DNA and Genetics Flashcards
Describe how mRNA is synthesised at a template strand of DNA.
RNA nucleotides align with complementary bases on DNA. RNA nucleotides join together by RNA polymerase/phosphodiester bonds.
Compare and contrast the process of transcription with the process of DNA replication
- both involve the formation of a polynucleotide/phosphodiester bonds
- both involve DNA helicase unzipping the DNA
- transcription uses mRNA nucleotides (AT) replication uses DNA nucleotides (AU).
- transcription uses RNA polymerase, replication uses DNA polymerase.
- transcription only copies template strand of dna/ produces a single strand of mRNA but replication copies both strands of DNA/produces double stranded of DNA.
Gene
A section of DNA nucleotides that codes for a specific protein.
Where is DNA found?
nucleus of eukaryotic cells
Where are proteins made?
ribosomes within the cytoplasm of eukaryotic cells.
RNA
ribonucleic acid; single-stranded nucleic acid that contains the pentose sugar ribose. It is a polynucleotide (made up of mononucleotides which contain phosphate groups) and is involved in protein synthesis (making proteins via translation). Contains bases (G,C,A,U (uracil)). There are three versions of it (MRNA,TRNA,rRNA)
genetic code
collection of codons of mRNA, each of which directs the incorporation of a particular amino acid into a protein during protein synthesis. (Adenine, uracil, guanine, cytosine).
Number of amino combinations
20 (2 bases)
Number of triplet combinations
64 (3 bases)
Protein synthesis
the formation of proteins by using information contained in DNA and carried by mRNA. (Translation and transcription)
Transcription definition
Process by which information on a DNA strand is transferred to an mRNA molecule. Occurs in the nucleus and is controlled by the enzyme RNA polymerase.
Transcription process
- occurs in the nucleus
- RNA polymerase binds to the gene being transcribed
-DNA helicase unzips the double helix and breaks the hydrogen bonds between the base pairs which exposes the part of the gene that will be transcribed.
-free RNA nucleotides that are complementary to the exposed DNA bases on the template are joined by phosphodiester bonds (forms the phosphate-sugar backbone of the mRNA molecule)
-once made, the mRNA leaves the nucleus, through the nuclear pores, into the cytoplasm, onto a ribosome.
Translation definition
The process of converting mRNA into amino acids that form proteins. Happens in ribosomes in the cytoplasm.
Translation process
- amino acids in the cytoplasm are activated for protein synthesis
- ribosomes bind to the mRNA (messenger)
- in the cytoplasm there are free molecules of tRNA (transport) which have a triplet of unpaired bases at one end (anticodon) and a specific amino acid binding site at the other.
- the mRNA reads 3 bases at a time as each triplet is read a tRNA delivers the corresponding amino acid, which is added to a chain of amino acids, that once complete folds into a complex shape to form the protein’s secondary, tertiary (and quaternary) structure.
Allele
Alternative forms of the gene on the same position (loci) on a chromosome.
Phenotype
An organism’s physical appearance, or visible traits.
Genotype
genetic makeup of an organism/an organism’s combination of alleles
Dominant
Alleles that can be express their phenotypic character with only one example in a body cell.
Recessive
Alleles which will be expressed only if homozygous in a body cell and dominant allele not present.
Where does translation occur?
ribosome within the cytoplasm
Where does transcription occur?
Nucleus
What does degenerate mean?
redundant code (codons that encode the same amino acid).
Meselson and stahl experiment
Meselson and stahl originally grew DNA in a culture containing N-15 for several generations so that all the bases contained this isotope. They then grew the DNA in a culture of N-14 for one generation. The DNA is then extracted and separated through centrifugation after 1 and 2 (and more) cell cycles. DNA shifts down the diagram from band A to band D throughout the cycles.
