Topic 5 - DNA and protein synthesis Flashcards
what does mRNA stand for
messenger RNA
what is mRNA
the RNA formed in the nucleus that carries the genetic code out into the cytoplasm
what is an antisense strand
the DNA strand that codes for proteins
what is RNA polymerase
the enzyme that polymerises nucleotide units to form RNA in a sequence determined by the antisense strand of DNA
what does tRNA stand for
Transfer RNA
what is tRNA
small units of RNA that carries particular individual amino acids to ribosomes during protein synthesis to align with the mRNA
what is an anticodon
a sequence of 3 bases on tRNA that are complementary to the bases in the mRNA codon
what does rRNA stand for
ribosomal RNA
what is rRNA
RNA that makes part of sub-units of ribosomes
what are polysomes
groups of ribosomes, joined by a thread of mRNA, that can produce large quantities of a particular protein
what is a sense strand
a DNA strand that is not transcribed, and is identical to the mRNA transcribed from the antisense strand
what are 3 differences between RNA and DNA
- RNA contains ribose, and DNA contains deoxyribose
- RNA has the base uracil, and DNA has the base thymine
- RNA consists of a single strand, and DNA consists of a double helix
what are 2 similarities between RNA and DNA
- both don’t form large complex molecules
- Both have the bases Adenine, Guanine and Cytosine
what are 3 functions of RNA in protein synthesis
- it carries the instructions for a polypeptide from the DNA in the nucleus to the ribosomes
- It picks up specific amino acids from the protoplasm and carries them to the surface of the ribosomes
- it makes up the bulk of the ribosomes
what are the 4 stages of DNA replication
- DNA unwinds
- single strand acts as a template
- sugar-phosphate backbone is formed
- DNA rewinds
explain in step 1 of DNA replication, how the DNA unwinds
the hydrogen bonds holding the bases together beak, catalysed by DNA helicase. When the 2 halves of the molecule separate, the DNA bases are exposed
explain in step 2 of DNA replication, how the single strands act as a template
Each strand of DNA acts as a template for the new strands. Free nucleotides enter the nucleus from the cytoplasm and assemble on the template DNA according to the law of base pairing. The nucleotides are held in place by hydrogen bonds
explain in step 3 of DNA replication, how the sugar-phosphate backbone is formed
Condensation reactions link the new nucleotides together, to form the sugar-phosphate backbone, which is catalysed by DNA polymerase. This enzyme also ‘proofreads’ each new strand, correcting any mistakes made
where do phosphodiester bonds form
between each nucleotide
where do hydrogen bonds form
between each base
what does DNA ligase catalyse
the joining of different segments
explain in step 4 of DNA replication, how the DNA rewinds
each daughter DNA molecule rewinds into a double helix
what are the 4 enzymes that catalyse in the process of DNA replication
- helicase
- polymerase
- DNA polymerase
- ligase
what is transcription
the process by which a mRNA sequence is produced from a DNA template
what is a gene
a sequence of DNA that is transcribed into RNA
what is the shape of tRNA
it has a complex clover leaf shape due to the hydrogen bonds between the different bases
what is translation
the process of protein synthesis in which genetic information encoded in the mRNA is translated into a sequence of amino acids on a polypeptide chain
what do the ribosomes do during translation
- catalyse the formation of peptide bonds between adjacent amino acids via condensation reactions
- move along the mRNA molecule, synthesising a polypeptide chain until it reaches a stop codon
where is the ribosome produced
ribosomes are made in the nucleus under the control of the nucleoli, and then moves out into the cytoplasm, where it binds with proteins to form ribosomes
what are polysomes
groups of ribosomes joined by a thread of mRNA
what is the function of polysomes
are involved in the mass production of a particular protein
how many different codon combinations are there
64 (20 * 20 * 20)
what shape does the anticodon have
clover leaf
