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Genetics for agriculture > genes and transcription > Flashcards

genes and transcription Flashcards

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1
Q

Structure of DNA

A
  • double-stranded and complementary but anti-parallel
  • each nucleotide is bonded together with a phosphodiester bond
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2
Q

what is complementary base pairing

A
  • advantage of having complementary DNA strand
  • One side of DNA is 5 prime
  • The other side of DNA is 3 prime
  • direction is always 5 to 3 prime
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3
Q

complementary base pairing transcribing

A

T-A
G-C
- MRNA is complementary to DNA when transcribed

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4
Q

what is a gene

A
  • a functional unit of hereditary (DNA) which carries information from one generation to the next (or from 1 cell to another during cell replication)
  • they occur on chromosomes and are short segments of DNA
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5
Q

what is a chromosome

A
  • where genes are located
  • packaging unit of DNA located in the nucleus
  • nucleus component is inherited from both parents
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6
Q

chromosomes in prokaryotic organism

A
  • DNA is located in the CELL not the nucleus
  • single circular DNA naked as its not wrapped around proteins
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7
Q

chromosomes in eukaryotic individuals

A
  • made up primarily of linear DNA and bound to proteins called histones
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8
Q

genome

A

all genetic information inside a cell
- one cell has half of the chromosomes from each parent (each chromosome has 2 copies)

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9
Q

Whats transcription

A

DNA in the nucleus is transcribed by RNA and translated to a polypeptide protein
- (mRNA is transcribed in the nucleus and exits the nucleus to the cytoplasm when it’s ready for translation)

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10
Q

gene expression key process

A

INPUT DNA, OUTPUT is RNA
1. Initiate (transcription)
2. elongate
3. termination

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11
Q

initiate/ transcription

A
  • plus 1 nucleotide will be transcribed
  • unwinds DNA and starting at +1 uses TEMPLATE strand to produce complementary RNA (based on complementary base pairing) until reach terminator
  • RNA uses uracil instead of thymine
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12
Q

RNA

A

is the main component of ribosome used as a translationary machinery (how mrna can be translated into a protein)

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13
Q

Trna

A

transfer rna (single strand) transfer amino acid for making polepeptide

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14
Q

gene expression in prokaryotes vs eukaryotes

A
  • pro: transcription happens from circular DNA
  • euka: needs processing and moving from nucleus to cytoplasm
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15
Q

why is there modified ends to DNA

A
  • to promote export of mrna from the nuclues and protect from degradation
  • cap is located at 5 prime siteand poly-a to 3 prime
  • in order to translate properly
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16
Q

splicing

A
  • removal of INTRONS which are noncoding regions interspersed within the encoding regions called EXONS
    INTRON: after pre mature mrna is transcribed cap and poly a is added and then remove intron to make mature RNA
    EXON: expressed part (we want)
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17
Q

why is splicing needed

A
  • we can use one coding sequence (template) to create different VARIATIONS of protein for different purposes
  • (not in prokaryote)
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18
Q

Not all genes are expressed all the time…

A

eg:disease defense
- it is controlled so it can be expressed in the right time and place (we want disease resistant gene to function when the pathogen attacks, not be delayed)
- also energy saving as it comes with a metabolic cost

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19
Q

Activator binding site

A
  • will only be expressed (transcripted) if this activator exists (protein binds to activator site)
    eg: if the pathogen attacks plant produces protein which activates transcription
    (positive regulation)
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20
Q

repressor binding site

A

STOP trasncription
(negative regulation)

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21
Q

ribosomes

A
  • composed of rRNA and proteins
  • large and small subunits
  • contains P and A sites for tRNA binding during translation
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22
Q

the genetic code

A

AUG is START codon (starting point of tranlation)
STOP codon UGA,UAG,UAA

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23
Q
  1. translation initiation
A
  • When the mRNA is released from the nucleus it goes to the cytoplasm
    • The small subunit will bind to the mRNA and scan to find the start codon
    • The tRNA will bind as a complementary to the start codon so UAC
      Then they recruit their large subunit, the tRNA located in the P site of the large subunit
24
Q
  1. translation elongation
A
  • Then the A site on the large subunit will use trna to be complementary on the mrna site
    • Each trna has its own unique amino acid (the condensation reaction occurs and the 2 amino acids bind together
    • Then the disarmed trna will be released
    • The p side is then empty and the translation can move forward
      This process continues until reach stop codon (as there is no trna that can bind to the stop code)
24
Q
  1. translation termination
A
  • RNA subunits release
  • the polypeptide chain is released into the cytoplasm
24
Q

mutations (genetic variation)

A
  • they are alterations to DNA sequences
  • they are genetic variation
    MUTATION IS CAUSE, GENETIC VARIATION IS CONSEQUENCE
25
Q

why is complementary base pairing important

A
  • vital for accurate conservation of informationduring the production of DNA, RNA and protein
  • DNA-> DNA base pairing during DNA replication
  • DNA-> RNA base pairing during transcription
    RNA-> RNA base pairing during translation
25
Q

structures of polypeptide

A

Primary structure
- Simple chain of amino acids (each amino acid has its own properties)

Secondary structure
- Can make a beta sheet (3 strands)
- Can make an alpha helix

Tertiary structure
- Can be a combination of sheet, alpha helix and loops
- The loop is the most unstable part of the protein
The final product (not necessarily functional) sometimes binds to other proteins and makes another structure
- 3 copies of the same protein or 2 different proteins come together

25
Q

functions of protein

A
  • can be tragted to particular organelles
  • can store nutrients
25
Q

Consequence of mutation in DNA

A
  • may change the protein function
  • if there is a mutation in DNA it will be transcribed to the mRNA and will create a different protein
    (could be more or less efficient)
26
Q

spontaneous mutation

A

mutation that arises naturally and not as a result of exposure to mutagenic agents
(occur due to natural causes)

27
Q

induced mutations

A
  • mutation that is produced by treatment with a physical or chemical agent that affects the dna or an organism
  • occurs due to exposure to mutagens
28
Q

what are mutagens

A
  • electromagnetic radiation like X rays, Gamma rays, UV
  • chemicals like thy
  • natrual disasters
29
Q

consequences of mutations are dependent on

A

where (cell/tissue) the mutation occurs (somatic vs germline mutation)
- if the mutation is NOT genetically inherited its no use for agriculture

30
Q

Somatic mutation

A
  • does NOT transfer to progeny (won’t inherit it to the next gen)
31
Q

Germ-line mutation

A
  • is the mutation which happens in the germ-line, the entire organism carries the mutation which will be passed onto the next gen
32
Q

where the mutation occurs?

A
  • mutation can occur in the coding region or the non coding region
33
Q

coding mutation

A
  • may affect the gene product
34
Q

noncoding mutation

A

may affect the expression of the gene

35
Q

small scale mutation

A
  • single or small scale changes in the nucleotide of the DNA
36
Q

point mutations

A

Silent mutation: no change in gene product
Missense mutation: amino acid changes, likely affect protein tertiary structure and change the protein function
Nonsense mutation: truncated (or shorter) protein, most likely reduced function or no function
Frameshift mutation: change in amino acid sequence, most likely reduced or no function or change of function

37
Q

why is DNA replication important

A
  • is the basis for biological inheritance
38
Q

what is DNA replication

A

biological process by which produces 2 identical replicas of DNA from one original DNA molecule

39
Q

process of dna replication

A
  1. the ori sequence binds the pre-replication complex
  2. two replication forks move away from one another and unwinds the DNA
    (1 replication origin)
    (bi-directional synthesis)
  3. needs rermination replication
40
Q

role of helicase

A
  • helicase seperates strands of dna
  • creates a single stranded dna in the localised area (which is very vulnerable)
  • other proteins keeps the strand open and protects from other enzymes
41
Q

DNA polymerase

A
  • reads template 3-5
  • adds bases to the 3 end of the growing strand
  • needs a short double stranded region to start DNA replication
42
Q

primase enzyme

A
  • read the bottom strand and synthesis a short primer RNA
43
Q

B clamp

A

keeps the DNA polymerase in place (allowing for smooth progression)

44
Q

Lagging strand

A

5-3 (polymerase can’t read this strand)
- primase adds RNA primers to start replication
- dna POLYMERASE 3 will form new strands on the complementary template
- okazaki fragments are formed on the lagging strand

45
Q

Okazaki fragments

A
  • are joined by ligase
  • gaps are filled with complementary basis by dna pol 1
46
Q

Errors in dna (nucleotide mismatches) (DNA polymerase)

A
  • have proofreading mechanisms for newly synthesised dna
  • if mismayching was found cuts out the error and replaces with new base
47
Q

DNA repair by mismatch repair (MMR)

A
  • MMR proteins excise sections of dna
  • DNA pol 1 adds correct sequence
    DNA ligase repairs
48
Q

telomeres

A
  • protective chromosome ends
  • protects ends of chromosomes from deterioration
49
Q

chromosoemns need 3 elements

A
  1. origins of replication- DNA replication
  2. centromers- essential for segregation at cell division
  3. telomeres- crucial for structural stability
50
Q

difference between prokaryotic and eukaryotic replication

A

in p dna synthesis is not cell cycle dependednt, whereas for e it is

Genetics for agriculture (6 decks)

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