Ch 1 Relationship between nucleic acid and proteins Flashcards
What are the differences between eukaryotes and prokaryotes?
eukaryotes
- membrane bound organelles
- DNA is in nucleus in long strands called chromosomes
- circular DNA is also found in chloroplasts and mitochondria
prokaryotes
- lack membrane bound organelles
- DNA is in cytosol as singular circular chromosome
- smaller circular pieces of DNA called plasmids in cytosol
What are Nucleic Acids?
definition and what it provides
definition -> basic building blocks or sub-units of DNA and RNA consisting of phosphate group, base, five-carbon sugar
- provide genetic blueprint that provides information for protein synthesis
What are the two types of nucleic acids?
deoxyribonucleic acid -> nucleic acid consisting of nucleotide sub-units containing sugar deoxyribose and bases (A, C, G, T)
-> polymer of nucleotides
-> forms major component of chromosomes
-> ‘spiral’ double helix/ladder structure
ribonucleic acid -> single chained containing ribose (A, U, G, C)
What are forms of RNA?
three forms
1. Messenger RNA (mRNA) transfer DNA code from nucleus to ribosomes
- carries genetic message from DNA within nucleus to ribosomes (message is turned into protein)
- made up of groups of three nucleotides (aka codon)
- pre-mRNA is made through transcription in nucleus
2. Transfer RNA (tRNA) bring specific amino acids to ribosomes
3. Ribosomal RNA (rRNA) make up parts of ribosomes
What is a genetic code?
definition + degenerate triplet code
definition contain information for joining amino acids to form polypeptides
1. genes usually** contain coded information** for assembling amino acids to make polypeptides
2. polypeptides are made of combinations of 20 amino acid sub-units
- degenerate because same nucleotides codes for same amino acid
What are the steps of Gene expression?
1. Transcription genetic instructions from DNA are copied into messenger RNA (mRNA) and leaves nucleus
- RNA polymerase (enzyme) attaches to specific promotor sequence of DNA (upstream region of template region -> double-stranded DNA unwinds and exposes bases of template strand
- base sequence of DNA sequence guides building of complementary copy of mRNA sequence ->. RNA polymerase moves along 3’ to 5’ direction
- after RNA polymerase moves past coding region and into downstream region, transcription stops and pre-mRNA is released from template
2. RNA processing in eukaryotes
- Capping 5’ end is capped with altered guanine base -> protecting pre-mRNA from enzyme attack and contributes to stablility (help with attachment to ribosomes
- Adding tail poly-adenine (A) tail added to 3’ end
- Splicing introns are splices and exons are joined together(done by sliceosomes)
3. Translation sequence of mRNA is decoded and translated into protein chain by addition of corresponding amino acids
- mRNA moves to ribosomes (read in codons)
- each amino acid is brought to mRNA on ribosomes by transfer RNA (tRNA)
- ribosomes continue along mRNA and tRNA deliver appropriate (free-floating) amino acids
- codon representing STOP is reached and polypeptide is released from ribosome
What is the structure of genes?
- coding region part of the gene that contains coded information for making protein
- flanking region regions on either side of coding region of gene
- promotor region - upstream part of upstream flaking region
- exons contains instructions for synthesis of proteins and are transcribed and translated -> providing instruction that code for amino acid
- introns transcribed but not translated
** - leader region (attenuators)**
- operator regions found in operon where repressor binds
What are types of genes?
two types
structural genes produce proteins that become part of structure and functioning of organism
regulator genes produce proteins that control action of other genes
What does the Trp Operon consist of?
structural genes codes for any RNA or protein product other than regulator
regulatory gene codes for product that controls expression of other genes codes for repressor that binds to DNA when active by decreasing rate of transcription
promotor RNA polymerase attaches and starts transcription
operator provides binding site for repressor so transcription cannot occur
leader contain leader peptide and attenuator section that is able to further regulate transcription
What happens when tryptophan is present?
- tryptophan binds to repressor protein causing it to change shape to become more active
- repressor binds to operator
- RNA polymerase is unable to bind to promotor and transcription does not occur
What happens when tryptophan is absent?
- repressor is unable to bind to operator due to being inactive
- RNA polymerase can bind to promotor and start transcription of structural genes
What is the purpose and function of the trp operon?
- allow prokaryotes to make tryptophan when it is unavailable
What are the functions of proteins?
- provides structural support for cells and tissues
- provides ability for humans and animals to move
- facilitates transport of small molecules around body
- controls rates of chemical reactions in humans
What are amino acids?
What are they made of and structure.
**definition -> ** monomers of proteins
- vary only in R-group
How are polypeptide chains formed?
condensation polymerisation
- joining of amino acids by peptide bonds
- process requires input of energy
- water is released as monomers are being bonded together to form polymer
