information from a1 biology : protein synthesis and it's control

Question 1

what components make up a DNA nucleotide?

Answer 1

phosphate, deoxyribose, organic base

Question 2

what is transcription?

Answer 2

transcription takes place in the nucleus of the cell and involves the formation of pre-mRNA, that is a complementary sequence of bases to the DNA

Question 3

a gene is made up of 756 base pairs, the mRNA transcribed from this gene is only 524 nucleotides long. explain why there is a difference.

Answer 3

pre-mRNA is spliced to remove introns and leave only the coding exons which are used for translation.

Question 4

compare DNA and mRNA

Answer 4

DNA
- double polynucleotide chain
- largest molecule of the three
- double helix shape
- pentose sugar is deoxyribose
- bases found are A, T, C and G
- found in nucleus of cell
- chemically stable

mRNA
- single
- smaller than DNA, bigger than tRNA
- single linear strand
- ribose
- bases found are A, U, C and G
- nucleus and cytoplasm
- unstable

Question 4

define genome

Answer 4

genome- the complete set of genes in a cell including those in mitochondria and/or chloroplasts

Question 5

define proteome

Answer 5

proteome- the full range of proteins produced by the genome. this is sometimes called the complete proteome, in which case the term proteome refers to the proteins produced by a given type of cell under a certain set of conditions.