RNA degradation
some mRNA are rapidly destroyed before translation chemically
exons
spliced together to form the mature mRNA that leaves the nucleus to be translated
DNA
store information that each cell needs to produce proteins
assembly stage of viral replication
subunits of protein coat surround the virus's other proteins and the genetic material
double helix
sugar-phosphate backbones, alternating units of deoxyribose and phosphate joined with covalent bonds
protein coat
surrounds the viral genetic material, shape determines form
vaccine
teaches the immune system to recognize one or more molecular components of a virus without actually exposing the person to disease
translation
the information in RNA is used to assemble proteins
initiation 3 of translation
the large ribosomal subunit attaches the small ribosomal subunit
termination 3 of translation
the polypeptide, ribosomal subunits, and remaining tRNA molecules separate
elongation 5 of translation
the process repeats for subsequent codons, tRNAs, and amino acids
elongation 3 of translation
the ribosome moves down one codon on the mRNA, and the first tRNA is released
termination 1 of translation
the ribosome reaches a stop codon
elongation 2 of translation
the second amino acid binds tot he first amino acid with a covalent bond
anticodon
three-base loop that is complementary to one mRNA codon in tRNA
pyrimidines (single ring structure)
thymine, cytosine, uracil
RNA contains _______ instead of thymine
uracil
naked DNA
wrapped around histone proteins