20) Genetic nature and molecular causes of genetic diseases and defects

Question 1

Genetic nature causes of genetic diseases and defects can be split into…

Answer 1

• Monogenic inheritance
• Polygenic inheritance

Question 2

Monogenic inheritance

Answer 2

• Single gene
• Mendelian inheritance

Question 3

4 types of Mendelian inheritance

Answer 3

1. Autosomal recessive
2. Dominant
3. X-linked dominant/recessive
4. Complex inheritance

Question 4

Give an example of complete inheritance

Answer 4

Manx cat

• No tail*
• If two none-tailed cats breed → Misscariage*

Question 5

Give an example of co-dominant inheritance

Answer 5

Merle colour in dogs is linked with deafness

Question 6

Recessive inheritance

Answer 6

Most typical inheritance type

Question 7

Monogenic diseases are…

Answer 7

• Usual autosomal
• Rarely x-linked

Question 8

Give examples of x-linked diseases

Answer 8

• Tremor
• Haemophilia
• Nephritis

Question 9

Polygenic inheritance

Answer 9

• Several genes
• Inborn errors of metabolism
• Phenocopy

Question 10

Inborn errors of metabolism

Answer 10

• Enzyme mutation causes enzyme deficiency
• Pathway of enzyme is blocked
• Abnormal accumulation in tissues

Question 11

Phenocopy

Answer 11

• Alternation of phenotype by nutritional factors or environment
• Rickets = phenocopy due to vitamin D deficiency

Question 12

Molecular causes of genetic diseases and defects

Answer 12

1. Point mutations
2. Trinucleotide expansion and insertion mutations
3. Chromosomal abbreviations and abnormalities

Question 13

Types of point mutation

Answer 13

1. Frequent and typical
2. Mis sense
3. Non sense
4. Same sense

Question 14

Frequent and typical

Answer 14

Base change in a change

Question 15

Mis sense

Answer 15

• A nucleotide is substituted for another
• Codon will code for another amino acid
• Canine haemophilia
• Bovine leukocyte adhesion deficiency (BLAD)

Question 16

Non-sense

Answer 16

• Results in a premature stop codon of mRNA
• Results in a non-functional protein
• Inherited goiter in Afrikander cattle and dutch goat

Question 17

Same sense mutation

Answer 17

• ‘Silent mutation’
• Doesn’t result in an amino acid change

Question 18

Trinucleotide expansion and insertion mutations

Answer 18

Subsets of unstable microsatellites inserted or doubled in abnormal ways.

Question 19

Chromosomal abbreviations and abnormalities

Answer 19

• Leads to genome mutation.
• Caused by mistakes during mitosis, meiosis, fertilization – aberrant karyotype
• Change in number of chromosomes

Question 20

Changes in the number of chromosomes

Answer 20

• Monosomy
• Trisomy

Question 21

Monosomy

Answer 21

• XO
• Turner’s syndrome

Question 22

Trisomy

Answer 22

• XXX → Two Barr bodies
• XXY → Klinefelter’s syndrome
• XXXY → Not recognised except in tortoiseshell male cats