Biochem Module 7 Flashcards
DNA Replication
Genetic information contained in the DNA is transferred to RNA molecules and then expressed in the structure of synthesized proteins.
The Central Dogma of Molecular Biology
DNA Replication
process by which DNA is copied with very high fidelity.
DNA Replication
DNA Replication
involves two replication forks, which move in opposite directions
DNA Replication is bi-directional
DNA Replication
- The leading strand copies continuously
- The lagging strand copies in segments (Okazaki fragments)
DNA Replication is semi-discontinuous.
DNA Replication
DNA in the chromosomes replicates itself every _____ (before mitosis and meiosis I occurs)
cell division
DNA Replication
an enzyme which separate the DNA strand breaking the H bonds at the replication fork
DNA Helicase
DNA Replication
replicates DNA using each strand as a template for the newly synthesized strand by adding complementary nucleotides.
DNA polymerase III
DNA Replication
DNA polymerases have “_________” (exonuclease) activity.
proof reading
DNA Replication
an enzyme that unknots and uncoils
topoisomerase
DNA Replication
synthesizes short RNA segments called primers that are starting points for DNA polymerase
DNA primase
binding to single-stranded DNA
SSB (Single-Stranded DNA binding Proteins)
DNA Replication
filling the gaps; eliminates primers
DNA Polymerase I
DNA Replication
Ligates Okazaki fragment to rest of lagging strand; enzyme that catalyzes the formation of the phosphodiester bond between pieces of DNA.
DNA Ligase
DNA Replication
______ is synthesized as a single strand from the point of origin toward the opening replication fork
Leading strand
DNA Replication
is synthesized discontinuously against overall direction of replication
Lagging Strand
DNA Replication
series of short segments on the lagging strand
Okazaki fragments
DNA Replication
Must be joined together by an enzyme
DNA Ligase
DNA Replication
Replication of the leading strand occurs ______in the _____ direction of the new strand.
continuously; 5’ → 3’
DNA Replication
Replication of the lagging strand occurs _______. Short DNA fragments are initially synthesized and then ligated together.
discontinuously
Transcription
process by which the DNA genetic code is read and transferred to messenger RNA (mRNA). This is an intermediate step in protein expression.
Transcription
Transcription
Only one of the DNA strands is copied
coding or antisense strand
replicates the DNA sequence into a complementary sequence of mRNA (template or sense strand).
RNA Polymerase
He isolated nuclein from the nuclei of pus cells
Friedrich Miescher
Nuclein was shown to have
acidic properties, hence it was called ____?
nucleic acid
Nucleic acid was previously known as?
Nuclein
Two types of nucleic acids
- Deoxyribonucleic acid (DNA)
- Ribonucleic acid (RNA)
carrier of genetic information
DNA
an intermediate in the expression of genetic information and other diverse roles
RNA
The amino acid sequence of a polypeptide is programmed by a unit of inheritance called ____?
gene
True or False
Nucleic acids are polynucleotides
True
Building blocks of nucleic acids
nucleotides
linkage between the sugar and organic base residues
N-glycosidic bond
linkage between the sugar and phosphate residues
Phosphoester bond
Nucleotides structure
- pentose sugar
- nitrogenous bases
- phosphate group
What is the difference between Deoxyribose and Ribose in terms of structure, sugar, and nitrogenous base
DNA structure:
* double helix
* Carbon 2 does not have oxygen (H)
* A=T ; C=G
RNA structure:
* single strand
* Carbon 2 has oxygen (OH)
* A=U ; C=G
What are the 2 types of nitrogenous bases
- pyrimidines (C, T, & U)
- purines (A & G)
have six-membered ring
Pyrimidines
- have a six-membered ring fused to a five-membered ring
- Both present in DNA and RNA
Purines
pyrimidines attach to the pentose via the ____ position while purines attach through the ____ position
N-1 ; N-9
Energy currency in cellular metabolism
ATP
Derived from phosphoric acid, H3PO4, at physiological pH exists in the ionic form.
PHOSPHATE GROUP
A portion of a nucleotide without the phosphate group
Nucleoside
nucleoside = ?
nitrogenous base + sugar
True or False
The stereochemistry of the glycosidic bond found in nucleic acids is β
True
Nucleotide = ?
phosphate + sugar + nitrogenous base
2 to 10 nucleotide residues
Oligonucleotides
more than 10 nucleotide residues
Polynucleotides
Sigma factors recognize two highly conserved regions of the promoter.
Transcription: Initiation
Nitrogenous bases are attached to the?
1st carbon
Refers to the helix formed by the interaction of two DNA strands
Secondary Structure of DNA
Tertiary Structure of DNA: ____
Supercoils
Transcription: Initiation
two regions within promoters that are highly conserved:
- Pribnow box
- −35 region
Transcription: Initiation
Stretched of 6 nucleotide (TATAAT) located 10 bases before the start of transcription (−10 region)
Pribnow box
Transcription: Initiation
located ~35 bases upstream of transcription
-35 region
- the promoter region has been recognized by the holoenzyme
- RNA polymerase begins to synthesize the transcript of the DNA sequence, with the release of the sigma factor.
Transcription: Elongation
does not require a primer
RNA polymerase
(ahead of the transcription site) – relaxed by gyrase
+supercoil
(behind) – relaxed by topoisomerase
-supercoil
- RNA polymerase encounter a stop signal or transcription terminator (e.g. rho protein in prokaryotes; C-G rich hairpin loop)
- the RNA polymerase dissociate from the DNA template
- the RNA transcript is released.
Transcription: Termination
are sections that code for proteins, and are spliced
together with spliceosomes
Exons
which do not code for proteins
Introns
The process by which the genetic code is converted to a protein, the end product of gene expression
Translation
A change in the nucleotide sequence of DNA altering the sequence of amino acids which will affect the structure and function of a protein in a cell.
Mutation
types of mutation
- BASE SUBSTITUTION “POINT MUTATION”
- BASE DELETION OR INSERTION
BASE SUBSTITUTION “POINT MUTATION”
The codon containing the changed base codes for the same amino acid
Silent Mutation
BASE SUBSTITUTION “POINT MUTATION”
The change results in a new different amino acid
Missense
BASE SUBSTITUTION “POINT MUTATION”
The change leads to premature termination if the codon containing the changed base become a termination codon.
Non-Sense Mutation
BASE DELETION OR INSERTION
Insertion or deletion of one or two bases will alter the reading frame and this cause extensive change in the translated protein.
Frame Shift Mutation
BASE DELETION OR INSERTION
This lead to the addition of new amino acids (if three bases were inserted), or to the deletion of one amino acid (if three bases were deleted).
Insertion or deletion of one codon or “3 nucleotides”
True or False
Each cell contains
about 2 meters of DNA
True
Arises from supercoiling that involves double helices being twisted into tighter, more compact shapes
Tertiary Structure of DNA
DNA is “packaged” by coiling around a core of proteins known as?
histones
rich in lysine and arginine residues
histones
DNA-histone assembly
nucleosome
Types of RNA
- Messenger RNA (mRNA)
- Ribosomal RNA(rRNA)
- Transfer RNA (tRNA)
carrier of genetic information from the DNA in the cell nucleus to the site of protein synthesis in the cytoplasm
mRNA
True or False
mRNA directs amino acid sequence of proteins and is complementary copy of the gene
True
True or False
mRNA has a short lifetime and Has the codon (three bases) for an amino acid in a protein
True
mRNA is also known as?
The starting point of translation
- forms ribosomes by reacting with proteins
- accounts for 80-85% of the total RNA of the cell
rRNA
- Transfers amino acids to the site of protein synthesis
- Has the anticodon
tRNA
True or False
tRNA is the largest of the nucleic acids
False
tRNA is the smallest