BIOLOGY 1A03 Chapter Notes - Chapter 19: Rna Splicing, Histone Code, Messenger Rna

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BIOLOGY 1A03 Full Course Notes

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Gene regulation encompasses the ways in which cells control gene expression. Gene expression can be in uenced by chemical modi cation on dna or. The manner in which dna is packaged in the nucleus in eukaryotes provides an important opportunity for regulating gene expression. Regulation at this level of gene expression is determined in part by whether the proteins necessary for transcription can gain physical access to the genes they transcribe. Dna in eukaryotes is packaged as chromatin, a complex of dna, rna, and proteins that gives chromosomes their structures. Dna must be loosened to allow space for transcriptional enzymes and proteins to work. This is accomplished through chromatin remodelling, in which the nucleosomes are repositioned to expose different stretches of dna to the nuclear environment. One way in which chromatin is remodelled is by chemical modi cation of the histones around which dna is wound.

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5. Alpha amanitin is a drug that binds RNA polymerase andprevents it from functioning in the cell (this is the compound thatis found in poison mushrooms). The reason people die when theyconsume alpha amanitin is:

a) Alpha amanitin prevents gene expression from occurring in thecell

b) DNA replication is directly inhibited by alpha amantin

c) Alpha amanitin binds tightly to the messenger RNAs that aremade in the cell, preventing translation

d) Alpha amanitin binds to nuclear pores preventing thetransport of messenger RNA into the cytoplasm

6. In order for transcriptional initiation to begin in E. colithe following elements are needed:

a) an origin and RNA polymerase

b) initiator protein and a promoter

c) the sigma subunit of RNA polymerase and an RNA template

d) RNA polymerase and a promoter

e) helicase and primase

Questions 7 and 8. You are studying two species of closelyrelated snakes, one species lives in sandy desert area and has paletan skin and the species lives in a volcanic rock area and has darkbrown skin. You a sequence the DNA from each type of snake anddiscover a gene encoding a protein that transports pigment into theskin cells. The pigment transporter protein is responsible for skincolor. When you analyze the DNA coding sequence of the pigmenttransporter from each snake you find these two DNA sequences (hashmarks have been added to indicate the reading frame):

pale tan snake: GCG/TTG/GAC/TGC/ACC (DNA template strand)CGC/AAC/CTG/ACG/TGG (complementary strand) dark brown snake:ACG/TTG/GAC/TGC/ACC (DNA template strand) TGC/AAC/CTG/ACG/TGG(complementary strand)

7. From these sequences you conclude:

a) that the amino acid sequence of the pigment transporters forthe two proteins are almost identical

b) that the amino acid sequence of the pigment transporters forthe two proteins are very dissimilar

c) that the amino acid sequence of the pigment transporters forthe two proteins are identical

8. Since the skin color is different in each snake, you concludefrom the sequence data above that:

a) the genetic code in the skin cells in each of these snakes isdifferent

b) the DNA sequence encoding the entire gene for pigmenttransporters in these two snakes is different

c) that one of the codons in the gene for the pigmenttransporter in these two snakes is different

9. You are analyzing eukaryotic cells that have been exposed tothe radioactive uracil. In most cells the radioactive uracil isinitially localized in the nucleus and then moves from the nucleusto the cytoplasm. However, you observe that in some cells theradioactive molecules stay in the nucleus and never arrive in thecytoplasm. This is most likely a defect in:

a) the transcription of the DNA

b) the processing of the mRNA

c) the translation of the RNA

d) the labeling of the RNA

e) the replication of the DNA

10. Which of the following is true of both eukaryotic andbacterial transcription? (select all that are true)
a) Transcription factors must bind the promoter before RNApolymerase initiates transcription

b) Messenger RNAs must be spliced before translation begins inorder to produce the appropriate gene product

c) During transcription only one DNA strand is used as atemplate to make the messenger RNA

d) Termination of transcription occurs when the RNA polymerasetranscribes a hairpin structure in the RNA followed by a string ofU

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What step in DNA replication precedes the pairing of complementary bases?

	A.	polymerization of DNA.
	B.	formation of the histone core.
	C.	mitotic division.
	D.	separation of the two strands.
	E.	joining of the two strands.

In eukaryotes, transcription occurs in the

	A.	ribosome.
	B.	mitochondria.
	C.	cell membrane.
	D.	cytoplasm.
	E.	nucleus.

Normal human body cells contain how many chromosomes?

	A.	46
	B.	22
	C.	23
	D.	44
	E.	42

Hershey and Chase performed an experiment in which they used radioactive isotopes to phosphorus and sulfur to label different components of bacterial viruses. Their results clearly showed that

	A.	the viruses did not contain protein.
	B.	genetic material normally contains radioactive isotopes.
	C.	the viruses did not contain DNA.
	D.	protein was entering into the infected bacteria.
	E.	DNA was entering into the infected bacteria.

A package of histones with DNA wrapped around them forms spherical structures called

	A.	nucleosomes.
	B.	lysosomes.
	C.	ribosomes.
	D.	nucleoli.
	E.	chromatin.

DNA replication

	A.	does not require proteins.
	B.	is constantly happening in a cell.
	C.	occurs in G1 of interphase.
	D.	takes place in the nucleus of the cell.
	E.	occurs in the cytoplasm of the cell.

The two subunits of the ribosome join during

	A.	promotion of transcription.
	B.	initiation of translation.
	C.	termination of transcription.
	D.	termination of translation.
	E.	elongation.

DNA replication of a single DNA molecule is referred to as semiconservative because

	A.	each of the two DNA molecules will consist of one parental strand and one newly synthesized strand.
	B.	all the DNA strands in the two DNA molecules will have both parental and newly synthesized DNA.
	C.	it results in two nonidentical DNA molecules.
	D.	of the two DNA molecules, one is made up totally of parental DNA, while the other is entirely newly synthesized DNA.
	E.	one DNA strand is replicated continuously, while the other must be replicated discontinuously.

The bases are bonded to what part of the backbone of the DNA molecule?

	A.	the 4â carbon atom of the sugar molecule.
	B.	the 3â carbon atom of the sugar molecule.
	C.	the 5â carbon atom of the sugar molecule.
	D.	the 1â carbon atom of the sugar molecule.
	E.	the 2â carbon atom of the sugar molecule.

Chapter 10

1.Outline the history of our knowledge on DNA up to Watson and Crick. What were the main contributions made by each researcherâs key experiment?

2.Explain the setup of the Hershey and Chase experiment, what would the results have been if protein was the genetic material?

3.Draw the structure of a DNA nucleotide, labeling each main component correctly. How does an RNA nucleotide differ?

4.If a section of double stranded DNA contains 19% Adenine, how much Thymine is present?

5.You are a researcher studying the genetic basis of heart attacks and have been working to determine the expression levels of different genes that might contribute to cancer formation. You obtain the DNA methylation status of five genes of interest (the data are shown in the table below). The plus (+) sign indicates the level of DNA methylation; more plus signs correlates with increased methylation levels.Based on this information which genes would you predict to have the highest rate of transcription?

Gene	Methylation levels
1	++
2	+++++
3	+++
4	++
5	+

What are the characteristics of the 3 main DNA forms?

Chapter 11

What are the different types of chromatin?

What are the structures and important roles for telomeres and centromeres?

What are the differences found between eukaryotic chromosomes and mitochondrial?

Chapter 12

Explain each of the different models of replication.

If you grow a culture of bacteria in media with radioactive nucleotides so that all DNA in the cells include radioactive nucleotides and then place the bacteria in new non radioactive media. After two rounds of replication what proportion of the DNA molecules will contain radioactivity?

Summarize the similarities and differences between rolling-circle replication, theta replication and linear eukaryotic replication.

What are the functions of the different DNA polymerases found in eukaryotic cells?

Draw a replication fork and include all key components and orientations. (Leading/lagging strands, DNA helicase, RNA primer and DNA gyrase)

What is the Holliday model of recombination and what are the necessary steps?

Chapter 13

What are the different types of RNA and what roles do they play?

Describe the properties and functions of each of the RNA polymerases and how they differ depending on the organism.

Describe in detail the process and mechanisms of transcription in both prokaryotes and eukaryotes.

Chapter 14

What are the primary purposes of each of the three post transcriptional modifications that occur in eukaryotic cells.

What is alternative splicing and what role does it play in the cell?

How is ribosomal RNA processed after transcription?

How do siRNA and miRNA work, describe/draw out the process in detail.

BIOLOGY 1A03 Chapter Notes - Chapter 19: Rna Splicing, Histone Code, Messenger Rna

BIOLOGY 1A03 Full Course Notes

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