Transcription and translation Flashcards
how many chromosomes does each human have?
46 chromosomes
23 pairs
what is the structure of a chromosome?
DNA is tightly coiled many times around a protein called histone that supports its structure
what is a the histone protein?
histones are proteins inside the nucleus
histones are proteins that coil and structure the DNA of a nuclei into units called nucleosomes.
Protein blocks are histones
how are nucleosomes formed?
formed by histones
DNA coils twice around eight histone protein (octamer)
what is the structure of nucleosomes?
the nucleosome core is formed of two H2A-H2B dimers and a H3-H4 tetramer
what is the function of histone H1?
histone H1 holds DNA in place and anchors the nucleosome together.
what is nucleotide?
nucleotide is the building block of the DNA and RNA
what is the structure of nucleotides?
they are composed of 3 subunits
.nitrogenous base
.five carbon sugar (5C)can be ribose or deoxyribose
.1 phosphate group
what is the function of the 5C sugar and phosphate?
they give the DNA its structural element
what is the function of the nitrogenous base?
encloses genetic information
gives identity
what is the pentose ring (5C) sugar made of?
carbohydrates
what are the two types of 5C sugar?
ribose = RNA has an OH group deoxyribose = DNA has no oxygen
what are the 4 possible nitrogenous bases available in the DNA?
- Adenine
- Thymine
- guanine
- cytosine
what are the 2 types of bases?
purines
pyrimidines
what is the structure of purines?
two interlocking nitrogen - containing rings
larger space.
which nitrogenous bases are found in purines?
A and G
what is the structure of pyrimidines?
contain a single nitrogen-containing ring
less space
which nitrogenous bases are found in pyrimidines?
C and T
how are nitrogenous bases joined to the sugar?
nitrogenous bases are joined to C1 of the deoxyribose sugar
what is the function of the phosphate group?
joins 3 to 5 carbon with a phosphodiester bond
how to bind 2 nucleotides together?
to bind 2 nucleotide together we have a phosphodiester linkage
what kind of interaction is between DNA bases on different strands?
DNA bases on different strands are held together by H-bonds
what does adenine pair with?
adenine pairs with thymine by 2 hydrogen bonds
what does cytosine pair with?
cytosine pairs with guanine by 3 hydrogen bonds
why does purine bind to pyrimidine?
double ring binds to a single ring .
what is the properties of the DNA double helix
- two helical polynucleotides chains are coiled around common axis
2.the chains run in opposite direction- antiparallel
3.complementary bases are held together by hydrogen bonds
bases are at 90 degrees
the large number of hydrogen bonds provide stability of the DNA however on their own they are quite week
4.nitrogenous bases are covalently bonded to the 1 carbon of deoxyribose
how does mitochondria make its DNA?
they contain their own DNA which encode the mitochondrial proteins and some RNA
where does mitochondria contain its DNA?
contains its DNA in plasmid ring- contains genetic info for enzymes for the mitochondria such as in oxidative phosphorylation
what is the tRNA?
genes for synthesis of transfer
what is rRNA?
genes for synthesis of ribosome
what is the function of RNA
RNA help assemble amino acids into functioning proteins
what is RNA?
RNA is a sequence of nuclotides
what is the main difference between RNA and DNA
ribose rather than deoxyribose
RNA is single stranded
thymine is substituted for uracil
what do purines in RNA contain?
purines contain two interlocking nitrogen-containing rings
A and G
what do pyrimidine in RNA contain?
pyrimidines contain a single nitrogen containing ring
C and U
how are nitrogenous bases joined to sugar?
bases are joined to C1 of the ribose sugar
how does our genetic code translate into what we are?
this done through the process of translation and transcription
summarise the process of transcription and translation?
- the genetic code from DNA is transcribed (copied )into shorter sequence RNA
- this is then read (translated) by a ribosome
- the ribosome generates a sequence of amino acid
- amino acid join to form a protein
what is the process of transcription?
the production of (mRNA) by the RNA
and the processing of the resulting mRNA molecule
what are the four steps of the process of transcription?
. initiation
.elongation
.termination
.processing
what is a gene?
gene contains genetic code to make one protein
what is our genetic material?
genetic material is a chain which is split into 20,000 regions, each region called a gene
what else does a gene contain?
it contains coding sequence called TATA box
for example repetition of T and A
what is a TATA box?
it is a binding region/promoter where proteins can bind
these proteins are called transcription factors.
what is the function of the transcription factors?
they bind to DNA to recruit an enzyme called RNA polymerase 2
what is the function of the enzyme RNA polymerase 2?
it opens up the DNA and starts the reading of genetic material ( transcription process) and starts producing RNA chain.
describe the first step of transcription - initiation?
- transcription factors bind to the TATA box
- transcription factors recruit an enzyme called RNA polymerase 2
- this enzyme opens up the DNA and starts the transcription process
describe the the second step of transcription - elongation?
- RNA polymerase 2 moves along template strand , synthesising an mRNA molecule
- phosphate group- joins 3 to 5 carbon with phosphodiester bond
describe the third process of transcription-termination?
involves the addition of adenine to the RNA transcript
process is called polyadenylation
what are exons?
exons are coding area that are read and produce proteins
between exons you have non -coding DNA (introns)
what are introns?
introns are non - coding area
introns are removed by the process of RNA splicing to form mature mRNA
describe the final process of transcription-processing?
RNA splicing removes introns
mRNA is produced this leaves the nucleus through nuclear pores
what is the process of translation?
conversion of the nucleotide sequence of mRNA into amino acid sequence of a protein
what does mRNA bind to ?
in order to be read mRNA binds to ribosome
what do ribosomes recruit ?
tRNA
what are the 4 steps involved in translation?
.initiation
.elongation
.termination
.post-translation processing of the protein
what does a mRNA nucleotide contain?
mRNA nucleotides contain a sequence of bases that are read in group of three
e.g. GTC ACA . TGA
each triplet is referred to as a codon
what does each codon specify ?
an amino acid used to make a protein chain
what are ribosomes?
ribosomes catalyse the assembly of protein chains - enzymes
what is the function of ribosome?
.ribosomes read mRNA sequence and bind tRNA
.they place amino acids next to each other in a sequence that will produce protein read from mRNA code
what is structure of ribosomes?
ribosomes consist of a large and small subunit
65% rRNA and 35% protein
where are ribosomes found ?
found on nuclear envelope
rough ER
free floating in the cytosol
how many binding sites does a ribosome have?
ribosomes have a binding site for mRNA and 3 binding sites for tRNA
E , P , A sites
what is the function of tRNA?
tRNA helps decode mRNA into protein
what is the structure of tRNA?
one chain double backed on its self 3 times creating 3 loops
what are the 3 loops in the tRNA structure?
D loop
T loop
anticodon loop
what is an anticodon?
.series of 3 nitrogenous bases creating a specific sequence.
.each anti codon binds to its complementary codon.
.there are the same number of codon and anticodon.
describe the first step of translation?-initiation
- mRNA binds to ribosome
- anticodon is able to read it
- AUG is the first codon in every protein
- AUG recruits tRNA
describe the second step of translation?-elongation
- codon of the mRNA determine which tRNA molecule is recruited into ribosome
- this enters binding site A as the first tRNA moves into site p
- new peptide bond is formed between amino acids at the other end of tRNA
- small subunit moves a distance of codon along the mRNA ejecting the spent tRNA molecule
- steps continue and create a polypeptide
What does the nitrogenous base actsas?
R-group
gives idenetiy as a part of the genetic code
How is a phosphate-sugar backbone made?
sugar and phosphate link together with adjacent nucleotides
What is h-bond pairing is due to?
reactivity and specificity
How to get a linear space between the phosphate- sugar backbone?
binding of purine and pyradmine
How many genes sre in the mitochondrial dna?
37genes so can produce 37 proteins
describe the process of translation?termination
- translation is terminated when ribosomal complex reads a stop codon
e. g. UUA - this codon binds a release factor
- stop codon results in hydrolysis of last amino acid
- release factor disconnects polypeptide from tRNA in the p-site
- ribosome dissociates into its two separate subunits
What is gene expression?
multiple RNA copies can be made from the same gene
Each RNA molecule can direct the synthesis of many identical protein molecules
each gene can be transc and transl with different efficiency
RNA polymerase requires tf - genes are up or down regulated by tf
transc and transl is regulated
How to control gene expression?
transcription control- most common geentic regulation
post-transcriptional control- regulation of the processing of a pre- mRNA into a mature mRNA
Translational contorl- regulation of the rate of initiation
post-translational control- regulation of the modification of an immature or inactive protein to form a active protein
