gene expression

Question 1

types of RNA

Answer 1

tRNA, mRNA, rRNA

Question 2

RNA

Answer 2

single stranded molc that’s responsible for carrying the code and making protein synthesis possible
- has a ribose sugar, phosphate, base

Question 3

mRNA

Answer 3

carries complementary copy of DNA code from nucleus to ribosome in the cytoplasm
- at the ribosome its translated into proteins

Question 4

tRNA

Answer 4

carries its specific amino acid to ribosome
- has a triplet base called anticodon at one end of the amino acid attachment site to the other
- looped structure

Question 5

rRNA

Answer 5

• small spherical structures
• subunits consisting of ribosomal RNA and associated proteins
• translation occurs here

Question 6

difference between DNA and RNA

Answer 6

DNA - 2 stands, double stranded helix shape, in nucleus

RNA - 1 strand, can be folded into many shapes, in nucleus, cytoplasm and part of ribosomes

Question 7

what is transcription

Answer 7

process where a primary mRNA transcript is produced from a molecule of DNA within the nucleus

Question 8

stages of transcription

Answer 8

1. RNA polymerase moves along DNA unwinding double helix and breaking H bonds between bases
2. one DNA stand acts as template strand
3. RNA polymerase synthesises a primary transcript of mRNA using free RNA nucleotides
4. complementary base pairing between DNA temp strand and synthesised mRNA which produces primary mRNA transcript
5. RNA polymerase adds on nucleotides onto the 3’ end of growing mRNA chain
6. primary mRNA transcript produced and released from DNA

Question 9

introns

Answer 9

non-coding regions of primary transcript which are removed

Question 10

exons

Answer 10

coding regions of genes joined together to form mature transcript
- order unchanged during splicing

Question 11

RNA splicing

Answer 11

1. introns are removed after mRNA is transcribed
2. remaining exons are joined together forming continuous sequence called mature mRNA transcript
3. mature mRNA transcript leaves nucleus to cytoplasm and moves to ribosomes carrying complementary code

Question 12

what’s translation and where does it take place

Answer 12

the synthesis of a protein from specific amino acids using mRNA code
- in ribosomes

Question 13

translation stages

Answer 13

1. ribosomal RNA units bind around mRNA strand
2. tRNA mol carry specific amino acids to ribosome
3. codons on mRNA temporarily bond to anticodons of tRNA by complementary base pairing
4. peptide bond joins amino acids together
5. genetic code of mRNA is translated into sequence of amino acids

Question 14

how is polypeptide formed

Answer 14

by a long chain of amino acids

Question 15

how is a polypeptide formed

Answer 15

• tRNA molc carry amino acid to ribosome
• anticodon binds to complementary codon on mRNA
• new amino acid is brought by tRNA and peptide bond formed between adjacent amino acids
• mRNA releases amino acid then leaves the ribosome and polypeptide is formed

Question 16

3 stop codons on mRNA

Answer 16

UAA, UAG, UGA
don’t code for amino acid but allow polypeptide to detach and release from ribosome

Question 17

start codon

Answer 17

indicates where translation of mRNA should begin

Question 18

alternative RNA splicing

Answer 18

different proteins can be expressed from one gene
this is by:
- different axons being spliced together to produce diff mature RNA transcripts
- different proteins also produced as diff base triplets code for diff combo of amino acids

Question 19

primary transcript of mRNA contains

Answer 19

introns and exons

Question 20

same primary transcript can produce…

Answer 20

different mature mRNA transcripts

Question 21

phenotype

Answer 21

physical attributes of an organism

Question 22

genotype

Answer 22

combination of genes an organism possesses