Topic 2: Protein synthesis (transcription) Flashcards
Gene definition (2 points)
- a section of DNA WITH A SPECIFIC SEQUENCE OF BASES which codes for the sequence of amino acids in a {polypeptide/protein},
- and occupies a particular locus on a chromosome.
e.g. The CFTR gene (specific DNA sequence) codes for the CFTR protein
Key Summary: Explain the genetic code
4 points
- It is A TRIPLET CODE – 3 BASES in DNA code for {each/one} specific amino acid. Some triplet codes are start and stop signals.
- It is NON-OVERLAPPING – each base is only part of one triplet.
- It is DEGENERATE – several triplets can code for the same amino acid.
- It is UNIVERSAL: the code is the same in all living organisms
What do the ORDER OF MONONUCLEOTIDES in {a gene/DNA} determine?
(1 point)
- The specific order of amino acids in a protein (primary structure)
What are the two steps (in order) involved in protein synthesis?
- Transcription
2. Translation
Gene (DNA) is in the cell ________.
________ are made on ribosomes which are found in the __________.
DNA is too _______ to move out of the nuclear pores.
mRNA is _______ ________ so can travel out of the _________ into the cell __________.
Just a small section of the DNA (the gene for the protein which is to be made) is copied to make ____________ ______.
nucleus
proteins
cytoplasm
large
single stranded
nucleus
cytoplasm
messenger RNA (mRNA)
Describe the structure of mRNA
5 points
- it is a {nucleic acid /polynucleotide}
- single stranded (so can travel out of the nucleus into the cell cytoplasm)
- made of RNA mononucleotides. (each contains sugar, phosphate and one nitrogenous base)
- contains uracil, so does not contain thymine
- mononucleotides are joined by phosphodiester bonds in condensation reactions
Key Summary: Give an overview on transcription
- {What is the purpose of transcription/what is made}?
- What happens in the transcription process?
- Main enzyme {needed/involved}?
- Where in the cell does it take place?
- Makes messenger RNA (mRNA)
- {One/ANTISENSE} STRAND of the DNA in a gene is COPIED
- RNA polymerase
- In the nucleus
Key Summary: Explain what happens in transcription
6 steps
- DNA helicase breaks hydrogen bonds between the bases, DNA unwinds and TWO DNA STRANDS SEPARATE.
- The ANTISENSE STRAND (One DNA strand) is used as a TEMPLATE.
- Free RNA MONONUCLEOTIDES line up against and attach to the ANTISENSE STRAND (one DNA strand) by COMPLEMENTARY BASE PAIRING (between DNA and mononucleotides)
- RNA POLYMERASE (enzyme) joins the RNA mononucleotides together with PHOSPHODIESTER BONDS in CONDENSATION REACTIONS
- mRNA IS MADE, which DETACHES from the DNA
- mRNA carries the genetic code out of nucleus into cytoplasm and attaches to a ribosome
Key Summary: RNA Polymerase {role/function} in transcription
1 point
- An ENZYME (biological catalyst) which JOINS RNA MONONUCLEOTIDES WITH PHOSPHODIESTER BONDS in CONDENSATION REACTIONS TO FORM mRNA (copy of DNA antisense strand)
Key Summary: DNA template (antisense) strand {role/function} in transcription
(1 point)
- DNA antisense strand HAS A {MONONUCLEOTIDE/base} SEQUENCE which DIRECTS THE SYNTHESIS OF, and the ORDER OF BASES in, mRNA (a complementary copy of the antisense strand)
Key Summary: messenger RNA (mRNA) {role/function} in transcription
(2 points)
- mRNA is a COMPLEMENTARY COPY OF THE ANTISENSE STRAND, FORMED BY RNA POLYMERASE, WHICH IS MADE UP OF CODONS WHICH EACH CODE FOR A SPECIFIC AMINO ACID.
- mRNA carries the genetic code out of the nucleus, into the cytoplasm, to the ribosome.
Key Summary: What are the similarities of transcription and DNA replication
(4 points)
- Both use A, G, C mononucleotides to form new DNA strands
- Both involve complementary base pairing
- Both involve an enzyme which joins mononucleotides with phosphodiester bonds in condensation reactions
- Both are copying DNA
Key Summary: What are the differences of transcription and DNA replication
(7 points)
- DNA replication uses DNA polymerase, transcription uses RNA polymerase
- DNA replication copies both template DNA strands, transcription copies only one template DNA strand (antisense)
- DNA replication copies all of the DNA molecule but transcription only copies part of the DNA
- DNA replication uses thymine (T), transcription uses uracil (U)
- DNA replication uses DNA mononucleotides, but transcription uses RNA mononucleotides
- DNA replication makes two double-stranded DNA molecules, but transcription makes one single-stranded mRNA
- DNA replication is semi-conservative, but transcription is not semi-conservative
