dna

Question 1

charged amino acid

Answer 1

glutamic acid

Question 2

3 types of substitutions mutations

Answer 2

1. silent - no change in aa code
2. missense - still code for an amino acid, but not necessarily the right one
3. nonsense - change an amino acid codon into a stop codon

Question 3

what are insertions or deletions

Answer 3

additions or losses of nucleotide pairs in a gene
- have a disastrous effect on the resulting protein more often than substitutions
- may alter the reading frame, producing a frameshift mutation

Question 4

control of gene expression in prokaryotes

Answer 4

operons = A cluster of functionally related genes can be under coordinated control by a single on-off “switch” - the switch = OPERATOR - generally found within promoter

Question 5

2 types of regulation of gene expression in prokaryotes

Answer 5

positive and negative

Question 6

whats negative regulation of gene expression

Answer 6

uses 2 types of repressors that block RNA polymerase
- repressible - usually on (trp operon)
- inducible - usually off (lac operon)

Question 7

repressible type of repressor

Answer 7

e.g. trp operon
- generally on
- anabolic metabolism
- compressor helper - tryptophan

Question 8

whats in every lactose

Answer 8

1,6 allolactose

Question 9

inducible type of repressor

Answer 9

e.g. lac operon
- generally off
- catabolic metabolism
- inducer helper - allolactose

Question 10

whats positive regulation of gene expression in prokaryotes

Answer 10

• CAP) = an activator of transcription - stimulatory protein
• When glucose is scarce, CAP is activated by binding with cyclic AMP
• Activated CAP attaches to the promoter of the lac operon + increases the affinity of RNA polymerase, thus accelerating transcription

Question 11

what happens when glucose levels are low

Answer 11

cyclic AMP levels are high - high levels of transcription

Question 12

what happens when glucose levels are high

Answer 12

cyclic AMP levels are low - low levels of transcription

Question 13

DNA organization

Answer 13

DNA -> HISTONES -> NUCLEOSOMES -> CHROMATIN

Question 14

control of gene expression in eukaryotes

Answer 14

• regulation of chromatin structure
• histone modification
• DNA methylation

Question 15

regulation of chromatin structures

Answer 15

• genes can be packed into EUCHROMATIN (open / on) + HETEROCHROMATIN (closed / off)

Question 16

histone modifications

Answer 16

• histone acetylation: acetyl groups are attached to positively charged lysines in histone tails - loosens chromatin structure - promotes initiation of transcription
• methylation: addition of methyl groups can condense chromatin
• phosphorylation: addition of phosphate groups next to a methylated amino acid can loosen chromatin
• HISTONE CODE HYPOTHESIS - specific combinations of modifications help determine chromatin configuration and influence transcription

Question 17

DNA methylation

Answer 17

add methyl groups to certain C bases
- can cause long-term inactivation of genes
- it is transgenerational

Question 18

regulation of transcription initiation

Answer 18

CONTROL ELEMENTS = segments of non-coding DNA that bind transcription factors
- ENHANCERS = may be far away from a gene or even located in an intron
- PROXIMAL CONTROL ELEMENTS = located close to the promoter
- activator - binds to an enhancer and stimulates transcription of a gene
- repressors - inhibiting expression of a particular gene

Question 19

Combinatorial control of gene activation

Question 20

mechanisms of post transcriptional gene regulation

Answer 20

allow a cell to fine-tune gene expression rapidly in response to environmental changes e.g. Gcap, splicing, mRNA degradation (mRNA can exist in the cytoplasm for long time)

Question 21

imitation of translation

Answer 21

mRNAs can be blocked by:
- RNA structure
- proteins
- other RNAs

Question 22

protein processing and degradation

Answer 22

After translation, various types of protein processing e.g. cleavage + the addition of chemical groups, are subject to control
- PROTEASOMES = giant complexes that bind protein molecules and degrade them

Question 23

2 types of RNAs that alter gene expression

Answer 23

• Micro RNAs (miRNAs) - bind to mRNA and degrade it / block its translation
• Small intefering RNAs (siRNAs) - bind to chromatin - form heterochromatin