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Y13 Biology > Genetics / Inheritance and Variation > Flashcards

Genetics / Inheritance and Variation Flashcards

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1
Q

What is a mutation?

A

A mutation is a change in the sequence of bases in DNA - this interrupts protein synthesis

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2
Q

Types of mutations

A

Types of mutations: subsitution, deletions or insertions of one or more nucleotides within a gene

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3
Q

What is a point mtuation?

A

A point mutation is when only one nucleotide is affected

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4
Q

Effect of a substitution mutation

A

A subsitution mutation of a nucleotide changes the codon on which it occurs - diff amino acid - diff primary structure - may be no effect due to degenerate nature

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5
Q

Effect of an insertion or deletion of a nucleotide

A

Insertion or deletion of a nucleotide leads to a frameshift mutation - reading frame of bases changed

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6
Q

Effects of different mutations

A

Effects of different mutations:
-No effect
-Damaging ie non-functional protein synthesis
-Beneficial

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7
Q

What are mutagens?

A

Mutagens increase the rate of mutation - it is a chemical, physical or biological agent which causes mutations

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8
Q

Causes of mutations

A

Causes of mutations:
-Mutagens
-Rare spontaneous loss of a base
-Free radicals which are oxiding agents affecting nucleotide structures and therefore base pairing

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9
Q

Examples of mutagens

A

Examples of mutagens:
-Physical - x rays - break DNA strands
-Chemical - deaminating agents - altering bases
-Biological - virus - insertion of DNA into a genome

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10
Q

Changes in chromosome structure due to chromosome mutations

A

Changes in chromosome structure due to chromosome mutations:
-Deletion - section of chromosome broke off and lost
-Duplication - section duplicated
-Translocation - sections broken off and joins other non-homologous chromosome
-Inversion - section broken off reversed then joined back onto chromosome

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11
Q

What are housekeeping genes?

A

Housekeeping genes are genes that code for enzymes necessary for metabolic reactions

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12
Q

What are tissue-specific genes?

A

Tissue-specific genes code for protein-based hormones required by certain cells at certain times for a short-lived response

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13
Q

Why is gene regulation needed?

A

Gne regulation is required for cells to specialise and work in a coordinated way

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14
Q

Levels of which genes operate which determine how they are regulated:

A

Levels of which genes operate which determine how they are regulated:
-Transcriptional (genes turned of/off)
-Post-transcriptional (mRNA modified to regulate transcription and types of protein produced)
-Translational (stopped or started)
-Post-translational (proteins modified after syntheses to change functions)

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15
Q

What are chromatins?

A

Chromatins is the complex formed when histones are wound around DNA

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16
Q

What is an operon?

A

An operon is a group of genes that are under the control of the same regulatory mechanism and are expressed at the same time

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17
Q

Why are operons effecient?

A

Operons are efficient way of saving recourses as when certain gene products are not needed, genes involved can be switched off

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18
Q

What is used when glucose is in short supply as a respiratory substrate for bacteria?

A

When glucose is in short supply, lactose is used as a respiratory substrate for bacteria

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19
Q

Structural genes involved in the lac operon

A

Lac operon - group of three genes - lacZ lacY lacA - structural genes that code for enzymes and are transcribed onto mRNA

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20
Q

Regulatory genes - lacoperon

A

Regulatory gene is located near the operon and codes for a repressor protein which prevents transcription of structural genes in the absence of lactose

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21
Q

What are repressor proteins in the lacoperon?

A

Repressor proteins prevents the transcription of the structural genes in the absence of lactose
-Constantly produced and binds to operator

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22
Q

Effect of repressor protein binding to an operator (lacoperon)

A

When the repressor protein binds to the operator, RNA polymerase is prevented from binding to DNA and beginning transcription - down regulation

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23
Q

What is a promotor in gene regulation? (lacoperon)

A

The section of DNA that is the binding site for RNA polymerase is called the promoter

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24
Q

What happens when lactose is present - lacoperon?

A

Lactose present -> binds to repressor protein -> changes shape and can’t bind to operator - so RNA polymerase binds to promoter and three structural genes are transcribed and enzymes are synthesies

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25
Q

How can bindings of RNA polymerase for transcription be increased?

A

Binding of cAMP receptor protein (CRP) speeds up transcription of genes - possible when CRP bound to cAMP (secondary messenger)

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26
Q

What happens in the lacoperon when glucose is present?

A

When glucose present -> levels of cAMP decreased -> reduces transcription of genes responsible for metabolism of lactose

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27
Q

Product of gene transcription

A

Product of gene transcription = pre-mRNA -> modified forming mature mRNA -> binds to ribosome for protein synthesis

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28
Q

Role of caps on mRNA

A

Cap = modified nucletode added to ends - helps stabilise mRNA and delay degradation in cytoplasm - also aids binding to ribosomes

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29
Q

Pre and post transcriptional control

A

Pre and post transcriptional control:
-Adding caps
-Splicing (removing introns and exons joining together)

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30
Q

How can RNA/mRNA be edited?

A

RNA can be edited through addition, deletion or subsitution -> results in synthesis of different proteins

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31
Q

Mechanisms that regulate the process of protein synthesis

A

Mechanisms that regulate the process of protein synthesis:
-Degradation of mRNA
-Binding of inhibitory proteins
-Activation of initiation factors that aid binding of mRNA

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32
Q

Degradation of mRNA as a way to regulate protein synthesis

A

Degradation of mRNA as a way to regulate protein synthesis = more resistant the molecule -> longer itll last in cytoplasm -> greater quantity of protein synthesised

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33
Q

How RNA can be edited?

A

nucleotide sequence of some mRNA molecules can be changed through base addition, deletion or subsitution which results in syntheses of different proteins

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34
Q

What are protein kinases?

A

Protein kinases are enzymes that catalyse the addition of phosphate groups to proteins -> changes tertiary structure + function
-Enzyme activated by phosphorylation
-Regulators of cell activity’
-Also activated by cAMP

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35
Q

What does post-translation control protein modification include?

A

-Addition of non-protein groups ie lipids
-Modifying amino acids and formation of bonds
-Folding or shortening of proteins
-Modification by cAMP

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36
Q

What is morphogenesis?

A

Morphogenesis is the regulation of the pattern of anatomical development

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37
Q

What are homeobox genes?

A

Homeobox genes are a group of genes which all contain a homeobox

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38
Q

What is a homeobox in homeobox genes?

A

The homeobox in homeobox genes is a section of DNA180 base pairs long coding for a part of the protein 60 amino acids long that is highly conserved (the homeodomain)
-> The homeodain binds to DNA and switches other genes on/off
->Meaning homebox genes are regulatory genes

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39
Q

What are hox genes?

A

Hox genes are one group of homebox genes that are present in aimals and responsible for the correct positioning of body parts

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40
Q

What are diploblastic animals?

A

Diploblastic animals have two primary tissue layers

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41
Q

What are triploblastic animals?

A

Triploblastic animals have three primary tissue layers

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42
Q

Control of vertebrae

A

Vertebrae have developed from segments in the embryo called somites

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43
Q

Different symmetry seen in animals

A

Symmetry:
-Radial symmetry is seen in diploblastic animals - only top and bottom - eg jellyfish
-Bilateral symmetry - both left and right, head, tail
-Asymmetry - no lines of symmetry - ie sponges

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44
Q

Difference between mitosis and aptosis?

A

Mitosis results in cell division and therefore growth, wheras aptosis is programmed cell death - removing unwanted cells and tissues - also stimulates mitosis leading to tissue remodelling elsewhere

45
Q

Factors affecting the expression of regulatory genes

A

Factors affecting the expression of regulatory genes:
Influenced by inernal and external environment - change in temp, light, hormones, psychological stress, drugs (eg thalidomide)

46
Q

Stages of apotosis

A

Stages of aptosis:
-Internal or External signals
-Caspases break down key elements that maintain cell function
-DNAses destroy the DNA inside the nucleus
-The dead cells is ingested by a macrophage

47
Q

Aptosis mechanism

A

Aptosis mechanism:
-Tightly controlled
-Signals internal or external
-Capsases break down key elements that maintain cell function
-DNAses destroy DNA inside nucleus
-Macrophage digests dead cell

48
Q

What influences phenotypic variation?

A

Phenotypic variation is caused by a combination of both genes and the environment

49
Q

What are the causes of genetic variation?

A

Causes of genetic variation include:
-Mutation
-Recombination
-Independant segregation
-Random fertilisation

50
Q

What is recombination?

A

during meiosis, the genes on homologous chromosomes are reshuffled through a process called recombination – produces new combinations of genes

51
Q

What is independant segregation?

A

Independant segregation is the segregation of chrmosomes into haploid cells, random seperation

52
Q

What is meant by random fertilisation as a cause of genetic variation?

A

Random fertilisation - fusion of gametes, increases variation as pairs of chromosomes from two seperate individuals are combined

53
Q

What is genetic linkage?

A

Linkase - when genes that are close to eachother on a chromosome are inhertied together as a single unit

54
Q

What is meant by Mendel’s law?

A

Mendel’s law states that genes do not influence the sorting of alleles into gametes - not always the case as some allele combinations are inherited together (linkage)

55
Q

What are autosomes?

A

Autosomes = all the chromosomes except sex chromosomes (X AND Y) - arranged in pairs (homologous chromosomes)

56
Q

What is meant by autosomal linkage?

A

Autosomal linkage = genes close together on the same autosome are more likely to be transmitted to a gamete together

57
Q

What are X-linked genes?

A

X-linked genes -> males only have one copy of an allele for X-linked genes 0> no allele for the same gene on the Y chromosome - known as hemizygosity

58
Q

What does hemizygosity mean?

A

Hemizygosity - males only have one copy of an allele for X-linked genes - no role of dominance and recessiveness

59
Q

What is haemophilia?

A

Haemophilia is an X-linked blood disorder

60
Q

Reasons for chlorosis in plants

A

Chlorosis in plants:
-Lack of mineral defficiency
-Disease
-Faulty cell division

61
Q

What are the ways in which meiosis can lead to genetic variation?

A

Meiosis can lead to genetic variation:
-Corssing over
-Independant assortment of chromosomes or chromatids
-Mutation
-Changes in chromsome number eg polypoidy plants, down syndrome

62
Q

What is continuous variation?

A

Continuous variation = quantitative, within a range, polygenic -> diff alleles at a single locus = smaller effect
-Affected by both genes and environment

63
Q

What is discontinous variation?

A

Discontinuous variation = qualitative, categories, monogenic - different alleles at a single locus = large effect
-Affected by genes only

64
Q

What is monogenic inheritance?

A

Monogenic inheritance is inheritance for a single gene

65
Q

What is meant by codominance?

A

Codominance is where two alleles are equally dominant

66
Q

What is haemophillia?

A

Haemophillia is an inherited blood disorder caused by a recessive hetereozygous allele - females are the carriers, males express it (as males have only one X chromosome

67
Q

What is dihybrid cross?

A

Dihybrid cross considers the inhertiance of two characteristics at the same time - 2 different genes on 2 different chromosomes

68
Q

What is an autosome?

A

Autosome = name given to any chromosome that isn’t a sex chromosome (X/Y)

69
Q

What is meant by genetic linkage?

A

Genetic linkage = tendency of alleles that are located close together on a chormosome - inherited as one unit during meiosis - no independant assortment
-Linkage crosses -> crossing over = few recombinants where genotype different to parents

70
Q

What affects frequency of recombinants?

A

Closer the genes are = less likely to be seperated = fewer recombinants

71
Q

How to find recombinant frequency?

A

Recombinant frequency = (number of recombinant offspring x 100%) / (total number of offspring)

72
Q

What is the chi squared test used for?

A

The chi squared test is used to see if results fit the pattern expected -> checking different between actual and predicted results are due to chance or due to significant difference

73
Q

When are results significant/not significant?

A

-less than critical value = no significance = accept the null hypotheses
-more than critical value = significance = reject the null hypotheses

74
Q

How to find degree of freedom in the chi squared test

A

Degree of freedom -> columns - 1

75
Q

What is meant by epistasis?

A

Epistasis = gene interaction - when genes on different loci interact to affect one phenotypic characteristic -> so action of one gene modified by another gene

76
Q

What are the was in which epistasis may work?

A

Epistasis may work:
-Antagonistic - results in masking, expressed = epistatic, masked gene = hypostatic
-Complementary - works together

77
Q

What are the three types of epistasis?

A

3 types of epistasis:
-Recessive
-Dominant
-Complementary

78
Q

What is recessive epistasis?

A

Recessive epistasis = homozygous recessive allele of one gene locus masks the affect of the allele at another gene locus

79
Q

What is dominant epistasis?

A

Dominant epistasis = dominant allele of one gene masks the effect of an allele at another gene

80
Q

What is complimentary epistasis?

A

Complimentary epistasis = both dominant alleles of a pair of genes are required to produce a given phenotype

81
Q

What is meant by population genetics?

A

Population genetics investigate how allele frequencies change over time

82
Q

What is a gene pool?

A

Gene pool refers to the sum of all genes in a population

83
Q

What is meant by allele frequency?

A

Allele frequency = relative frequency of an allele - in diploid ppulations with two potential alleles frequency is always 1 (Hardy-Weinberg Principle)

84
Q

What is meant by the Hardy-Weinburg principle?

A

The Hardy-Weinburg Priniciple = In a stable population, with no disturbing factors, the allele frequencies remains constant -> no evolution between generations

85
Q

What are the factors affecting evolution?

A

Factors affecting evolution:
-Mutation (different alleles)
-Sexual selection (increase in allele frequency)
-Gene flow (movement of alleles between populations due to immigration/emmigration
-Genetic drift (change in allel frequency due to mutation - greater impact in smaller populations
-Natural selection (increased characteristics that aid survival

86
Q

What affects population stability

A

Factors that affect population stability:
-Selection pressures
-Predation
-Natural seelction
-Variation
-Survival of the fittest

87
Q

What are the three types of selection?

A

Three types of selection:
-Stabilising
-Directional
-Disruptive

88
Q

What is meant by stabilising selection?

A

Stabilising selection = selection in favour of the norm eg birth weight

89
Q

What is meant by directional selection?

A

Directional selection = positive selection for one of the extremes eg peppered moths

90
Q

What is meant by disruptive selection?

A

Disruptive selection = norm is selected against eg galapgos finches

91
Q

What is genetic drift?

A

Genetic drift is when chance dictates passing of alleles -> becomes common -> not due to survival

92
Q

What is meant by population bottleneck?

A

Population bottleneck = large reductions in population size which last for at least one genreation

93
Q

What is meant by density-dependant factors in evolution

A

Density-dependant = competition, predation, disease
Density-independant = affect populations at all sizes - natural disasters, seasonal changes

94
Q

What is meant by the founder effect?

A

The founder effect = small population can arise due to establishment of new colonies by a few isolated individuals -> small gene pools, less genetic variation, but more advantageous alleles as passed on from original generation

95
Q

What is speciation?

A

Speciation is the formation of new species through evolution -> new organisms can’t interbeed to produce fertile offspring with organisms of the original species

96
Q

What causes speciation?

A

Speciation occurs due to:
-Organisms isolated isolated and can’t interbreed with rest of population -> no gene flow
-Alleles undergo mutations - different environment / selection pressures - diff mutations
-Accumulations of mutations leads to phenotype changes

97
Q

What is meant by allotropic speciation?

A

Allotropic speciation = form of speciation - some members of population seperated by physical barrier - different selection pressures - isolation results in founder effect and genetic drift
-Eg galapagos finches

98
Q

What is meant by sympatric speciation?

A

Sympatric speciation = occurs within populations that share the same habitat
-No geographical isolation
-Involves reproductive isolation within a randomly mating population
-Caused by rapid genetic change that alters morphology, behaviour, habitat preference

99
Q

What are reproductive barriers to speciation?

A

Prezygotic reproductive barriers prevent fertilisation and formation of a zygote - as a result of hybridisation

100
Q

What is artificial selection?

A

Artificial selection - selective breeding of desirable characteristics - closely related = inbreeding of species

101
Q

What are the limitations of artificial selection?

A

Limitations of artificial selection:
-Limits gene pool - limits genetic diversity - less adaptations
-Closely related - same recessive alleles - offspring more likely to be affected by homozygous recessive genetic disorders

102
Q

What are gene banks?

A

-Seed banks keep seeds
-Gene banks store biological samples other than seeds eg sperms
-Outbreeding - causes genetic diversity - reduces occurrence of homozygous recessives

103
Q

What is adaptive radiation?

A

Adaptive radiation = where rapid organism diversification takes place) - eg galapagos finches evolving to adapt to different environments

104
Q

What is an operon?

A

An operon is a cluster of genes under control of a promoter

105
Q

Where does lactose bind to?

A

Lactose binds to the repressor protein (allows RNA to then bind to the promoter)

106
Q

Why are Hox genes consistent over every being?

A

Hox genes are highly conserved - mutation would have large effect potentially lethal

107
Q

What is a homeobox gene?

A

A homeobox gene contains a homeobox which is 180 base pairs long, regulates gene expression and is responsible for the development of the body plan

108
Q

Difference between regulatory genes and structural genes?

A

Regulator genes - makes transciption factors, regulates gene expression/transcription of the structural genes
Structural genes - makes the protein - transcribed by the regulatory genes

Y13 Biology (19 decks)

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