Definitions Flashcards
1
Q
Define Gamete
A
Haploid cell, single set of genetic instructions - sperm/egg
2
Q
Define Zygote
A
diploid cell, double set of genetic instructions - fertilised egg/body cells
3
Q
Define Locus
A
location of a genetic instruction on a chromosome
4
Q
Define Allele
A
alternative forms at a particular locus
5
Q
Define Homozygote/Heterozygote
A
identical/non-identical copies of an allele
6
Q
Define Phenotype
A
Physical appearance of an individual with a certain genotype
7
Q
Define Genotype
A
genetic constitution that makes up phenotype
8
Q
Define Dominant
A
allele that when heterozygous, masks effect of other allele
9
Q
Define Incomplete Dominance
A
expression of heterozygote phenotype is an intermediate of dominant heterozygotes e.g 4 O’clock plant
10
Q
Define Codominance
A
phenotypic traits of a gene’s allele are both fully expressed in heterozygotes
11
Q
Define Multiple Alleles
A
more than 2 alleles at a locus e.g Drosophila, Blood types
12
Q
Define Lethal Alleles
A
Homozygotes are lethal e.g. Brachydactyly, Manx Cat
13
Q
Define Pleiotropy
A
one gene affects many characters e.g. blue eyed white cats, sickle cell, tabby cats
14
Q
Define Gene Interaction
A
Several genes affect one character e.g. sex limitation
15
Q
Define Complementation
A
2 strains of an organism with different homozygous recessive mutations produce the same phenotype e.g. Deafness, Foxgloves
16
Q
Define Thomas Hunt Morgan
A
came up with chromosome theory
17
Q
Define Sex-Linked Inheritance
A
inheritance from mutant gene on either X or Y chromosome e.g. colour blindness, Lesch-Nyhan Syndrome, Haemophilia
18
Q
Define X-Chromosome Inactivation
A
genes in one of X-chromosome pair are silenced e.g. tortoiseshell cat, red-green colour blindness, Duchenne muscular dystrophy
19
Q
Define Lyonisation
A
All X-chromosomes of cells in excess of 1 are inactivated randomly (see X-chromosome inactivation)
20
Q
Define Barr Body
A
Inactive X chromosome in a female somatic cell
21
Q
Define Cytogenetics
A
study of chromosomes
22
Q
Define Centromere
A
section where the chromosome attaches to the spindle during cell division
23
Q
Define Telomeres
A
repeated sequences at the end of each chromosome
24
Q
Define Polytene Chromosomes
A
oversized chromosomes developed from normal chromosomes
25
Define Metacentric Chromosomes
centromere at centre of chromosome
26
Define Acrocentric Chromosomes
centromere closer to one end of chromosome
27
Define Telocentric Chromosomes
centromere near very end of chromosome
28
Define P/Q arm
each side of centromere, P=short arm, Q=long arm
29
Define Somatic Cell Hybridisation
Use Sendai virus to fuse HeLa cells to human and mouse cells, used for mapping chromosomes
30
Define Fluorescent in situ Hybridisation (FISH)
Used to detect specific DNA sequences on chromosomes using fluorescent probes
31
Define Chromosome Deletion
section of chromosome removed e.g. Notch Wing, Cri-Du-Chat
32
Define Deletion mapping
zap chromosomes with X-rays to knock out bit of chromosome, can the figure out which genes it coded for
33
Define Chromosome Duplication
section of chromosome doubles up e.g. Globin, Huntington’s, Bar eye (an unnatural ability to find a bar in any situation)
34
Define Inversion
section of chromosome rotated and replaced, loop forms to ensure A-A
35
Define Dicentric chromosomal fragment
Contains two centromeres
36
Define Acentric chromosomal fragment
Contains no centromeres
37
Define Crossover Suppressors
prevent crossover between inverted and normal segments of chromosome
38
Define Translocation
when two non-homologous chromosomes exchange parts e.g.
39
Define Aneuploidy
Individuals with an excess/deficiency of chromosomes e.g. Downs Syndrome
40
Define Nondisjunction
When homologous chromosomes fail to separate and migrate to opposite poles = Trisomy/monosomy e.g Downs Syndrome (trisomy 21), Klinefelters Syndrome (XXY), Turners Syndrome (X0)
41
Define Trisomy
3 chromosomes present instead of the usual 2, form of aneuploidy caused by nondisjunctio
42
Define Monosomy
1 chromosome present instead of the usual 2, form of aneuploidy can be caused by nondisjunction
43
Define Somatic Aneuploidy
Irregular variation in chromosome number in cells in a tissue
44
Define Gynandromorph
Organism which contains both male and female characteristics e.g. Red/White eyed drosophila
45
Define Polyploidisation
changes in the number of chromosome sets, usually lethal in humans, odd numbers cannot pair in meiosis = infertile
46
Define Haplodiploidy
sex determination system, males come from unfertilised eggs (haploid), females come from fertilised eggs (diploid), e.g. Bees, Wasps
47
Define Autopolyploid
polyploid condition from duplication of one diploid set of chromosomes
48
Define Allopolyploidy
polyploid condition formed by union of 2+ different chromosome sets (diff. species), leads to a chromosome number doubling, e.g. origin of wheats
49
Define Synteny
2+ genomic regions derived from single ancestral genomic region, from speciation or polyploidy
50
Define Backcross
cross with a parental type
51
Define Testcross
cross with a double mutant
52
Define Coupling
2 mutants/wild types in each parental strain
53
Define Repulsion
parent has one mutant & one wild type
54
Define Homologues
2 copies of each chromosome (paternal & maternal)
55
Define Chiasma
point where crossing over occurs
56
Define 3 point cross
crossing of an individual heterozygous at 3 loci, with an individual homozygous recessive at 3 loci
57
Define Alfred Sturtevant
Developer of the 3 point cross
58
Define recombination frequency
number of recombinants/total (smaller frequency, fewer chiasmata, closer loci)
59
Define One Map unit
recombination frequency of 1%
60
Define Linkage map
genetic map of a species which shows the position of its genes
61
Define Crossover Interference
interaction between recombination events caused by chiasma influencing chance of another nearby chiasma
62
Define Coefficient of Interference
1 - [(proportion observed)/(proportion expected)]
63
Define Sex-averaged maps
linkage maps averaged over both sexes, due to more recombination in females
64
Define Temperature sensitive mutants with examples
gene expression determined by temperature e.g. Siamese Cat (fur colour), Drosophila (white blood)
65
Define Light sensitive mutants with examples
gene expression determined by light e.g. Arctic Hares, Plants
66
Define Chemical sensitive mutants with examples
gene expression determined by chemicals e.g. E. coli, phenylketonuria, porphyria
67
Define Pharmacogenetics
study of genetic effects on drug metabolism, variable responses to drugs depending on person
68
Define Age Sensitive mutants
gene expression determined by age, phenotypes only expressed after a particular age (or before) e.g. Huntington’s, Cancer, Heart Disease
69
Define Incomplete Penetrance
individuals who fail to express phenotypic trait even thought they carry mutant allele
70
Define Sex-Limitation
autosomal - genes present in both sexes, but phenotypic traits only expressed in one sex due to hormonal environment e.g. Dorset Horned Sheep, male pattern baldness, polycystic ovary
71
Define Single Nucleotide Polymorphisms (SNiPS)
DNA sequence variation occurring commonly in population in which a single nucleotide differs between members of the same species
72
Define Qualitative Genetics
inheritance of character that do not fall into distinct classes e.g. height, weight
73
Define Variance
[sum of(x - Ẍ)2]/n
74
How is Standard deviation found from variance?
Standard Deviation = sqrt.variance
75
Define Heritability
proportion of total variation in population that is due to genetic variation, proportion of total phenotypic variance due to genetic variance
76
Define Heritability equation
H2 = VG/VP (V = variation, G=genotype, P=phenotype)
77
Define Alternate Heritability equation
H2 = VG/(VG + VE + VGE) (g=gene, e=environment)
78
Define Correlation coefficient equation
[Covariance (fathers,sons).(1/(n-1)] /[rho(fathers).rho(sons)]
79
Define Covariance
(height - mean height: of father) x (height - mean height: of son), works out the way fathers and sons jointly deviate from the average
80
What can the correlation coefficient vary between?
0 and 1, 1 for identical twins, 0.5 for siblings, 0.125 for cousins etc
81
Define MRCA
Most recent common ancestor
82
Define Identity By Descent (IBD)
alleles created when homozygous individual receives both copies of allele from the same ancestor e.g. spanish royal family (Charles II), IBD increases with inbreeding
83
Does IBD increase or decrease with inbreeding?
Increase, inbreeding leads to loss of heterozygosity, distinct inbred lines formed
84
Define Coefficient of Inbreeding (F)
probability that a pair of alleles at a locus will be identical by descent
85
What is the equation for the Coefficient of Inbreeding (F)?
F = sum of N.(1/2)^n (N = no. of loops/paths, n=no. of ancestors in each loop) e.g. brother sister = 2x(1/2)^3 = 1/4
86
What is the coefficient of inbreeding between cousins?
1/16 -> 2 x (1/2)^5
87
Define Inbreeding depression
reduction in fitness associated with inbreeding e.g. King Charles Spaniel - syringomelia, Sunny the Bull, Song sparrow, Tutankhamun
88
What are all slugs?
Fucking degenerate snails
89
Define Anisogamy
union of 2 gametes which differ in size (males=smaller gamete, females=larger gametes)
90
Define Patrilineal inheritance
male line of inheritance
91
Define Y-Chromosome inheritance
Y chromosome differential regions recombine with X where recombination takes place
92
Define Pseudo-autosomal regions
homologous nucleotide sequences on X and Y chromosomes which allow recombination to occur between X and Y chromosome, many genes ‘lost’ to X, but SRY gene makes males male
93
Define Matrilineal inheritance
female line of inheritance, occurs in chloroplast & variegated plants = green/white splotches on leaves —> mothers phenotype only expressed
94
What cellular organelle shows matrilineal inheritance?
Mitochondrial genes are only passed down through mother, slow growth (poky) phenotype in neurospora transferred with cytoplasm microinjection,
95
What shape is a mitochondrial map?
ircular, tests using chlamydomonas resistant to different drugs proved this, 3 point cross, gene order diff. in each experiment
96
Define the Endosymbiotic theory
key organelles of eukaryotes originated as symbiosis between different single celled organisms
97
Which diseases are associated with deletions in the mitochondrial genome?
Ragged red fibre muscle weakness
98
Which diseases are mitochondrially inherited?
Leber’s Hereditary optic neuropathy, degeneration of retinal ganglion cells, leads to acute loss of central vision
99
Give an example of bacteria which are passed through maternal lineage
Wolbachia, through female cytoplasm
100
Define Hardy-Weinberg equilibrium
allele/genotype frequencies will remain constant from generation to generation (w/out evolutionary influences) -> p^2 + 2pq + q^2 = 1
101
What things can alter the Hardy-Weinberg equilibrium?
Genetic drift (random change), migration (admixture between Blacks and Whites), non-random mating (incompatible alleles, BRUCE in mice), natural selection
102
Would a dominant or recessive allele take longer to increase in frequency?
Recessive alleles take much longer to increase in frequency than dominant alleles
103
What are 3 classes of mutation?
morphological, conditional and lethal
104
Cancer is usually caused by somatic mutations, but somatic genome instability can cause a predisposition to cancer, what is an example of this?
Retinoblastoma
105
How are mutations detected in bacteria?
Bacteria grown on medium with an antibiotic or lacking an amino acid
106
How are mutations detected in maize?
white allele is recessive, cross cc x CC -> Ccc (triploid), any mutation = single white seed
107
How are mutations detected in mice?
aa bb cc ++ ++ x ++ ++ ++ dd ee -> cross, if mutation occurs at + in c locus then a+ b+ cc d+ e+ = white coat mice (calculate mutation rate)
108
How are mutations detected in humans?
Ames test, use Salmonella to test whether chemical is a mutagen, spontaneous dominant mutations can be used to calculate mutation rate e.g. neurofibromatosis
109
What is the direct method to detect mutations?
Direct massive protein and DNA screens for changes between offspring and parents
110
Define Mutagen
agents that massively increase mutation rate
111
What caused many watch-dial painters to die in the 1920s?
Radon in paint gave them bone cancer
112
Why were low doses of radiation much less harmful than anticipated?
ue to DNA repair mechanisms repairing mutational damage over time, naked mole rat is very radiation resistant
113
What is an example of natural selection in humans?
loss of skin pigment since escape from africa, chimpanzees -> humans (large deletions in human DNA compared to apes), origin of language (FOXP2 locus)
114
What is the name of the locus where language developed?
FOXP2
115
Between chimpanzees and humans, which has more DNA?
Chimpanzees, large deletions in the chimp DNA led to humans -> loss of ability to digest raw food, diminished sexual selection, but increase in brain size/neuronal connectivity
116
What is a synaptomenal complex?
Protein structure that forms between homologous chromosomes during meiosis and mediates chromosome pairing, synapsis and recombination
