Chapter 1_2 Flashcards Preview

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Flashcards in Chapter 1_2 Deck (27)
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1
Q

what are proteins made of?

A

proteins are made of one or more polypeptide molecules

2
Q

what are the basic repeat units of polypeptides?

A

amino acids

3
Q

what is a hydrogen bond?

A

hydrogen bond:

> weak electrostatic bond between positively charged hydrogen atoms and negatively charged atoms

> e.g. oxygen atoms in the case of water

4
Q

in which direction is a DNA strand usually described?

(and read out)

A

5’ to 3’ direction

5
Q

which enzyme is used to unwind the DNA helix?

(in DNA replication)

A

helicase

6
Q

genes contain … and …

> which functions?

A

exon segments: genetic instructions for making mRNA or noncoding RNA

intron segments: separate exon segments, do not contribute genetic information to the final product

7
Q

what is the GT-AG rule?

A

dinucleotides at the ends of introns are highly conserved:

> vast majority of introns start with GT and end with AG

> GT - AG rule

8
Q

RNA splicing is mediated by?

A

RNA splicing is mediated by the spliceosome

> a large RNA protein complex

9
Q

what is 5’ capping?

A

5’ capping:

> in RNA synthesis of primary RNA transcript (before splicing)

> methylated nucleoside is added by a 5’-5’ phosphodiester bond and the 5’ end of the transcript

10
Q

what are the functions of capping?

A
  1. protection
  2. facilitation of

> transport

> RNA splicing

> attachment to ribosome during translation

11
Q

what are untranslated regions in mRNA?

why?

A

untranslated regions 5’UTR and 3’UTR

> those regions are not translated into polypeptides (only a central segment of mRNA is)

> they assist in binding and stabilizing mRNA on the ribosomes and promote efficient translation

12
Q

how are polypeptides made from RNA?

A

RNA is scanned from 5’ to 3’ in groups of 3 nucleosides (codons)

> each codon specifies 1 amino acid

> proces is mediated by tRNA molecules

13
Q

genetic code is degenerate: what does this mean?

A

genetic code is a 3 letter code with 4 possible bases to choose: 4³ = 64 possiblities

> only 20 major types of amino acids

> many amino acids are coded for by multiple codons

14
Q

there are more than 60 codons that specify an amino acid, but there are less cytoplasmic tRNA molecules and only 22 types of mitochondrial tRNA to read them

> how is this possible?

A

base pairing in RNA is more flexible than in DNA

> first two base positions in codon follow the normal AU and GC rule

> third base pair, there is some flexibility >>> GU base pairs tolerated

15
Q

transcription: how many basepairs does polymerase cover?

A

about 30 bp of the template DNA

> including the transcription bubble

>>> which holds the growing transcript to the template strand for about 8 RNA-DNA basepairs

16
Q

how is the end of transcription signaled?

A

end of transcription is signaled by an upstream AAUAAA signal

> in combination with a GU rich region

17
Q

what happens after transcription?

why?

A

end of transcription:

> poly A tail is added by poly A polymerase

function:

> helps transport mRNA to cytoplasm

> stability of the mRNA molecule

> enhance recognition of mRNA by ribosomal machinery

18
Q

what are 4 steps in RNA processing?

A

RNA processing:

1) end-modification > poly A tail and capping
2) splicing - removal of introns
3) cutting events - molecule is cut into pieces
4) chemical modification - addition of new chemical groups

19
Q

what are 2 examples of non-coding RNA?

A

non coding RNA

  1. rRNA = ribosomal RNA

> is the RNA component of a ribosome

> provides mechanism for decoding mRNA into amino acids

  1. tRNA = transfer RNA

> transfer a specific active amino acid to a growing polypeptide chain (during translation)

20
Q

peptide bond direction?

A

peptide ponds go from N-terminal to C-terminal

21
Q

tRNA: what does

> acceptor arm?

> anticodon arm?

A

acceptor arm: amino acids attached

anticodon arm: forms basepairs with mRNA

22
Q

in which direction does polymerase run?

A

from 3’ to 5’

> basepairs get attached to 3’ end of new RNA/DNA strand

23
Q

how many levels of protein structure are there?

A

4:

> primary - quartenary

24
Q

what is a proteome?

A

proteome: final product of all genome expression

> all proteins present in a cell at a given time

> different types of human cells have different proteomes

> most proteins are “housekeeping” proteins

> proteins that specialize cells are rare

25
Q

5’ capping: which base is added using which bond?

A

5’ capping:

5’-5’ phosphodiester bond is used to attach m7G

> 7-methylguanosine

26
Q

3’ polyadenylation, what is added to 3’ end of RNA transcript?

A

about 200 bases adenylate are attached

27
Q

RNA polymerase 1/2/3

> differences in transcription termination?

A

-> RNA polymerase 1/3 recognize transcription terminate site in code (AAUAAA)

> RNA polymerase 2 terminates transcription when exonuclease reaches the RNA polymerase