Nucleic Acids and Transcription Flashcards
nucleotides
DNA subunits; made of 5-carbon sugar, a nitrogen-containing base, and one or more phosphate groups
purines
double ring structue; adenine (A) or guanine (G)
pyrimidines
single-ring structure; thymine (T) or cytosine (C)
nucleoside
molecule consisting of a 5-carbon sugar and a base
phosphodiester bond
covalent bond that forms when a phosphate group in one nucleotide is joined to the sugar unit in another nucleotide; joins 3’ carbon to 5’ carbon via C-O-P-O-C
polarity
top of a strand has free 5’ posphate and the bottom has free 3’ hydroxyl
antiparallel
individual DNA strands in the double helix run opposite to each other; 5’ to 3’ paired with 3’ to 5’
complimentary pairings
A-T (2 H-bonds) and G-C (3 H-bonds)
base stacking
figure E
stabilizing force that occurs because nonpolar, flat surfaces of the bases group away from water molecules and thus stack on top of one another as tightly as possible
figure E
replication
the process of copying DNA so genetic information can be passed from cell to cell or from parent to offspring
replication steps
two strands of parental doible helix unwind → separate into single strands → each parental strand serves as a tamplate for the synthesis of a complementary daughter strand → when the process is complete there are two molecules, each containing one parental strand and one daughter strand
mutation
an unrepaired error in DNA replication which changes the genetic information/sequence of DNA
gene regulation
transcription and translation are regulated at all times in all cells even though all cells in an individual contain the same DNA
ribonucleic acid
a molecule chemically related to DNA that is synthesized by proteins from a DNA template
transcription
figure F
genetic information of DNA is used as a template to generate a molecule of DNA
figure F
translation
figure F
a molecule of RNA is used as a code for the sequence of amino acids in a protein
figure F
prokaryotes
transcription and translation occur in the cytoplasm
eukaryotes
transcription occurs in the nucleus while translation occurs in the cytoplasm
RNA complimentary groups
A-U (uracil instead of thymine)
RNA qualities
in DNA is a monopsphate while in RNA it is a triphosphate; RNA is shoter and single-stranded
RNA world hypothesis
the hypothesis that the earliest organisms relied on RNA for both catalysis and information storage
RNA transcript
figure G
the RNA sequence synthesized from a DNA template
figure G
RNA polymerase
the enzyme that carries out polymerization of ribonucleoside triphosphates from a DNA template to produce a RNA transcript
initiation (1st stage)
RNA polymerase and other proteins are attracted to DNA → DNA strands are separated → transcription of the template begins
elongation (2nd stage)
RNA polumerase adds successive nucleotides to the 3’ end of the RNA transcript (RNA transcript is synthesized 5’ to 3’ while DNA template is read 3’ to 5’)
termination (3rd step)
RNA polymerase encounters a sequence in the template strand which causes the transcription to stop → RNA transcript is released
promoter
figure H
initiates transcription; regions of a few hundred base pairs where RNA polymerase and associated proteins bind to DNA duplex
figure H
TATA box
DNA sequence present in many promotes in eukaryotes and archaeons that serves as a protein-binding site for a key general transcription factor; includes sequence 5’-TATAAA-3’
terminator
transcription stops at terminator → transcription is released
sigma factor
a protein associated with RNA polumerase in bactera that facilitates its binding to specific promoters
general transcription factors
proteins that assemble at the promoter of a gene; assembly is necessary for transcription to occur, but not sufficient
transcriptional activator protein
figure I
binds to a specific DNA sequence known as an enhancer; helps to control when and in which cells transcription of a gene will occur
figure I
mediator complex
once transcriptional activator proteins have bound to enhancer DNA sequences, they can attract a mediator complex of proteins which recruits RNA polymerase complex to the promoter
primary transcript
RNA transcript that comes off template DNA strand; contains complement of eery base transcribed from DNA template
messenger RNA (mRNA)
RNA molecules that combine with the ribosome to direct protein synthesis; carries the genetic “message” from DNA to the ribosome
RNA processing
converts primary transcript into finished mRNA, which can then be translated by the ribosome
5’ cap
figure J
5’ end of primary transcript is modified by the addition of 7-methylguanosine; ribosome recognizes an mRNA by its 5’ cap
figure J
5’ cap
figure J
5’ end of primary transcript is modified by the addition of 7-methylguanosine; ribosome recognizes an mRNA by its 5’ cap
figure J
polyadenylation
the addition of 250 consecutive A-bearing ribonucleotides to the 3’ end; forming a poly(A) tail
exons
regions of protein-coding sequence
introns
noncoding regions
RNA splicing
figure K
process of removing an intron; catalyzed by a complex of RNA and protein known as “spliceosome”
figure K
alternative splicing
primary transcripts from the same gene can be spliced in different ways to yeild differnt mRNAs; results in different protein products
ribosomal RNA (rRNA)
makes up the bulk of ribosomes; essential for translation; in eukaryotic cells genes and transcipts for rRNA are concentrated in the nucleolus
transfer RNA (tRNA)
carries individual amino acids for the use in translation
small nuclear RNA (snRNA)
essential component of spliceosome required for RNA processing; miRNA and siRNA)
