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116 Cards in this Set

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Who demonstrated that DNA, not protein, is the genetic material of bacteriophages?

Alfred Hershey and Martha Chase

Who showed that the DNA composition varies b/w species; the number of A & T bases are equal, whereas the number of G & C bases are equal?

Erwin Chargaff

Who used X-ray crystallography to produce an X-ray diffraction image of DNA which served as the most critical piece of data in the elucidation of this molecule's structure?

Roslyn Franklin

Who proposed the correct structure of DNA: a double helix with external sugar-phosphate backbones and internal nitrogenous bases that hydrogen bond to each other via specific base pairings?

Watson and Crick

What are the 3 parts of a DNA nucleotide?

Sugar


Phosphate


Nitrogenous base

Name the 4 nitrogenous bases of DNA & identify each as either a purine (2 ring base) or a pyrimidine (1 ring base)

Adenine (A)-Purine


Guanine (G)-Purine


Thymine (T)-Pyrimidine


Cytosine (C)-pyrimidine

Name the DNA base pairings that occur in the DNA molecule.

A & T


G & C



What kind of bonds hold the base pairs together in DNA?

Hydrogen bonds

What kind of bond links the sugars of 2 adjacent nucleotides together via a phosphate group?

Phosphodiester

How is DNA's sugar phosphate backbone oriented in its 3-D structure?

Anti-parallel. 3'-5' the other side is 5'-3'

Does DNA have a charge? If yes, what is causing this charge?

Yes. Negative b/c of the phosphates

Who performed experiments which supported the semi-conservative model for DNA replication?

Matthew Meselson & Franklin Stahl

Where does DNA replication begin?

Origins of replication

Which enzyme unwinds the DNA double helix at the replication fork?

Helicase

Which enzyme synthesizes RNA primers using potential DNA as the template?

Primase

When referring to the DNA strand as either running in the 5'-3' direction or 3'-5' direction, what do the 5' & 3' refer to?

The carbons of the 5 carbon sugar

In which direction is DNA synthesized?

5'-3'

The ______ strand of DNA is synthesized continuously, growing in the direction of the replication fork.

Leading

The ______ strand of DNA is synthesized in fragments, and grows away from the replication fork.

Lagging

The fragments of the lagging strand are called________.

Okazaki fragments

Which enzyme catalyzes the elongation of the daughter DNA strands?

Polymerase 3

Which enzyme replaces RNA primers with DNA nucleotides?

DNA polymerase 1

Which enzyme joins fragments together in the lagging strand (3'-5')

DNA ligase

Which enzyme cuts out and replaces damaged stretches of DNA?

nuclease

A permanent change in the DNA sequence is called a ________.

mutation

Are mutations always bad? Why or why not?

No, changes can help species adapt to different environments

Chromatin consists of DNA associated with proteins called ________.

Histones

When chromatin is highly condensed, it is called _________.

heterochromatin

When chromatin is less compacted, its called_______.

enchromatin

Which form of chromatin is accessible for transcription?

Euchromatin

Circular pieces of DNA found in bacterial cells that are used as cloning vectors (vehicles) for carrying genes of interest to target cells are called _______.

Plasmids

What kind of enzymes cut DNA strands at specific DNA sequences?

Restriction enzymes

Which technique is used to separate DNA fragments based on size?

Gel Electrophoresis

Which technique is used to mass produce specific target sequences of DNA?

(PCR) polymerase chain reaction

How does RNA differ from DNA?

Sugar consists of ribose instead of deoxyribose


The base Uracil (U), rather than thymine (T)


RNA is single stranded instead of double stranded

Differentiate b/w the following terms replication, transcription, and translation.




Where in the cell do each of these events take place?




Replication

DNA is being replicated into another strand of DNA (nucleus)

Differentiate b/w the following terms replication, transcription, and translation.Where in the cell do each of these events take place?



Transcription

Conversion of DNA to RNA (nucleus)

Differentiate b/w the following terms replication, transcription, and translation.Where in the cell do each of these events take place?



Translation

Going from RNA to protein. (Ribosomes in cytoplasm)

Why does transcription and translation occur almost simultaneously in prokaryotes, but not in eukaryotes?

In eukaryotes transcription occurs in the nucleus while translation occurs in the cytoplasm. Since prokaryotes lack nuclei, both events occur in the cytoplasm and can thus occur simultaneously.

How many consecutive nucleotides on the mRNA transcript code for a specific amino acid?

3

What is the set of nucleotides on a RNA called?

A codon

In which direction are codons read on the mRNA transcript?

5'-3'

Why is the genetic code considered redundant, but not ambiguous?

Several codons can code for the same amino acid, but each codon only codes for one amino acid.

How many different amino acids are used to build proteins?

20

How many different codons exist in the genetic code?

64

How many RNA triplets (codons) code for amino acids?

61

How many are "start" codons?

1

How many are stop codons?

3

What is the first amino acid added to any new polypeptide chain?

Methionine

How does the genetic code provide for the unity and the diversity of life?

Unity: genetic code is universal in all living things




Diversity: different sequences code for different proteins which promote different developments/traits and in turn different organisms.

Which enzyme catalyzes RNA synthesis?

RNA polymerase

Does RNA polymerase need another enzyme to unwind the DNA?

No the enzyme can untwist the DNA strndds w/o the assistance of another enzyme

In which direction does the RNA polymerase assemble the polynucleotide?

5'-3'

Does RNA Polymerase require a primer to elongate the chain?

No

The region of DNA which signals where RNA polymerase binds and transcription starts is called the ________.

Promoter

List the sequential stages of transcription

Initiation


Elongation


Termination

The non-coding regions of the mRNA are called ______, while the coding regions are called ______.

Introns


Exons

How is the pre-mRNA modified before exiting the nucleus?

Modified guanine nucleotide cap is added to the 5' end of transcript


A poly-A tail is added to the 3' end of the transcript


Introns are spliced out and exons joined

What are the functions of these modification?

Faciliatates export out of nucleus


Protects mRNA from degradation by hydrolytic enzymes


Helps ribosome attach to 5' end of transcript


mRNA contains continuous coding sequence.

The ______ is the complex involved in cutting out introns and "splicing" together the exons of the pre-mRNA.

spliceosome

How do some genes give rise to more than one polypeptide?

Alternative RNA splicing

Describe the structure of the RNA molecules

RNA molecules consist of a single RNA strand that is only about 80 nucleotides long


RNA molecules can base pair with themselves. Looks like a clover leaf


It carries a specific amino acid on one end that corresponds to a specific nucleotide triplet located on the other end of the molecule


Flattened info one plane a RNA molecule

What does RNA do?

Each RNA can translate a particular mRNA codon into a given amino acid

Distinguish b/w the anticodon and the codon

The anti-codon is the region in the RNA which is complementary to a specific codon in the mRNA

Where does translation occur?

Ribosomes in cytoplasm

Where are the ribosomal subunits synthesized?

Nucleolus

What kind of RNA makes up the bulk of these structures and catalyzes protein synthesis?

rRNA

What occurs during the initiation stage of translation?

Assembly

What occurs during the elongation stage of translation?

Codon recognition


Peptide bond formation


Translocation

What occurs during the termination stage of translation?

Termination occurs when the stop codon in the mRNA reaches the end


The s site accepts a protein called a release factor


the release factor causes the addition of a water molecule instead of an amino acid


The reaction releases the polypeptide and the translator assembly then comes apart.

Where does all protein synthesis begin?

Cytosol

Differentiate b/w free and bound ribosomes.

Free: free floating in cytoplasm that makes proteins that end up in cytoplasm




Bound: create proteins that are secreted or membrane proteins. (on ER)

Are mRNA transcripts translated by more than one ribosome before degradation?

Yes

Mutations represent changes in the ________.

DNA

Distinguish b/w silent mutations, missense mutations and nonsense mutations.




Silent

have no effect on the amino acid produced by a codon b/c of redundancy in the genetic code

Distinguish b/w silent mutations, missense mutations and nonsense mutations.



Missense

Still code for an amino acid, but not the correct amino acid (ex. substitution mutations)

Distinguish b/w silent mutations, missense mutations and nonsense mutations.



Nonsense

Change in amino acid codon into a stop codon, nearly always leading to a nonfunctional protein.

What is a frame shift mutation?

When the insertion or deletion of nucleotides alters the reading frame of genetic message.

Given the following template strand of DNA what would be the corresponding mRNA sequence?




TACATGTCA

AUGUACAGU

What amino acid sequence would be coded by a DNA template strand that reads:




TACGGCAGT

AUGCCGUCA




MetProSer

How does the addition of acetyl groups (acetylation) to histones affect chormatin structure and function?

Loosens chromatin structure, promoting the initiation of transcription.

How does the addition of methyl groups (methylation) to histones affect chromatin structure and function?

Condenses chromatin and leads to reduced transcription

What is epigenetic inheritance?

Inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence

Why is DNA methylation an example of epigenetic inheritance?

Methylation pattern (not part of nucleotide sequence) is inherited in daughter DNA strand

How does DNA methylation affect gene transcription?

Makes gene inaccessible for transcription (gene is not expressed)

Control elements are segments of noncoding DNA that serve as a binding site for __________.

Transcription factors

Distal control elements are also called

enhancers

_______ bind to enhancers.

Activators

What are repressors?

Transcription factors that inhibit expression of a particular gene

The presence of available _______ in different cell types specific for certain enhancer, regulate cell type specific transcription in eukayotic cells

Activators

How are all the genes that produce products for a given metaboilc pathway coordinately regulated?

All co-expressed genes possess the same combination of control elements that are recognized by specific activators: transcription of those genes is simultaneously promoted.

Discuss alternative RNA splicing as a post-transcriptional mechanism for gene expression

Differnet mRNA molecules are produced from the same primary transcript, depending on which segments of the pre-mRNA are treated as introns or exons.

Which part of the mRNA transcript influences its life span?

Untranslated region (UTR) at the 3' end

The addition of ______ to a protein tags it for destruction.

Ubiquitin

What does a significant amount of the genome code for?

Noncoding RNAs (ncRNAs)

What are examples of Noncoding RNAs

MicroRNAS(mRNAs), small interfering RNAs (siRNAs)

What do these noncoding RNAs do?

Interfere with translation, degrade mRNA, or block translation. Or may prevent transcription by modifying chromatin to heterochromatin

What needs to be isolated from cells to determine which genes are being expressed?

mRNA

Which technique is used to make complementary DNA from mRNA?

RT-PCR

Which technique uses genome-wide expression studies to nalyze differential gene expression b/w two samples (e.g. tumor vs normal tissue)?

DNA microarray assays

What is genomics?

The study of whole sets of genes and their interactions

What was the Human Genome Project?

Sequencing of all of the DNA in the human genome

How long did it take to complete the Human Genome Project?

13 years

Which techniques greatly accelerated the sequencing of the human genome?

Automated DNA sequences


Whole-genome shotgun approach

What is GenBank?

a U.S. government regulated database of sequenced genes, predicted protein sequences, etc. that is available to the public on the internet

What are the units used to measure the size of the genome?

Million base pairs (Mb)

Approx. how many genes are in the human genome?

21,000

How does the gene density in the human genome compare to the gene density in prokaryotic genomes?

Lower gene density in human genome

What is missing from the genome of bacterial cells?

Introns (e.g. 7 gnes per Mb in human genome as 950 genes per Mb in e. coli

What percentage of human genome code consists of exons that code for proteins, tRNA or rRNA?

1.5%

_____________ represent regions of DNA that move from one site to another in a cell's DNA.

Transposable elements

Evaluation of repetitive DNA such as short tandem repeats (STRs) is used for _________.

genetic profiling

What underlies the evolution of the genome?

Mutation, incorporated during meiosis

What can we learn with comparative genome studies?

The evolutionary histroy of life

Which species shares the highest homology with the human genome?

Chiimpanzees

Genes that are evolving the fastest code for __________.

Transcription factors