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A Level Biology > C19 Genetics of Living Systems > Flashcards

C19 Genetics of Living Systems Flashcards

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1
Q

Definition mutation

A

Change in the sequence of bases in DNA

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2
Q

What occurs to protein synthesis, during mutation

A

Disrupted if mutation occurs within that gene

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3
Q

What can a change in the sequence of bases be caused by?

A

Substitution, Deletion, Insertion of one or more nucleotides (or base pairs) within a gene.

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4
Q

Point mutation

A

If only one nucleotide affected

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5
Q

Substitution

A

Substitution of single nucleotide, changes codon. If new codon, new amino acid, lead to change in primary change
Consider the degeneracy nature

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6
Q

Insertion/ Deletion of nucleotide(s)

A

Frameshift mutation
Triplet code means sequence transcribed (read) consecutively in non -overlapping groups of three.
Addition/ Deletion off one nucleotide change whole sequence
If multiple of three, reading frame not changed but protein formed still affected, as new AA acid added/ deleted).

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7
Q

What does the position and involvement of AA in R groups interactions within proteins determine

A

Determines the impact of new AA on function on function of protein

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8
Q

Effects of different mutations
(No effect):

A

No effect on phenotype of organism because normally functioning proteins still synthesised

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9
Q

Effects of different mutations
(Damaging)

A

Phenotype affected in negative way
Because proteins no longer synthesised, or the ones that are no functional
This can interfere with one or more essential processes

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10
Q

Effects of different mutations
(Beneficial)

A

Very rarely protein synthesised, resulting with new and useful characteristic in phenotype

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11
Q

Give two examples of beneficial mutations

A

Change phenotype, where cell surface membrane in human cells, where HIV can’t bind and enter these cells, making host immune to HIV.

Ability digest lactose (sugar in milk) and preventing lactose intolerance (prevent osteoporosis).

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12
Q

Whats the difference between a gene mutation and chromosome mutations

A

Gene mutations occurs in single gene or section of DNA whereas chromosome mutations affect whole chromosome or no. chromosomes within a cell, can also be caused by mutagens and normally occur during meiosis

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13
Q

Gene mutations

A

Can be silent, but often lead to developmental difficulties

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14
Q

Change in chrom structure include

A

Deletion
Duplication
Translocation
Inversion

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15
Q

(Chromosome Mutations) Deletion:

A

A section of chrom breaks off and lost within cell

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16
Q

(Chromosome Mutations) Duplication:

A

Sections get duplicated on a chrom

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17
Q

(Chromosome Mutations) Translocation:

A

Section one chrom breaks off, joins another non-homologous chrom

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18
Q

(Chromosome Mutations) Inversion:

A

Section of chrom breaks off, is reversed, and the joins back onto the chrom.

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19
Q

How and when do mutations occur

A

They occur spontaneously
Often during DNA replication

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20
Q

What increases the rate of mutations

A

Mutagens

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21
Q

Mutagens

A

A chemical,.physical or biological agent which causes mutations

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22
Q

Free radicals

A

Oxidising agents, can affect structures of nucleotides and also disrupt base paring during DNA replication

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23
Q

Antioxidants examples

A

Vitamins A, C, E

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24
Q

Antioxidants

A

Known as anticarcinogens, because ability to negate effects of free radicals

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25
Q

Physical Mutagens

A

Ionising radiations (i.e x-rays) breaks one or both DNA strands, some breaks can be repaired (mutations in process)

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26
Q

Chemical mutagens

A

Deaminating agents, chemically alter bases in DNA, such as converting cytosine to uracil in DNA, changing base sequence.

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27
Q

Biological Mutagens

A

Alkylating agents
Methyl or Ethyl groups are attached to bases resulting, incorrect base paring of usual base, changing base sequence

(Viral DNA may insert itself into genome,changing base sequence).

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28
Q

At which 4 stages can gene expression be controlled

A

-Transcriptional control
-Post-Transcriptional control
-Translational control
-Post-Translational control

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29
Q

Transcription Factors

A

proteins that bind to specific DNA sequences (e.g enhancer or promoter regions).

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30
Q

How can transcription factors effect the expression of a gene

A

The right complex of transcription factors, required for transcription begin. By increasing / decreasing production specific transcription factors, transcription other genes can be controlled (RNA polymerase not a transcription factor).

31
Q

Chromatin remodelling

A

-Methylation of DNA and histones causes nucleosomes to pack tightly together (methylation makes histones more hydrophobic). Result, transcription factors cannot bind DNA, genes are not expressed.

-Acetylation and phosphorylation reduce the positive charges on the histones. This results in looser packing of nucleosomes, allowing transcription factors to bind the DNA.

32
Q

The charge of DNA and Histones

A

DNA negatively charged, histones positively charged

33
Q

Structure of DNA including (histone proteins), in eukaryotes.

A

In eukaryotes, DNA is associated with histone proteins, forming chromatin. DNA wraps twice around 8 histones, forming a chromatin subunit called a nucleosome.

34
Q

Transcriptional Control (4)

A

The following mechanics regulate, process of protein synthesis.

Degradation of mRNA
Binding of inhibitory proteins
Activation of initiation factors
Protein Kinases

35
Q

Post-Transcription Control
(Exon)

A

Expressed region

36
Q

Post-Transcription Control
(Intron)

A

intergenic region (i.e. region within the gene)

37
Q

Translational Control:
Degradation of mRNA

A

the more resistant the mol, longer it will last in cytoplasm (causing a greater quantity of protein synthesised).

38
Q

Transcriptional Control:
Binding of inhibitory proteins

A

to mRNA prevent binding to ribosomes (and synthesis of proteins).

39
Q

Translation Control:
Activation of initiation factors

A

aid the binding of mRNA to ribosomes.

40
Q

Protein Kinases:

A

enzymes that catalyse the addition of phosphate groups to proteins, which changes tertiary structure and so the function. Many enzymes activated by phosphorylation. Protein kinases are therefore important regulators of cell activity, and themselves often activated by secondary messenger, cAMP.

41
Q

Post-translational Control, involves…

A

Involves modifications to synthesised proteins.

42
Q

Post-translational Control: (4)

A

-Addition of non-protein groups (such as carb chains, lipids, or phosphates).

-Modifying AA’s and formation of bonds (such as disulfide bridges).

-Folding or shortening of proteins.

-Modification by cAMP (e.g in lac operon cAMP binds to the cAMP receptor protein, increasing rate of transcription of the structural gene).

43
Q

Post-Transcription Control
(Modification of pre-mRNA)

A

Transcription produces a mol called pre-mRNA, which must then be processed to form mature mRNA

-A cap and tail are added, while ‘splicing’ by spliceosomes removes introns (non-coding DNA).

-During process, the RNA can also be edited (e.g addition, deletion, substitution etc). These modifications mean a single length of DNA can produce range different strands of mRNA.

44
Q

(The Lac Operon)
What’s an operon, and what’s it composed off?

A

-An operon is a group genes that are under the control of the same regulatory mechanism. An operon is comprised of structural genes and control sites/ region.

45
Q

What the Lac Operon applicable to

A

Only found in prokaryotes

46
Q

The Lac Operon

A
47
Q

What does the control region consist off

A

Promoter and Operator regions

48
Q

The control sites (promoter and operator region) are what?

A

regulatory genes, they dont code for polypeptides.

49
Q

What area does RNA polymerase bind too for transcription

A

The promoter is the area to which RNA polymerase binds for transcription.

50
Q

Operator controls…

A

-Operator controls the switching on or off of genes. If a repressor protein is bound to the operator RNA polymerase cannot bind to the promoter.
-Repressor protein is coded for by a regulatory gene.

51
Q

E. coli bacteria- The Lac Operon:
-Beta galactoside permease (aka lactose permease), enables what:

A

-Beta galactoside permease (aka lactose permease), enables cell take up lactose.

52
Q

E. coli bacteria- The Lac Operon:

Beta galactosidase (aka lactase), enables what

A

-Beta galactosidase (aka lactase), enables the cell to hydrolyse lactose to glucose and galactose.

-Lactose is the inducer

53
Q

Structural genes in prokaryotes can form an operon: a group or a cluster of genes that are controlled by the same promoter

The lac operon controls what?

A

The lac operon controls the production of the enzyme lactase (also called β-galactosidase) and two other structural proteins
Lactase breaks down the substrate lactose so that it can be used as an energy source in the bacterial cell
It is known as an inducible enzyme (this means it is only synthesised when lactose is present)
This helps prevent the bacteria from wasting energy and materials

54
Q

Morphogenesis:

A

the regulation of the pattern of anatomical development.

55
Q

What control Morphogenesis?

A

-Morphogenesis is controlled by a specific group of regulatory genes (Homeobox genes).

56
Q

Homeobox Genes:
(Structure and what do they code for)?

A

Homeobox genes are ancient, highly conserved regions of DNA found in eukaryotes. Homeobox genes, 180 base pairs long, code for homeodomains, protein segments (60AA’s) that act as transcription factors.

57
Q

Homeobox genes exhibit high levels of…

(Homeobox genes have scarcely changed overtime, implying what)?

A

conservation between distant species, e.g last common ancestor of fruit fly and mice lived half billion years ago, yet homeobox gene scarcely changed, implying their activity, absolutely fundamental to development of a body that works (any mutations would be fatal).

58
Q

Hox genes

A

Hox genes, one specific group of homeobox genes, only found animals.

59
Q

Hox gene’s role:

A

-Responsible for the positioning, body parts

-Highly conserved across great evolutionary distances

60
Q

Hox genes tend exhibit ‘colinearity’ (meaning)?

A

meaning the order they appear along chrom is the order which their effects are expressed in organism.

61
Q

Radial Symmetry:

A

Organisms that have an up and down, but no left or right side.

62
Q

Bilateral symmetry:

A

Organisms have a left and right side (and a top and bottom).

63
Q

Asymmetry:

A

Organisms have no lines of symmetry.

64
Q

The Layout of Living Organisms:

A

-Body plans usually represented as cross-sections through the organism, showing fundamental arrangement of tissue layers.

-Common feature of animals, they’re segmented. These segments have multiplied over time and specialised to preform different functions (i.e Hox genes in head control development of mouthpiece, Hox genes in thorax control development of wings, limbs, or ribs).

-Individual vertebrae and associated structures have all developed from segments in the embryo called somites, which are directed by Hox genes to develop in particular way, depending their position in sequence.

65
Q

Mitosis results in…

A

cell division and proliferation

66
Q

Apoptosis results in…

A

programmed cell death

67
Q

Role of Mitosis?

A

increase no. cells, leading to growth

68
Q

Role of Apoptosis?

A

removing unwanted cells and tissues, also cells undergo apoptosis can release chemical signals, stimulate mitosis and cell proliferation leading to remodelling of tissues.

69
Q

What regulates both apoptosis and mitosis?

A

Hox genes

70
Q

Factors Affecting the Expression of Regulatory Genes:

A

The expression of regulatory genes can be influenced by environment (internal and external).

71
Q

Factors Affecting the Expression of Regulatory Genes:
(“Stress”)?

A

Stress defined as, condition produced when homeostasis balance is upset. This can be due to external factors (e.g change temp, intensity of light). Internal factors can change due to release hormones or physiological stress. These factors will have greater impact during growth and development stages.

72
Q

Factors Affecting the Expression of Regulatory Genes:
(Drugs)?

A

Drugs also affect activity, regulatory genes (e.g thalidomide given pregnant women, treat morning sickness, later discovered, prevented the normal expression, particular Hox gene)
Resulted birth babies shorter limbs. Currently used, treatment some forms of cancer.

73
Q

Explain the 4 stage process of apoptosis:

A

1) Cell shrinkage DNA fragmentation
2) Membrane blebbing
3) Apoptotic bodies
4) Phagocytosis of apoptotic bodies

74
Q

The development of the hand is an example of what?

A

Morphogenetic Apoptosis

A Level Biology (20 decks)

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