genes

Question 1

gene

Answer 1

a unit of DNA which performs one function. Usually equted with the production of one RNA or protein

in order to provide useful function, a gene needs to be:

1. expressed
2. regulated

Question 2

chromosome

Answer 2

a structure in the cell nucleus containg nucelar DNA together with a number of proteins

Question 3

genome

Answer 3

the total DNA contained in an organism, one full copy in each cell

Question 4

‘central dogma’

Answer 4

the process by which the instructions in DNA are converted into a functional product

DNA stores information
RNA reads, decodes and uses that information to make proteins via ribosmes

• DNA synthesis ( replication )
• RNA synthesis ( transcription )
• protein synthesis ( translation )

Question 5

RNA

Answer 5

ribonucleic acid

• ribose sugar
• Uricil instead of Thymine

mRNA - messenger
tRNA - transfer
rRNA - ribosomal 
snRNA - small nuclear 
miRNA - micro

Question 6

codon

Answer 6

a group of 3 DNA nucleotide bases that codes for a specific amino acid

postition 1 = most conserved
posistion 3 = least conserved

Question 7

codon : expression

Answer 7

4 different bases - 64 different codons

3 of the possibe 64 codons are stop codons

remaing 61 codons specify 20 different amino acids

Question 8

genetic code

Answer 8

a collection of codons of DNA and RNA that contains the information for synthesis of proteins

degenerate - more than one codon will code for the same amino acid

universal - same proteins being coded for by a particular base sequence in different organisms

Question 9

gene structure

Answer 9

promotor + START codon

exons : coding sequence
introns : non-coding sequence

terminator + STOP codon

Question 10

transcription

Answer 10

double stranded DNA unwinds - enzyme helicase

single starnd copied into a single stranded mRNA molecule - enzyme RNA polymerase

promotor sequences tells the RNA polymerase where to start and the eterminator tells where to finish

resulting primary mRNA transcript finaly ‘edited’ and introns removed (splicing)

promotors and termintors are used during transcription

Question 11

translation

Answer 11

single starnded mRNA to a protein via transfer RNA ( tRNA ) and ribosomes ( = rRNA + ribosomal proteins )

1. mRNA moves from nucleus ( atttaching to ribosome )
2. tRNA decodes codons into amino acids

during translation protein synthesis always starts with a ‘start’ codon ( often methionine, AUG ) and stops with a ‘stop’ codon ( TAA, TGA or TAG )

start and stop codons are used during translation

Question 12

eubacteria/archaea ( differencesto eukarya )

Answer 12

• rigid outer cell wall
• single cellular compartment
• single circular chromosome attached to the cell wall
• transcribed mRNA is translated directly into proteins

Question 13

eukaryotes ( different to bacteria/archaea )

Answer 13

• internal cytoskeleton
• complex set of internal membranes, subdivide cell into micro-environments specialised for particular functions
• set of linear chromosones located within a nuclear membrane
• transcription in nucleus
• translation in cytoplasm

Question 14

alternative splicing

Answer 14

the process of selecting different combinations of splice sites within a messenger RNA precursor (pre-mRNA) to produce variably spliced mRNAs.