Genetics Quiz 2 Study

Question 1

Mutations can have a positive, negative, no effect, or all of the above?

Answer 1

All of the above

Question 2

Mutations are caused by?

Answer 2

Spontaneous replication errors, Spontaneous chemical changes, Radiation, or can be chemically induced.

Question 3

Mutations that are somatic changes (i.e. changes in the body or cells due to epigenetic/environmental influences) will or will not be inherited?

Answer 3

Will not be inherited as they are classified as somatic mutations, thus not part of the genome.

Question 4

What are the 3 types of point mutations?

Answer 4

1: Missense mutation - changes the amino acid2: Silent mutation - no changes in amino acid due to the ‘wobble’ effect3: Nonsense mutations - changes amino acid to a translational stop codon

Question 5

Insertions or deletions are what type of mutations?

Answer 5

Frameshift mutations.

Question 6

How do non-frameshift mutations differ from traditional mutations?

Answer 6

They shift the amino acid sequence by 3 or multiples of 3 base pairs. This does not shift the frame, but it does mean the protein sequence will have additional or missing amino acids.

Question 7

What is transposition?

Answer 7

A special kind of mutation whereby the movement of a small segment of DNA (transposable element) moves from one position to another in the genome.

Question 8

If you have two mutations in a gene, one mutation from codon X to codon Y whereby X and Y have a similar acidic/non-acidic structure, and another mutation whereby codon A and codon B have very different amino acid structures, which one is more likely to be the cause of the mutation?

Answer 8

The codons that create amino acids with very different structures.

Question 9

Would a premature stop codon more likely create a larger or small protein length?

Answer 9

Most likely it will create a truncated/shorter protein. In some rare cases, it can create a larger protein, but there’d likely have to be an issue with the stop codon for that to happen.

Question 10

When DNA polymerase reaches the nucleotides encoding for the premature stop codon it will?
A. stop when it reaches the first nucleotide encoding for the premature stop codon.
B. stop when it reaches the last nucleotide encoding for the premature stop codon.
C. not be affected by this base change and will continue to read through the mutation.

Answer 10

C. not be affected by this base change and will continue to read through the mutation.Reason: DNA polymerase is the enzyme responsible for synthesizing DNA strands; it reads the template strand and adds complementary nucleotides to the growing DNA strand. DNA polymerase’s activity is not directly affected by the coding sequence of the DNA, including regions that may code for stop codons. Stop codons are relevant during the process of translation, not DNA replication.

Question 11

The 5’ UTR is before the start codon, but after the promoter and transcription start site? True or false

Answer 11

True

Question 12

The promoter is?

Answer 12

The promoter is the DNA sequence where RNA polymerase binds to initiate transcription.

Question 13

The transcription start site is?

Answer 13

The transcription start site is the first nucleotide that gets transcribed into RNA.

Question 14

The 5’ UTR is?

Answer 14

The 5’ UTR is a region of the mRNA that is transcribed from DNA and is upstream (5’) of the start codon, which signals the beginning of the protein-coding sequence. The 5’ UTR plays a critical role in the regulation of translation, influencing how efficiently ribosomes bind and initiate protein synthesis.

Question 15

A stop codon is?

Answer 15

A stop codon is a nucleotide triplet within mRNA that signals the termination of protein synthesis. There are three stop codons - UAA, UAG, and UGA - that do not code for any amino acid, effectively instructing the ribosome to stop translation. When a ribosome encounters a stop codon during translation, it triggers the release of the newly synthesized protein and the dissociation of the ribosomal subunits from the mRNA.

Question 16

The transcription termination site is?

Answer 16

The transcription termination site is a specific sequence of nucleotides in the DNA that signals the end of transcription to RNA polymerase, the enzyme responsible for synthesizing RNA from the DNA template. Upon reaching this site, RNA polymerase and the newly synthesized RNA transcript are released from the DNA, marking the conclusion of the transcription process.

Question 17

In which region could you find a regulatory sequence?
a) promoter region
b) exon 2
c) intron 2
d) between the stop codon and transcription termination site?
e) all of the above

Answer 17

e) all of the above.

Regulatory sequences can be found in multiple regions relative to a gene, as they play various roles in controlling gene expression. Here’s how each option relates to regulatory sequences:

a) Promoter region - This is a primary regulatory sequence where transcription factors and RNA polymerase bind to initiate transcription. It is crucial for the regulation of gene expression.

b) Exon 2 - While exons primarily contain coding sequences for proteins, regulatory elements can also be found within exons, affecting mRNA splicing or translation efficiency.

c) Intron 2 - Introns can contain regulatory sequences such as enhancers, silencers, or elements that influence RNA splicing, thereby indirectly affecting gene expression.

d) Between the stop codon and transcription termination site - This region can contain regulatory sequences that influence the process of transcription termination or the stability and localization of mRNA.

Thus, regulatory sequences can be found in all the options provided, each playing different roles in the regulation of gene expression.

Question 18

What are the 4 main levels gene regulation can occur at?

Answer 18

1) transcriptional
2) post-transcriptional
3) translational
4) post-translation

Question 19

Give examples for the 4 types of gene regulation

Answer 19

1) transcriptional: chromatin remodeling, DNA methylation, transcription factors

2) post-transcriptional: alternative splicing, mRNA transport, mRNA stability

3) translational: initiation factors, miRNA’s, mRNA accessibility

4) post-translational: protein stability, protein modification

Question 20

What are the differences between activators/repressors vs enhancers/silencers?

Answer 20

Activators/repressors are proteins that affect transcription while enhancers and silencers are DNA elements that can increase/decrease transcriptional amounts.

Question 21

Histone acetylation causes DNA to unwind? True or False

Answer 21

True, histone acetylase (HAT) makes the gene more accessible and less condensed.

Question 22

If a histone is deaceytlated, it will not unwind, and thus transcription will occur? True or False

Answer 22

False. Histones need to be acetylated to unwind, which allows the transcription machinery to do its work.

Question 23

HDAc helps to unwind the DNA?

Answer 23

False. Histone deacteylase removes the acetyl group which is what allows the DNA to unwind.

Question 24

Define a form of alternative splicing?

Answer 24

Cell specific proteins can bind to the 5’ or 3’ splice site, and block them, thus causing the spliceosome to alternate towards another site.

Question 25

By removing the 5’ cap, you will increase mRNA stability? True or False

Answer 25

False - removing the 5’ cap decreases the stability of the mRNA leaving it vulnerable to attack by exoribonucleases which can degrade it.

Question 26

Lengthening the poly A tail or the binding of proteins increases the mRNA stability? True or False

Answer 26

True, the longer the poly A tail, the more stable the mRNA is from producing an accurate location for transcription to stop.

Question 27

Name two types of non-coding RNA’s involved in post-transcriptional regulation.

Answer 27

siRNA’s and miRNA’s.

siRNA’s are used to protect cells from viral RNA’s used to target mRNA’s for degradation, thus inhibiting certain genes from getting expressed

miRNA’s are important for mRNA gene regulation by inhibiting mRNA’s from being translated, or also targeting a specific mRNA for degradation.

Question 28

Protein modifications only increase protein activity? True or False

Answer 28

False, protein modifications can either increase or decrease protein activity, thus affecting post-translational gene expression.

An example is phosphorylation which can modify the the activity of the proteins, like PKA in GPCR’s.

Question 29

Please explain what ubiquitin does to protein modification and gene expression?

Answer 29

Ubiquitin tags specific proteins for degradation and is part of the natural cycle for proteins to be degraded. So a protein is set to be degraded by its natural cycle, and it will get tagged by ubiquitin. This will connect to the protein so when it enters a proteasome, the proteasome will recycle the components by breaking them down into fragments to be used again.

Question 30

From the list below, which represent post-translational regulation?
A. Binding of a “silencer” transcription factor to a DNA regulatory
sequence.
B. Activation of a protein kinase by phosphorylation.
C. Binding of a protein to the 3’UTR of the mature mRNA.
D. Decreasing the level of an mRNA through RNA interference

Answer 30

B - post-translational regulation involves specific changes to the proteins made from translation. All of the other choices involve prior aspects of gene regulation (A = transcriptional factors/regulation, C = same, D = post-transcriptional regulation via siRNA or miRNA)