4.2 DNA and protein synthesis

Question 1

where does protein synthesis occur?

Answer 1

on ribosomes of the RER

Question 2

What are the 2 stages of protein synthesis?

Answer 2

transcription
translation

Question 3

where does transcription occur?

Answer 3

in the nucleus

Question 4

What is transcription?

Answer 4

where one gene on the DNA is copied into mRNA

Question 5

What is translation?

Answer 5

where the mRNA joins with a ribosome and corresponding tRNA molecules bring the specific amnio acid the codon codes for

Question 6

Why is a copy of DNA made (mRNA) in protein synthesis?

Answer 6

DNA is too large to leave the nucleus and mRNA is much shorter and can fit through the nuclear pores

Question 7

Why dont we want the DNA to leave the nucleus?

Answer 7

in the cytoplasms there may be enzymes that could damage the DNA

Question 8

What is the process of Transcription?

Answer 8

1. DNA helix unwinds and unzipps which is catalysed by DNA helicase to expose bases as a template
2. DNA helicase breaks the H bonds between bases - unzipps
3. one DNA chain acts as a template
4. free mRNA nucleotides in the nucleus align with complementary DNA base
5. RNA polymerase moved along the strand of nucleotides forming single standed pre-mRNA
6. mRNA carries complementary codons
7. at the end of the sequence mRNA is detached and DNA rewinds
8. mRNA leaves nucleus where it attaches to ribosomes

Question 9

What does DNA helicase do?

Answer 9

unwinds and unzipps the DNA helix by breaking the H bonds between bases

Question 10

What does RNA polymerase do?

Answer 10

bonds together the RNA nucleotides by phosphodiester bonds to create a new RNA polymer of the genes thats been copied

Question 11

Why is the mRNA in transcription called pre-mRNA?

Answer 11

it has to be modified before it can leave the nucleus

Question 12

What is splicing?

Answer 12

removing introns

Question 13

What protein is responsible for Splicing?

Answer 13

a splicesome

Question 14

how does a splicesome work?

Answer 14

attaches to DNA
it splices and breaks the phosphodiester bonds so therefore splices out the introns

Question 15

What happens during translation?

Answer 15

the polypeptide chain is created using the mRNA base sequence and the tRNA

Question 16

Where does translation occur?

Answer 16

in the cytoplasm

Question 17

What is thr role of the ribosome in translation?

Answer 17

it holds the mRNA and tRNA in place

Question 18

How many tRNA molecules can the ribosome hold at one time?

Answer 18

2

Question 19

Why is ATP required in translation?

Answer 19

to make the peptide bond between amino acids

Question 20

where does splicing occur?

Answer 20

in the nucleus

Question 21

What is made after splicing?

Answer 21

mature-mRNA

Question 22

In what type of cell does splicing occur in?

Answer 22

eukaryotes

Question 23

What are the differences of DNA replication and transcription?

Answer 23

DNA polymerase in DNA rep, RNA polymerase in transcript
1 template strand in transcript, 2 template strands in DNA rep
free DNA nucleotides in rep, free RNA nucleotides in transcript

Question 24

What is the process of translation?

Answer 24

1. mRNA attaches to the ribosome
2. tRNA brings its specific amino acid
3. tRNA anticodon are complementary to mRNA codon
4. another tRNA molecule brings its amino acid to the mRNA codon at the ribosome site
5. amino acids join together by peptide bonds with the use of ATP
6. ribosome moves along to the next codon and the process repeats until a stop codon is reached, forming a polypeptide chain,

Question 25

Where is the amino acid attachmtn site on the tRNA?

Answer 25

at the opposite end to its anticodon

Question 26

What indicates what direction the mRNA should be read?

Answer 26

a start codon

Question 27

what is a proteome?

Answer 27

The number of different proteins the genome can code for

Question 28

What occurs during post transcriptional modification?

Answer 28

1. removal of methionine from the start of the primary structure 2. RER buds off as transport vesibles containing the polypeptide to be transferred to the golgi body

Question 29

What happens to the polypeptide in the golgi body?

Answer 29

1. chemical modification - adding a functional group 2. packages it into lysosomes or secretory vesicles

Question 30

What do lysosomes do?

Answer 30

contain hydrollytic enzymes, lysosymes, that digest the bacterial cell wall made of murein

Question 31

What is the chemical group on the end of the polypeptide chain?

Answer 31

the amine group

Question 32

How are tRNA and mRNA similar?

Answer 32

single stranded adenine and uracil base pair made of ribose unpaired bases

Question 33

How are tRNA and mRNA different?

Answer 33

H bonds in tRNA, phosphodiester bonds in mRNA clover structure in tRNA amino acid attachment point in tRNA

Question 34

What is meiosis also known as?

Answer 34

reduction divison

Question 35

Why is meiosis referred to as reduction division?

Answer 35

the number of chromosomes halves

Question 36

How are amino acids added to a polypeptide chain during translation?

Answer 36

TRNA brings specific amino acid to ribosome  Anticodon on tRNA binds to codon   Amino acids join by condensation reaction 

Question 37

What are 2 molecules ribosomes are made of?

Answer 37

nucleic cids and proteins

Question 38

What is the role of a ribosome during in the formation of a poylypeptide?

Answer 38

1. mRNA binds to ribosome 2. codons at the binding site 3. allows tRNA with anticodons to bind 4. catalyses formation of peptide bond between amino acids 5. moves along mRNA to next codon

Question 39

Where are the non-coding regions multiple repeats positioned in the genome?

Answer 39

positioned between genes