AP BIOLOGY

Detailed explanation-1: -Some chromosomes have fragile spots where breaks occur which result in the deletion of a part of chromosome. The breaks can be induced by heat, viruses, radiations, chemicals. When a chromosome breaks, a part of it is deleted or lost, the missing piece of chromosome is referred to as deletion or a deficiency.

Detailed explanation-2: -Deletions. Deletions occur when a chromosome breaks and some genetic material is lost. Deletions can be large or small, and can occur anywhere along a chromosome. Duplications.

Detailed explanation-3: -Deletions occur when there is homologous but unequal recombination between gene sequences. Similar sequences in the human genome can cross over during mitosis or meiosis, resulting in a shortened portion of the gene sequence.

Detailed explanation-4: -Normally, meiosis causes each parent to give 23 chromosomes to a pregnancy. When a sperm fertilizes an egg, the union leads to a baby with 46 chromosomes. But if meiosis doesn’t happen normally, a baby may have an extra chromosome (trisomy), or have a missing chromosome (monosomy).