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LGS A-Level OCR Biology > Unit 6 - Genetics of living systems > Flashcards

Unit 6 - Genetics of living systems Flashcards

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1
Q

Characteristics of genetic code

A

Universal
Triplet code
Degenerate
Non-overlapping

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2
Q

Properties of DNA

A

Introns

Exons

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3
Q

Introns

A

Sections of DNA that do not code for a polypeptide
Regulatory sequences
Acts as a buffer for mutations

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4
Q

Regulatory sequences

A

Promoter regions
Terminator regions
Operator regions (prokaryotes)

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5
Q

Exons

A

Sections of DNA that code for polypeptides

Regulatory or structural genes

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6
Q

Regulatory genes

A

Genes that code for proteins used in DNA regulation

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7
Q

Structural genes

A

Genes that code for regular proteins

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8
Q

Mutagens

A

Chemical, physical, or biological agents which cause mutations e.g. viruses (viral DNA inserts itself into the genome), radiation (Breaks one or both DNA strands)

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9
Q

Where can genes be turned on or off

A

Transcriptional
Post-transcriptional
Translational
Post-translational

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10
Q

When does up/down regulation occur

A

Post trasncriptional
Translational
Post translational

Either increases/ decreases rate of protein synthesis

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11
Q

When are proteins modified

A

Translational

Post translational

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12
Q

Where are ribosomes assembled

A

Nucleolus

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13
Q

Why is there a ribosomal groove

A

So mRNA can be read for transcription

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14
Q

Types of mutations

A

Genes

Chromosomal

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15
Q

Point mutations

A

Mutations that occur at a spp point

Insertion
Substitution
Deletion

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16
Q

Effects of point mutations of proteins

A

Silent
Missense
Nonsense

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17
Q

Insertion mutations

A

Addn. of one or more nucleotide base pairs into a DNA sequence

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18
Q

Substitution mutation

A

Occurs when a base pair is substituted for another

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19
Q

Deletion mutation

A

Occurs when a base pair is deleted from the DNA sequence

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20
Q

Frameshift

A

A mutation caused by the addn. or deln. of a base pair(s) resulting in the translation of the genetic code from an unnatural reading frame from the point mutation to the end of the gene

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21
Q

Silent mutations

A

Change in the DNA sequence that results to the change in nucleotide base pairs having no subsequent effect on on the amino acid produced
May have occurrred in introns

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22
Q

Missense mutations

A

A single nucleotide change leads to a different codon and therefore a different AA

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23
Q

Nonsense mutations

A

Change in nucleotide sequence that leads to one of codons being converted to a terminator codon so the protein produced is truncated

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24
Q

Class of mutations

A

Beneficial - depends on environment
Neutral - No effect on chances of survival
Disadvantageous - Causes genetic diseases, lessens chances of survival

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25
Q

Histones

A

Basic proteins that associate w/ DNA in the nucleus and help to condense the DNA into a smaller volume
Little balls in which DNA wraps around

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26
Q

Chromatin

A

Complex of DNA and proteins that condense to form chromosomes within the nucleus of eukaryotic cells

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27
Q

Euchromatin

A

Lightly packaged DNA; RNA polymerase can access the bases to transcribe the genes –> genes can be turned on

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28
Q

Heterochromatin

A

Tightly packaged DNA; RNA polymerase cannot access the bases to transcribe the genes so they are turned off

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29
Q

Promoter regions

A

Region of DNA that acts as the binding site for RNA polymerase to start transcription
Intron
Usually upstream

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30
Q

Operator regions

A

Short region of DNA that is close to the promoter region

Interacts w/ regulatory proteins that controls the transcription of operons

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31
Q

Downstream

A

To the right

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32
Q

Upstream

A

To the left

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33
Q

Operon

A

Functioning unit of DNA containing a group of structural genes expressed together
Controlled by one promoter
Only found in prokaryotes

34
Q

How is gene expression regulated in operons

A

Transcription factors bind

35
Q

Transcription factors

A

Coded for by regulatory genes
Proteins which affects rate of transcription
Activates or inhibits transcription of DNA by binding to promoter region w/ RNA polymerase or blocking the promoter region

36
Q

Repressor protein

A

A protein that binds to DNA/RNA inhibiting transcription by binding to the operator

37
Q

Gene expression

A

Production of proteins from a genome

38
Q

Control of gene expression

A

Whether genes are turned on or off

39
Q

Why is the control of gene expression necessary

A

In specialisation and differentiation of cells
Increasing/ decreasing complexity
Prevent vital resources being wasted

40
Q

Why is gene expression more complex on eukaryotes

A

Have to respond to changes in the internal and external environments
Histones - DNA not exposed, genes expression is harder
Prokaryotes don’t have histones

41
Q

Housekeeping genes

A

Genes that code for proteins which are necessary for reactions in metabolic pathways and are constantly required (enzymes)

42
Q

Who has only exons

A

Prokaryotes and eukaryotes without jaw bones

Jaw boned eukaryotes have introns and exons

43
Q

Terminator region

A

Does not code for protein
Regulatory site
RNA polymerase is released to stop trancription

44
Q

RNA-coding sequence

A

Genes turn into mRNA

Has both introns and exons but introns are removed from premature mRNA during splicing to form mature mRNA

45
Q

Methods to regulate gene expression at transcriptional level

A

Histone modification

Transcription factors

46
Q

Histone modification

A

Histones are +vely charged and DNA. -vely charged –> attraction
Modify charges to change degree of packaging
Acetylation and phosphorylation reduce +ve charge so transcription happens
Methylation increase +ve charge so transcription doesn’t occur

47
Q

Transcription factors as a method of gene expression

A

Control rate of transcription by binding to spp DNA sequences
Regulate genes to make sure they are expressed correctly
Work alone or w/ others as an activator or repressor of RNA polymerase

48
Q

Regulating gene expression at the post transcriptional level

A

RNA processing
RNA editing
siRNA

Happens simultaneously

49
Q

RNA processing

A

Pre-mRNA is modified –> mature-mRN A binds to ribosme and code for synthesis
Adenine cap is added at 5’ and tail at 3’
Stabilises mRNA and delays degradation in cytoplasm, aids binding
Splicing and the addn. of adenine cap and tail occur in the nucleus

50
Q

RNA editing

A

Some mRNA can be changed through base pair add., deln. or subn. Same effects as point mutations and results in synthesis of diff proteins w/ diff function s
Increases range of proteins that can be produced from one mRNA strand

51
Q

Regulating gene expression at the translational level

A

Degradation of mRNA
Binding of inhibitory proteins
Protein kinases

52
Q

Degradation of mRNA

A

More resilient the molecule, the longer it lasts in cytoplasm, more translation

53
Q

Binding of inhibitory proteins

A

Occurs when protein is produced in wrong location or substrate is not available

54
Q

Regulation of gene expression at the post translational level

A

Protein activation - allows protein to carry out its function

55
Q

Protein activation

A

Occurs in Golgi
Adding non protein groups e.g. carbs, phosphates
Phosphorylation by protein kinases and ATP
Folding/ shortening proteins (2’ structure)
Modification by cAMP

56
Q

Control sites

A

Operator region and promoter region

57
Q

Beta galactoside

A

An enzyme that catalyses the hydrolysis of lactose to glucose and galactose

58
Q

Lactose permease

A

A protein that transports lactose into the cell

59
Q

Lac i

A

Regulatory gene
Codes for repressor protein (transcription factor)
Always transcribed

60
Q

Lac p

A

Promoter region

Rna polymerase binds here

61
Q

Lac o

A

Operator region of control site
Repressor protein binds here
When lactose is present causes a conformational change in repressor protein allowing it to bind to lactose instead

62
Q

Lac z

A

Structural gene codes for beta galactoside

63
Q

Lac y

A

Structural gene that codes for lactose permease

64
Q

Lac operon

A

Inducible operon (only occurs when lactose is present from diffusion through lactose channels )
Example of transcriptional regulation
Group of 3 genes involved in metabolism of lactose

65
Q

Mechanism of apoptosis

A

Cytoskeleton broken down by enzymes, loses function
Cell shrinks and the membrane blebs, chromatin condenses
Lysosomes release enzymes which break down cell components
Cell breaks up into membrane-bound fragments
Cell fragments are ingested and digested by phagocytic cells

66
Q

Uses of apoptosis

A

Morphogenesis - eliminating excess cells (webbed fingers)
Selection - eliminates non functional cells
Immunity - T killer eliminates dangerous cells (cancer)
Organ size - eliminates excess cells
Tissue remodelling - eliminates cells no longer need (breastfeeding)

67
Q

Somatic cell

A

Body cell

68
Q

Germ line cells

A

Gametes

69
Q

Germline mutations

A

Mutations in gametes so can cause genetic diseases and are passed on

70
Q

Somatic mutations

A

Not inherited but can cause ageing and cancer

Result of mutations in normal diploid cells

71
Q

Homeobox genes

A

Regulatory genes that contain a homeobox sequence (180 bp)
Highly conserved in animals, plants and fungi
Regulates mitosis and apoptosis in the embryonic stage
Control body plans of an organism

72
Q

Homeotic genes

A

Set of genes that control morphology

73
Q

Homeodomain

A

Section of the protein coded for by the homeobox sequence (60 AA)

74
Q

Hox genes

A

Sub type of homeobox genes
Only found in vertebrates and animals
Found in clusters on chromosomes
Controls body plans and morphology

75
Q

What do Hox genes code for

A

A group of TF’s that controls expression of structural genes associated w/ the development of an organism’s appendages during its embryonic stage to form a mature body plan

76
Q

What does a mutation of a Hox gene lead to

A

Diff body plan

77
Q

What ensures features are expressed correctly

A

Hox genes in a Hox cluster are activated in a particular order depending on where its found on the chromosome
This matches order genes are expressed along H to T
So structural genes are activated in a carefully coordinated sequence

78
Q

Why are Hox genes highly conserved

A

V. important
Mutations alter body plans
Mutations are selected against

79
Q

Polypeptides that control the physical development of an organism

A

Structural proteins
Enzymes used in metabolic pathways
Hormones
Receptor proteins

80
Q

Protein kinases

A

Activated by cyclic AMP and activate proteins through phosphorylation using ATP

81
Q

siRNA

A

Small interfering RNA - only needed when cell has made sufficient protein
Complementary base sequence to mRNA that’s to be degraded
Binds to mRNA and activates an enzyme that breaks it down
RNA nucleotides recycled to nucleus

LGS A-Level OCR Biology (42 decks)

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