DNA & RNA, mutations

Question 1

define transformation

Answer 1

a change in genotype and phenotype due to assimilation of external DNA by a cell

Question 2

what is a bacteriophage

Answer 2

a virus that infects bacteria

Question 3

what is the basic concept of DNA replication

Answer 3

1. parent has two complementary strands of DNA
2. first step is the separation of the two DNA strands
3. each parental strand now serves as a template that determines the order of nucleotides along a new complementary strand
4. the nucleotides are connected to form the sugar-phosphate backbones of the new strands

Question 4

what is the leading strand

Answer 4

replicated towards the replication fork

Question 5

what is the lagging strand

Answer 5

replicated away from the replication fork

Question 6

what are Okazaki fragments

Answer 6

the nucleotide pieces that make up the lagging strand

Question 7

what are helicases

Answer 7

enzymes which untwist and separate the DNA helix

Question 8

what is a mismatch repair

Answer 8

incorrectly paired nucleotides are fixed by an enzyme

Question 9

what is nucleotide excision repair

Answer 9

excised DNA section filled in by a polymerase and ligase

Question 10

what is the 5’ problem

Answer 10

as polymerase can only add nucleotides to the 3’ end, there is no way to complete the 5’ end

prokaryotes have circular DNA which avoids this problem
eukaryotes have telomeres

Question 11

what are telomeres

Answer 11

100-1000 repeated short sequences of DNA such as TTAGGG in humans

Question 12

what is telomerase

Answer 12

an enzyme containing RNA which further lengthens the 3’ end to allow completion of the 5’ end

Question 13

what are telomeropathies

Answer 13

disorders which cause premature telomere shortening due to defects in the telomere maintenance machinery

Question 14

what is a triplet code

Answer 14

3 DNA bases code for a single amino acid

Question 15

what is a template strand

Answer 15

the coding strand of DNA for a gene

Question 16

what is a codon

Answer 16

the mRNA triple code for an amino acid

read in the 5’ to 3’ direction

Question 17

what is the role of RNA polymerase

Answer 17

pries apart the DNA helix and hooks together the RNA nucleotides

Question 18

what is a promoter

Answer 18

region of DNA where RNA polymerase attaches and initiates transcription

Question 19

what is the role of introns

Answer 19

• some control the activity of specific genes once excised
• allows alternative RNA splicing, where different sections are excised from pre-RNA to code for different proteins
• allow beneficial crossing-over in non-coding regions

Question 20

what are exons

Answer 20

sections of DNA and RNA that become ‘expressed’ or translated into protein

Question 21

what are introns

Answer 21

intervening, non-expressed regions of DNA and RNA

Question 22

what is the function of the ribosome

Answer 22

acts to couple tRNA and mRNA

Question 23

what are differences in protein synthesis in prokaryotes vs eukaryotes

Answer 23

prokaryotes - transcription and translation of the same mRNA can occur simultaneously
eukaryotes - the nucleus prevents simultaneous transcription and translation, allowing for additional regulation of the cell’s activity

Question 24

define point mutation

Answer 24

changes in one base pair of a gene

Question 25

in terms of mutations, what are substitutions

Answer 25

replacement of one nucleotide and its 'partner' with another pair of nucleotides

Question 26

in terms of mutations, what are silent mutations

Answer 26

no effect on coding proteins

Question 27

in terms of mutations, what are missense mutations

Answer 27

coding protein changes to another non-stop codon can be good or bad

Question 28

in terms of mutations, what are nonsense mutations

Answer 28

coding changes to a stop codon and polypeptide is prematurely terminated almost always bad

Question 29

in terms of mutations, what are insertions / deletions

Answer 29

adding or losing a nucleotide pair in a gene, generally leads to a frameshift mutation, where insertion or deletion is not a multiple of three so amino acids translated incorrectly