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Biology > Genetics Of Living Systems 2 > Flashcards

Genetics Of Living Systems 2 Flashcards

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1
Q

Transcription factors

A

Proteins that bind to dna at specific sites
This way they regulate transcription turn genes on and off

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2
Q

Homeobox genes

A

Encode transcription factors
Contain a homeobox
Control the growth and development of organisms
Switch on head develop genes thorax genes etc in foetus

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3
Q

Homeobox

A

Section of DNA 180 base pairs
Codes for a region of transcription factor called the homeodomain (60AA)

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4
Q

Homeodomain

A

Allows transcription factor bind to dna

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5
Q

Homeobox genes common ancestors

A

Homeobox genes in mice and humans have identical nucleotide sequences
Eg Pax6 eye development if genes not turned on blindness

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6
Q

Body plans

A
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7
Q

Morphogenisis

A

Regulation of the pattern of anatomical development

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8
Q

Evolution effect on Homeobox genes

A

Homeobox sequence is highly conserved has changed very little during evolution
Naturally selected against

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9
Q

Discovery and fruit flies

A

Studied flies w mutations legs on head
Mutations found in genes in a section of dna 180bp in length similar for all flies except mutated

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10
Q

Homeodomain function

A

Allows transcription factor to bind to dna
Conserved region of protein
When mutate certain genes weren’t turned on or off result in defects

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11
Q

Hox genes

A

Group of Homeobox genes only present in animals
Correct positioning from head to tail

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12
Q

Vertebrates development

A

Develop from segments in embryo called somites
Directed by hox genes to develop particular way depending on sequence

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13
Q

Human development

A

humans have 39 hox genes organised into 4 clusters each on different chromosomes - expressed in different body segments

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14
Q

Order of genes

A

= order in which effects are expressed in the organism

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15
Q

Sequence / gene structure

A

Promoter - trans start site - 5’ untranslated region - start codon - coding region- stop codon - 3’ untranslated region

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16
Q

Stages of gene expression control

A

Transcriptional
Post transcriptional level
Translation level
Post translational level

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17
Q

Transcriptional level control

A

Increased trans more mRNA make more proteins

18
Q

Chromatin varieties

A

Heterochromatin tightly wound DNA causing chromosomes to be visible during cell division
Euchromatin is loosely wound- present in interphase

19
Q

Transcription of chromatin

A

Transcription not possible when tightly wound RNA polymerase cannot access genes
Euchromatin can be freely transcribed interphase replication

20
Q

Histone

A

Dna is wrapped round it
DNA negatively charge Histone positively charged because made of lysine AA

21
Q

Histone modification

A

Addition of acetyl groups or phosphate groups
Addition of methyl groups

22
Q

Addition of acetyl/phosphate groups

A

reduces positive charge of histones causing dna to coil less tightly - allow certain genes to be transcribed

23
Q

Addition of methyl groups

A

makes histones more hydrophobic so they bind more tightly to each other preventing DNA transcription

24
Q

Epigenetics

A

Study of heritable changes in gene expression that do not involve changes to the underlying DNA sequence

25
Q

Using transcriptional factors

A

Trans factors help or block the binding of rna polymerase to dna
Start= activators
Stop= repressors
Shape determines whether it binds to dna or not - altered by binding w certain molecules

26
Q

Environment on transcription factors

A

Amount of some mol in an environment control synthesis of proteins by affecting transcription factor binding

27
Q

Lac operon in E.coli

A

Operon is a cluster of genes that are transcribed together
Ecoli can respire lactose if glucos not present control via operon

28
Q

Lac operon group of genes

A

•Regulatory gene codes for a repressor protein prevent trans when no lactose
•Structural genes :Lac Z Lac Y Lac A
Code for 3 enzymes in the breakdown of lactose

29
Q

Repressor protein

A

Constantly produces and bonds to operator
•Prevents RNA polymerase binding to DNA and beginning trans - regulation
•When lactose present repressor protein binds changing its shape allowing RNA to bind to promoter - enzymes transcribed

30
Q

Role of cAMP

A

Binding of RNA polymerase is slow rate of transcription
Up regulated by cAMP receptor protein CRP
Transport of glucose into cell decreases levels of cAMP reducing transcription of genes responsible for metabolism of lactose

31
Q

Post transcriptional pre translation control

A

•RNA processing - modifies pre mRNA to mature mRNA before translating
Cap added to 3’ & 5’ end stabilise mRNA prevent degradation
•RNA editing sequence can be changed through base addition deletion or sub - range of proteins prod

32
Q

Translation control

A

•degradation of mRNA more resistant molecule longer it will last more protein
•bind of inhibitory proteins prevent synthesis of proteins
• activation of initiation factors which aid binding of mRNA to ribosomes

33
Q

Mutation

A

Change in the sequence of bases in dna

34
Q

Mutation types

A

Substitution deletion insertion
If only one nucleotide change called one point mutation

35
Q

Substitution mutation

A

Changes the codon in which may code for a different amino acid changing primary structure
May not affect due to degenerate code

36
Q

Insertion/deletion

A

Frameshift mutation shifts the reading frame of the sequences of bases read in 3 change every successive codon from mutation point

37
Q

Effects of mutations

A

None- normally func still synthesised
Damaging- phenotype is affected as protein synthesised non func
Beneficial- new beneficial phenotype eg immunity to HIV

38
Q

Causes of mutation

A

Increased by mutagens - loss of a purine or pyrimidines base lead to insertion of the wrong base in DNA rep
Chemical physical or biological agent

39
Q

Physical mutagens

A

Ionising radiation x rays
Break dna strands some breaks repaired mutations occur

40
Q

Chemical mutagens

A

Deamination agents
Chemically alter bases in DNA changing base sequences

41
Q

Biological mutagens

A

Alkylating agents- methyl groups attach to bases incorrect pairing
Base analogs- change base sequence
Viruses - viral dna insert changing base sequence

42
Q

Chromosome mutations

A

Deletion- a section chrom breaks off and lost
Duplication- section duplicated
Translocation break off and join to another non homologous chromosome
Inversion- a section of chromosomes break off and reversed and join back

Biology (24 decks)

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