biology paper 1 Flashcards
genetics, biodiversity, classification (23 cards)
three components of a nucleotide
pentose sugar, phosphate group, organic base
describe structure of dna
- deoxyribose sugar
- phosphate group
- one of four organic bases (A-T, C-G)
- double stranded
- hydrogen bonds between bases form a helix shape
role of dna
- carries genetic information
- determines our inherited characteristics
structure of rna
- ribose sugar
- phosphate group
- one of four organic bases (A-U, C-G)
- single stranded
role of rna
transfers genetic information from dna to ribosomes for protein synthesis
which bases are purine and which are pyrimidine
purine (double ring) = adenine, guanine
pyrimidine (single ring) = cytosine, thymine, uracil
how is dna in eukaryotic cells different from that of prokaryotic cells
eukaryotic cells = found in nucleus, long and linear, associated with histone proteins to form chromosomes. mitochondria and chloroplasts contain prokaryotic-like dna
prokaryotic cells = short and circular, not associated with proteins
what is the genetic code
order of bases on dna, consists of codons (triplets of bases which code for a specific amino acid)
features of the genetic code
- non overlapping (each triplet only read once)
- degenerate = more than one triplet codes for the same amino acid
- universal = same bases and sequences used by all species
what is a gene
- sequence of bases on a dna molecule that codes for a specific sequence of amino acids to make a polypeptide
- can also code for functional rna
what is a locus
fixed position on a dna molecule occupied by a gene
what is an allele
different versions of the same gene, found at the same locus on a chromosome
what are exons and introns
coding and non-coding parts of dna
- exons are non-coding
- introns are coding
where are introns found
between exons within genes
what is the genome
complete set of genetic information contained in the cells of an organism
what is the proteome
complete set of proteins that can be produced by a cell
describe the structure of messenger rna (mRNA)
- long, single strand
- base sequence is complementary to the DNA that it was transcribed from
advantages of using mrna rather than dna for translation
- shorter and contains uracil = breaks down quickly so no excess polypeptide forms
- single stranded and linear = ribosome moves along strand and tRNA binds to exposed bases
- contains no introns
describe the structure of transfer rna (tRNA)
- single strand of around 80 nucleotides that is folded into a clover-leaf shape
- on one end is an anti-codon, on the opposite end is an amino acid binding site
what is produced by transcription
mRNA
where does transcription take place
in the nucleus
process of transcription
- dna uncoils into two strands with exposed bases. one is used as a template
- free nucleotides line up next to their complementary bases and are joined together by rna polymerase
what happens to mRNA after transcription
