Genetics and inherited genetic disorders Flashcards
(135 cards)
1
Q
Define GENETICS
A
The study of characteristics and how they are passed on. Every normal body cell contains sufficient genetic information to make a whole animal, but each cell only uses the part of the genetic code it needs to live and function correctly.
2
Q
Define a GENE
A
A group of DNA nucleotides. It determines a particular characteristic or part of it. They have specific locations on the chromosomes, which are known as a gene locus
3
Q
Define LOCUS
A
Literally means ‘location’, it is a specific, fixed position on a chromosome where a particular gene or genetic marker is located.
4
Q
Define an ALLELE
A
One or more forms of a gene held on the same locus of each chromosome pair. They may be dominant or recessive. They are ‘gene variants’
5
Q
Define GENOTYPE
A
The genetic code of an organism
6
Q
Define PHENOTYPE
A
The appearance and characteristics of an organism, as determined by its genotype
7
Q
Define HAPLOID
A
Half the number of total chromosomes - half of the homologous pairs are maternal and come from the mother, whereas half are paternal and come from the father
8
Q
Define DIPLOID
A
A normal number of chromosomes. It refers to a cell containing two sets of homologous chromosomes wherein each set is obtained from each of the two parent cells
9
Q
Define CHROMOSOMES
A
A type of DNA that is packed with protein
10
Q
Define HOMOLOGOUS CHROMOSOMES
A
The chromosomes that possess similar or corresponding genes for certain traits. In animals, at each genetic locus alleles are present and these have been inherited from the parent
11
Q
What is the total number of chromosomes in an organism made up of?
A
Heterosomes and autosomes
12
Q
What are autosomes?
A
Non sex chromosomes; they come in homologous pairs (diploids)
13
Q
What are heterosomes?
A
Sex chromosomes - in males it is XY and in females XX. They determine the sex of an individual. There is only one pair of haploids
14
Q
How is sex in mammals determined?
A
By the heterosomes
15
Q
How many genes does the X chromosome contain?
A
About 2000 genes - it is the larger of the two heterosomes
16
Q
How many genes does the Y chromosome contain?
A
Fewer than 100 - it is the smaller of the two heterosomes
17
Q
What is a homogametic sex?
A
Females are the homogametic sex, as they have gametes with the same sex chromosomes
18
Q
What is a heterogametic sex?
A
Males are the heterogametic sex as they have gametes with differing sex chromosomes
19
Q
How many chromosomes are there in the normal dog?
A
78, which is made up of 38 pairs of autosomes and 1 pair of heterosomes
20
Q
How many chromosomes are there in a normal cat?
A
38, which is made up of 18 pairs of autosomes and 1 pair of heterosomes
21
Q
What are recessive genes?
A
Genes that are only able to display in the phenotype when they are both present. They are displayed as a lower case letter
22
Q
What are co dominant alleles?
A
In cases where the alleles are different but they are both expressed
23
Q
What are dominant genes?
A
Genes that are able to display in the phenotype with only one present - they stop other genes having an effect, and are written using a capital letter
24
Q
What is a heterozygous allele?
A
If the gene locus on each chromosome of a homologous pair has different alleles, they will have the same location, but different information.
25
What is a homologous allele?
Sometimes at a certain gene locus on each chromosome of a homologous pair is the same allele. The animal has an identical pair of genes for that characteristic (same location, with the same information).
26
Define EPISTASIS
The interaction between genes that influences a phenotype
27
What is important to consider when trying to work out the phenotype of an animal's offspring?
The phenotype is not necessarily the same as the genotype - the animal's genotype can include lots of recessive genes which may not be visible when you look at the animal
28
What is the F1 generation in the context of genetic experimentation?
The F1 generation is the offspring of the first 2 animals mated with one another (e.g. two purebreeds crossed, so their offspring is 50/50). They are also called First Filial generation. If these offspring are mated, their respective offspring is called the F2 generation and so on.
With a wider gene pool, the line can become pure again around F7
29
What causes hereditary conditions?
Mutations in genes that are transmitted between generations by reproduction. The mutations are spontaneous and random, and only passed through reproduction
30
When is a disease suspected of being hereditary?
If it appears in animals of the same breed, usually pedigree cats and dogs
31
What is pedigree analysis?
Offers a straightforward means of demonstrating hereditary and determination of the mode of inheritance of simple genetic disorders
32
What are the downsides of pedigree analysis?
It requires a details clinical history and examination, and lab testing on large numbers of related individuals which is often impractical.
Some hereditary diseases present late in life and may be missed on clinical exams when the animal is young.
33
What can new panel DNA tests screen for?
- disease associated with mutation
- tests for coat colour
- to examine genetic diversity
34
What are the potential disadvantages of panel DNA testing?
Most of the panel DNA tests are not relevant to the breed being tested so the results can be misinterpreted e.g. in the case of a genetic disease being unlikely to affect a certain breed.
35
What genetic test has the KC come up with?
Combi-breed, it is an all in one test for multiple genetic disorders.
36
What are estimated breeding values?
A tool for breeders to use to help reduce disease prevalence - they allow breeders to determine relative genetic risk of an individual for a certain trait that may be passed onto their offspring via mating.
37
How are estimated breeding values calculated?
By using the results of health screening for an individual and all of its relatives. It is compared with the breed average which is always set at zero.
38
How are EBVs read?
The breed average is always set at zero, so a negative EBV represents a lower genetic risk, and a positive EBV represents a higher genetic risk than the breed average
39
What is the function of health schemes?
To identify animals affected by hereditary diseases - they can then be removed from the breeding population, and disease prevalence can be reduced over time.
40
How are most DNA tests carried out?
Via buccal mucosal swabs, which means that breeders and owners are able to test at home. They can therefore be more aware of the genetic diseases which may affect their pet
41
What are some examples of hereditary diseases that affect cats and dogs?
Autosomal dominant progressive retinal atrophy, Collie eye anomaly (choroidal hypoplasia), Bobtail, Hereditary cataracts,
Multidrug resistance, Primary open angle glaucoma, von Willebrand’s disease, Progressive rod-cone degeneration, Copper toxicosis, Cerebellar ataxia, Gangliosidosis 1 and 2, Hypertrophic cardiomyopathy, Polycystic kidney disease, Pyruvate kinase deficiency, Spinal muscular atrophy
42
What is autosomal dominant progressive retinal atrophy?
A hereditary condition that involved progressive deterioration to the optic nerve, causing vision loss.
43
What breeds are commonly affected by autosomal dominant progressive retinal atrophy?
Bullmastiffs and English Bullmastiffs
44
What is collie eye anomaly?
Also called choroidal hypoplasia - it involves the underdevelopment of the choroid (the vascular layer) and may result in vision problems, pupil abnormalities, ocular abnormalities and photophobia. It is recessive, and both parents must have the gene for it to be passed on
45
What breeds are commonly affected by collie eye anomaly?
Border collie, Rough collie, Smooth collie, Shetland Sheepdog
46
What is another name for collie eye anomaly?
Choroid hypoplasia
47
What is bobtail?
A hereditary condition that affects tail length. It can be lethal in utero in its homozygous form
48
What breeds are commonly affected by Bobtail?
Australian shepherd, Welsh corgi, Brittany spaniel, Spanish water dog
49
What are hereditary cataracts?
Cataracts that are a result of genetic mutation - affected animals have a higher likelihood of cataracts developing, and earlier in life
50
What breeds are commonly affected by hereditary cataracts?
Australian Shepherd, Boston Terrier, French Bulldog, Staffies
51
What is multidrug resistance?
Resistance to multiple drugs that may be a result of a hereditary disorder
52
What breeds are commonly affected by multi drug resistance?
Australian Shepherd, Border Collie, Old English Sheepdog
53
What is primary open angle glaucoma?
A hereditary condition affecting the anterior chamber of the eye, leading to an increased IOP
54
What breeds are commonly affected by primary open angle glaucoma?
Beagle, Bassett Hound, Shar-Pei, Petit Basset Griffon Vendeen
55
What is von Willebrand's disease?
A hereditary clotting disorder that affects bleeding times
56
What breeds are commonly affected by von Willebrand's disease?
Bernese Mountain dog, Dobermann, German Pinscher, German Shorthaired Pointer, Kerry Blue Terrier, Shetland Sheepdog, Welsh Corgi
57
What is progressive rod-cone degeneration?
A hereditary disorder - it is a form of progressive retinal atrophy that leads to regression of photoreceptor cells in the retina. Often mistaken for cataracts
58
What are some clinical signs associated with progressive rod-cone degeneration?
Night blindness, dilated pupils and increased reflection from the eye
59
What breeds are commonly affected by progressive rod cone degeneration?
Cocker spaniel, American cocker spaniel, Labrador, Miniature Poodle, Yorkshire Terrier
60
What is copper toxicosis?
A hereditary condition in which a dog's system accumulates copper instead of naturally excreting it. It can result in severe liver disease and liver failure
61
What breeds are commonly affected by copper toxicosis?
Bedlington, WHWT
62
What is cerebellar ataxia?
A hereditary disease - it is a form of ataxia caused by abnormalities in the cerebellum
63
What breeds are commonly affected by cerebellar ataxia?
The Italian Spinone
64
What is gangliosidosis 1 and 2?
A hereditary disorder in which the animal lacks the beta-galactosidase enzyme, meaning they are unable to break down certain carbohydrates. Can cause depression, seizures, deafness, blindness etc
65
What breeds are commonly affected by gangliosidosis 1 and 2?
Korat, Siamese, Burmese
66
What is hypertrophic cardiomyopathy?
A hereditary condition in which the heart muscle is abnormally thickened
67
What breeds are commonly affected by hypertrophic cardiomyopathy?
Maine Coons and Ragdolls
68
What is polycystic kidney disease?
A hereditary disease in which multiple cysts form on the kidneys and affect their function
69
What breeds are commonly affected by polycystic kidney disease?
Persian
70
What is pyruvate kinase deficiency?
A hereditary disorder affecting red blood cells, which results in repeated haemolytic anaemia
71
What breeds are commonly affected by pyruvate kinase deficiency?
Abyssinian and Somali cats
72
What is spinal muscular atrophy?
A hereditary neuromuscular disorder that affects motor neurons in the spinal cord, causing progressive muscle degeneration and weakness
73
What breeds are commonly affected by spinal muscular atrophy?
Maine Coon cats
74
Which two organisations work together to offer health screening services for dogs?
The BVA and the KC. Collectively these are known as the canine health schemes
75
Define DYSPLASIA
Generally it means abnormality of development and usually refers to either a hip or an elbow
76
What is hip dysplasia?
A canine genetic condition in which there is a tendency towards development of hip laxity later in life. Affected dogs are born with normal hips, and the condition develops. The ligaments around the joint become loose and the socket becomes flattened and deformed. Secondary arthritis will develop in the joint too.
77
Is hip dysplasia congenital or hereditary?
It is hereditary - affected dogs are born with morphologically normal hips, and the condition develops later in life.
78
What do all dogs with hip dysplasia develop?
Secondary arthritis of the affected joint.
79
What breeds are commonly affected by hip dysplasia?
Labrador retrievers, golden retrievers, German shepherds, Rottweilers, Bernese Mountain dogs, Newfoundlands
80
What breeds is the hip dysplasia scheme open to?
Open to all breeds and crossbreeds - the basis of the scheme is radiographic assessment of young adult dogs at least 12 months of old prior to breeding
81
What is the minimum age requirement for screening via the hip dysplasia scheme?
12 months old, prior to breeding
82
How does the BVA/KC hip dysplasia scheme work?
Radiographs are taken to screen for abnormalities of the hip joint - the radiographs are assessed by BVA approved scrutineers for any anatomical or pathological changes that are indicative of hip dysplasia
83
How is hip dysplasia scored in dogs?
Each hip is scored 0-53, and the total is given out of 106
84
What is the breed median score in relation to hip dysplasia?
85
What is elbow dysplasia?
86
What can elbow dysplasia result in?
87
What breeds are commonly affected by elbow dysplasia?
88
How is elbow dysplasia judged?
89
How is elbow dysplasia severity scored?
90
What is the key difference for elbow and hip dysplasia scoring?
91
What is the ideal score for elbow dysplasia for a dog to be bred?
92
What is the hereditary eye disease scheme?
93
What hereditary eye diseases are tested for?
94
What is multifocal retinal dysplasia?
95
What is total retinal dysplasia?
96
What is primary lens luxation?
97
What is progressive retinal atrophy?
98
What are photoreceptor cells?
99
What are the two forms of progressive retinal atrophy?
100
What is entropion?
101
What is ectropion?
102
What is goniodysgenesis?
103
What is primary closed angle glaucoma also known as?
104
What are multilocular defects?
105
What breeds are commonly at risk from hereditary eye conditions?
106
What is Chiari-like malformation?
107
What is Chiari-like malformation also referred to as?
108
What are syrinxes?
109
What does Chiari-like malformation result in?
110
What breeds is Chiari-like malformation most often seen in?
111
What is the minimum and maximum age for submission to the Chiari-like malformation/syringomyelia health scheme?
112
What is the recommended age for screening for Chiari-like malformation?
113
What are the clinical signs associated with syringomyelia?
114
What is intervertebral disc disease?
115
What is the IVDD scheme?
116
What breed is commonly affected by IVDD?
117
What factors can affect the likelihood of IVDD developing?
118
What are the clinical signs of IVDD?
119
What is the treatment for IVDD?
120
What is the University of Cambridge Respiratory Function Grading Scheme?
121
What breeds can be screened under the University of Cambridge Respiratory Function Grading Scheme?
122
How often should dogs be screened under the University of Cambridge Respiratory Function Grading Scheme?
123
What is the conformation of an animal?
124
What is the Governing Council of the Cat Fancy?
125
What health problems can be related to exaggerated conformation?
126
What are some examples of genetic conditions that the Governing Council of the Cat Fancy encourage screening against?
127
What is the significance of deafness at birth?
128
What is the BAER test?
129
What are some limitations of the BAER test?
130
What is the ideal age to test a litter using the BAER test?
131
At what age do ear canals open in neonates?
132
What is heterochromasia?
133
What breeds are commonly affected by congenital deafness?
134
What is another name for heterochromasia?
135
What are some ways that breeds can preserve genetic diversity and minimise inbreeding?
