Biology Exam 3

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DNA stores

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DNA stores

genetic material

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______ encodes the information to make polypeptides and RNA molecules

DNA (1)

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________ is packaged in chromosomes and stored in the __________

DNA; nucleus

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DNA ------> mRNA

transcription

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mRNA------>protein

translation

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The 5 levels of organization in DNA structure are

  1. nucleotides, 2. single strand, 3. double helix, 4. chromosome, 5. genome

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Chromosomes are composed of

chromatin

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chromatin

DNA wound around histone proteins

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Humans have how many chromosomes?

46 (23 pairs)

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DNA nucleotide

phosphate group, sugar (deoxyribose), base

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What are the bases of DNA?

Adenine, Thymine, Guanine, Cytosine

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RNA nucleotides

phosphate group, sugar (ribose), base

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What are the RNA bases?

Adenine, Uracil, Cytosine, Guanine

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Nucleotide numbering system

Sugar carbons are 1' to 5' Hydroxyl group (-OH) attached to 3' carbon on sugar Phosphate attached to 5' carbon on sugar Base attached to 1' on carbon sugar

<p>Sugar carbons are 1&apos; to 5&apos; Hydroxyl group (-OH) attached to 3&apos; carbon on sugar Phosphate attached to 5&apos; carbon on sugar Base attached to 1&apos; on carbon sugar</p>
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single strand

phosphodiester bonds link nucleotides forms sugar-phosphate backbone bases project away from backbone has directionality-5' to 3'

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In a nucleotide single strand

sugars and phosphates alternate 5' has free phosphate group 3' has free sugar group

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double helix

-double stranded helix -strands run antiparallel -bases project toward the center

<p>-double stranded helix -strands run antiparallel -bases project toward the center</p>
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complementary base pairing rules

A always pairs with T G always pairs with C

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purines

Adenine and Guanine

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Pyrimidines

Cytosine and Thymine

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more characteristics of the double helix

-uses base pairing rules -antiparallel strands (3' to 5' with 5' to 3')

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Chromosomes

consists of chromatin which is highly compacted DNA wrapped around histone proteins

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To compact DNA and package into chromosomes:

  1. double helix is wound into nucleosomes

  2. nucleosomes to chromatin

  3. 30 nm fiber

  4. radial loop domain

  5. compacted radial loop domain

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2 broad forms of chromatin

euchromatin (less compacted DNA, active genes) and heterochromatin (highly compacted DNA, inactive genes)

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genome

all of an organism's genetic material

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autosomal chromosomes

non-sex chromosomes 22 pairs in humans

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sex chromosomes

Chromosomes that determine the sex of an individual 1 pair in humans

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DNA replication

the process of making a copy of DNA for cell division

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gamete production, cell renewal/growth, embryogenesis

DNA replication

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DNA replication follows the __________ rule

AT/GC

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during DNA replication

parental/original strands sperate and serve as template for the synthesis of a new/daughter strand

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True or False: DNA replication is semi-conservative

True

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Replication proceeds in _______ directions from an ________________________

both; origin of replication

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origin of replication

Site where the replication of a DNA molecule begins.

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replication fork

A Y-shaped region on a replicating DNA molecule where new strands are growing.

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steps of the formation and movement of the replication fork

  1. DNA helicase unwinds DNA at replication fork

  2. Single-strand binding proteins bound to prevent reforming double helix

  3. DNA topoisomerase prevents tangling of DNA ahead of replication fork

  4. DNA polymerase links nucleotides together to form DNA strands

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DNA polymerase

Enzyme involved in DNA replication that joins individual nucleotides to produce a DNA molecule

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DNA polymerase adds nucleotides to which prime end?

3'

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A ______ primer is needed to start DNA replication

RNA

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DNA primase

synthesizes short RNA primers

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DNA replication process

On a strand 3' to 5':

  1. RNA primer is laid down

  2. leading strand of DNA is laid down to the replication fork From replication fork to origin (5' to 3')

  3. RNA primer laid in front of origin of replication

  4. Okazaki fragment is laid down from end to origin

  5. process repeats to create the lagging strand

<p>On a strand 3&apos; to 5&apos;:</p><ol><li><p>RNA primer is laid down</p></li><li><p>leading strand of DNA is laid down to the replication fork From replication fork to origin (5&apos; to 3&apos;)</p></li><li><p>RNA primer laid in front of origin of replication</p></li><li><p>Okazaki fragment is laid down from end to origin</p></li><li><p>process repeats to create the lagging strand</p></li></ol>
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leading strand

The new continuous complementary DNA strand synthesized along the template strand in the mandatory 5' to 3' direction toward replication fork

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lagging strand

A discontinuously synthesized DNA strand that elongates by means of Okazaki fragments, each synthesized in a 5' to 3' direction away from the replication fork.

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Okazaki fragments

Small fragments of DNA produced on the lagging strand during DNA replication, joined later by DNA ligase to form a complete strand.

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True or False: The RNA primer can stay in the lagging strand.

FALSE: it must be replaced with DNA nucleotide AKA DNA polymerase

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DNA ligase

Seals gaps between Okazaki fragments

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True or False: DNA replication is very accurate

True, DNA polymerase has a proofreading mechanism to check for errors.

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To fill in the 3' ends of the DNA strands, ___________ must be attached to the ends

telomeres

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Telomeres

Repeated DNA sequences at the ends of eukaryotic chromosomes. -prevent loss of genetic material -added by enzyme telomerase -as we grow, telomeres are shortened

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Genome

the complete instructions for making an organism, consisting of all the genetic material in that organism's chromosomes

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Proteome

the entire set of proteins expressed by a given cell or group of cells

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Gene

segment of DNA that encodes a functional product -can encode polypeptides or functional RNA molecules

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gene expression

  1. DNA stores info in genes

  2. Transcription of DNA to produce RNA copy of gene

  3. mRNA, the copy of gene that will be used to make polypeptide

  4. Translation produces polypeptide using mRNA

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DNA to RNA to polypeptide

gene expression (transcription and translation)

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Where does the gene expression processes take place?

Prokaryotic- cytosol and ribosomes Eukaryotic-takes place in nucleus and ribosomes (either free or ones attached on Rough ER)

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Transcription

synthesis of an RNA molecule from a DNA template

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mRNA is complementary to

template strand (NONCODING STRAND)

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mRNA sequence is the same as

non-template strand (CODING STRAND)

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structure of a gene

promoter, regulatory sequence, terminator, transcribed region

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Briefly describe the promoter, regulatory sequence, terminator, and transcribed region of a gene

promoter-START of transcription; place where RNA polymerase binds regulatory sequence-transcription factors (regulatory proteins) bind and control the rate of transcription terminator-END of transcription transcribed region-contains info that specifies an amino acid sequence; MIDDLE of gene

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What are the three stages of transcription?

initiation, elongation, termination

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Transcription initiation

sigma factor recognizes promoter and recruits RNA polymerase; DNA is unwound to separate strands; sigma factor released and RNA polymerase proceeds down DNA

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Transcription Elongation

RNA polymerase continues down DNA strand using the template strand to make complementary RNA

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Transcription Termination

When RNA polymerase reaches terminator, transcription stops & RNA chain is released

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RNA processing in eukaryotes

-addition of 5' cap -addition of polyA tail -splicing AKA (Capping, Splicing, and tailing)

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RNA splicing

Process by which the introns are removed from RNA transcripts and the remaining exons are joined together. (exons-expressed regions) (introns-intervening regions) -alternative splicing allows different proteins to be produced from the same gene

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Organization of mRNA

ribosomal binding site-ribosome binding site, start codon-first amino acid, coding sequence-interchanging codons, stop codon-specifies stop

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Codons

The three-base sequence of nucleotides in mRNA that specify a particular amino acid

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The ______________ specifies amino acids within polypeptide

genetic code

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The genetic code is _________________.

degenerate (same amino acid can be used repetitively)

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tRNA contains what type of codon?

anticodon

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Anticodon

group of three bases on a tRNA molecule that are complementary to an mRNA codon -carries amino acid specified by codon (tRNA)

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AUG

start codon

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UGA, UAA, UAG

stop codons

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Where does translation occur?

ribosome

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Characteristics of ribosomes

two subunits- Large and Small subunits composed of rRNA and proteins 3 sites where tRNA binds during translation: A, P, and E sites

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________________ alter DNA sequence of a gene

Gene Mutation

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Mutation

A change in a gene or chromosome. -heritable change -source of variation for natural selection -most are harmful -genetically inherited diseases result from harmful mutations

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point mutation

gene mutation in which a single base pair in DNA has been changed -caused by base substitution

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Three types of point mutations

silent, missense, nonsense

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silent mutation

A mutation that changes a single nucleotide, but does not change the amino acid created. -causes no change in protein structure or function

<p>A mutation that changes a single nucleotide, but does not change the amino acid created. -causes no change in protein structure or function</p>
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missense mutation

A base-pair substitution that results in a codon that codes for a different amino acid. -may change protein structure/function or may not -usually neutral or negative outcome

<p>A base-pair substitution that results in a codon that codes for a different amino acid. -may change protein structure/function or may not -usually neutral or negative outcome</p>
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nonsense mutation

A mutation that changes an amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein. -usually negative outcome

<p>A mutation that changes an amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein. -usually negative outcome</p>
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indel mutation (base insertion or deletion)

a mutation in which one or more nucleotide pairs is added or deleted -may cause change in reading frame -addition or deletion shifts the reading frame and changes codons and resulting amino acids

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