Mutation and Gene Regulation

Question 1

point mutation

Answer 1

one nucleotide is replaced with another

Question 2

missense mutation

Answer 2

One amino acid substituted for another

Question 3

nonsense mutation

Answer 3

premature stop codon

Question 4

Frameshift mutation

Answer 4

all/most amino acids changed

eliminate one letter, all the codons will shift

Question 5

silent mutation

Answer 5

o No change to function

Question 6

how do we get mutations

Answer 6

• Most spontaneously arise during DNA replication
o Can be detected and deleted by DNA repair enzymes (polymerase and others)
o Some slip by
• Other mutations can be induced by exposure to mutagens,

Question 7

mutagens

Answer 7

a substance that causes mutations

Question 8

Radiation induced mutations

Answer 8

• UV rays
• X rays
• Nuclear power plants

Question 9

chemical induced mutations

Answer 9

• Exhaust
• Chemicals in cigarette smoke
• Chemicals in plastics

Question 10

loss-of-function mutations

Answer 10

o Something you could before, but can’t do now
• Missense and frameshift
• Gene is nor expressed
• Gene no longer codes for a functional protein

Question 11

gain of function mutations

Answer 11

o Now do something you didn’t do before or of more of something than you did before
o Mutation in cell cycle control gene now results in more cell division
o Replication of genes on the chromosome leads to greater expression

Question 12

chromosomal mutations

Answer 12

• Large chunks of DNA can be duplicated/moved/mutated/deleted, etc when changes come to the chromosomes themselves
o Chunks of DNA from one chromosome might move to another chromosome

Question 13

genetic regulation

Answer 13

• Almost every cell in your body has your complete genome
• Not all genes are needed all the time in every cell
• Organize compress regulate

Question 14

Cell differentiation

Answer 14

o The process by which cells become specialized for their role in the body
o We start with stem cells, which can become any cell type
o Cells progressively become more and more specialized, until they are well suited to one or a few tasks, but unable to perform others

Question 15

Differentiation

Answer 15

• Starts with a pluripotent stem cell
• During cytokinesis, not all the same cytoplasmic components will end up in each daughter cell
• As the cells divide, different transcriptional programs are turned on via signals from the environment
• Each division is asymmetric: produces one cell that retains its undifferentiated capacity as a stem cell
• The other cell from each cell division acquires new traits through the transcription of genes

Question 16

mechanisms for gene regulation

Answer 16

• Control over RNA polymerase and the initiation of transcription
• Stretches of non-coding DNA that promote or suppress transcription of genes
• Alternations in the structure of chromatin near the gene to make it easier/harder for the transcription enzymes to access the gene

Question 17

transcription factors

Answer 17

o Proteins that recruits RNA polymerase to the promoter sequence of particular genes
o Are often under control of cell signaling cascades

Question 18

histones

Answer 18

• Histones are sticky proteins and are attracted to each other
• Histone attraction can hide the DNA, making it inaccessible for transcription
• Adding acetyl groups to the histones reduces their attraction to each other, spreading out the DNA and making it available for transcription
• Reversible

makes genes more accessible to transcription factors

Question 19

DNA methylation

Answer 19

add methyl groups to the nucleotides themselves, preventing access by DNA polymerase
• DNA methylation is relatively permanent once methylated (even during embryonic development) genes stay that way for life
• DNA methylation is necessary: mutation of methylating enzymes leads to developmental abnormalities

Question 20

other facts about methylation

Answer 20

• Cells pass on methylation to daughter cells
• As a cell differentiates it gains methylation
• New research is able to dedifferentiate skin cells into stem cells buy de-methylation of DNA and addition of other factors

Question 21

alternative splicing

Answer 21

different protein products can be achieved from the same transcript by altering which exons are spliced out

very popular with viruses

Question 22

• RNA processing and breakdown

Answer 22

o Cap and tail length can determine how long a transcript will remain in the cytoplasm, and therefore how much protein will be made

Question 23

initiation of translation

Answer 23

o Cell may make functional RNA but delay the start of translation until conditions are optimal
o Ex: RBCs will not initiate translation unless there is sufficient iron in the cell

Question 24

microRNAs

Answer 24

miRNAs) are partially complementary to mRNAs and inhibit their translation
• low affinity attraction with the mRNA
• will bind temporarily to start inhibition
• will eventually fall off so transcription can continue
• mRNA: UAGCCAGUAC
• siRNA: AUCGCUCAUG

Question 25

short interfering RNAs

Answer 25

• are exactly complementary to mRNAs and cause them to be degraded
• high affinity with mRNA so it will bind for a looong time
• single strand of mRNA will not be translated
• single-double stranded molecule=translation can’t happen

Question 26

preventing translation

Answer 26

• regulatory proteins can tempo. Block until conditions are optimal

Question 27

protein activation

Answer 27

• some proteins are made in an inactive form, and then are activated under the right conditions
 insulin is made in an inactive form, a separate enzyme cleaves it and activates it

Question 28

epigenetic and disease

Answer 28

o Epigenetics appear to play a role in the development of cancer by turning on/off genes that control cell replication
o May play a role in development of type II diabetes (methylation or de-methylation of genes involved in regulating metabolism)
o As we age, we progressively de-methylate our genome. May be linked to increase in cancer