1.3

Question 1

how many genes are expressed in a cell

Answer 1

only a fraction of the genes in a cell are expressed

Question 2

what is gene expression controlled by

Answer 2

gene expression is controlled by the regulation of transcription and translation

Question 3

RNA difference’s between DNA

Answer 3

• RNA is single stranded
• RNA has the same bases a DNA except for uracil which replaces thymine
  -RNA has the sugar ribose whereas DNA has the sugar deoxyribose.

Question 4

mRNA

Answer 4

carries a copy of genetic code of DNA from the nucleus to ribosome

Question 5

rRNA

Answer 5

binds to proteins to form ribosomes

Question 6

tRNA

Answer 6

carries a specific amino acids to the ribosomes

Question 7

what are the complimentry base pairs in transcription.

Answer 7

cytosine + guanine , adenine + uracil

Question 8

1 - TRANSCRIPTION

Answer 8

1. RNA polymerase unwinds DNA and breaks hydrogen bonds between bases.
2. RNA polymerase aligns free RNA nucleotides with there complementry nucleotides on the DNA template strand.
3. The template strand is seperated from the complementry strand.
4. A primary transcript containing exons ( coding regions ) and introns ( noncoding regions ) is produced .
5. introns are removed from this primary transcript
6. exons are spliced together to form mature mRNA.
7. mature mRNA attaches to ribosome

Question 9

2 - TRANSLATION

Answer 9

10 - tRNA carries specific amino acids to the mRNA at a ribosome.

11- Anticodons on tRNA pair with complementry codons on mRNA.

12. tRNA binds to their specific amino acids on the cytoplasm
13. peptide bonds from between amino acids and a polypeptide forms
14. amino acids are alligned into sequence