Chromosome errors

Duplication

Sex chromosomes are what

Pseudohomologs

What are reciprocal crosses?

When you swap around sex linked traits, and the embryo’s change as well depending on genotype the parents.

Nondisjunction

An error in chromosome segregation during meiosis or mitosis.

Nondisjunction in meiosis 1

Homologs fail to separate

N+1 ×2 (homologs together)

N-1 ×2

Nondisjunction during meiosis 2

Sister chromatids fail to separate

N+1 (sister together)

N-1

N x 2 (normal)

Polyploidy

Changes in whole sets of chromosomes. So nondisjunction would result in ALL chromosomes during meiosis.

2n+2n+2n→ 3n 3n 3n

3n+3n→ n n

Aneuploidy

Changes in numbers of individual chromosome. So nondisjunction would result in a change of ONE pair of chromosomes during meiosis.

2n+2n+2n→ 3n 2n 2n

Inversion

Cut DNA and invert it into another region. No loss of sequences, all the same sequences are there, just rearranged. The effect depends on location and type of genes inverted.

Deletion

Effects vary, but some diploid organisms likely have a healthy copy of that deleted gene that they can use instead,

Translocation

Non-homologous material inserted into a chromosome- a disruption. Material can be exchanged, but this may disrupt expression.

Duplication

A large region that is duplicated in a chromosome. Effect depends on the specific region that is duplicated

Monosomic

2n-1. Removing 1 copy in the whole genome.

What does a chromosomal duplication look like?

During homolog pairing in meiosis 1, the region will loop out. May lead to complication during crossing over.

What the two types of inversions and what do they mean?

Para centric= outside of centromere. The strands inverted will have off centered centromeres that are not included in the strand.

Peri centric= spans centromere. The inversion strand will include the centromere within the strand.

Both lead to duplications and deletions.

How does translocation affect meiosis?

Homologous bits will be on different chromosomes, so they will form a structure that allows homologs to pair. This unique configuration will lead to abnormal pairing in meiosis 1 which may lead to inviable progeny. Of course, may lead to duplication or deletion.