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

Unit 6 - Genetics of living systems Flashcards

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
Histones
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
26
Chromatin
Complex of DNA and proteins that condense to form chromosomes within the nucleus of eukaryotic cells
27
Euchromatin
Lightly packaged DNA; RNA polymerase can access the bases to transcribe the genes --> genes can be turned on
28
Heterochromatin
Tightly packaged DNA; RNA polymerase cannot access the bases to transcribe the genes so they are turned off
29
Promoter regions
Region of DNA that acts as the binding site for RNA polymerase to start transcription Intron Usually upstream
30
Operator regions
Short region of DNA that is close to the promoter region | Interacts w/ regulatory proteins that controls the transcription of operons
31
Downstream
To the right
32
Upstream
To the left
33
Operon
Functioning unit of DNA containing a group of structural genes expressed together Controlled by one promoter Only found in prokaryotes
34
How is gene expression regulated in operons
Transcription factors bind
35
Transcription factors
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
Repressor protein
A protein that binds to DNA/RNA inhibiting transcription by binding to the operator
37
Gene expression
Production of proteins from a genome
38
Control of gene expression
Whether genes are turned on or off
39
Why is the control of gene expression necessary
In specialisation and differentiation of cells Increasing/ decreasing complexity Prevent vital resources being wasted
40
Why is gene expression more complex on eukaryotes
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
Housekeeping genes
Genes that code for proteins which are necessary for reactions in metabolic pathways and are constantly required (enzymes)
42
Who has only exons
Prokaryotes and eukaryotes without jaw bones | Jaw boned eukaryotes have introns and exons
43
Terminator region
Does not code for protein Regulatory site RNA polymerase is released to stop trancription
44
RNA-coding sequence
Genes turn into mRNA | Has both introns and exons but introns are removed from premature mRNA during splicing to form mature mRNA
45
Methods to regulate gene expression at transcriptional level
Histone modification | Transcription factors
46
Histone modification
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
Transcription factors as a method of gene expression
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
Regulating gene expression at the post transcriptional level
RNA processing RNA editing siRNA Happens simultaneously
49
RNA processing
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
RNA editing
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
Regulating gene expression at the translational level
Degradation of mRNA Binding of inhibitory proteins Protein kinases
52
Degradation of mRNA
More resilient the molecule, the longer it lasts in cytoplasm, more translation
53
Binding of inhibitory proteins
Occurs when protein is produced in wrong location or substrate is not available
54
Regulation of gene expression at the post translational level
Protein activation - allows protein to carry out its function
55
Protein activation
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
Control sites
Operator region and promoter region
57
Beta galactoside
An enzyme that catalyses the hydrolysis of lactose to glucose and galactose
58
Lactose permease
A protein that transports lactose into the cell
59
Lac i
Regulatory gene Codes for repressor protein (transcription factor) Always transcribed
60
Lac p
Promoter region | Rna polymerase binds here
61
Lac o
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
Lac z
Structural gene codes for beta galactoside
63
Lac y
Structural gene that codes for lactose permease
64
Lac operon
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
Mechanism of apoptosis
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
Uses of apoptosis
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
Somatic cell
Body cell
68
Germ line cells
Gametes
69
Germline mutations
Mutations in gametes so can cause genetic diseases and are passed on
70
Somatic mutations
Not inherited but can cause ageing and cancer | Result of mutations in normal diploid cells
71
Homeobox genes
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
Homeotic genes
Set of genes that control morphology
73
Homeodomain
Section of the protein coded for by the homeobox sequence (60 AA)
74
Hox genes
Sub type of homeobox genes Only found in vertebrates and animals Found in clusters on chromosomes Controls body plans and morphology
75
What do Hox genes code for
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
What does a mutation of a Hox gene lead to
Diff body plan
77
What ensures features are expressed correctly
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
Why are Hox genes highly conserved
V. important Mutations alter body plans Mutations are selected against
79
Polypeptides that control the physical development of an organism
Structural proteins Enzymes used in metabolic pathways Hormones Receptor proteins
80
Protein kinases
Activated by cyclic AMP and activate proteins through phosphorylation using ATP
81
siRNA
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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