Destroyer Bio Questions

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datgirl1

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After going through the bio section destroyer, I have a few questions I would like more clarification on.

1) A protein of 210 amino acids is made from how many DNA nucleotides?
I understand that the answer is 210 x 3=630 but in the answer key is says that 3 codons make one amino acid. I'm not sure if this is a typo or my misunderstanding but I thought that 3 nucleotides make 1 codon, therefore 1 amino acid. So that 210 amino acids is made from 210 codons and 630 nucleotides. Is this correct?

2) What is the difference between natural killer T cells and cytotoxic killer T cells (if any)?

3) I don't understand the relationship between linked genes, recombinant genes and crossing over. I believe that the closer two genes are on a chromosome, the greater chance they will be linked, and the farther they are the more likely there will be recombination. Also know that crossing over makes recombinant dna. Any more information about these topics and the sort of questions that might be tested would be great.

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1) A protein of 210 amino acids is made from how many DNA nucleotides?
I understand that the answer is 210 x 3=630 but in the answer key is says that 3 codons make one amino acid. I'm not sure if this is a typo or my misunderstanding but I thought that 3 nucleotides make 1 codon, therefore 1 amino acid. So that 210 amino acids is made from 210 codons and 630 nucleotides. Is this correct?

The answer key's explanation is wrong; 3 codons do not make one amino acid - one codon corresponds to one amino acid, while 3 nucleotides make 1 codon (as you stated). Destroyer is incorrect and your assessment on codon amino acid counts is right. Stick with your understanding of the material.

2) What is the difference between natural killer T cells and cytotoxic killer T cells (if any)?

The two are similar. Most T-cells (including cytotoxic killer T-cells) recognize peptide (protein) antigens presented by MHC molecules on other cells. Natural killer T cells recognize glycolipid antigens presented by a different type of molecule (the specifics of this molecule aren't important, just know that it isn't MHC). Once it recognizes an antigen that causes a reaction, natural killer T-cells can then produce cytotoxins and cytokines (effectively behaving as both cytotoxic killer T-cells and helper T-cells).

I would be surprised if the DAT would ever expect that level of detailed knowledge (distinguishing natural killer T-cells from cytotoxic killer T-cells). It's fairly low yield.

3) I don't understand the relationship between linked genes, recombinant genes and crossing over. I believe that the closer two genes are on a chromosome, the greater chance they will be linked, and the farther they are the more likely there will be recombination. Also know that crossing over makes recombinant dna. Any more information about these topics and the sort of questions that might be tested would be great.

Your understanding of linked genes is correct - the closer together they are on the same chromosome, the higher chance they will be inherited together (i.e. less likely for there to be recombination) and vice versa. Say two genes were right next to each other on a chromosome - their recombination frequency would be low because it would be incredibly unlikely that recombination would occur at the exact spot separating the two genes. But if two genes were on completely opposite ends of the same chromosome, any recombination event along the length of the chromosome would separate the two - these genes wouldn't be considered linked, and would have a very high recombination frequency. Recombination occurs during crossing over (which happens during meiosis I) when homologous chromosomes pair up and can "exchange" genetic information. I think further details on crossing over/recombination are best learned visually. I'd suggest starting with this video, but if it doesn't clarify the topic or provide sufficient detail, let me know and I'd be happy to point you in the right direction of more error-free resources.

 
After going through the bio section destroyer, I have a few questions I would like more clarification on.

1) A protein of 210 amino acids is made from how many DNA nucleotides?
I understand that the answer is 210 x 3=630 but in the answer key is says that 3 codons make one amino acid. I'm not sure if this is a typo or my misunderstanding but I thought that 3 nucleotides make 1 codon, therefore 1 amino acid. So that 210 amino acids is made from 210 codons and 630 nucleotides. Is this correct?

2) What is the difference between natural killer T cells and cytotoxic killer T cells (if any)?

3) I don't understand the relationship between linked genes, recombinant genes and crossing over. I believe that the closer two genes are on a chromosome, the greater chance they will be linked, and the farther they are the more likely there will be recombination. Also know that crossing over makes recombinant dna. Any more information about these topics and the sort of questions that might be tested would be great.

Indeed a typo and it has been corrected.

3 nucleotides make one amino acid.

Good luck to you

Dr. Romano
 
Thanks @FeralisExtremum and @orgoman22 .
I was just doing an achiever question on amino acids and would like to see if the answer is correct.
The question was "how many mRNA nucleotides would be involved in synthesizing a polypeptide with 100 amino acids?"
I thought the answer would be 300, but the correct answer on achiever was 303 nucleotides because you add 3 nucleotides to stop translation. Is the answer key correct?
 
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Thanks @FeralisExtremum and @orgoman22 .
I was just doing an achiever question on amino acids and would like to see if the answer is correct.
The question was "how many mRNA nucleotides would be involved in synthesizing a polypeptide with 100 amino acids?"
I thought the answer would be 300, but the correct answer on achiever was 303 nucleotides because you add 3 nucleotides to stop translation. Is the answer key correct?
Check your messages.
Dr. Romano
 
Thanks @FeralisExtremum and @orgoman22 .
I was just doing an achiever question on amino acids and would like to see if the answer is correct.
The question was "how many mRNA nucleotides would be involved in synthesizing a polypeptide with 100 amino acids?"
I thought the answer would be 300, but the correct answer on achiever was 303 nucleotides because you add 3 nucleotides to stop translation. Is the answer key correct?

To include the stop codon, 303 nucleotides would be correct. It's a bit of a tricky question and the real DAT is much more straightforward when it comes to this topic. Feel free to check any other questions you are unsure of here, as Destroyer's biology section has been known to have numerous errors in the past - I'm always happy to help clear up any errata or ambiguous topics.
 
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