Breaking News
January 23, 2019 - The Tiny Camera That Could Revolutionize Cardiovascular Surgery
January 23, 2019 - Peptide isolated from soil fungi has antitumor and antibacterial properties
January 23, 2019 - TGen identifies polio-like virus as potential cause of Acute Flaccid Myelitis outbreak
January 23, 2019 - Migrants and refugees do not bring disease and are at greater health risk themselves says WHO
January 23, 2019 - Examing the effects of menopause in workplace
January 23, 2019 - Enemy number 1 – Air pollution and climate change top of WHO agenda
January 23, 2019 - Two Positive Phase III studies of Tafenoquine for the Radical Cure of Plasmodium vivax Malaria Published in The New England Journal of Medicine
January 23, 2019 - World Trade Center responders at increased risk for head and neck cancers
January 23, 2019 - Low-sugar diet leads to significant improvement in nonalcoholic fatty liver disease in boys
January 23, 2019 - Chaos in bodily regulation can optimize our immune system, finds study
January 23, 2019 - Short, text-based exercises can increase happiness for adults recovering from substance use disorders
January 23, 2019 - Body size may have greater influence on women’s lifespan than men
January 23, 2019 - Groundbreaking tool helps visualize neuronal activity with near-infrared light
January 23, 2019 - Holocaust survivors with PTSD and their offspring exhibit more unhealthy behavior patterns
January 23, 2019 - Scientists discover new genetic mutations causing inherited deaf-blindness
January 23, 2019 - UC team designs new naloxone-dispensing smart device
January 23, 2019 - Torrent Pharmaceuticals Limited Issues Voluntary Nationwide Recall of Losartan Potassium Tablets, USP and Losartan Potassium and Hydrochlorothiazide Tablets, USP
January 23, 2019 - Brain activity shows development of visual sensitivity in autism
January 23, 2019 - Two hour gap between dinner and sleep is overrated says Japanese research
January 23, 2019 - Fear and embarrassment are causing smear test numbers to plummet
January 23, 2019 - Protein-secreting device implanted in epileptic rats reduces seizures, improves cognition
January 23, 2019 - Reintroduction project recovers current wild population of green turtle in Cayman Islands
January 23, 2019 - Cancer survivors face greater financial burden related to medical bills
January 23, 2019 - PSA screening reduces prostate cancer deaths by 30%
January 23, 2019 - LSTM receives grant to help improve health of people living in informal settlements
January 23, 2019 - Hemochromatosis Mutation Linked to Other Morbidity
January 23, 2019 - Why early diagnosis of autism should lead to early intervention
January 23, 2019 - Aspirin May Lower Stroke Risk in Women with History of Preeclampsia
January 23, 2019 - Exposure to certain chemicals may be linked to decrease in blood pressure during pregnancy
January 23, 2019 - Bowel cancer on the rise among younger Australians
January 23, 2019 - Scientists have reversed memory loss in a mouse model of Alzheimer’s
January 23, 2019 - Defective molecular master switch could lead to age-related macular degeneration
January 23, 2019 - Researchers identify how concussions may contribute to seizures
January 23, 2019 - Short interval between last meal of the day and bedtime may not affect blood glucose levels
January 23, 2019 - Still Too Many Highway Deaths Tied to Speeding
January 23, 2019 - Prenatal valproate exposure linked to increased ADHD risk
January 23, 2019 - Compound identified that may help treat heart failure
January 23, 2019 - Undiagnosed Asthma in Urban Adolescents May Be Common
January 23, 2019 - Study describes metabolism of intestinal microbiota in babies for the first time
January 22, 2019 - Study links concussions to development of epilepsy
January 22, 2019 - Specialist-led hospital bereavement service may help restrain legal action after difficult deaths
January 22, 2019 - Genetic study reveals possible new routes to treating osteoarthritis
January 22, 2019 - Blood test may detect early signs of lung-transplant rejection
January 22, 2019 - Blood marker could aid in early prediction of Alzheimer’s progression
January 22, 2019 - Orthodontic treatment does not guarantee future dental health
January 22, 2019 - Rutgers researchers discover cause of bone loss in people with joint replacements
January 22, 2019 - Diversity among rural Africans extends to their gut microbiomes
January 22, 2019 - Newly developed biological system lets cells to create self-curving cornea
January 22, 2019 - VTv Therapeutics Announces Publication of Comprehensive Data in Science Translational Medicine Detailing the Discovery and Clinical Development of TTP399, including Results of Phase 2 AGATA Study
January 22, 2019 - about one in three adults with prediabetes has arthritis
January 22, 2019 - A look at how data is democratizing health care
January 22, 2019 - Alcohol-Linked Disease Overtakes Hep C As Top Reason For Liver Transplant
January 22, 2019 - Researchers identify new genes linked with age-related macular degeneration
January 22, 2019 - MPFI researchers identify synaptic logic for connections between two brain hemispheres
January 22, 2019 - New approach to reduce toxic protein production in ALS
January 22, 2019 - New study extends our knowledge of the link between miRNAs and cancer
January 22, 2019 - Asthma, eczema are not barriers to active lifestyle in teenagers
January 22, 2019 - Genetic changes may predict likelihood of relapse in breast cancer patients
January 22, 2019 - Antiepileptic drug use by people with Alzheimer’s disease linked to accumulation of hospital days
January 22, 2019 - IUPUI researcher receives $2.85 million grant to find ways to improve bone strength
January 22, 2019 - Precision medicine can help keep astronauts healthy during deep space missions
January 22, 2019 - Detecting signs of neurodegeneration earlier and more accurately
January 22, 2019 - Mouse studies challenge ‘inhibition’ theory of autism
January 22, 2019 - SSB launches BIOSTAT RM TX single-use bioreactor for producing consistent quality cellular products
January 22, 2019 - Experimental drug can positively modify key characteristic behavior in FXS patients
January 22, 2019 - Low-Income Women Lack Menstrual Hygiene Supplies
January 22, 2019 - Better mouse model built to enable precision-medicine research for Alzheimer’s
January 22, 2019 - Molecular profiling of precancerous lung lesions could lead to early detection and new treatments
January 22, 2019 - Genetic factors influence where fat is stored in our bodies
January 22, 2019 - The Psychology Behind Sticking to Your New Year’s Resolutions
January 22, 2019 - Scientists aim to find genetic causes of developmental abnormalities in the vagina and uterus
January 22, 2019 - New survey reveals scale of preventative healthcare challenge in the UK
January 22, 2019 - Looming Global Crisis Means People’s Diets Must Change: Experts
January 22, 2019 - Excessive social media use is comparable to drug addiction
January 22, 2019 - Researchers show how mechanical stress affects bone development
January 22, 2019 - Study takes a step closer to understanding the body’s response to opioid painkillers
January 22, 2019 - Unexpected connection found between feeding and memory centers of the brain
January 22, 2019 - A revolutionary approach transforms bone trauma treatment
January 22, 2019 - Early studies and recent clinical trials on nerve growth factor
January 22, 2019 - Dry Mouth and Older Adults: Information for Caregivers
Scientists identify gene responsible for evolution of recombination rates

Scientists identify gene responsible for evolution of recombination rates

image_pdfDownload PDFimage_print

Genetics is a crapshoot. During sexual reproduction, genes from both the mother and the father mix and mingle to produce a genetic combination unique to each offspring. In most cases, the chromosomes line up properly and crossover. In some unlucky cases, however, “selfish DNA” enters the mix, causing abnormal crossovers with deletions or insertions in chromosomes, which can manifest as birth defects.

Scientists have long recognized that the exchange of genetic material by crossing over–known as recombination–is vital to natural selection. Yet some species display far more crossover than others. Why? Researchers hypothesize that crossover rates have evolved to balance the benefits of crossing over with the risks of selfish DNA.

“There’s a bit of a mystery being solved now about how certain molecular, biological, and genome phenomena have evolved in response to selfish genetic elements,” says Daven Presgraves, a dean’s professor of biology at the University of Rochester. “The role of natural selection in an ecological context is essentially a solved problem, but the role of natural selection in response to selfish genetic elements is still being worked out.”

Presgraves and PhD candidate Cara Brand recently accomplished an important milestone in learning about these evolutionary dynamics. By studying two species of fruit flies, they discovered a gene, MEI-218, that controls the rate of recombination. In a paper published in Current Biology, they explain how MEI-218 controls differences in the rate of crossing over between species and the evolutionary forces at play.

“This is the first gene I know of that anyone has shown to be responsible for the evolution of recombination rates,” Presgraves says.

The team focused on two closely related species of fruit flies–Drosophila melanogaster and its sister species, Drosophila mauritiana–because large differences have evolved in their rates of recombination: D. mauritiana does about 1.5 times more crossing over than D. melanogaster. When they compared genes in the two different species, the researchers found that the DNA sequences of MEI-218 were extraordinarily different.

“Natural selection works best when there’s a diversity of genotypes to act upon,” says Brand, the lead author of the paper. “Shuffling combinations of alleles through recombination generates the diversity upon which natural selection acts.”

Recombination is therefore important for two main reasons:

1. Imagine two chromosomes with genes A and B. On one chromosome you might have a “good” (beneficial) A allele and a “bad” (deleterious) B allele. On the other chromosome you might have the opposite; a bad A allele and a good B allele. Which chromosome would be a better? “It’s a mixed bag where one chromosome can’t necessarily outcompete the other,” Brand says. “Recombination can shuffle our allele combinations so that one chromosome can end up with the good A and B alleles together, while the other can get the bad A and B alleles together. Now when these chromosomes compete, the two good alleles will win out in future generations.”

2. We have combinations of alleles that are good in our current environment, but the environment is always changing. The good alleles that are adaptive and healthy now may not be so in the next generation. Recombination can shuffle these combinations of genes so that some will be bad and those offspring will die, but some will be good and these offspring will survive.

“Recombination is important–it’s not hard to convince anyone of that–but when we look across different species, we see that the rates of crossing over are different,” Brand says. “Why increase or decrease the recombination rate?”

There is no single ideal rate or distribution of crossovers, Brand says. Crossovers are necessary to produce viable offspring, but crossing over also has risks. Selfish DNA sequences known as transposons–repetitive genetic elements that do not seem to have benefits to their hosts–are distributed throughout the genome. Transposons are akin to viruses, but instead of injecting themselves in cells, they invade genetic material. If abnormal crossovers occur between transposons in different locations on the chromosomes, the chromosomes do not line up properly and important genes may be duplicated or deleted.

Brand and Presgraves hypothesize that the change in recombination rates between D. mauritiana and D. melanogaster may have evolved because the species have different amounts of transposons in their genomes. The D. melanogaster genome has more transposons than D. mauritiana, so D. melanogaster may therefore have evolved a lower rate of crossing over in order to avoid the higher risk of harmful crossovers between transposons.

This means, then, that the MEI-218 gene is constantly evolving to an ever-changing optimum. The evolution of MEI-218 is similar to genes involved in immunity, Presgraves says. “That should make some intuitive sense because genes involved in immunity are constantly adapting to the changing community pathogens that are challenging us all the time.”

Evolutionary biologists refer to these kinds of evolutionary dynamics as “evolutionary arms races” because, through positive natural selection, genes are chasing a constantly changing fitness optimum. “Maybe you just adapted, but a few generations from now you’re not at the optimum anymore. You have to evolve again and again and again,” Presgraves says.

The MEI-218 gene has so far only been investigated in fruit flies, but the research into recombination has applications for humans. “During meiosis at least one crossover per chromosome, in general, is required to make sure the chromosomes separate properly,” Brand says. “Either a lack of crossing over or crossing over in the wrong regions of the genome is what leads to many birth defects like Down Syndrome.”

Tagged with:

About author

Related Articles