Retroviruses | Cells | MCAT | Khan Academy

[@zakeriaabdi693]

Very clear explanation, but those wanting a more advanced understanding for essays or exams might want to read up on the other accessory proteins and how they help to avoid the cells immune system and restriction factors like SAMDH 💪

[@lol-ly4su]

By the way, according to comments, and responses from the official Khan Academy website, she makes some mistakes. 1 of them is saying that the cDNA strands bind to each other. According to ppl in the comments what actually happens is that the reverse transcriptase binds to the RNA, and then 1 cDNA strand is created, and then the reverse transcriptase binds to the cDNA strand, to make a complementary cDNA strand. Sorry if I’m a couple years late. Haha, ap bio exam tomorrow 😢😭

[@lithium0005]

Why would two identical cDNA molecules associate to form a double stranded DNA? If they're identical, they're not complimentary...unless the second half of the molecule is reverse complimentary to the first half (something like 5'ATTCAC-GTGAAT3') Is that how it is? Or does the cell's machinery build the strand complementary to the cDNA?

[@corndog4ever]

Instead of two cDNA molecules associating to form dsDNA, the RNA associated to the newly formed cDNA is degraded and the (+) strand DNA is made off of the cDNA. This is all done by reverse transcriptase.

[@pareshpriyadarshanrana2932]

lithium0005 to give you a better picture, Retroviral Reverse Transcriptase (RT) enzyme has RNaseH activity, so it can “partially degrade” the RNA after cDNA is formed. Also, RT enzyme has DNA dependent DNA Pol activity, so it can use the partially degraded RNA as primer on cDNA and make new strand of DNA.

[@IceCream-ey2kg]

glad I'm not the only one who wondered this. I thought I was imagining things

[@nachinathan3846]

Helpful feedback: This was not up to par to the Khan Academy standard I'm used to. But thank you anyway:)

[@TotemLofi]

disagree this is very detailed

[@lol-ly4su]

Roselee Lauper but she made multiple mistakes.

[@matthewmackey5049]

I'm fairly certain HIV needs a receptor protein, such as CCR5, to be present in order for endocytosis to occur. Thank you for the video. Nice drawings are always super helpful!

[@simrannisha8793]

yess HIV attaches to the CD4 present on the T helper cells...CCR5 is a chemokine co receptor present on monocytes and macrophages... these all help in the entry/invasion of virus into host cell

[@JasonVaysberg]

Yes. I noticed that the Kaplan book discussed this and she said the opposite. That's why I came to the comments.

[@mj2068]

great lesson

[@jocelynjchan]

I thought that reverse transcriptase reads the RNA 3' to 5' (so produces the DNA in 5' to 3' direction) and that the only reason why it's 'reverse' is that it goes against the central dogma by making DNA from RNA. Is the video inaccurate or am I mistaken? Thanks in advance if anyone can clarify!

[@vistian]

I thought so too.

[@backstreetfan2887]

Thanks

[@BossChronicles]

Have a channel for Law ?

[@michaelhernandez4656]

please have someone knowledgable making these videos.

[@osielcecenas7669]

are retroviruses negative sense, positive sense, or could they be either?

[@vistian]

To correct the video, Reverse Transcriptase reads the template strand from 3' to 5' and writes the daughter strand in the 5' to 3' direction. These are MCAT points lost with this misinformation.

[@donutxerica]

Thanks so much for the video!

[@MichaelHarrisIreland]

It's like a welcome visitor who eats you out of house and home. Are our cells like us and can't resist a beautiful stranger calling because one day it will be great and work out.

[@Nico55RS]

RT does no produce two identical cDNAs which then form a dsDNA molecule. RT has two functions: RNA-Dependent-DNA-Polymerase and the typical DNA-Dependent-DNA-Polymerase. RT will produce the first cDNA from the positive sense RNA strand and then will proceed to transcribe the complementary DNA strand using the cDNA as a template. www.ncbi.nlm.nih.gov/pmc/articles/PMC3475395/ Go to figure 1, and read from there.

[@RichHupper]

Hi could you tell me how retroviruses are spread from animal to animal?

[@jorgeguerrapiresphd]

Hi +Rich H (Ditch) I am not sure if you are still interested to know, but if I understood properly your question, it is done normally, by "contact." Retrovirus incorporates their DNA inside the host cell's, after it is out, it is a normal virus. I am an expert, but I believe it could be possible that in direct contact, you may leave contaminated cells, or even "pieces of DNA," that that point on, the virus can go on, normally inside its new host. That is just a guess. Best,

[@AnkeetKumar]

2:28 ,but only in those viruses that have DNA dependent DNA polymerase activity in RT ,what about others?

[@RNA_Dec]

You didn't mention that there is 2 ss RNAs within a single viron particle, which gives it a psuedodiploid nature.

[@aslanr6]

question: Why doesnt this video mention 2 single stranded RNAs?

[@SC-sf6eq]

yes two identical strands

[@LIVINGWITHBIPOLARDISORDER]

Lol! Viruses actually do not exist.

[@jackedbyrohit3236]

@@LIVINGWITHBIPOLARDISORDER are you an idiot?

[@osielcecenas7669]

@@jackedbyrohit3236 anti-vac back at it again smh

[@paulcrooks4467]

Up problem can be solved

[@hanaeelkholti5473]

my eyes hurt !!! would be a lot better if it was a bit bigger. sheesh it is all crowded

[@jackiechun4741]

Yes mommy, tell me about retroviruses.

[@LNGUYEN724]

The audio was terrible and made me dizzy and want to vomit!

[@improbablyhiking1742]

Second this! I couldnt understand what the heck was going on in the last bit of the video because of the volume changes, apologies and hesitating ahhh!!

[@jumpingrabbit7921]

The audio made you dizzy? How does that work?

[@jackedbyrohit3236]

@@jumpingrabbit7921 It was like a bad orgasm