Genetics Of Living Systems 2

Question 1

Transcription factors

Answer 1

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

Question 2

Homeobox genes

Answer 2

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

Question 3

Homeobox

Answer 3

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

Question 4

Homeodomain

Answer 4

Allows transcription factor bind to dna

Question 5

Homeobox genes common ancestors

Answer 5

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

Question 6

Body plans

Question 7

Morphogenisis

Answer 7

Regulation of the pattern of anatomical development

Question 8

Evolution effect on Homeobox genes

Answer 8

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

Question 9

Discovery and fruit flies

Answer 9

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

Question 10

Homeodomain function

Answer 10

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

Question 11

Hox genes

Answer 11

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

Question 12

Vertebrates development

Answer 12

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

Question 13

Human development

Answer 13

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

Question 14

Order of genes

Answer 14

= order in which effects are expressed in the organism

Question 15

Sequence / gene structure

Answer 15

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

Question 16

Stages of gene expression control

Answer 16

Transcriptional
Post transcriptional level
Translation level
Post translational level

Question 17

Transcriptional level control

Answer 17

Increased trans more mRNA make more proteins

Question 18

Chromatin varieties

Answer 18

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

Question 19

Transcription of chromatin

Answer 19

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

Question 20

Histone

Answer 20

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

Question 21

Histone modification

Answer 21

Addition of acetyl groups or phosphate groups
Addition of methyl groups

Question 22

Addition of acetyl/phosphate groups

Answer 22

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

Question 23

Addition of methyl groups

Answer 23

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

Question 24

Epigenetics

Answer 24

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

Question 25

Using transcriptional factors

Answer 25

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

Question 26

Environment on transcription factors

Answer 26

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

Question 27

Lac operon in E.coli

Answer 27

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

Question 28

Lac operon group of genes

Answer 28

•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

Question 29

Repressor protein

Answer 29

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

Question 30

Role of cAMP

Answer 30

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

Question 31

Post transcriptional pre translation control

Answer 31

•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

Question 32

Translation control

Answer 32

•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

Question 33

Mutation

Answer 33

Change in the sequence of bases in dna

Question 34

Mutation types

Answer 34

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

Question 35

Substitution mutation

Answer 35

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

Question 36

Insertion/deletion

Answer 36

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

Question 37

Effects of mutations

Answer 37

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

Question 38

Causes of mutation

Answer 38

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

Question 39

Physical mutagens

Answer 39

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

Question 40

Chemical mutagens

Answer 40

Deamination agents Chemically alter bases in DNA changing base sequences

Question 41

Biological mutagens

Answer 41

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

Question 42

Chromosome mutations

Answer 42

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