Topic 13 Flashcards
In Prokaryotes transcription and translation occurs differently than eukaryotes by which of the following?
are performed coupled one after the other
Which part of Eukaryotic mRNA is coding sequence for the actual genes?
exons
In Transcription occurs where in Eukaryotes?
nucleus
According to the mRNA sequence 5’ AUG UUG UCA ACC 3’, what amino acids would be translated?
Met-Leu-Ser-Thr
Going from DNA to RNA is ____, and from RNA to Amino acids is____?
Transcription, Translation
What is the role of tRNA in protein synthesis?
Transferring amino acid to the ribosomes & Using anticoding sequence to match the mRNA sequence
RNA polymerase binds to a _________ to initiate _________.
promoter; transcription
mRNA in Eukaryotes differs from Prokaryotes in which of the following ways?
Presence of introns in eukaryotes RNA & contains a single gene per mRNA for Eukaryotes
___ is a triplet code of nucleotides that correspond to an amino acid?
codon
In the genetic code, one codon
consists of three bases & specifies a single amino acid
Central Dogma of Molecular biology
involves the nature of information flow in cells, from the conversion of genes (Genotype) to their expression (phenotype) occurs the same in all organisms.
Genes (DNA) to RNA copy – Transcription
RNA copy to amino acids (proteins) - Translation
DNA Replication
The basic mechanism of DNA replication is semiconservative, DNA replication involves opening up the DNA helix, and making copies of both strands to produce two daughter helices, each consisting of one old strand and one new strand.
Transcription
is the process of creating a RNA copy of DNA, using RNA polymerase
DNA information coded in mRNA
Happens in the nucleus
Genes (DNA) to RNA copy
the role of mRNA is for Transcription.
Translation
RNA copy to amino acids (proteins
mRNA decoded by Ribosomes to assemble polypeptides
Happens in the cytoplasm
Use mRNA of the ribosome and tRNA
is the process of making a protein (Polypeptide chain) from RNA, using ribosomes, mRNA, and tRNA
Purines
adenine and guanine
A purine contains a pyrimidine ring fused with an imidazole ring (a five-member ring with two non-adjacent nitrogen atoms). This two-ringed structure has nine atoms forming the ring: 5 carbon atoms and 4 nitrogen atoms. Different purines are distinguished by the atoms or functional groups attached to the rings
Pyrimidines
Cytosine, uracil, thymine
Pyrimidines are organic rings consisting of six atoms: 4 carbon atoms and 2 nitrogen atoms.
Adenine
Amino acid sequence is determined by the order of nitrogen bases in the gene
Guanine
Amino acid sequence is determined by the order of nitrogen bases in the gene
Thymine
Amino acid sequence is determined by the order of nitrogen bases in the gene
Cytosine
Amino acid sequence is determined by the order of nitrogen bases in the gene
Uracil
RNA differs from DNA, uses Uracil (U) rather than Thymine (T) base
Leading Strand
The leading strand as the name suggests is a complete continuous strand that is synthesized rapidly during DNA replication on the 3’→5′ polarity template of DNA. Its direction is 5’→3′.
Lagging Strand
it lags behind and is always very slowly synthesized in the form of various small fragments on the 5’→3′ polarity template of DNA. Its direction is 3’→5′. It is synthesized in short, discontinuous fragments called Okazaki fragments
Helicase
DNA Helicase – unwinds the double helix of DNA for replication to take place
Primase
Primase makes an RNA primer, or short stretch of nucleic acid complementary to the template, that provides a 3’ end for DNA polymerase to work on
DNA gyrase
DNA gyrase – relieves torque in the strand
DNA polymerase III
Synthesizes the New DNA strand.
DNA polymerase I
Erases primer and fill gaps in lagging strand
DNA ligase
joins the ends of DNA segments, also repairs DNA
Semi-discontinuous replication
DNA replication is semi-discontinuous because one strand is synthesized continuously, while the other strand is synthesized discontinuously by the formation of Okazaki fragments.
Okazaki Fragments
Okazaki fragments are short sequences of DNA nucleotides (approximately 150 to 200 base pairs long in eukaryotes) which are synthesized discontinuously and later linked together by the enzyme DNA ligase to create the lagging strand during DNA replication
Messenger (mRNA)
a type of RNA
RNA transcript – termed messenger RNA (mRNA), which is directly used for synthesis of the polypeptides
mRNA – messenger RNA, - the intermediate information containing that can be transferred out of the nucleus.
(Chain of nucleotides which are the codons = mRNA)
Transfer (tRNA)
tRNA – transfer RNA - contain short segments of anticodons RNA that code for a specific amino acid, which is carried to the Ribosome-mRNA
(1 Anticodon + 1 amino acid = tRNA)
Ribosomal (rRNA)
Ribosomal RNA (rRNA) - along with proteins, forms the ribosomes, which consist of two subunits, one large, one small.
The two subunit types combine to form functional ribosomes, which are the sites of protein synthesis
Structural component of ribosomes
Where protein synthesis occurs
Works with tRNA to translate message from mRNA into polypeptide.
introns
noncoding segments
exons
Portion of the genes that codes for amino acids
gene
A segment of DNA, that codes for one polypeptide
Template strand
is the strand of DNA that is used to make the copy of RNA. Since DNA is double-stranded and RNA is single stranded, and only one of the two DNA strand needs to be copied.
coding strand
is the strand of DNA not used as a template for RNA, but will have the same sequence as the RNA transcript – termed messenger RNA (mRNA), which is directly used for synthesis of the polypeptides
genetic code
codon is the basic unit of the genetic code
Amino acid sequence is determined by the order of nitrogen bases in the gene.
(Adenine, Guanine, Thymine, and Cytosine)
Triplet code – called a codon.
Sequences of 3 nitrogen bases: AGTC
Each Triplet specifics the code for a particular amino acid but each amino acid can be coded for by more than one triplet
GGC code for amino acid proline
GCC codes for amino acid arginine
Three-base sequence of DNA (triplet code)
Complementary three-base sequence on mRNA called codon
There are 64 possible codons
4 bases (A, U, C, G) and 3 places, so 43 = 64
There are 3 “stop” codons,
20 possible amino acids,
Some amino acids are represented by more than one codon. Redundancy helps protect against transcription errors.
codon
basic unit of the genetic code, sequence of three adjacent nucleotides in DNA or mRNA, that codes for one amino acid
Complementary three-base sequence on mRNA called codon
There are 64 possible codons
There are 3 “stop” codons
mutations
A genetic mutation is a change to your DNA sequence by removing, adding or replacing pieces of your DNA
point mutations
or single nucleotide variation, that alters a single base, causing either deletions, or additions of a single base
silent mutations
is when a base substation does not change the amino acid due to codon repetition.
nonsense mutations
occurs when a base is changed in such a way, a codon is converted to a stop codon.
missense mutations
is when a base substation changes an amino acid of a protein
frameshift mutations
addition or a deletion of a single base, can cause a shift in the codon changing large amounts of amino acids
chromosomal mutations
more extensive changes can alter the structure of the chromosome itself, and results many types of cancers.
deletion
is the loss of a portion of a chromosome, which can be caused by one or more frameshift mutations
duplication
may or may not lead to phenotypic consequences depending on the location where the duplication occurs
inversion
results when a segment of a chromosome is broken in two places, reversed, and place back together
translocation
one chromosome is broken off and joined to another chromosome
Identify and understand the enzymes involved in DNA replication, and the different roles of types of RNA in RNA translation
DNA Helicase – unwinds the double helix of DNA for replication to take place
DNA polymerase III – Synthesizes the New DNA strand.
DNA polymerase I – Erases primer and fill gaps in lagging strand
DNA ligase – joins the ends of DNA segments, also repairs DNA.
DNA gyrase – relieves torque in the strand
mRNA – messenger RNA, - the intermediate information containing that can be transferred out of the nucleus.
(Chain of nucleotides which are the codons = mRNA)
tRNA – transfer RNA - contain short segments of anticodons RNA that code for a specific amino acid, which is carried to the Ribosome-mRNA
(1 Anticodon + 1 amino acid = tRNA)
Ribosomal RNA (rRNA) - along with proteins, forms the ribosomes, which consist of two subunits, one large, one small.
Identify and understand the differences between Eukaryotic RNA transcription and translation, and Prokaryotic RNA transcription and translation (refer to slide 36)
Introns – present in most Eukaryotes genes, none in Prokaryotes
Number of Genes in mRNA – Prokaryotes may have several genes transcribed into a single mRNA molecule, while Eukaryotes will only have one gene per mRNA molecule
Site of Transcription and Translation – all is completed in the cytoplasm of Prokaryotes, while transcription occurs in the nucleus of Eukaryotes,
Transcription and translation are coupled in prokaryotes, while mRNA is first modified before translation in Eukaryotes before translation (introns removed, exons spliced together, 5’cap and poly-A tail is added)
