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Genetics > Chapter 14 > Flashcards

Chapter 14 Flashcards

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Biology 101 flashcards
1
Q

Gene organization

A
  • Colinearity and noncolinearity
  • Nucleotides and animo acids in encoded protein should be PROPORTIONAL
  • DNA is longer than mRNA (shown in hybridization)
  • without proteins, bacterial genes are coli near, but eukaryotic genes are not
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2
Q

Colinearity

A

Continuous sequences of nucleotides in DNA encodes a continue amino acid sequence in proteins

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3
Q

Noncolinearity

A
  • coding sequences are NOT continuous
  • Discovered by hybridizing DNA with the mRNA transcribed from it
  • discovered noncoding regions as the loops
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4
Q

Introns

A
  • spliced out in RNA processing
  • Vary from gene to gene
  • ## common in eukaryotes, less in prokaryotes
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5
Q

Exons

A
  • exit the DNA, exported
  • code for proteins
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6
Q

Genes

A
  • includes DNA sequences that code for all exons and introns
  • RNA sequences at the beginning and end are NOT translated into a protein (i.e. promoter and terminator)
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7
Q

Start codons

A
  • codes for starting translation
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8
Q

Stop codons

A
  • codes for stopping translation
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9
Q

Pre-mRNA

A
  • found in eukaryotes (WHY? Adds complexity)
  • adds the 5’ cap (DESCRIBE?nucleotide, RNA, 7 methylguanine, 5’-5’ bond at the end of 5’ RNA)
  • adds the polyA tail (50-250 adenine nucleotides to 3’ end of RNA), most eukaryotic have the 3’ polyA tail
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10
Q

RNA Splicing

A
  • Cutting out the introns out of RNA
  • uses consensus sequences: 5’ consensus sequence (GU(A/G)AGU) 5’ splice site, 3’ consensus sequence (CAGG), branch point (adenine A is ~18-40 nucleotides upstream of 3’ splicing site)
  • spliceosome: five RNA molecules and 300 proteins
  • REQUIRES consensus sequences
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11
Q

Pre-mRNA processing steps

A
  1. 5’ end cleaved, folded over and attaches to the branch point (lariat structure)
  2. 3’ end cleaved, exons brought and spliced together
    - Intervening intron removed
    - Within the spliceosome
    - 5’ end of intron 1 is promixal to the 3’ end of exon 1
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12
Q

spliceosome

A

RNA splicing takes place here
Assembles sequentially
WHAT? RNA protein complex
IMPACT? removes introns from pre-mRNA
WHERE? found in the nuclei
WHEN? during transcription

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13
Q

Minor splicing

A
  • WHAT? uses minor spliceosome
  • IMPACT? splices out special pre-mRNA introns
  • WHERE? U12 type (of introns)
  • WHEN? during transcription
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14
Q

Alternative splicing

A
  • WHAT? type of alternative processing
  • IMPACT? pre-mRNA can form different options for mRNA –> different amino acid sequences –> different proteins developed
  • WHERE? pre-mRNA
  • WHEN? during transcription
  • exons are able to be spliced together in different combination to yield mRNAs to encode different proteins
  • create multiple different proteins from the same sequence, increase complexity from one sequence
  • different mRNAs produced from a single pre-mRNA
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15
Q

Multiple Cleavage sites

A
  • HOW? mRNAs can be cleaved and add the polyA tail from different places
  • WHERE? mRNA on the 3’ end
  • IMPACT? Different lengths —> different form —> different structure —> structure means FUNCTION
  • WHAT? different mRNAs produced from a single pre-mRNA
  • WHEN? transcription

THINK! alternative splicing impacts

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16
Q

Alternative processing

A
  1. Alternative splicing
  2. Multiple cleavage sites
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17
Q

Guide RNA

A

RNA that adds nucleotides to the mRNA that were not encoded by the DNA

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18
Q

tRNA structure

A

Rare modified RNA nucleotide bases
‒ Ribothymine
‒ Pseudouridine
- Common secondary structure—the cloverleaf structure
- Anticodon

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19
Q

Ribosome structure

A

Large ribosome subunit
&
Small ribosome subunit
(Prokaryotes AND eukaryotes have)
50S —> could be large subunit, “S” refers to the unit of ribosomes

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20
Q

rRNA

A

processed after transcription, subunits are the result of splicing original rRNA

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21
Q

Small interfering RNA function

A
  • RNA interference: protects from invasion of foreign genes, regulates its own gene regulation
  • Types of small RNAs
  • Processing and function of microRNAs
  • Piwi interacting RNAs inhibit transposons, found in GERM cells
  • CRISPR RNAs defend against foreign genes (bacteriophages and plasmids from DNA) in PROKARYOTIC cells
22
Q

Small interfering RNAs and microRNAs

A

Produced from double-stranded RNAs

23
Q

Perfectly paired double stranded RNAs

A

Silencing or cutting

24
Q

Long noncoding RNAs (lnRNAs)

A
  • do NOT encode proteins
  • control gene expression
  • enhancer RNAs transcribed from enhancers and play a role in control of gene expression
25
Q

One gene one enzyme hypothesis

A
  • Genes function by encoding enzymes, each gene encodes a separate enzyme
  • One gene, one polypeptide hypothesis (more specific)
26
Q

amino acids

A

Common ones have similar structures
Joined together by PEPTIDE bonds

27
Q

Protein functions

A
  • ATP drives production of light in lightning bugs (bioluminescence)
  • ricin, toxic molecules to defend themselves
28
Q

Types of bonds and WHERE

A
29
Q

Protein levels of structures

A

Primary, secondary, tertiary, quanternary

30
Q

Structure of a ribosome

A
31
Q

Codons

A
  • Triplet RNA code
  • 64 possible codons: 3 stop codons, 61 sense codons
  • No start codon —> “nitrogen formal methionine” start amino acid, specific enzymes to recognize it
32
Q

Degeneracy of the Code

A
  • Degenerate code: amino acid specified by more than one codon
  • synonymous codons: specify the same amino acid
  • isoaccepting tRNAs: different tRNAs that accept the SAME amino acid, but DIFFERENT anticodons (think isosceles triangle)
33
Q

Codons cont.

A
  • sense codons: encoding amino acids
  • initiation codon: AUG
  • termination codon: UAA, UAG, UGA
34
Q

Wobble hypothesis

A

base at 5’ end of tRNA anticodon can pair with several different bases in codon
mRNA and tRNA pair in an anti parallel fashion

35
Q

Methionine

A

AUG
Recognized by other enzymes to allow initiation to occur
Start codon

36
Q

Reading Frame (Triplet Code)

A

Sequence is read in groups of three, messing it up messes up all of the amino acids & functions, each different three part sequence encodes a different amino acid

37
Q

Nonoverlapping (Triplet Code)

A

A single nucleotide may not be included in more than one codon

38
Q

The universality of the Triplet code

A

Near universal across the board

39
Q

Translation, Steps

A

Amino acids bind to tRNAs
Initiation (initiation factors, 3, energy factors)
Elongation (elongating polypeptides and creating polypeptide bonds, elongation factors, 2)
Termination (release factors, 1 & 2)
Happens on a ribosome

40
Q

N

A

Amino acid end of the protein

41
Q

C

A

Carboxyl end

42
Q

Binding amino acids to tRNAs

A

Aminoacyl-tRNA synthetases load amino acid onto tRNA (charging it)
Specificity between
20 aminoacyl tRNA synthetases in a cell, corresponds with the 20 amino acids

43
Q

Amino Acids

A

Attach to the 3’ end of tRNAs, C-terminase binds to it

44
Q

Initiation

A

Initiation factor signals (IF 3, 2, 1…)
TRNA loaded with N-formylmethoin attached = fmet tRNA
Energy molecule GTP
REQUIRES INITIATION FACTORS AND GTP
3’ cap strengthens structure of the ribosome for this process

45
Q

Shine-Dalgarno Consensus Sequence

A
46
Q

IF-3, IF-1

A

Binds to the small subunit, prevents large subunit from binding
During translation

47
Q

IF-2

A

Binds informal methionine,
During translation

48
Q

Elongation

A

Factors: Tu, Ts, G (EF-TU (forms complex with GTP and charged tRNA)
, E-Ts, EF-G (works with GTP to move ribosomes down the mRNA))
* Exit site E
* Peptidyl site P
* Aminoacyl site A
GTP drives it
Peptides binding on tRNAs

49
Q

Termination

A

When ribosome hits termination codon
UAA, UAG, UGA
Release factors that were bound at initiation, releasing:
– The polypeptide from the last tRNA
– The tRNA from the ribosome
– The mRNA from the ribosome
RF-1 —> release factors

50
Q

Ribosome Structure cont.

A

3D structure
Polyribosome: an mRNA with several ribosomes attached
Longest polypeptide chain is the RNA that’s produced first

51
Q

Spliceosome

A

The splicing of pre-mRNA takes place within this large complex
snRNAs and proteins present

Genetics (10 decks)

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