Gene duplication adds an extra copy of a DNA region containing a gene. It is an important source of new genetic material and can occur through errors in DNA replication and repair or through changes involving entire chromosomes or genomes.
During meiosis, homologous chromosomes can become misaligned. If they exchange DNA at corresponding but unequal positions, an event called unequal crossing-over occurs. One chromosome receives a duplicated region, while the other receives a reciprocal deletion. The likelihood of this event is influenced by how much repetitive DNA the chromosomes share.
All flashcards
What is unequal crossing-over?
It is an exchange between misaligned homologous chromosomes during meiosis. It typically creates a duplication on one chromosome and a reciprocal deletion on the other.
How does replication slippage cause duplication?
DNA polymerase pauses or dissociates, then realigns at the wrong position. The misalignment can cause a previously copied segment to be copied again.
What is a retrogene?
A retrogene is a gene copy formed when cellular mRNA is reverse-transcribed into DNA and inserted elsewhere in the genome. It often lacks introns and may have altered regulation.
What is the difference between aneuploidy and polyploidy?
Aneuploidy changes the number of particular chromosomes. Polyploidy adds one or more complete sets of chromosomes, duplicating the whole genome.
Why can polyploidy contribute to speciation?
An organism with a different chromosome-set number may be unable to interbreed successfully with its non-polyploid relatives, creating reproductive isolation.
Quiz questions
What is gene duplication?Answer: An extra copy of a DNA region containing a gene.
What are the typical reciprocal products of unequal crossing-over?Answer: A duplicated region on one chromosome and a deleted region on the other.
How can replication slippage produce a duplicated sequence?Answer: DNA polymerase realigns incorrectly and copies a segment more than once.
Which feature is commonly found in a retrogene compared with its parental gene?Answer: It often lacks introns and may contain a poly(A) sequence.
Why can polyploidy be less disruptive to gene dosage than aneuploidy?Answer: It adds copies of the entire genome, tending to preserve relative gene dosage.
Based on the Wikipedia article Gene duplication, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.