BIO SCI 98 Lecture Notes - Lecture 1: Ribosomal Rna, Transfer Rna, Uracil

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blushmammoth506

19 Jun 2018

School

UC-Irvine

Department

Biological Sciences

Course

BIO SCI 98

Professor

RAZORENOVA/INLAY/MORRISETTE

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CHAPTERS 6 (192-203),15 (pp. 520-546) & 16 (pp. 554-562)

The central dogma

Replication = DNA → Transcription = RNA → Translation = protein

50 X 10^12 = 50 trillion

Gene expression: large scale, tightly controlled

Humans: 50 x 1012 cells, each with the same 30,000 genes

Our proteins are 99% similar to chimpanzee proteins

Transcription

-The process by which genetic information represented by a sequence of DNA nucleotides

is copied into newly synthesized molecules of RNA, with the DNA serving as a template

Replication (DNA) Transcription (RNA)

- both strands of DNA are copied

(complementary sequences)

- all DNA is copied (the entire genome)

- primer needed for DNA polymerase to

synthesize complementary strand 5' → 3'

- bases are A, T, C, G

- Selective stretches of DNA are copied into

RNA

- only one strand of DNA is used as a

template

- RNA polymerases do not require a primer

for complementary RNA synthesis

- template is copied 3' → 5' to make 5' → 3'

RNA

- Bases are A, U, C, G

RNA forms

-Messenger RNA

-Transfer RNA

-Ribosomal RNA

-Other RNAs (snRNPs, etc)

-We will focus mainly on mRNA transcription (directs protein synthesis)

Chemical differences between RNA and DNA

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The inherent chemical properties of the nucleotide bases and of the sugar backbone are key to

the specific functions of DNA (long-lived, stable) and RNA (short-lived, labile)

Uracil belongs in RNA

-DNAs are long-lasting while RNAs are short lived

-Uracil is "cheaper" for RNAs because it is structurally simpler than thymine

-Less energy to make

Uracil wouldn't work in DNA

-Cytosine in DNA can deaminate and become uracil

-If uracil were used in DNA in place of thymine, repair enzymes would not be able to

distinguish the appropriate use of this base from deaminated cytosine

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Function Follows Chemistry

-The nucleic backbone of RNA and DNA is broken down by non-enzymatic hydrolysis

-DNA is the genome (mostly)

-Genome is the master copy of the instructions to build organism and must be

stable over long periods of time

-Deoxyribonucleic acid backbone is much less prone to hydrolysis than the

ribonucleic backbone

-RNA is the adaptable message (mostly)

-RNA transcripts vary in abundance in response to developmental or

environmental cues

-RNA is most responsive if it is unstable and rapidly degraded

-RNA is susceptible to hydrolysis and is short lived

Transcription

-Direction of transcription: 5' → 3' synthesis

-The enzymatic production of an exact complementary copy of RNA on DNA template

-Protein coding regions: mRNA

-Non-protein coding regions: RNAs used in riboproteins

-(rRNAs, tRNAs, splicing factors)

-Selectively copies parts of the DNA genome into RNAs

-Begins at the promoter

-Region of DNA required for transcription initiation

-RNA polymerase binds to promoter to initiate transcription

-Promoters have specific DNA sequences that are recognized by RNA polymerase in

combination with transcription factors

-ATG/Met start codon is downstream of the transcription start site (TSS, +1) where

mRNA begins

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Document Summary

Replication = dna transcription = rna translation = protein. Humans: 50 x 1012 cells, each with the same 30,000 genes. Our proteins are 99% similar to chimpanzee proteins. The process by which genetic information represented by a sequence of dna nucleotides is copied into newly synthesized molecules of rna, with the dna serving as a template. Both strands of dna are copied (complementary sequences) All dna is copied (the entire genome) Primer needed for dna polymerase to synthesize complementary strand 5" 3" Selective stretches of dna are copied into. Only one strand of dna is used as a template. Rna polymerases do not require a primer for complementary rna synthesis. Template is copied 3" 5" to make 5" 3" We will focus mainly on mrna transcription (directs protein synthesis) The inherent chemical properties of the nucleotide bases and of the sugar backbone are key to the specific functions of dna (long-lived, stable) and rna (short-lived, labile)

Related Questions

In addition to identifying the genetic material, the experiments of Avery, MacLeod, and McCarty with different strains of Streptococcus pneumoniae demonstrated that

	DNA is a double helix.
	DNA may be taken up by bacterial cells and be active.
	DNA is present in bacteriophage T2.
	eukaryotic cells may be genetically transformed.
	DNA binds to the cell wall of the bacterium.

In order to show that DNA in cell extracts is responsible for genetic transformation in Streptococcus pneumoniae, important corroborating evidence should indicate that _______ also destroy transforming activity.

	temperatures high enough to kill cells
	enzymes that hydrolyze proteins
	enzymes that hydrolyze DNA
	enzymes that hydrolyze polysaccharides
	enzymes that hydrolyze RNA

Based on what you have learned about the experiments conducted by Griffith and Avery and colleagues with bacteria, which of the following would result in transformation of living R cells?

	Pure RNA from S cells
	Cell-membrane extracts from S cells
	A mixture of pure RNA and protein from S cells
	Cell-free extracts from S cells
	Pure protein from S cells

A-T base pairs in a DNA double helix

	form three hydrogen bonds with each other.
	are more heat-stable than G-C base pairs.
	are of a substantially different length than G-C base pairs.
	are not accessible to DNA binding proteins.
	are chemically distinct from G-C base pairs.

If 23 percent of the bases in a sample of double-stranded DNA are adenine, what percentage of the bases are uracil?

	27
	50
	0
	73
	23

The uniform diameter of the DNA structure provides evidence for

	antiparallel DNA strands.
	a right-handed helix.
	a double-stranded helix.
	3â² end phosphorylation.
	purineâpyrimidine pairing.

If a sequence of one strand of DNA is 5â²-TGACTATC-3â², what is the complementary strand?

	5â²-ACTGATAG-3â²
	3â²-TGACTATC-5â²
	3â²-ACTGATAG-5â²
	3â²-ACTGATAG-3â²
	5â²-TGACTATC-3â²

What structural aspect of the DNA facilitates dissociation of the two DNA strands for replication?

	3â² end phosphorylation
	Purineâpyrimidine pairing
	Antiparallel DNA strands
	Covalent bonds between sugars and phosphate groups
	Hydrogen bonding between paired bases

If the MeselsonâStahl density gradient experiment had resulted in two bands of DNA molecules after only one round of replication, one containing only ¹⁵N and the second only ¹⁴N, this result would have indicated that replication was

	unidirectional.
	dispersive.
	conservative.
	bidirectional.
	semiconservative.

10.

The nucleoside analogue acyclovir, which is used to treat herpes simplex virus (HSV) infections, lacks a 3â² hydroxyl group (âOH). Predict what will happen if the host cell DNA polymerase incorporates a molecule of acyclovir into an elongating strand of HSV DNA.

	The replication complex will no longer bind to origins of replication.
	The DNA polymerase will only incorporate acyclovir molecules.
	Acyclovir will bind single-strand binding proteins.
	DNA polymerase will not be able to link a successive nucleotide.
	Acyclovir will block the activity of the DNA helicase.

11.

Which of the following does not demonstrate the stability of the DNA double helix?

	Single-strand binding proteins are required to keep the strands apart.
	Paired bases form hydrogen bonds.
	High temperatures are required to denature it.
	DNA synthesis requires energy.
	DNA helicases require ATP.

12.

What effect would a primase inhibitor have on DNA replication?

	DNA polymerase would not be able to add bases to the DNA.
	Primase would be blocked from joining the DNA replication complex.
	Primase would not be able to provide primers for DNA polymerases.
	DNA polymerase would not be able to use DNA as a template.
	There would be no effect on DNA replication.

13.

To replicate their DNA in a timely manner, most eukaryotic chromosomes

	normally have uncoiled DNA.
	have multiple origins of replication.
	contain linear molecules of single-stranded DNA.
	have two replication forks that move in the same direction.
	are composed entirely of DNA.

14.

Which statement about DNA replication is false?

	Okazaki fragments are synthesized as parts of the leading strand.
	Error rates for DNA replication are reduced by proofreading of the DNA polymerase.
	The sliding clamp increases the rate of DNA synthesis.
	Replication forks represent areas of active DNA synthesis on the chromosomes.
	Ligases and polymerases function in the vicinity of replication forks.

15.

In many eukaryotes, there are repetitive sequences called telomeres at the ends of chromosomes. After successive rounds of DNA replication, the _______ strand becomes shorter. In some cells, an enzyme called _______ repairs the shortened strand.

	leading; telomerase
	lagging; telomerase
	lagging; DNA polymerase I
	leading; DNA polymerase I
	leading; replicase

16.

A researcher studies normal human fibroblast cells. They can be maintained in culture but die off after about 30 cell generations. Unexpectedly, a colony of cells continues to survive and divide past 30 generations. Which scenario is most likely true for these cells?

	DNA polymerase is constantly active.
	Primase is able to extend the telomeres.
	The mismatch repair system is extra efficient.
	The telomerase gene is being expressed.
	The cells do not need the ends of their chromosomes.

17.

If DNA polymerase III introduces an incorrect nucleotide, what is the first corrective action made by the DNA repair system?

	The replication complex excises the incorrect nucleotide.
	The excision repair proteins remove the incorrect nucleotide.
	The mismatch repair system scans for base-pairing mismatches.
	There is no correction, because nucleotide errors by DNA polymerases are not repaired.
	DNA ligase connects the correct nucleotide.

18.

Choose the correct order of the following four events in the excision repair of DNA:
(1) Base-paired DNA is made complementary to the template.
(2) Damaged bases are recognized.
(3) DNA ligase seals the new strand to existing DNA.
(4) Part of a single strand is excised.

	1, 2, 3, 4
	2, 1, 3, 4
	3, 4, 2, 1
	2, 4, 1, 3
	4, 2, 3, 1

19.

Six complete cycles of PCR should result in a _______-fold increase in the amount of DNA.

	64
	32
	12
	128
	6

20.

When double-stranded DNA is heated to temperatures above 90Â°C, it denatures. Denaturation is a process that

	breaks covalent bonds.
	hydrolyzes DNA.
	separates double-stranded DNA into two single strands.
	causes new hydrogen bonds to form.
	irreversibly destroys the double helical structure.

BIO SCI 98 Lecture Notes - Lecture 1: Ribosomal Rna, Transfer Rna, Uracil

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