Class Three Major Histocompatibility Complex
Author's Note: This takes place sometime between New Earth and Idiot's Lantern.
He knew that there was something wrong because he couldn’t get the taste of her out of his mind. It hadn’t been like that before. Of course he’d cared for her. More than cared for. But this was different. This was downright biological.
“Rose, could you open your mouth for me?”
Sitting in the kitchen in an oversized t-shirt drinking a morning cuppa, she wasn’t quite awake yet. She slitted her eyes at him distrustfully. “Why?”
“Oh, just a little swab, eh? See? Just need a little DNA.”
She sipped her tea and considered him and the mouth swab that he was flourishing. “What are you up to?”
“Test.”
“For what?”
“Class Three Major Histocompatibility Complex.”
“Wot?”
“It’s in your DNA, part of your genetic structure; sits on chromosome six.”
“Are you making this up because you want to put something nasty in my mouth?”
"No, I can get a better scan if the DNA is on the swab."
She looked him up and down. "Why do you look so ... jumpy? It's like that time on Hetaterra. And that was horrid."
“Right! Fine!” He sat down across from her, popped the swab in his own mouth, pulled it out, scanned it with the sonic screwdriver. Frowning at the reading, he shoved the screwdriver back in his pocket.
She sighed. “Fancy a cuppa?”
“Yeah.”
Rose padded over to the counter and then slid a mug in front of him. As she bent over him, he breathed in her scent. Groaning, he buried his nose in his mug and closed his eyes.
“Alright,” she was studying him over the rim of her mug, “you gonna explain what’s going on this morning?”
“My DNA changed when I regenerated.”
“Yeah, I got that. New man. Disappointingly not ginger.”
“My class three major histocompatibility complex is different.”
“Yeah?”
“Yeah.”
She waited for a bit and then asked, “So, why is this a concern?”
“Not a concern, well,” he paused, “no, not a concern.”
“If you don’t want to tell me, you shouldn’t ‘a brought it up.”
The Doctor sighed. “Humans and, ah, other species show a preference for mates that possess genes dissimilar to their own at the major histocompatibility complex. The preference helps choose genetically compatible mates or increase heterozygosity and thereby immunocompetence of offspring. A genetically complimentary mate leads to initial attraction, more female orgasms, and better chances of conception.”
Rose blinked. The Doctor took a breath but Rose raised her palm. “Hold on, I’m gettin’ it.” She took another sip of tea. “You want some toast? We’ve got marmalade.”
“Yeah.”
She popped the toast down. “So, how do we know?”
“Smell, mostly, and taste. You … I” he cleared his throat and then mumbled, “My scent would be … good.”
“Huh.”
She was standing directly behind him. He could feel the heat coming off her body, hear her heartbeat, smell her. She rested her forearms on his shoulders and buried her nose in his hair. “What..” he squeaked, cleared his voice and tried again, “What are you doing?”
“Science experiment. Testing your DNA.”
Slowly, her nose moved from the top of his head and down the side. Breath wafted warm against his neck as her tongue tasted his ear. The toast popped up, she moved away, and he started breathing again.
She sat the plate of toast down in front of him. “Yeah.”
“Yeah?”
She snagged a triangle of his toast and sat across from him, munching on it. Her eyes glittered with speculation. “Yeah.”
He knew that there was something wrong because he couldn’t get the taste of her out of his mind. It hadn’t been like that before. Of course he’d cared for her. More than cared for. But this was different. This was downright biological.
“Rose, could you open your mouth for me?”
Sitting in the kitchen in an oversized t-shirt drinking a morning cuppa, she wasn’t quite awake yet. She slitted her eyes at him distrustfully. “Why?”
“Oh, just a little swab, eh? See? Just need a little DNA.”
She sipped her tea and considered him and the mouth swab that he was flourishing. “What are you up to?”
“Test.”
“For what?”
“Class Three Major Histocompatibility Complex.”
“Wot?”
“It’s in your DNA, part of your genetic structure; sits on chromosome six.”
“Are you making this up because you want to put something nasty in my mouth?”
"No, I can get a better scan if the DNA is on the swab."
She looked him up and down. "Why do you look so ... jumpy? It's like that time on Hetaterra. And that was horrid."
“Right! Fine!” He sat down across from her, popped the swab in his own mouth, pulled it out, scanned it with the sonic screwdriver. Frowning at the reading, he shoved the screwdriver back in his pocket.
She sighed. “Fancy a cuppa?”
“Yeah.”
Rose padded over to the counter and then slid a mug in front of him. As she bent over him, he breathed in her scent. Groaning, he buried his nose in his mug and closed his eyes.
“Alright,” she was studying him over the rim of her mug, “you gonna explain what’s going on this morning?”
“My DNA changed when I regenerated.”
“Yeah, I got that. New man. Disappointingly not ginger.”
“My class three major histocompatibility complex is different.”
“Yeah?”
“Yeah.”
She waited for a bit and then asked, “So, why is this a concern?”
“Not a concern, well,” he paused, “no, not a concern.”
“If you don’t want to tell me, you shouldn’t ‘a brought it up.”
The Doctor sighed. “Humans and, ah, other species show a preference for mates that possess genes dissimilar to their own at the major histocompatibility complex. The preference helps choose genetically compatible mates or increase heterozygosity and thereby immunocompetence of offspring. A genetically complimentary mate leads to initial attraction, more female orgasms, and better chances of conception.”
Rose blinked. The Doctor took a breath but Rose raised her palm. “Hold on, I’m gettin’ it.” She took another sip of tea. “You want some toast? We’ve got marmalade.”
“Yeah.”
She popped the toast down. “So, how do we know?”
“Smell, mostly, and taste. You … I” he cleared his throat and then mumbled, “My scent would be … good.”
“Huh.”
She was standing directly behind him. He could feel the heat coming off her body, hear her heartbeat, smell her. She rested her forearms on his shoulders and buried her nose in his hair. “What..” he squeaked, cleared his voice and tried again, “What are you doing?”
“Science experiment. Testing your DNA.”
Slowly, her nose moved from the top of his head and down the side. Breath wafted warm against his neck as her tongue tasted his ear. The toast popped up, she moved away, and he started breathing again.
She sat the plate of toast down in front of him. “Yeah.”
“Yeah?”
She snagged a triangle of his toast and sat across from him, munching on it. Her eyes glittered with speculation. “Yeah.”