Nucleic acids & protein synthesis

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1

Genetic information

instructs cells how to construct proteins; stored in DNA

2

Gene

segment of DNA that codes for one protein

3

Allele

different versions of a gene

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Genome

complete set of genes

5

Genetic code

method used to translate sequence of nucleotides of DNA into a sequence of amino acids

6

Structure of DNA

•Double helix made of two strands of nucleotides
•Backbone of each strand is a sugar phosphate chain
•Bases of complementary strands hydrogen bond to each other: C-G, A-T

7

DNA

Deoxyribonucleic acid (deoxyribose, phosphate, & nitrogenous base)

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DNA bases

adenine, guanine, cytosine & thymine

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DNA purines

adenine & guanine

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DNA pyrimidines

cytosine & thymine

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DNA wrapped around ____ form ____.

histones, chromosomes

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DNA replication

•Hydrogen bonds break between bases
•Double strands unwind and pull apart
•New nucleotides pair with exposed bases
•What phase of the cell cycle does this happen?

13

Replication begins at a specific point in the DNA called the ____.

origin of replication

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DNA replication step 1

Helicase binds at the origin of replication and begins to unwind and separate DNA strands (unzips)

15

DNA replication step 2

Single strand binding proteins stabilize the separated strands of DNA

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DNA replication step 3

Primase adds an RNA primer at the origin

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DNA replication step 4

DNA polymerase adds nucleotides to the RNA primer to form new complementary strand

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DNA replication step 5

RNA primer is enzymatically removed & replaced with appropriate sequence of DNA

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DNA replication step 6

Because DNA polymerase only works in one direction & the strands are oriented in opposite directions, replication of the leading strand is continuous while replication proceeds discontinuously on the lagging strand forming Okazaki fragments between RNA primers

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Helicase

An enzyme that untwists the double helix of DNA at the replication forks.

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Single strand binding proteins

Proteins that bind to and stabilize the signle strands of DNA exposed when helicase unwinds the double helix in preparation for replication.

22

Primase

An enzyme that joins RNA nucleotides to make the primer.

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RNA primer

Sequence of RNA primers bound to a region of single-stranded DNA to initiate DNA replication.

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DNA polymerase

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

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Leading strand

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

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Lagging strand

A discontinuously synthesized DNA strand that elongates in a direction away from the replication fork.

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Okazaki fragments

Short fragments of DNA that are a result of the synthesis of the lagging strand during DNA replication.

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Guide to making proteins is encoded in the ____.

DNA sequence

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Proteins are made in the ____ & DNA is in the ____.

cytoplasm, nucleus

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Message needs to get from DNA to ____.

cytoplasm

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mRNA

messenger RNA; type of RNA that carries instructions from DNA in the nucleus to the ribosome

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Transcription

Process of copying DNA into mRNA

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RNA bases

ribose, phosphate, nitrogenous base

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RNA bases

adenine & guanine, cytosine & uracil

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RNA purines

adenine & guanine

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RNA pyrimidines

cytosine & uracil

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Transcription Process

•RNA polymerase binds to a promoter region on DNA
-Sigma factor recognizes the promoter
•Synthesis of mRNA begins with sequence AUG (DNA: TAC)
•Synthesis of mRNA by RNA polymerase continues until it reaches the transcription terminator sequence (forms a hairpin structure)
•RNA polmerase & mRNA strand dissociate from the DNA

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RNA polymerase

transcription enzyme that links RNA nucleotides together

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Promoter Region

A regulatory region a short distance upstream from the 5' end of a transcription start site that acts as the binding site for RNA polymerase. A region of DNA to which RNA polymerase binds in order to initiate transcription.

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Sigma Factor

controls the binding of RNA polymerase to the promoter

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Transcription Terminator

sequence after a gene that causes RNA polymerase to stop and fall off

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Translation

mRNA is translated from the nucleic acid sequence to form polypeptide chains

43

Peptide bond formation during translation requires ___ ATPs.

3

44

Codons

three-nucleotide sequence of mRNA that codes for a single amino acid

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tRNA

transfer RNA; type of RNA that carries amino acids to the ribosome

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Anticodon

group of three bases on a tRNA molecule that are complementary to an mRNA codon

47

Proteins that function inside the cell are formed on ____.

free ribosomes

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Proteins that are secreted or become part of membranes are made by ____.

ribosomes docked to ER (RER)

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Chaperones

fold amino acid sequence into the proper conformation

50

How is gene transcription controlled?

DNA structure, DNA methylation, Regulatory proteins

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DNA structure transcription control

tightly packed DNA is less accessible to transcription proteins

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DNA methylation

addition of a methyl group to cytosine

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Regulatory proteins transcription factors

can be activated or inactivated by signal molecules like hormones

54

Mutations

-Bases are added, deleted, or changed
-May or may not change the protein
-Most mutations that change the protein are deleterious

55

Mutagens

Agents that induce mutations
-Chemicals
-Reactive oxygen species (ROS)
-Metals: iron, mercury, chromium, arsenic, etc.
-Viruses
-Radiation

56

Reactive oxygen species

toxic oxygen molecules or radicals that are formed by the reaction between oxygen molecules and water during the electron transport chain

57

DNA repair enzymes

Protection against mutation, detect mismatched base(s) and replace with correct base(s)