47. Chromosomal (structural) mutations - definition, different rearrangements, “chromosomal diseases”.

Question 1

Translation - refers to an exchange of chromosome segments. With centric fusion, 2 complete chromosomes are involved
Reciprocal translation - only a part of the 2 chromosomes is exchanged

Answer 1

Translation - refers to an exchange of chromosome segments. With centric fusion, 2 complete chromosomes are involved
Reciprocal translation - only a part of the 2 chromosomes is exchanged

Question 2

Genetic fusion of afrocentric chromosomes:

• chromosome 14 and chromosome 21 pair during meiosis, different gametes are formed after fertilisation, the corresponding zygotes contain:
• either only 1 chromosome 21 (unviable monosomy 21)
• a normal chromosome complement
• on balanced chromosome complement with the fused chromosome
• 3 chromosome 21 (trisomy 21) - leads to down syndrome

Answer 2

Genetic fusion of afrocentric chromosomes:

• chromosome 14 and chromosome 21 pair during meiosis, different gametes are formed after fertilisation, the corresponding zygotes contain:
• either only 1 chromosome 21 (unviable monosomy 21)
• a normal chromosome complement
• on balanced chromosome complement with the fused chromosome
• 3 chromosome 21 (trisomy 21) - leads to down syndrome

Question 3

Reciprocal translocation:

• chromosome material is either lost or gained as a result it doesn’t cause clinical signs (it’s balanced)
• carriers may form gametes with unbalanced chromosome complements

Answer 3

Reciprocal translocation:

• chromosome material is either lost or gained as a result it doesn’t cause clinical signs (it’s balanced)
• carriers may form gametes with unbalanced chromosome complements

Question 4

Balanced and unbalanced effects:

• balanced rearrangement - no chromosomal material has been lost or gained - no effect on phenotype
• unbalanced abberations - chromosomal material has either been added (partial duplication or lost, partial deficiency)

Answer 4

Balanced and unbalanced effects:

• balanced rearrangement - no chromosomal material has been lost or gained - no effect on phenotype
• unbalanced abberations - chromosomal material has either been added (partial duplication or lost, partial deficiency)

Question 5

Isochromosomes - arises when a normal chromosome divides transversely instead of longitudinally so that it is composed of 2 long or 2 short arms

Dicentric chromosomes:

• contain 2 centromeres
• unstable - torn apart during mitosis - parts are divided between two daughter cells

Answer 5

Isochromosomes - arises when a normal chromosome divides transversely instead of longitudinally so that it is composed of 2 long or 2 short arms

Dicentric chromosomes:

• contain 2 centromeres
• unstable - torn apart during mitosis - parts are divided between two daughter cells

Question 6

Ring chromosomes

• arise after 2 breaks followed by joining of 2 cap ends
• distal segments are lost
• .’. a ring chromosome is unbalanced

Answer 6

Ring chromosomes

• arise after 2 breaks followed by joining of 2 cap ends
• distal segments are lost
• .’. a ring chromosome is unbalanced

Question 7

Inversion - an inversion is a 180* change in direction of a chromosomal segment

Interchromosomal and intrachromasomal mutations - translocations

Intra - deletion - structural chromosomal diseases resulting from deletions = Prader-Willi’s

Answer 7

Inversion - an inversion is a 180* change in direction of a chromosomal segment

Interchromosomal and intrachromasomal mutations - translocations

Intra - deletion - structural chromosomal diseases resulting from deletions = Prader-Willi’s