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Biology > DNA & RNA > Flashcards

DNA & RNA Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Topoisomerase

A

unwinds the DNA strands

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2
Q

DNA helicase

A

breaks the hydrogen bonds between the nitrogenous bonds of each nucleotide

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3
Q

Replication Fork

A

the opening in the DNA molecule created by DNA helicase

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4
Q

Semiconservative

A

parent & new strand of DNA

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5
Q

DNA polymerase

A

-creates new daughter strands
-reads the parent DNA strand & creates a complementary, antiparallel strand
always reads 3’ to 5’ creating a daughter strand in the 5’ to 3’ direction
-one daughter strand is the leading strand and the other is the lagging strand

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6
Q

Leading strand

A

continually synthesized by DNA polymerase, which attaches nucleotides to the exposed 3’ end of the parent strand and follows the replication fork to the 5’ end

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7
Q

Lagging strand

A

synthesized discontinually because the 5’ end of the parent strand is the one exposed

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8
Q

Okazaki fragments

A

the short fragments that result from this discontinuous synthesis

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9
Q

DNA ligase

A

joins fragments together

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10
Q

The genetic code

A
  • DNA is made up of four different nucleosides: adenine, thymine, cytosine, and guanine
  • in RNA, thymine is replaced with uracil
  • DNA is transcribed into mRNA & arranged into triplets (codons) & then translated into amine acids (20)
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11
Q

Ribonucleic Acid

A
  • its sugar is ribose
  • contains uracil instead of thymine
  • it is single stranded
  • can be found in the nucleus & cytoplasm of the cell
  • there are three major types of RNA: mRNA, tRNA, & rRNA
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12
Q

Messenger RNA (mRNA)

A
  • carries the complement of a DNA sequence
  • transports the coplement from the nucleus to the ribosomes for protein synthesis
  • made from ribonucleotides complementary to the template strand of DNA
  • it has the complementary code to the original DNA
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13
Q

Transfer RNA (tRNA)

A
  • found in the cytoplasm
  • assists in the translation of mRNA’s nucleotide
  • code into a sequence of amino acids
  • brings the amino acid coded for in the mRNA sequence to the ribosomes during protein synthesis
  • one end of tRNA contains the anti-codon and the other end is the site of attachment of the corresponding amino acid
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14
Q

Ribosomal RNA (rRNA)

A
  • structural component of ribosomes & is the most abundant of all RNA types
  • the mRNA sequence passes through two subunits of the rRNA structure & is translated into amino acids
  • rRNA is synthesized in the nucleolus
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15
Q

Transcription

A

-the process through which information coded in the base sequence of DNA is used to direct the synthesis of a strand of mRNA, which leaves the nucleus through nuclear pores

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16
Q

Steps of Transcription

A
  1. Transcription occurs when RNA polymerase binds to the DNA at a promoter region (TATA-box)
  2. Transcription factors help RNA polymerase bind to the DNA molecule & initiate transcription
  3. RNA polymerase recruits & adds complementary RNA nucleotides based on the DNA sequence
17
Q

Post-Transcription

A
  • extra sequences may exist and are called introns
  • exons are nucleotides necessary to make the protein
  • introns are spliced out by the spliceosome leaving the exons behind
  • a guanine cap & a series of adenine known as poly-A tail are added to the ends of the new molecule to provide protection from enzyme degradation once the RNA leaves the nucleus
18
Q

Translation

A
  • the process through which mRNA codons are translated into a sequence of amino acids
  • occurs in the cytoplasm & involves tRNA, ribosomes, mRNA, amino acids, enzymes, & other proteins
19
Q

Translation Steps

A
  1. Initiation
    - begins when the ribosome binds to the mRNA near its 5’ end. The ribosome scans the mRNA until it binds with a start codon AUG. Methionine tRNA base pairs with the start codon
  2. Elongation
    - hydrogen bonds form between the mRNA codon in the A site of the ribosome & its complementary anticodon on the incoming amino-acyl tRNA complex
    - a peptide bond is formed between the amino acid attached to the tRNA in the A site & the amino aicd attached to the tRNA in the P site of the ribosome
  3. Translocation
    - the cycle is complete in which the ribosome advances three nucleotides along the mRNA in the 5’ to 3’ direction
    - concurrently, the uncharged tRNA from the P site is expelled & the peptidyl tRNA from the A site moves to the P site
  4. Termination
    - happens when one of the termination or stop codons arrives in the A site
    - these codons do not code for amino aicds
  5. Ribosomes
    - where translation takes place, composed of two subunits (small & large) - contains proteins & rRNA
    - contains three binding sites: A, P, & E
    - A site: binds to the next incoming tRNA complex
    - P site: where the tRNA contributes its amino acid to the growing polypeptide chain
    - E site: this is the exit site

Biology (17 decks)

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