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Year 12 Biology > Topic 3 > Flashcards

Topic 3 Flashcards

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1
Q

gene structure

A

segment of DNA that codes for proteins

  • template strand contains coded information-called antisense, non coding strand-mRNA codes from this
  • complementary strand called non-template strand- mRNA is exactly same apart from thymine being replaced by uracil
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2
Q

part of gene the contains coded information

A

coding region

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3
Q

feature of coding region in eukaryotes

A

non continuous, interrupted by other segments of DNA, called introns

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4
Q

introns

A

non-coding region of DNA-transcribed but not translated

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5
Q

exons

A

coding region of DNA- transcribed and translated

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6
Q

transcription

A

process of copying genetic instructions present in DNA to mRNA

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7
Q

transcription process

A
  • enzyme RNA Polymerase binds to specific base sequence on template DNA strand of promoter region of gene to be transcribed
  • DNA double helix unwinds and exposes template strand bases
  • base sequence of template DNA strand, guides formation of complementary copy of messenger RNA.
  • free floating RNA nucleotides pair with DNA and are joined together to form a chain of mRNA/ pre-mRNA in eukaryotes
  • enzyme RNA polymerase catalyses this reaction, copies DNA until reaching stop codon-signal to terminate RNA production
  • single stranded mRNA/pre-mRNA molecule is formed, and is complimentary to DNA template strand (T replaced by U)
  • mRNA/pre-mRNA is released and double helix reforms.
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8
Q

pre-mRNA processing`

A
  • methylated cap is added

- poly-A tail added-introns spliced out.

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9
Q

translation

A

process of decoding genetic instructions where order of bases in mRNA transcript is used to produce specific polypeptide chain built of amino acids.

  • requires tRNA-carry amino acids to correct position on mRNA-contains anticodons
  • mRNA- carries code from DNA, contains codons
  • ribosomes- provide tRNA environment attachment and amino acid linkage.
  • pool of amino acids
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10
Q

translation process

A
  • mRNA carrying code transcribed from DNA is transported from nucleus, through nuclear pore to ribosome in cytoplasm
  • small ribosomal subunit bonds to methylated cap on mRNA and scans along for start codon (AUG).
  • once found, large ribosomal subunit joins with small one and translation commences when start codon is translated
  • tRNA molecule with complimentary anticodon pairs momentarily with codon on mRNA, releasing its amino acid
  • as ribosome moves along mRNA, more and more amino acids are added to growing polypeptide chain and peptide bonds form between adjacent amino acids
  • this is catalysed by enzymes in ribosome.
  • when ribosome reaches stop codon, protein synthesis stops and polypeptide chain is released.
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11
Q

purpose of alternative pre-mRNA splicing

A

one way in which one gene can produce different protein products at different developmental stages in different tissues

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12
Q

difference between prokaryotic and eukaryotic DNA

A

prokaryotic- main chromosome is circular molecule of DNA, with additional DNA in the form of plasmid

  • DNA is naked (not wrapped around histones), and is free within the cell
  • DNA comprises of a unique nucleotide sequence
  • coding sequence is uninterrupted-no introns

Eukaryotic-linear molecule of DNA, interrupted by introns

  • DNA exists in proteins called histones
  • contains many repeated nucleotide sequences
  • enclosed within a nucleus
  • contain no plasmids.
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13
Q

comparing processing of gene information between prokaryotic and eukaryotic

A

prokaryotic

  • no nuclear envelope, so mRNA can associate with ribosomes as mRNA is being formed
  • thus translation can occur before transcription is completed
  • mRNA often contain transcripts of several genes
  • by placing genes with related function on same mRNA, bacteria can coordinate synthesis of these proteins

Eukaryotic

  • due to possessing a nucleus, mRNA is completely formed and must cross nuclear envelop before translation begins
  • mRNA is modified by removal of introns and methylated cap an poly A tail before translation can begin
  • translation begins at ribosomes in cytoplasm
  • mRNA usually specifies only one protein, therefore no operons.
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14
Q

what does it mean when gene is expressed

A

means gene is transcribed and translated therefore protein is produced

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15
Q

gene expression based on

A
  • type of cell
  • stage of development
  • conditions within and around the cell
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16
Q

Gene Regulation

A

cells do not express all of the genes of their genome at their same time

  • results in suitable amounts of proteins being produced when required
  • advantage of expressing genes only when required- conserve energy and resources for organisms
17
Q

Regulatory Gene

A
  • produce signalling protein- controls action of other genes, determining whether gene is switched on or off.
  • also control rate at which product is made.
  • repressor protein, coded by regulator gene-inhibits action or operator, therefore preventing transcription of structural gene
18
Q

Structural Gene

A

region of DNA codes for a particular protein, required for normal cell functioning- also called coding region

19
Q

Operator region

A

lies between promoter region and structural gene- binding site of repressor protein

20
Q

Promoter Region

A

situated close to structural gene (upstream flanking region)- controls start of decoding process and rate of production of protein products by gene action.
-binding site of RNA polymerase

21
Q

Homeotic region

A
  • control embryonic development of insects and vertebrates
  • these are examples of regulator genes
  • control building of animal body parts and ensures they are built in correct locations
22
Q

operon

A

group of genes under control of single operator site

23
Q

Lac Operon

A

consists of

  • operator-binding site of repressor protein
  • promoter- binding site of RNA polymerase
  • three genes that code for enzymes involved in lactose breakdown
  • repressor protein regulates three genes by binding to operator thus inhibiting transcription
  • lactose acts as signal molecule
  • if lactose is present, binds to repressor-altering its shape so that it cant bind to operator, thus three genes are transcribed
  • if lactose absent, repressor protein is able to bind to operator covering part of promoter.- stops RNA polymerase from binding to promoter, transcription of genes is blocked.
24
Q

what does switched on gene mean

A

a switched on gene is transcribing mRNA

Year 12 Biology (16 decks)

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