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PCAT: BIOLOGY > DNA and RNA > Flashcards

DNA and RNA Flashcards

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1
Q

how does one go from a gene to protein

(central dogma)

A
  • genes composed of DNA which is transcribed into RNA and translated into protein
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2
Q

DNA is capable of _____ making it able to be passed onto other generations

A
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3
Q

what is the basic unit of DNA and its structure

A
  • basic unit = nucleotide
  • composed of deoxyribose sugar, bonded to phosphate and a nitrogenous base
  • base can be purine or pyrimidine
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4
Q

what are the pruines and what are the pyrimidines

A
  • purines - adenine and guanine ( 2 rings)
  • pyrimidines = cytosine and thymine )1 ring)
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5
Q

what forms the chain between nucleotides

A

phosphate and sugar

  • nucleotide bases are off to side and form the h bonds
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6
Q

how is double helix held together, what is the structure

A
  • via hydrogen bonds
  • sugar phosphate on outside and nitrogenous bases on inside h bonding
  • T forms 2 h bonds with A
  • G forms 3 H bonds C
  • antiparallel arrangement
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7
Q

how does DNA strands separate to prepare for replications

A
  • uncoiled by topoisomerase and DNA helicase breaks the h bonds
  • opening of DNA known as replciation forl
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8
Q

replication is referred to as _____

A

semi conservative

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9
Q

what is responsible for synthesis of daughter strand, how does it work

A
  • DNA polymerase
  • reads parent strand and creats complementary antiparallel daughter strand
  • have leading strand (continuously synthesized adding nucleotides to exposed 3’ end) and the lagging strand (5’ end is exposed so forms okazaki fragments DNA ligase stitches the fragments together)
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10
Q

what is the difference between RNA and DNA

A
  • ribsoe sugar

contains uracil not thymine

usually single stranded

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11
Q

where is RNA found? what are the major types

A

found in nucelous and cytoplasm

  • major types are mRNA, tRNA and rRNA
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12
Q

describe mRNA

A
  • carries the complement of the DNA sequence (but T sub for U)
  • transports compliment from nucleous to the ribosomes for proteins nthesis
  • mRNA made of ribonucelotides complementary to template strand of DNA
  • one mRNA strand codes for one polypeptide
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13
Q

describe tRNA

A
  • small RNA mol in cytoplasm
  • assis with translation of mRNA nucleotide code into a seq of amino acids
  • helps by bringing the amino acids coded for in the mRNA sequence to ribosomes during protein syn
  • one end of tRNA has anticodon and other end has aa
  • each aa has its own aminoacyl-tRNA synthetase which has an active site that binds to both the amino acid and its corresponding tRNA to cat attachment

*there is at least one type of tRNA for each aa

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14
Q

describe rRNA

A
  • ribosomal RNA is a structural component of ribosomes and is most abundant of all RNA
  • mRNA seq passes thru two subunits of rRNA and is translated into amino acids

*rRNA is syn in nucleolus

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15
Q

what is transcription

A
  • proces by which info coded by DNA is transcribed into a strand of mRNA that leaves the nucleus thru nuclear pores
  • eacch human chromosome is a long strand of DNA used to make approx 1000 diff seq of RNA

*RNA much smaller than DNA, onyl seg of DNA strand is sued as a template

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16
Q

what is the first step of transcription

A

rna pol binds to DNA at promoter region

  • in humans usually TATA box
17
Q

how does RNA polymerase do its job

A

binds to DNA mol and initiates transctipion

  • RNA pol surrounds the DNA mol after its been opened and recruits and adds in the complementary RNA nucelotides based on the DNA seq
18
Q

what occurs once trancription is complete

A

mRNA undergoes post transcriptional modifcations

  • introns are spliced out by spliceosomes while exons stay in
  • gets guanine cap and poly A tail to protect it in cytoplasm
19
Q

what is translation

A
  • prcoess through which mRNA codons are translated into a seq of amino acids

0 ocurs in cytoplasm and involes tRNA, ribosomes, mRNA, amino acids, enzymes and other prot

  • divided into initiation, elongation, translocation and termination
20
Q

describe initiation

A

ribosome binds to mRNA near its 5’ end

  • ribosome scans the mRNA until binds to start codom AUG
  • initiator aminoacyl tRNA complex (methionine tRNA) base pairs with start codon
21
Q

describe elongation

A

hydrogen bonds forms between mRNA codon in A site of the ribosome and its complementary anticodon on the incoming aminoacyl tRNA compelx

  • peptide bond if formed between the amino acid in attached to tRNA in the A site and that in the Psite
  • after bond is formed a ribsome carries uncharged rTNA in the P site to the A site
22
Q

describe translocation

A
  • ribosome advances 3 nucleotides along mRNA
  • the uncharged tRNA from P site is expelled and the peptidyl tRNA in A site moves to P site
  • aminoacyl-tRNA of next codon can now enter the empty A site
23
Q

describe termination

A

occurs when it encounters stop codon UAA UAG or UGA

24
Q

what is a polyribosome

A

frequently numerous ribosomes simultaneously translate a single mRNA molecule forming a structure called polyribosome

25
Q

what occurs after the release of the protein form the ribosome

A
  • assumes its characteristic #D conformation
  • this is determined by the primary sequence of amino acids
  • additional secondary and tertiary structural folding occurs based on primary seq
  • the polypeptide chains can form intramolecular and intermolecular cross bridges with disulfide bonds
26
Q

describe the structure of the ribosome

A

large and small subunits that are only associated during protein synrthesis

  • has A P and E sites
  • A site = aminoacyl tRNA complex binding site, it binds to the enxt incoming tRNA complex
  • the tRNA complex is then
27
Q

NOTE: humans and bacteria have diff subunits that make up the ribosome

  • take advantage of this when designing antibiotics that starget the structural diff in bacterial ribosomes leaving human ones un harmed
A

PCAT: BIOLOGY (18 decks)

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