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biology > DNA and protein synthesis > Flashcards

DNA and protein synthesis Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

describe the structure of DNA

A

-building blocks are nucleotides (phosphate, 5-carbon sugar, and nitrogen base)
-4 types of nitrogen bases: adenine, thymine, cytosine, and guanine
-double helix
-deoxyribose sugar and phosphates are bonded together to make up the sides
-strands run antiparallel
-5’ end = an attached free phosphate
-3’ end = an attached -OH group

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2
Q

which base matches with which? what percentage do they make up in human cells?

A

-a and t (31%)
-c and g (19%)

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3
Q

what happens in DNA replication?

A

-two DNA strands held together by hydrogen bonds are separated
-each old strand (side) acts as a template for teh new strand (semiconservative)
-DNA helicase unwinds DNA
-new nucleotides are complementary base-paired
-addition of new strand is completed by DNA polymerase (synthesizes in 5’ –> 3’ direction)
-any gaps/breaks are fixed by DNA ligase
-at each origin of replication a fork forms, and a buble forms around it (where replication occurs)

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4
Q

how are DNA and RNA’s structures similar?

A

-both nucleic acids
-both made of nucleotides
-both have a sugar-phosphate backbone
-both have 4 base types

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5
Q

how are DNA and RNA’s structures different?

A

-DNA is a double helix that’s strands run antiparallel, made of deoxyribose sugar, has bases of ATCG
-RNA is a single stand, made of ribose sugar, and has bases of AUCG

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6
Q

mRNA function

A

-made in nucleus where DNA serves as a template for mRNA during transcription
-carries genetic info from DNA (nucleus) to ribosomes (cytoplasm) for translation and protein synthesis

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7
Q

tRNA function

A

-produced in nucleus
-transfers amino acids present in cytoplasm to ribosomes
-each of the 20 amino acids has its own tRNA moleucle
-at the ribosome translation joins amino acid brought by tRNA to form polypeptide chain

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8
Q

rRNA function

A

-produced in nucleolus where portion of DNA serves as template for formation
-joins with proteins made in the cytoplasm to form ribosome subunits
-subunits leave nuclues and come together in cytoplasm where protein syntehsis will happen
-each subunit is a unique mix of proteins and rRNA
-ribosomes can exist in cytoplas as clusters or free standing, often attached to ER

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9
Q

what are the two parts of protein synthesis?

A

-transcription: portion of DNA serves as mRNA template
-translation: sequence of mRNA bases determines sequence of amino acids folded together to create protein

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10
Q

describe transcriptoin

A

mRNA is formed by:
-RNA polymerase binding to a promoter
-opening up DNA helix just in front of it
-complementary base pairing RNA nucleotides
mRNA is then processed in the nucleus by:
-adding a cap of altered guanine nucleotide
-adding a poly-A tail to the 3’ end
-splicing the extrons together after removing the introns

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11
Q

what is a promoter

A

-special nucleotide sequence making beginning of gene
-what RNA polymerase binds to when mRNA is being formed in transcription

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12
Q

what are introns?

A

-segments of mRNA that do not code for a protein and are removed in splicing

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13
Q

what are extrons?

A

-segments of mRNA that do code for a protein and are spliced together after introns are removed

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14
Q

what happens to the created/processed mRNA molecule after transcription?

A

-it passes from nucleus (formation and processing spot) to the cytoplasm so it can be translated into amino acids and eventually a protein

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15
Q

why are all genes not expressed in every cell?

A

-not every cell needs to express every gene
-most cells have a specialized fucntion that only requires certain genes to be expressed

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16
Q

what is the process of repressor?

A

-a regulatory gene outside the operon code for a repressor
-repressor binds to operator
-transcription of the gene for that specific gene cannot take place bc it makes it so RNA polymerase cannot bind to the promoter
ex. lac operon normally binds to operator which lies next to promoter, when repressor is attache dto the operator, transcriptoin of the lactose0metabolizing genses does not take place bc RNA polymerase cannot bind to the promoter, if lactose is present than the shape of the repressor changes after lactose binds to it and it is no longer able to bind to the promoter, so the RNA polymerase can.

17
Q

what are the three steps of translation?

A

-initiation
-elongation
-termination

18
Q

describe the initation phase of translation

A

-mRNA binds to small ribosomal subunit of ribosome
-large subunit joins to small

19
Q

describe the elongation phase of translation

A

-peptide (chain) lengthens one amino acid at a time

20
Q

describe the termination phase of translation

A

-one of three stop codons is reached (UAA, UAG, or UGA)
-release factor binds to it and causes ribosomal subunits and mRNA to dissociate
-complete polypeptide is released

21
Q

how does chromatin condensation regulate genes?

A

-keeps genes turned on or off
-the more tightly chromatin is condensed the less genes are expressed
-heterochramatic = darkly stained portionsof chromatin representing tight compaction
-once they become less tightly compacted they are euchromatin, active genes
-these still need further modification before they can be transcribed (no histones can be present)

22
Q

how does DNA transcription regulate genes?

A

-DNA binding proteins that help RNA polymerase and dramatically speed up translation bind to a promoter
-several needed for transcription form complex that helps full part DNA and position RNA polymerase

23
Q

how does mRNA processing regulate genes?

A

-removal of intron and splicing of extrons
-alternative mRNA processing- primary mRNA can produce different protein accoridng to which extrons are spliced together to create mature mRNA

24
Q

how does mRNA tranlation regulate genes?

A

-cytoplasm contians proteins controlling whether translation takes place
-ex. IF-2 inhiibts start of protein synthesis when phosphoylated by kinase protein
-environmental factors can delay translation
-ex. red blood cells do not produce hemoglobin unless heme, iron containing group is available
-also hormones and poly-A tails determine ow long mRNA remains active for translation

25
Q

how does protein activity regulate genes?

A

-some protiens are not active/used immediatley after synthesis because they arent needed
-ex. insulin
-protiens are short lived in cells because they are degraded or destroyed
-ex. cyclins destroyed by proteasomes

26
Q

how does cell signaling regulate genes?

A

-singals determine specific role cell will play/specialized function
-also coordinate growth and everyday funcitons
-occur because chemical signal binds to recetor protien in target cell’s plasma membrane
-causes receptor protein to initate set of reactions in the singal transduciton pathway
-end product of signal transduction pathway directly affects metabolism (growth only possible if certain genes have been turned on)
-also receptor protein activates transcription activator that enhances transcription of specific genes (lead to translation of mRNA and protein prodcut that stimulates cell cycle for growth

27
Q

who are alfred hershy and martha chase and what did they do?

A

-hershey and chase determiend DNA is the genetic material
-experimented with E.coli and DNA
-radiation showed that DNA, not proteins, enters the bacterium and guids info of new viruses, so it must be the genetic material

28
Q

who are james watson and francis crick and what did they do?

A

-watson and crick set out in 1951 to bring all the data they had on DNA and build a model
-called watson and crick model
-also suggested how replication works with their model

29
Q

who is erwin chargaff adn what did he do?

A

-made chargaff’s rules
-knew that DNA contained 4 types of nitrogen bases
-examined DNA from many species
-said amount of A, T, C, and G varies from species to species
-amnt of A always equals amnt of T and amnt of C always equals amnt of G

30
Q

who is rosalind franklin and what did she do?

A

-franklin studied DNA structure
-data (xrays) showed DNA to be a helix with some poritons repeating over and over

31
Q

what hold the complementary base pairs together? why is this importannt?

A

-hydrogen bonds
-they are weaked than covalent bonds meaning they are easily broken for quicker/more efficient DNA replication

32
Q

what is a codon?

A

-sequence of 3 base pairs coding for an amino acid in mRNA

33
Q

what is an anticodon?

A

-codon complementary to corresponding mRNA codon on tRNA

34
Q

what are the stop codons?

A

-UAA
-UGA
-UAG

35
Q

what is the start codon?

A

-AUG

biology (5 decks)

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