45. Genotype alteration. Mutations - definition, different kinds.

Question 1

Mutation: Change in the sequence of DNA encoding a gene. Any event that changes the gene structure. Mutations are the base for evolution.

Answer 1

Mutation: Change in the sequence of DNA encoding a gene. Any event that changes the gene structure. Mutations are the base for evolution.

Question 2

Mutations can be:

1. Spontaneous or induced
2. Straight (from dominant to recessive allele) or reverse (vice versa)
3. Somatic or generative (if sex chromosomes are affected)
4. According to expression. Morphological, biochemical, physiological
5. Physical, chemical or biological
6. chromosomal, structural, gene/ part or genomic/ numerical
7. Lethal or sublethal

Answer 2

Mutations can be:

1. Spontaneous or induced
2. Straight (from dominant to recessive allele) or reverse (vice versa)
3. Somatic or generative (if sex chromosomes are affected)
4. According to expression. Morphological, biochemical, physiological
5. Physical, chemical or biological
6. chromosomal, structural, gene/ part or genomic/ numerical
7. Lethal or sublethal

Question 3

1. Substitution
   - Transversion: purine pyrimidine

• Transition: purine ——> pyrimidine, pyrimidine ——> purine
• Exchange of one or more bases for other/s

Answer 3

1. Substitution
   - Transversion: purine pyrimidine

• Transition: purine ——> pyrimidine, pyrimidine ——> purine
• Exchange of one or more bases for other/s

Question 4

1. Substitution
   Silent: coding for the same amino acid

Missense: resulting in a wrong amino acid e.g. sickle cell anaemia Non-sense: produces a stop codon - non functional protein e.g. cystic fibrosis

Neutral: coding for a different amino acid, but similar chemically and in properties

Answer 4

1. Substitution
   Silent: coding for the same amino acid

Missense: resulting in a wrong amino acid e.g. sickle cell anaemia Non-sense: produces a stop codon - non functional protein e.g. cystic fibrosis

Neutral: coding for a different amino acid, but similar chemically and in properties

Question 5

2. Deletion: elimination of one or more bases or even a whole chromosome. When the missing part is at the end of the chromosome, it’s called deficiency [Point or Block]
3. Insertion: adding one or more bases
4. Inversion: switching a sequent of the sequence of DNA
   - paracentric

• pericentric - induces the centromere

Answer 5

2. Deletion: elimination of one or more bases or even a whole chromosome. When the missing part is at the end of the chromosome, it’s called deficiency [Point or Block]
3. Insertion: adding one or more bases
4. Inversion: switching a sequent of the sequence of DNA
   - paracentric

• pericentric - induces the centromere

Question 6

5. Translocation: a segment or the whole chromosome changes location. e.g. 46, t21/14 Down syndrome
   - reciprocal
   - transposition
6. Frameshift mutation: insertion or deletion of bases not in triplets, altering the reading of

the DNA molecule

Answer 6

5. Translocation: a segment or the whole chromosome changes location. e.g. 46, t21/14 Down syndrome
   - reciprocal
   - transposition
6. Frameshift mutation: insertion or deletion of bases not in triplets, altering the reading of

the DNA molecule

Question 7

7. Duplication: repetition of a chromosome
8. Robertsonian translocation: 2 acrocentric chromosomes fuse
9. Iso chromosome: when the chromosome is divided transversely receiving 2p arms or 2g arms
10. Ring chromsome: due to sequent loss, the two ends pin together
11. Dicentric chromosome: processing 2 centromeres

Answer 7

7. Duplication: repetition of a chromosome
8. Robertsonian translocation: 2 acrocentric chromosomes fuse
9. Iso chromosome: when the chromosome is divided transversely receiving 2p arms or 2g arms
10. Ring chromsome: due to sequent loss, the two ends pin together
11. Dicentric chromosome: processing 2 centromeres

Question 8

12. Aneuploidy: deviation in a single pair due to abnormal distribution during meiosis Monosomy (2n-1) monosomy of autosomes is lethal and OY
    Trisomy (2n+1) trisomy of chromosomes is lethal
13. Polyploidy: not visible in humans but common in plants and some animals. It consists of the presence of various bits of chromosomes - lethal in humans

Answer 8

12. Aneuploidy: deviation in a single pair due to abnormal distribution during meiosis Monosomy (2n-1) monosomy of autosomes is lethal and OY
    Trisomy (2n+1) trisomy of chromosomes is lethal
13. Polyploidy: not visible in humans but common in plants and some animals. It consists of the presence of various bits of chromosomes - lethal in humans

Question 9

Chromosomal diseases

1. Cri du chats syndrome: deletion 5p
2. Prader Willi syndrome: deletion 15q
3. Retinoblastoma: deletion 13q
4. Burkitt’s lymphoma: t8q —> 14
5. Myelocytic leukemia: philadelphia chromosome t9 —> 22

Answer 9

Chromosomal diseases

1. Cri du chats syndrome: deletion 5p
2. Prader Willi syndrome: deletion 15q
3. Retinoblastoma: deletion 13q
4. Burkitt’s lymphoma: t8q —> 14
5. Myelocytic leukemia: philadelphia chromosome t9 —> 22

Question 10

Human syndromes:

1. Patau’s (47, 13+)
2. Edward’s (47, 18+)
3. Down syndrome
   - sporadic, non disjunction (47, 21+)

• familial (46, t21/ 14)

Answer 10

Human syndromes:

1. Patau’s (47, 13+)
2. Edward’s (47, 18+)
3. Down syndrome
   - sporadic, non disjunction (47, 21+)

• familial (46, t21/ 14)

Question 11

4. Turner’s (45, XO) - monosomy
5. Klinefelter’s (47, XXY)
6. Superwoman (47, XXX)
7. Superman (47, XYY)

Answer 11

4. Turner’s (45, XO) - monosomy
5. Klinefelter’s (47, XXY)
6. Superwoman (47, XXX)
7. Superman (47, XYY)