Genetic Flashcards

1
Q

Eukaryotic DNA

A

Long linear chromosones
DNA in nucleus
DNA tightly wrapped around proteins called histones

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2
Q

Prokaryotic DNA

A

Supercoiled - condenses circular chromosones so they can fit inside the cell
Short and circular

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3
Q

Bases of DNA

A

Adenine
Guanine
Cytosine
Thymine

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4
Q

Locus

A

Specific physical location of a gene or other DNA sequence on a chromosone

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5
Q

Exons

A

Coding regions in a gene

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6
Q

Introns

A

Non coding regions in a gene

Removed during splicing

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7
Q

Features of the genetic code

A

Degenerate
Universal
Non - overlapping

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8
Q

Degenerate

A

More than one codon can code for the same amino acid

64 possible triplet codes but 20 amino acids

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9
Q

Universal

A

Same four bases (A,T,C,G) are used in the DNA of every organism
Codons in DNA are transcribed into mRNA and translated into amino acids in every organism

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10
Q

Non - Overlapping

A

No overlapping between triplet codes

Each triplet is separate from other triplets

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11
Q

Substitution mutation

A

One base is substituted for another

eg. ATCCGT - ACCCGT

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12
Q

Name the 3 types of substitution mutation

A

Silent
Misense
Nonsense

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13
Q

Silet mutation

A

Base changes but doesn’t change the amino acid

eg. UCU = Serine , UCC = Serine

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14
Q

Misense mutation

A

Base changes and it changes the amino acid (alters binding site)
eg. AAG = Lysine , AGG = Arginine

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15
Q

Nonsense mutation

A

Base changes and alters amino acid to have a stop codon (anticodon) that is complementary
eg. UCU = Cystine , UGA = Stop
Stops DNA replicating

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16
Q

Name the two types of frameshift mutation

A

Deletion

Insertion

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17
Q

Deletion

A

One base is deleted
Causes codons to change which results in different amino acids
Changes the primary structure of a protein which results in a potentially whole different protein / faulty - leads to disease

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18
Q

Insertion

A

A base is added

Changes the amino acid sequence

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19
Q

How do mutagenic agents work

A

Increase the frequency of a mutation occurring
Act as a base
Alter a base
Change structure of DNA

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20
Q

Name the 3 mutagenic agents

A

Xray
Ionising radiation
Chemicals

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21
Q

What are the effects of mutation

A

Production of new/superior protein - results = gain of reproductive advantage
Neutral mutation - results = no change
Production of an inferior / no protein - result = fatal/ disease killing

22
Q

Causes of mutation

A

A mutation can occur by mistake during DNA replication - spontaneously occur
DNA polymerase makes a mistake about once every 100,000,000

23
Q

Transcription

A

Occurs in the nucleus

24
Q

Transcription - Initiation

A

RNA polymerase attaches to the beginning of the DNA code - Promoter
The DNA molecule unwind and the weak hydrogen bonds between the complementary strands break
One strand now acts as a template for the formation of the mRNA strand

25
Transcription - Elongation
Free nucleotides in the nucleus bond to the complementary baes of the DNA template (Uraci replaces Thymine in mRNA) More free nucleotides bond to their complementary bases , to elongate the mRNA strand , until the entire code has been transcribed The RNA polymerase joins the nucleotides in condensation reactions (forms phosphodiester bonds)
26
Transcription - Termination
The mRNA will detach from the DNA template The RNA polymerase detaches and starts all over again at a different location where needed Now the pre-mRNA strand has to undergo modification and RNA splicing before it can leave the nucleus
27
Splicing
RNA splicing removes introns (non coding RNA) and joins exons (coding RNA) Creates a mRNA molecule with continuous coding sequence
28
RNA
Ribonucleic acid Single stranded Consists of - pentose sugar (ribose) , phosphate group, base (A,U,C,G)
29
mRNA
Transfers the DNA code from nucleus to cytoplasm Complementary to DNA code Small enough to leave nucleus pore Single stranded
30
tRNA
Small Single stranded - folded into a clover leaf shape Amino acid at top , Anti codon at bottom
31
Translation
A cell translates mRNA message into polypeptide
32
Translation - Initiation
Small ribosomal subunit binds with mRNA Small subunit moves along mRNA until it reach the start codon (AUG) The matching anti codon of the tRNA (with amino acid) bonds with start codon Large ribosomal subunit is added - complete translation initiation complex
33
Translation - Elongation
More tRNA anticodon attach to mRNA codons The amino acids attached to the tRNA' attach to one another by peptide bonds Amino acid form a long polypeptide chain tRNA releases Amino acids to pick up more amino acids
34
Translation - Termination
Occurs when a stop codon in the mRNA reaches the active site of a ribosome Releases polypeptide
35
Meiosis
Only takes place in sex organs - produces gametes Starts with a diploid cell - results in 4 identical haploid cells Contain individual chromosomes - not pairs
36
Homologus chromosones
One from mother and one from father Both chromosones in a homologous pair have the same genes Can inherit different alleles from each parent
37
Meiosis 1
Homologous chromosomes are separated from each other
38
Meiosis 2
Sister chromatids separated from each other
39
Meiosis - Interphase
Before meiosis the cell will have been through interphase During interphase - cell copies chromsones and organelles Chromosones not visible as distinct structures in interphase
40
Prophase 1
Chromosones condense and become visible Homologous chromosones link together forming chiasmata Crossing over takes place - exchanging alleles between homologous chromosones Nuclear membrane breaks down
41
Metaphase 1
Homologous pairs of chromosones now line up along the equator
42
Anaphase 1
Spindle fibres shorten and homologous chromosones move to opposite poles Chiasmata between homologous chromosones breaks
43
Telophase 1
Chromosones now reached poles of cell | Nuclear membrane reforms and chromosones move to opposite poles
44
Cytokinesis 1
Divides into 2 cells | Haploid
45
Cytokinesis 1
Divides into 2 cells | Haploid
46
Prophase 2
Chromosones condense and become visible again | Nuclear membrane breaks down and spindle fibres begin to develop
47
Metaphase 2
Chromosones are lined up on the equator
48
Anaphase 2
Centromere of each chromosome divides Spindle fibres shorten Chromatids pulled apart to opposite poles of cell
49
Telophase 2
Chromatids have reached the poles of the cell Chromosomes Nuclear membrane reforms and chromosones coil back to chromatid state
50
Cytokinesis 2
Produces 2 haploid cells