Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Bio 120 > Lecture 25 > Flashcards

Lecture 25 Flashcards

1
Q

Central dogma of molecular biology

A

DNA (dna replication)
to RNA through transcription
To proteins through translation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Gene expression

A

Genes encode for messenger RNA (mRNA) which code for proteins (central dogma)

Genes encode for functional RNAs such as transfer RNAs (tRNA) and rinosomal RNAs (rRNA)

Generally activity of proteins produce the inherited traits of organism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Can flow of genetic information be reversed?

A

No

Unless it’s an RNA virus whose rna can be used to code for DNA in a host cell (these viruses have the enzyme reverse transcriptase)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Gene expression is the process by which

A

Information from a gene is used in the synthesis of a functional gene product

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Gene products

A

Often coded for by messenger RNAs /mRNAs but they can also be functional RNAs such as transfer RNAs (tRNAs) or ribosomal RNAs (rRNAs)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Transcriptome

A

Totality of RNA transcripts expressed by a cell or an organism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Proteome

A

Entire set of proteins that is/ or can be expressed by a genome, cell, tissue, or organism at a certain time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Transcription

A

Synthesis of RNA molecule complementary to a portion of a strand of DNA acting as a template

Thousands of transcripts are being produced every second in cells

Occurs in 3 stages
Occurs in the nucleus in eukaryotes and cytoplasm in prokaryotes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

3 transcription stages

A

Initiation
Elongation
Termination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Where does transcription occur in a eukaryote and prokaryote

A

Eukaryote- nucleus

Prokaryote- cytoplasm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Gene consists of what? In terms of transcription

A

Promoter and a transcription unit

Specific sequences of nucleotide in prokaryote and eukaryote promoters differ

Eukaryotes have a TATA box within their promoter consisting of 30 bases pairs of Ts and As located upstream from the transcription start point

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q
A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Transcription unit

A

Stretch of DNA that transcribes a primary transcript (the RNA molecule)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Initiation steps

A

Transcription factor proteins bind to the promoter in the areas of the TATA box

Transcription factors recruit RNA polymerase.
- combination of transcription factors and RNA polymerase forms the transcription initiation complex
- only 1 of the strands to be transcribed is the template strand

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Elongation steps

A

As RNA polymerase slides along the transcription unit, it separates the DNA strands and opens the transcription bubble

RNA polymerase breaks the H bonds between the nitrogenous bases of the 2 DNA strands

This allows in of the DNA strands to function as a template for RNA synthesis

RNA is transcribed via complementary base pairing (just like dna except it’s AU/CG in RNA)

RNA transcribed from 5 to 3’ ends adding new RNA nucleosides to the 3’ end. Using triphosphate ribonucleosides

DNA left behind by RNA polymerase recoils back into double helix (note: newly synthesized RNA molecules consist of a single strand. Not a double helix)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

4 different ribonucleoside triphosphates used to form RNA molecule

A

Contain a 5 carbon ribose sugar instead of a deoxyribose sugar that is used in DNA nucleotides (note the hydroxyl OH group on the 2’ carbon)

This means an A encountered on the DNA template strand with result in uracil (U) nucleotide added to the growing RNA molecule

Instead of Thymine

Uracil is a pyrimidine like thymine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Which RNA sequence below is complementary to the given DNA sequence 5’ TTAAGGCC3’

A

Because RNA transcription is antiparallel, we rewrite the DNA sequence to

3’CCGGAATT5’
Then follow the AC/TG rule

5’GGCCUUAA3’

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Termination

A

When RNA polymerase reaches the end of a gene it encounters a terminator sequence of nucleotides

This signals termination of transcription

RNA polymerase and the RNA transcript are released from the DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Recap

DNA to RNA

A

initiation to
Elongation to
Termination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

mRNA

A

A long polynucleotide strand possessing the code for a particular polypeptide chain on it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

mRNA code

A

Only 4 letters

A. G. C. U

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

How many amino acids and what are they

A

Building blocks of protein

20 amino acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

mRNA codes of length 1,2,3 could code for

A

4 amino acids

Length 1 4^1=4

Length 2 4^2 =16
Length 3. 4^3=64

24
Q

Codons

A

3 letter words (ex. 3 nucleotide bases in a row) are called codons

As we saw this means there are 4^3 =64 possible codons that make up the genetic code

25
Genetic code
Start codon (AUG) starts translation but also encodes for amino acid methionine
26
Start codon
AUG Typically
27
Stop codons examples
UAA UAG UGA
28
Stop codons
Stop translation Don’t code for any amino acids
29
When can bacterial mRNAs be translated
They can be immediately translated into polypeptides once they are transcribed in the cytoplasm
30
Where are eukaryote mRNAs synthesized
In the nucleus and have to be processed or packaged for release into cytoplasm
31
Eukaryotic packaging
Initial mRNA transcribed in the nucleus is called pre-mRNA (precursor mRNA) After processing in nucleus RNAs are called mature mRNAs
32
RNA processing involves 3 steps
Additional of a guanine cap Addition of a poly (A) tail Removal of introns by splicing
33
Addition of a guanine cap stage in RNA processing
A guanine (or methylated) cap is added to 5’ end of a pre-mRNA by a capping enzyme while the mRNA is still being transcribed in the nucleus - protects mRNAs from degradation by RNA exonucleases once the mRNAs enter the cytosol - facilitates the transport of mRNAs from the nucleus, out through the nuclear pores, and into the cytosol - is the site where ribosomes attach to mRNA at the beginning of translation in the cytosol
34
Addition of poly (A) tail Stage in RNA processing
Polyadenylation signal allows enzyme poly(A) polymerase in the nucleus to attach to pre-mRNAs and add 50-250 adenine nucleotides one at a time to the 3’ end of the pre-mRNAs This forms a poly(A) tail at the 3’ end of each pre-mRNA
35
Why is the poly (A) tail important in RNA processing
To allow for export through nuclear membrane Makes translation of mRNA into amino acids and proteins easier Length of the tail may determine the number of times an mRNA is translated before it is enzymatically degraded in the cytosol by RNA exonucleases.
36
Removing of introns by splicing in translation of RNA
Pre-mRNAs contain alternating sections of introns and exons Introns are spliced out of the mRNA and the exons are connected together such that mRNA includes only exons Therefore all introns are excluded from mature mRNAs
37
Exons
Expressed sequences Exit nucleus RNA processing
38
Introns
Intervening sequences Staying in the INterior of the nucleus In RNA processing
39
Summary of packaging RNA
Transcription-> Addition of poly (A) tail and RNA splicing -> Mature mRNA
40
mRNA mature
Consists of a protein coding region, 2 untranslated regions (UTRs), 5’ cap and a 3’ poly(A) tail
41
Transfer RNA (tRNA)
No affinity between amino acids and mRNAs, so u need something that can connect them Like a code reader tRNAs are the code readers Small RNAs made in the nucleus (74-95 nucleotides in length) that are highly folded. Having both secondary and tertiary structure in addition to their primary structures
42
Primary structure
Sequence of nucleotides making up the RNA molecule
43
tRNA secondary structure
Like a clover leaf with 3 stem loops where they are double stranded due to complementary base pairing At one end of the tRNA there is a site that can associate with an amino acid Complementary base pairing between nucleotides in a stem loop At the end is a region of 3 nucleotide called an anticodon that is complementary to one of the mRNA codons
44
Add amino acids to the tRNA
Aminoacyl-tRNA synthetase enzymes in the cytosol add the correct amino acid into the tRNA with the appropriate anticodon
45
Translation
Synthesis of a polypeptide on a ribosome using the code from an mRNA (translated from DNA) Occurs in cytosol in both eukaryotes and prokaryotes 3 stages. Initiation, elongation, termination
46
Where does translation occur In prokaryotes? Eukaryotes?
Cytosol for both
47
3 stages of translation
Initiation Élongation Termination
48
Initiation translation
1st step. Binding together an initiator tRNA carrying the amino acid methionine, the mRNA and small ribosomal subunit Initiator tRNA has anticodon UAC Small ribosomal subunit with its tRNA binds initially to the mRNA at the mRNAs 5’ end Small subunit scans along the mRNA until it lines up over the start codon on the mRNA Base pairing occurs between the tRNA anticodon and the start codon AUG on the mRNA. This pairing establishes the correct reading frame for translation of the codons along the rest of the mRNA. Essential as there isn’t “punctuation” along the mRNA that separates one codon from the next Code is “commaless “ Large subunit binds onto small subunit, completing initiation stage of translation Completed ribosomal has 3 sites that can accommodate tRNAs: E,P, and A sites
49
Ribosomal subunits consist of
Molecules of both ribosomal RNA ( rRNA ) and proteins Although only a few rRNA are present in each ribosome, they make up about half the mass of the ribosome
50
Where are ribosomal subunits synthesized in eukaryotes
Nucleolus in nucleus Leave the nucleus and become functional in cytoplasm
51
Methionine represents the
First of many amino acids joined together one at a time by the ribosome to form a long polypeptide chain
52
Translation key
E=exit site P= peptidyl site A= aminoacyl site
53
Elongation cycle adds
One new amino acid at a time To the new forming polypeptide chain
54
Elongation Translation
At the begging of each cycle. Polypeptide chain is held by the tRNA in the P site At the end of the it’s held again by a new tRNA in the P site Chain increases in length by one amino acid during each cycle At the beginning of the first elongation cycle the P site is occupied by a charged tRNA with methionine attached to it. (E and A sites are empty) A tRNA with a new amino acid enters the empty A site with an anticodon complementary to the codon exposed in the A site (charged tRNA is entering the empty A site) Peptidyl transferase in the large subunit catalyzes the formation of a peptide bond between the 2 amino acids attached to the 2 tRNAs held in P and A sites Ribosome now translocates along the mRNA a distance of 3 nucleotides in the 5’ to 3’ direction This shifts the uncharged tRNA in the P site to the E site and the charged tRNA in the A site to the P site. A site left empty Uncharged tRNA in the E site exits ribosome Empty A site is no ready to receive a new tRNA bringing in the next amino acid to be added to the polypeptide chain This ends one elongation cycle with the polypeptide chain again held by a new tRNA in the P site Cycle is repeated over and over. Growing polypeptide chain 1 amino acid at a time. The genetic code is non overlapping. This means successive triplet codons are read in order to not successive nucleotides
55

Bio 120 (32 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions