DNA, genes, protein synthesis Flashcards
what are the differences between prokaryotic and eukaryotic DNA?
- Eukaryotes have linear DNA whereas prokayotes have circular DNA
- Eurkaryotes have their DNA in the form on chromosomes in the nucleus whereas prokayotes have their DNA free in the cytoplasm.
- Eukaryotes have their DNA wrapped around proteins called histones which also helps to support the DNA whereas prokayotes have no histones.
- Eukaryotes DNA is longer than prokayotes DNA which is shorter.
- Eukaryoitc DNA and the histone coils up tightly whereas prokaryotic DNA fits into the cell via super-coiling.
what is unique about Mitochondria and Chloroplasts ?
they have their own circular DNA so they bale to produce many proteins and enzymes required for their function.
what is a gene?
a section of DNA
what does a gene code for?
it codes for a polypeptide or for functional RNA (such as tRNA or mRNA)
what is the sequence of amino acids called?
the primary structure
what does a triplet codon code for?
amino acid
what is a genome?
the complete set of genes
what is a proteome?
the complete set of proteins
what is an intron?
sections of DNA that dont code for amino acids
what are exons?
sections of DNA that do code for amino acids
introns get removed during protein synthesis in what way?
splicing
what is an allele?
a different version of the same gene
how many pairs of homologous chromosomes do humans have?
23
what is protein synthesis?
the production of polypeptides (proteins
briefly outline transcription
DNA is copied into mRNA
briefly outline translation
mRNA joins with the ribosome and the code it carries is used to synthesis proteins.
where is mRNA made and what does it carry?
it is made during transcription and it carries the genetic code from the DNA to the ribosome
what us tRNA involved in and what does it carry?
it is involved in translation and it carries the amino acid used to make proteins to the ribosome
Explain the process of Transcription
- DNA helicase breaks the hydrogen bonds separating the DNA strands
- Free complementary RNA nucleotides bind to the exposed bases on the template strand (complementary base pairing)
- RNA polymerase catalyses the condensation reaction that joins the nucelotides together
- H-bonds reform
- This makes pre-mRNA (contains introns)
- Splicing occurs to remove the introns and then the exons join
Explain the process of translation
- mRNA leaves the nucleus via the nuclear pores
- mRNA attaches to the ribosome at the start codon
- Complementary tRNA carrying specific specific amino acids bind to the codon if they have the complementary anti-codon
- amino acids are joined via peptide bonds.
what is the genetic code?
the sequence of base triplets in mRNA which codes for specific amino acids
the genetic code is non-overlapping. What does this mean?
This means that successive triplets are read in order. Each nucleotide is part of only one triplet codon.
what is meant by degenerate?
the same amino acid can be coded for by multiple codons
How many amino acids are there and how many possible combinations are there?
20 amino acids
64 possible combinations
