Chapter 6:nucleic acids and protein synthesis(transcription Notes Got Deleted)

Question 1

What is a purine

Answer 1

2 carbon nitrogen rings.
Adenine and Guanine

Question 2

What is a pyramidine

Answer 2

1 carbon nitrogen ring.
Thymine, cystosine and Uracil

Question 3

Which two nitrogenous bases form 2 hydorgen bonds

Answer 3

Adenine and theymine

Question 4

Which two nitrogenous bases form 3 hydorgen bonds

Answer 4

Guanine and cytosine

Question 5

Give a property of hydrogen bonding in dna and why it’s useful

Answer 5

Individual bonds are weak, so strands can be separated easily which is important for transcription and dna replication

Question 6

Describe the structure of dna

Answer 6

-double helix structure
-made up of 2 polynucleotide strands, (each strand made up of deoxyribose sugars and phosphate groups bonded together to form a sugar phosphate backbone)
-both strands are antiparrallel to each other

Question 8

What is a gene, in detail

Answer 8

Specific sequence of nucleotide bases that codes for a specific sequence of amino acids that codes for production of s specific polypeptide

Question 9

What direction does dna polymerase move and what direction does rna polymerase move

Answer 9

DNA polymerase moves 5’ to 3’.
RNA polymerase moves 3’ to 5’

Question 10

What is transcription

Answer 10

Process of producing an mRNA molecule form a section of the template strand in dna

Question 11

Explain the 4 properties of the genetic code

Answer 11

-degenerate,
More than one triplet can code for one amino acid
(64 [ossibel cominations are possible even tho only need to code for 20 amino acids)
-universal
Same triplet can code for same amino acid in all organisms
(Therfore dna can be transferred eg in genetic engineering)
-non overlapping
-each base is read only once as part of a single triplet
—sequential
Sequence of amino acids stays in the same order

Question 12

The transcribed strand in transcription is the same as…. And the non tarsancribe strand is the same as…

Answer 12

Transcribed= antisense (think of it as anticodons bind to this)or as the non coding strand
Noun transcribed =sense strand, or coding strand (bc mRNA molecule produced has same base sequence as this)

Question 13

What is the starrt codon in dna and what amino acid does this code for

Answer 13

AUG, methionine

Question 14

What is a stop codon

Answer 14

Signal the end of translation , so stops the formation of the polypteide chain,
Bc it has no commentary anticodons

Question 15

The mRNA molecule formed during translation, has same sequence as…

Answer 15

The non transcribed strand, (sense strand), except thymine is replaced with uracil

Question 16

Explain the process of transcription

Answer 16

-Section of dna where the gene to be transcribed unwinds because hydrogen bonds between complimentary base pairs are broken by dna helicase
-only one of the strands is used as the template strand or transcribed strand to make the mRNA molecule, and the other one is called non transcribed strand
-free activated mRNA nuelcyodies base pair with combinatory bases on template strand though hydorgen bonds
-rna polymerase catalyses fomrtasion of phsosphodtser bonds between rna nucleotides to form sugar hsophate backbone of mRNA molecule (and its moves 3 prime to 5 prime)
-once gene has been transcribed, hydorgen bonds break and mRNA molecule leaves nucleus through a pore in the nuclear envelope

Question 17

What is translation

Answer 17

Process where sequence of bases in mRNA is converted into a sequence of amino acids to form polypeptide chain

Question 18

Explain process of translation

Answer 18

-mRNA molecule leaves nucleus and bins to small subunit on ribosome at the start codon of the mRNA, which is AUG, methionine
-TRNA meocluels, which has one side with anticodons on it and one side with an specific amino acid on it binds to large subunit n the ribosome
-tRNA binds bind to first anticodons on mRNA though comoliematry base pairing forming hydorgen bonds with mRNA molecule
-another tRNA molecules binds to second codon on mRNA (two tRNA molecules can fit in ribosome at one time)
-amino acids join by peptide bonds in condensation reactions
-tRNA molecule the detaches form amino acids
-new Trna molecules come and bring amino acids and process is repeated until a stop codon is produced and polypeptide chia is formed

Question 19

What is post transcription modification,(splicing)

Answer 19

Occurs after transcription in ekurotes, a Process where introns, non coding dna, are removed from the pre mRNA meocluels and the remaining exons, coding dna, are joined together to produce a mature mRNA meocluel.

Question 20

What is another word for the pre mRNA molecule in eukaryotes in the process of splicing

Answer 20

Primary transcript

Question 21

Explain which organisms splicing occurs in.

Answer 21

-in eukaryotes, because they have both coding and non coding sequences of dna.
So exons and introns.
Prokaryotes do not have this howver, they only have coding dna

Question 22

What are introns what are exons

Answer 22

Introns= non coding dna, removed in splicing
Exons= coding dna=fuse together in splicing to form mature mRNA in eukaryotes

Question 23

What substances can cause mutations

Answer 23

Ionizing radiation,
Chemicals

(This is diff to substances that form tumors, which are ionizing radiation and VIRUSES EG HIV)

Question 24

What is a gene mutation

Answer 24

A change. In the sequence of dna base pairs in a dna molecule, so a gene, which can result in an altered polypeptide

Question 25

Explain why most mutations do not alter the polypeptide chain

Answer 25

Because the genetic code is degenerate, so more than one triplet can code for an amino acid

Question 26

Explain how a mutation can alter a protein, beginning from a dna molecule to a protein

Answer 26

DNA molecule base sequence changed,
Altered codons in mRNA
So diff tRNA, so diff amino acid is brought
-change to polypeptide chain
-so change to primary structure and so diff protein is produced

Question 27

What is a substituon mutation, and state the three types

Answer 27

Mutation where a base in the dna sequence is randomly swapped for a different base.
Silent mutation, misense mutation and nonsense mutation

Question 28

What is a silent mutation

Answer 28

Where the different codon produced still produces the same amino acid, so polypeptide chain is not altered.
-this is bc genetic code is degenerate so more than one codon can code for same amino acid

Question 29

What is a misense mutation

Answer 29

Where one base is changed form dna sequence, and only one amino acid form polypeptide chain is changed,
Faulty protein is produced which may still be functional howver,
Example is sickle cell anemia

Question 30

What is a nonsense mutation

Answer 30

When one base sequence from dna is changed, and so a premature stop codon is produced, so translation of mRNA molecule stops and polypeptide chain is incomplete.
Protein produced in non functional
Example is cystic fibrosis

Question 31

What is deletion/insertion mutation

Answer 31

Mutation taht occurs when one nucleotide and therfore its base is inserted or deleted from the dna sequence and so this causes a frame shift mutation,
-bc subsequent amino acids will change and so diff polypeptide chain produced