3.10 Protein Synthesis

Why must the genetic code be copied onto mRNA?

DNA is too large to leave the nucleus, and proteins are synthesised by ribosome in the cytoplasm

What is the difference in the proteins made by ribosomes found on RER compared to proteins made by ribosomes that float in the cytoplasm?

ribosomes on the RER synthesise proteins which are later modified and packaged by the Golgi apparatus to be packaged into vesicle for excretion by exocytosis, whereas ribosome that float freely in the cytoplasm synthesis proteins that remain and are used within the cell, so aren’t packaged into vesicles

What is transcription?

the process by which the base sequence of a gene is converted into a complementary sequence of mRNA

What enzyme can ‘unzip’ a DNA molecule?

DNA helicase

How does the enzyme DNA helicase ‘unzip’ the DNA molecule?

it breaks the hydrogen bonds between the complementary base pairs

Which enzyme joins adjacent nucleotides by phosphodiester bonds during transcription?

DNA polymerase

Where does the mRNA pass through to leave the nucleus?

a nuclear pore

In transscription, what is the name of the strand that the free mRNA nucleotides binds to?

template strand

Fill in the blanks: At the start of transcription, the part of the DNA molecule, in the region of the gene, ____ and is _____ by the enzyme ____ breaking the ____ bonds between _____ ____.

unwinds, unzipped, DNA helicase, hydrogen, complementary bases

True or false: only 1 of the 2 strands of DNA contains the gene

true

Fill in the blanks: The gene being copied in transcription is found on the ____ strand. The other strand, the ____ strand is a ____ copy of the strand containing the gene. Free mRNA nucleotides from complementary base paires with the unpaired bases of the ____ strand.

coding, template, complementary, template

In transcription, describe the bonding between unpaired bases of DNA and RNA nucleotides?

A joins to U by 3 hydrogen bonds and C joins to G by 2 hydrogen bonds, always purine to pyrimidine

Fill in the blanks: In transcription, once the free RNA nucleotides have paired with the unpaired DNA bases, the enzyme ____ joins (a)____ nucleotides by ______ bonds, forming a (s) _____ (b)____ of the single strand of RNA, that is complementary to the ____ strand and a copy of the ____ strand.

RNA polymerase, adjacent, phosphodiester, sugar-phosphate backbone, template, coding

Fill in the blanks: Translation the assembly of ____ chains at the ___ based on the sequence of c____

polypeptide, ribosome, codons

Where in the cell are ribosomes formed?

nucleolus

True or false? In eukaryotic and prokaryotic cells, ribosomes are made of 2 subunits, one large and one small

false - only in eukaryotic cells

What are the subunits of ribosomes made of?

rRNA and proteins