Question

What can short repeated sequences within homologous chromosomes cause?

Answer 1

Short repeated sequences within homologous chromosomes can cause genetic variations through duplications and translocations during meiosis. Duplications generally do not affect the phenotype, while translocations can be harmful. These genetic changes contribute to the diversity of offspring by creating new combinations of genes.

Step-by-step explanation:

Short repeated sequences within homologous chromosomes can lead to genetic events like duplications and translocations, which can impact genetic diversity and organism viability. During meiosis, specifically in prophase I, homologous chromosomes may not repair errors perfectly, leading to such changes. Duplications often do not change the organism's phenotype and are typically retained, contributing to genetic variation without harmful effects. However, translocations, which involve the exchange of sequences between nonhomologous chromosomes, can be lethal or significantly alter the phenotype.

In the context of homologous recombination and crossover events during meiosis I, genetic variation is introduced. These events involve non-sister chromatids exchanging DNA, which shuffles alleles and can create new combinations of maternal and paternal genes. The resultant gametes contain unique DNA profiles, contributing to the genetic diversity of offspring. It is also important to note that in meiosis II, similar to mitosis, chromatids segregate into separate cells, but due to previous crossover events, they are not identical genomes.

Answer 2

Short repeated sequences within homologous chromosomes can cause various genetic phenomena, including but not limited to:

Instability: These repetitive sequences, known as microsatellites or short tandem repeats (STRs), can lead to genetic instability. The repetitive nature makes them prone to expansion or contraction during DNA replication or repair, causing mutations.

Genetic Disorders: Expansion of repeated sequences beyond a certain threshold can cause genetic disorders known as repeat expansion disorders. Diseases like Huntington's disease, Fragile X syndrome, and certain types of ataxias are caused by expanded repeat sequences in specific genes.

Mismatch Repair Errors: Repetitive sequences can cause errors during DNA replication and repair processes. The mismatch repair system may misalign the repeated sequences, leading to insertions or deletions within the genome.

Chromosomal Rearrangements: Unequal crossover events between repetitive sequences on homologous chromosomes can lead to chromosomal rearrangements such as deletions, duplications, inversions, or translocations.

Evolutionary Changes: These repetitive sequences can contribute to genetic diversity and evolution by facilitating recombination events that result in the creation of new gene combinations or alleles.

Diagnostic Markers: Short repeated sequences, particularly microsatellites, are often used as genetic markers in genetic studies, population genetics, forensics, and paternity testing due to their variability among individuals.

In summary, short repeated sequences within homologous chromosomes can have various effects, ranging from genetic instability and disease to evolutionary changes and serving as useful genetic markers in research and diagnostics.

Step-by-step explanation:

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