Protein Synthesis and Mutations

Question 1

What type of bond is formed when two nucleotides undergo a condensation reaction

Answer 1

Phosphodiester

Question 2

What is the role of mRNA

Answer 2

Transfer the genetic info from dna into the ribsones

Question 3

The sequence of bases on one strand of dna is important for protein synthesis. What is its role

Answer 3

determines the sequence of amino acids

Question 4

Why does DNA polymerase go in opposite directions

Answer 4

-DNA has anti parallel strands
-so the nucleotides align differently
-enzymes have specific active sites
-only substrates with complimentary shape can bind

Question 5

Explain how a gene codes for a protein

Answer 5

The base sequence of the dna codes for the amino acids

Question 6

What are homologous chromosomes

Answer 6

Pairs of chromosomes with the genes for the same features at the same loci

Question 7

Degenerate

Answer 7

Several triplets or codons that code for the same amino acid

Question 8

Why is the genetic code described as universal

Answer 8

Because the same triplets or codons code for the same amino acids in all organisms

Question 9

Explain how a change in the dna base sequence for a protein may result in a change

Answer 9

Different sequence of mRNA
Different sequence of amino acids
Hydrogen ionic and disunions binds form j different places do alters the tertiary structure

Question 10

Humans and grasshoppers have very similar % of each base but are very different organisms explain how this is possible

Answer 10

They have different genes
So different amino acids coded for

Question 11

Why is virus dna different to other organisms dna

Answer 11

-a≠t and c≠g
-so no base pair rulings
-so dna is not double standed its single stranded

Question 12

Explain how an activated oestrogen receptor affects the target cell

Answer 12

-The binding of oestrogen changes the shape of the transcription factor
-now allows it to bind to the promotor region
-which stimulates rna polymerase
-so transcription increases

Question 13

Oestrogen only affects target cells. Why can’t it affect other cells in the body

Answer 13

Other cells don’t have oestrogen receptors

Question 14

How does edoxifen reduce the growth rate of breast tumours

Answer 14

-edoxifen has a similar shape to oestrogen
-so binds to the transcription factor which prevents oestrogen from binding
-so RNA polymerase isn’t stimulated so no transcription occurs

Question 15

Suggest why siRNA only affects gene expression in cells infected with HIV

Answer 15

-only infected cells have the mRNA of HIV
-siRNA is only complementary to the mRNA of HIV

Question 16

Why is the mixture cooled down from 95-55 degrees C

Answer 16

To allow primers to join

Question 17

Explain the function of dna primer

Answer 17

Provide a starting sequence for DNA polymerase and prevent the DNA strands from joining back together

Question 18

describe how the proportion of DNA that contained 15N changed at each division when bacteria were grown on the 14N medium

Answer 18

-decreases by 50%
-per division

Question 19

the change in the production of DNA containing 15N is due to the way in which DNA replicates. explain how

Answer 19

-in DNA replication strands separate
-each strand acts as a template for the formation of a new strand
-semi conservative replication pccurs
-so that each starnd is made using 14N

Question 20

describe the structure of the DNA molecule that watson and crick suggested

Answer 20

-two polynucleotide strands
-held together by hydrogen bonds
-strands are twisted together (helical)

Question 21

state the property of DNA that causes it to settle as bands at different positions in a test tube

Answer 21

mass or denisty