Os estudos do monge Gregor Mendel foram a base para explicar os mecanismos de hereditariedade. Ainda hoje, são reconhecidos como uma das maiores descobertas da Biologia. Isso fez com que Mendel fosse considerado o “Pai da Genética”.

Experimentos de Mendel

Leis de Mendel

Primeira Lei de Mendel

“Cada caráter é determinado por um par de fatores que se separam na formação dos gametas, indo um fator do par para cada gameta, que é, portanto, puro”.

Essa Lei determina que cada característica é determinada por dois fatores, que se separam na formação dos gametas.

Mendel chegou a essa conclusão, quando percebeu que linhagens diferentes, com os diferentes atributos escolhidos, sempre geram sementes puras e sem alterações ao longo das gerações. Ou seja, plantas de sementes amarelas sempre produziam 100% dos seus descendentes com sementes amarelas.

Segunda Lei de Mendel

A Segunda Lei de Mendel também recebe o nome de Lei da Segregação Independente dos Genes ou Diibridismo. Ela possui o seguinte enunciado:

“as diferenças de uma característica são herdadas independentemente das diferenças em outras características”.

Nesse caso, Mendel também realizou o cruzamento de plantas com diferentes características. Ele cruzou plantas com sementes amarelas e lisas com plantas de sementes verdes e rugosas.

Mendel já esperava que a geração F1 seria composta por 100% de sementes amarelas e lisas, pois essas características apresentam caráter dominante.

Por isso, fez o cruzamento dessa geração, pois imaginava que iriam surgir sementes verdes e rugosas, e ele estava certo.

Os genótipos e fenótipos cruzados eram os seguintes:

• V_: Dominante (cor Amarela)
• R_: Dominante (forma Lisa)
• vv: Recessivo (cor Verde)
• rr: Recessivo (forma Rugosa)

Mendel descobriu na geração F² diferentes fenótipos, nas seguintes proporções: 9 amarelas e lisas; 3 amarelas e rugosas; 3 verdes e lisas; 1 verde e rugosa.

Leia também sobre Genótipos e Fenótipos.

Sierra Callaham was 23 when she had her first monthlong bout of daily abdominal pain, nausea, and cyclical vomiting. She was bewildered but chalked it up to stress—work had been rough, and she was on the outs with her family. Antinausea and antianxiety meds got her through most days, and in the evenings, when she wasn’t actively vomiting, she kept up her usual routine of smoking a little pot. She wanted so badly, she says, “to relax and not be as present in my body.”

Callaham lives in Washington State, where recreational cannabis has been legal since 2012, and she had long been a daily if moderate user: a bit each night, as a sleep aid. Before her first gastrointestinal ordeal, in late 2020, she was vaping concentrated cannabis oil from a battery-powered pen. After her symptoms seemed to pass, she switched to smoking pre-rolled joints for a few years before returning to vapes.

Then, in early 2024 came another weeks-long attack—debilitating stomach cramps and daily, uncontrollable vomiting—that sent her twice to the emergency room. On a visit to urgent care, a doctor asked if she used cannabis. Every night, Callaham said. She was shocked when the doctor gave her a provisional diagnosis: cannabinoid hyperemesis syndrome (CHS), sometimes simply called weed sickness.

Recurring episodes of nausea, vomiting, and abdominal pain are the classic symptoms of this puzzling gastrointestinal condition, which is associated with long-term frequent use of marijuana, particularly high-potency products. Doctors in Australia first described cannabinoid hyperemesis syndrome in 2004 (cannabinoids are compounds, like THC or CBD, found in marijuana; “emesis” is the clinical term for vomiting). Just how many suffer from CHS is unknown, but one 2018 study, extrapolating from a survey administered to ER patients, put the number as high as 2.75 million people in the United States each year. A recent research summary from the Journal of the American Medical Association suggests it is increasingly diagnosed: ER visits for CHS doubled in the U.S. and Canada between 2017 and 2021.

Sufferers of CHS, which is associated with frequent use of high-potency cannabis products, report debilitating effects from the rare but increasingly diagnosed condition.
What’s behind the rise? One factor, says Deepak Cyril D’Souza, a professor of psychiatry and director of the Yale Center for the Science of Cannabis and Cannabinoids, is the increasing potency of cannabis products. Thirty years ago, samples seized by the U.S. Drug Enforcement Administration averaged 4 percent THC content by weight. As of 2022, that average is about 16 percent; the oil in vape cartridges like what Callaham was using can reach as high as 85 percent.

Research also points to the broadening legalization of recreational weed. In one characteristic study, published in 2022 in the American Journal of Gastroenterology, researchers compared admissions for CHS at a large Massachusetts hospital between 2012 and 2020, noting a significant uptick after cannabis was legalized in the state in late 2016.

All the same, CHS is a frustratingly spotty affliction. “Why some people seem to be vulnerable to this and not others really seems to be a mystery,” D’Souza says.

Read more of our reporting in The New Cannabis

• Why synthetic pot could be the future of pain relief
• Does high-potency cannabis impair mental health?
• Inside the lab-driven quest for the ultimate high
• What exactly is in gas station weed?

Desperate for relief

Whatever the causes, the longer-term consequences of CHS can far exceed the lengthy stretches of intense discomfort. Complications can include severe dehydration and electrolyte imbalances, which can lead to kidney injury, heart-rhythm abnormalities, and seizures. In rare cases, such complications have even proved fatal.

As hard as its symptoms are to ignore, accurately diagnosing CHS can be tricky, physicians say, partly because those symptoms mimic other gastrointestinal conditions and because patients aren’t always straightforward about their habits. “The way to make the diagnosis,” Andrews explains, “is to [have the patient] come off cannabis, proving retroactively that it’s the cannabis” causing the symptoms.

Giving up pot is also the only known lasting CHS solution. And while the myth of nonaddictive cannabis persists, quitting cold turkey from regular use can cause symptoms like anxiety, irritability, sleep disturbances, and loss of appetite. Relief, moreover, can take weeks or months. “Since it can take such a long time to get better once cannabis is stopped,” Andrews says, “people often may think that the cannabis has nothing to do with their symptoms.” Even the prospect of abstinence may make some chronic users reluctant to come to terms with the condition.

Not Callaham. When her urgent care doctor first handed her literature about CHS, she was skeptical. “I was like, there’s no way—I’m so intentional about how I consume,” she says. “But as soon as I read the materials, I thought, Oh no. And that was the day that I quit.”

She’s been weed-sober ever since. It hasn’t been easy—she’s fought cravings and had to retrain herself to recognize what relaxation feels like when she isn’t high. But it’s easier when Callaham remembers what the depths of hyperemesis felt like. “I was so desperate,” she says. “I was so desperate to feel better.”

Um dos ícones da literatura de terror mais explorados na história do cinema, Drácula está mais uma vez de volta às telas. Baseado no personagem criado pelo escritor Bram Stoker, o filme Drácula – Uma História de Amor Eterno (2025) investe mais no romance do que no horror para contar a história do vampiro que passa os séculos bebendo sangue enquanto espera o retorno da amada morta.

Escrita e dirigida pelo francês Luc Besson, essa nova encarnação do conde demoníaco chega aos cinemas brasileiros sete meses depois do Nosferatu (2024) do cineasta Robert Eggers, que revisita o clássico do expressionismo alemão dirigido em 1922 por F. W. Murnau ⎯ por sua vez, uma versão não autorizada do romance gótico do irlandês Stoker.

A trama de Drácula – Uma História de Amor Eterno se inicia após a morte no século 15 de Elisabeta (Zoë Bleu Sidel), esposa do príncipe Vlad (Caleb Landry Jones). Desesperado com a morte da idolatrada companheira, o nobre da Transilvânia renuncia a Deus e acaba se transformando em um vampiro amaldiçoado com a imortalidade. Condenado a vagar pelos séculos, Drácula é guiado por uma única esperança: reencontrar seu amor perdido reencarnado no corpo de outra mulher.

Séculos depois, na Paris de fins do século 19, o conde finalmente topa com uma mulher que se parece impressionantemente com sua falecida esposa. Auxiliado por vítimas de sua sede de sangue como a bela jovem Maria (Matilda De Angelis), o obcecado vampiro não descansará enquanto não conquistar essa Elisabeta rediviva, enfrentando adversários como um excêntrico padre alemão caçador de monstros ⎯ vivido pelo ótimo ator Christoph Waltz, mais uma vez na pele de um tipo sagaz, irônico e poliglota.

Realizador que teve seu auge criativo nos anos 1980 e 1990 com títulos como Subway (1985), Imensidão Azul (1988), O Profissional (1994) e O Quinto Elemento (1997), Besson é conhecido pelas imagens visualmente tão requintadas quanto afetadas e maneiristas. Seu Drácula sofre dessa mesma artificialidade da forma e pobreza do conteúdo que caracteriza seus trabalhos, contentando-se em apenas contar uma corriqueira história de amor em clima de Belle Époque, como uma leitura meramente cosmética e exangue do Drácula de Bram Stoker (1992) de Francis Ford Coppola.

Assista ao trailer de Drácula – Uma História de Amor Eterno: