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FLS- MCQ Prep > Stuff > Flashcards

Stuff Flashcards

1
Q

Purines?

A

Adenine, Guanine (Purines have a short name, and long base- 2 rings)

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2
Q

What does 5’- 3’ mean?

A

The 5’ and 3’ mean “five prime” and “three prime”, which indicate the carbon numbers in the DNA’s sugar backbone. The 5’ carbon has a phosphate group attached to it and the 3’ carbon a hydroxyl group. This asymmetry gives a DNA strand a “direction”. For example, DNA polymerase works in a 5’ -> 3’ direction, that is, it adds nucleotides to the 3’ end of the molecule (the -OH group), thus advancing to that direction.

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3
Q

Major and Minor grooves?

A

The strand backbones are closer together on one side of the helix than on the other. The major groove occurs where the backbones are far apart, the minor groove occurs where they are close together.

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4
Q

Single strand binding protein?

A

Single-strand binding protein (SSBP) binds to and stabalizes the single strand to keep DNA unwound.

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5
Q

Primase?

A

Type of RNA polymerase, catalyses the synthesis of the Primer

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6
Q

Exonuclease?

A

Removes nucleotides from the end of a strand. Can go in either direction along the DNA.

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7
Q

Ligase

A

Joins ends of a single DNA strand by making new phosphate bonds

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8
Q

Gyrase

A

Gyrase (a topoisomerase) relaxes supercoils produced when the molecule is twisted during replication. Also facilitates unwinding at the beginning of replication.

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9
Q

Telomerase

A

Telomerase:- Uses a short RNA template to add short DNA repeats to the short ends of the linear chromosomes when the last primer is removed using the RNA template.

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10
Q

rRNA

A

Ribosomal RNA: With ribosomal proteins, makes up the ribosomes, the organelles that translate the mRNA.

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11
Q

snRNA

A

Small nuclear RNA: With proteins, forms complexes that are used in RNA processing in eukaryotes. (NOT found in prokaryotes.)

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12
Q

GPPP cap?

A

At the 5’ end, a cap is added consisting of a modified GTP (guanosine triphosphate). This occurs at the beginning of transcription. The 5’ cap is used as a recognition signal for ribosomes to bind to the mRNA.

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13
Q

AA*AA?

A

At the 3’ end, a poly(A) tail of 150 or more adenine nucleotides is added. The tail plays a role in the stability of the mRNA.

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14
Q

Splicing?

A

The intron loops out as snRNPs (small nuclear ribonucleoprotein particles, complexes of snRNAs and proteins) bind to form the SPLICESOME
The intron is excised, and the exons are then spliced together.
The resulting mature mRNA may then exit the nucleus and be translated in the cytoplasm.

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15
Q

How is a ribosome made up?

A

Whole thing:- 80s
P, A site
Small subunit:- 40S (18S rRNA + 30 ribosomal proteins)
Large subunit:- 60S (28S rRNA,5.8S rRNA, 5S rRNA + 50 ribosomal proteins)

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16
Q

tRNA

A

All tRNA’s have CCA at the 3’ end to which the aa attaches

At the other end of the tRNA is the anticodon which, during translation, reads the matching codon on the mRNA

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17
Q

Adding an aa to tRNA

A

An enzyme called AMINOACYL-t RNA SYNTHETASE adds the correct amino acid to its tRNA.
This process is called AMINOACYLATION or ‘charging’.
Since there are 20 amino acids, there are 20 aminoacyl- tRNA synthetases.
All tRNAs with the same amino acid are charged by the same enzyme, even though the tRNA sequences, including anticodons, differ

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18
Q

Process of adding aa to tRNA

A 
AA and enzyme join by way of ATP
AA loses two phosphate groups and binds to aa as AMP
uncharged tRNA binds 
aa tRNA leaves molecule 
enzyme returns to original shape
19
Q

Initiation of translation?

A

Small ribosomal subunit binds to mRNA at start codon region

20
Q

Termination of translation?

A

No anticodon on tRNA matches stop codon
RELEASE FACTOR binds to stop codon
Peptidyl transferase is triggered, causing release of polypeptide from tRNA, tRNA is ejected.

21
Q

Polysomes

A

Several ribosomes can translate a mRNA at the same time, forming a polysome.

22
Q

STOP codons

A

UAA
UAG
UGA

23
Q

Degenerate

A

In most cases more than one codon per aa

24
Q

ORF

A

An open reading frame (ORF) is a string of SENSE codons starting with the start codon ATG and flanked at the 3’ end by a stop codon.

25
Q

Histones: DNA ratio

A

1:1

26
Q

Histone facts

A

Small, highly positively charged, high degree of conservation (little evolution)

27
Q

The Nucleosome (Level 1 of packaging)

A

Four core histones (H2A x2) 28Kda, (H2B x 2) 28Kda, (H3 x2) 30Kda, (H4x2) 22Kda
H1- 24Kda
146bp of DNA left handed supercoil
DNA path:- 1.8 superhelical turns

28
Q

How is the Nucleosome formed?

A

H3,H4:- heterodimer, tetramer, histone handshake, horseshoe
H2A, H2B form Dimer, above and below H3, H4
H1:- Dyad axis, locks DNA in place
Histones are responsible for maintaining shape and structure of nucleosome

29
Q

Histone variants:- H2A.Z

A

Non-cannonical variants of histones-representing one or a few aa different
Histone H2AZ is a variant of histone H2A, and is used to mediate the thermosensory response, and is essential to perceive the ambient temperature. Nucleosome occupancy of H2A.Z decreases with temperature, and in vitro assays show that H2A.Z-containing nucleosomes wrap DNA more tightly than canonical H2A nucleosomes in Arabidopsis.

30
Q

Level 2: The 10nm fibre

A

Two nucleosomes bind together
20-30 bp
Beads on a string
6-7

31
Q

Level 3:- The 30nm Solenoid

A

6 nucleosomes, 10nm fibre wrapping around it
H1 essential
40

32
Q

Level 4:- 300nm Solenoid

A

Looped
Each loop contains 60-100 bp DNA tethered by nonhistone scaffold proteins
680

33
Q

Level 5:- 700nM fibre

A

Coiled Coil
10^4
This one looks like a flower

34
Q

Level 6:- Metaphase chromosome

A

1400nm

35
Q

Telomeres

A

Protect genome (don’t code for anything)

36
Q

Centromere

A

Repeating sequences, mediates chromosome cohesion, spindle attachment, Chromosome segregation

37
Q

Constituative Heterochromatin

A

Part of Telomeres and Centromeres
Highly repeated sequences
Permenantly heterochromatic

38
Q

Facultive Heterochromatin

A

Either H or E
Not consistent
X chromosomes
Regulated and often associated with morphogenesis or diffrentiation

39
Q

Nonpolar aa

A

Glycine, Alanine, Proline (also cyclic), Valine, Leucine, Isoleucine

40
Q

Aromatic

A

Phenylaline, Tyrosine, Tryptophan

41
Q

Polar,uncharged

A

Aspargenine, Glutamine, Serine, Threonine

42
Q

Sulfer containing

A

Methlonine, Cystine

43
Q

Charged

A

Asparate, Glutamate
Negative

Arginine, Lysine, Histidine
Positive

FLS- MCQ Prep (1 decks)

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