Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BIO 110 > Chapter 12 > Flashcards

Chapter 12 Flashcards

You may prefer our related Brainscape-certified flashcards:
Biology 101 flashcards
1
Q

Overview of Gene Expression
We can look at gene function at two levels:

A
  1. molecular function of the protein product
  2. organism’s trait conferred by the gene
    Two levels are connected – the molecular function affects the structure and function of cells to determine the trait
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Inborn errors of metabolism

A

1908, Archbold Garrod first proposed relationship between genes and the production of enzymes
Studied patients with metabolic defects, or “inborn errors of metabolism”
Alkaptonuria
Patient’s body accumulates abnormal levels of homogentisic acid (alkapton)
Recessive pattern of inheritance
Hypothesis: “Disease is due to missing enzyme”
The nature of the genetic material was completely unknown at the time

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

Beadle and Tatum

A

Early 1940s – Beadle and Tatum became aware of Garrod’s work
They worked on Neurospora crassa, common bread mold
Minimum requirements for growth
Carbon source (sugar), inorganic salts, and biotin
Neurospora can synthesize everything else it needs from those precursors

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

Beadle and Tatum cont.

A

Wildtype – normal Neurospora, can grow on minimal medium
Mutant strains – unable to grow unless supplemented with specific substances (vitamins or amino acids)
Each single mutation resulted in the requirement for a single type of vitamin
Hypothesis: “One gene, one enzyme”

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

Beadle and Tatum cont.

A

Multiple mutants required arginine to grow
Could they grow if supplemented with precursors instead?
Fell into three groups based on requirements
Conclusion – Supports one gene, one enzyme hypothesis

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

Modern understanding

A

A modification of the “one gene, one enzyme” hypothesis
Enzymes are only one category of cellular proteins – genes also encode other proteins
Also, some proteins are composed of several polypeptides that work together for one function
Example: Hemoglobin composed of 4 polypeptides
“One gene, one polypeptide”

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

The Central Dogma 1
Transcription

A

Produces a transcript (RNA copy) of a gene
This messenger RNA (mRNA) specifies the amino acid sequence of a polypeptide

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

Translation

A

Process of synthesizing specific polypeptide on a ribosome using the mRNA template
DNA -> RNA -> Protein

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

Eukaryotes also have an intervening step called RNA processing where pre-mRNA is processed into active mRNA

A

DNA -> pre-mRNA -> mRNA -> Protein

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

Some genes do not encode polypeptides
an RNA is the final functional product

A

Structural RNAs
Regulatory RNAs

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

How do genes determine traits?

A

Genes constitute the genetic material
The “blueprint” for organisms’ characteristics
Structural genes code for polypeptides
One or several polypeptides act as a protein to play some role in the cell
Activities of proteins determine the structure and function of cells
Cellular activity, taken together in an organism determines their traits or characteristics

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

Transcription

A

Gene - An organized unit of base sequences that enables a segment of DNA to be transcribed into RNA and ultimately results in the formation of a functional product
Other genes code for RNA itself as a product:
Transfer RNA (tRNA) - translates mRNA into amino acids
Ribosomal RNA (rRNA) - part of ribosomes

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

pre-mRNA

A

In eukaryotes, the mRNA transcript before any biochemical modifications are made to it.

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

mature mRNA

A

In eukaryotes, transcription produces a longer RNA, called pre-mRNA, which undergoes certain modifications before it exits the nucleus; mature mRNA is the final functional product.

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

terminator

A

A sequence of DNA within a gene that specifies the end of transcription.
Signals the end of transcription

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

transfer RNA (tRNA)

A

An RNA that carries amino acids and is used to translate mRNA into polypeptides.

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

ribosomal RNA (rRNA)

A

An RNA that forms part of ribosomes, which provide the site where translation occurs.

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

promoter

A

A sequence of DNA within a gene that controls when and where transcription begins.
Signals the begining of transcription

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

regulatory sequence

A

In the regulation of transcription, a DNA sequence that functions as a binding site for a regulatory protein, which influences the rate of transcription.

20
Q

Transcribed region:

A

Part of this region contains the information that specifies an amino acid sequence

21
Q

The Three Stages of Transcription

A

initiation
elongation
termination

22
Q

Intiation

A

The promoter functions as a recognition site for sigma factor. RNA polymerase is bound to sigma factor, which causes it to bind to the promoter. Following binding, the DNA is unwound to form an open complex.

23
Q

Elongation/synthesis of the RNA transcript:

A

Sigma factor is released, and RNA polymerase slides along the DNA in an open complex to synthesize RNA. RNA polymerase slides along the template strand in the 3’ to 5’direction, while it synthesizes RNA In the opposite, 5’ to 3’, direction.

24
Q

Termination:

A

When RNA’polymerase reaches the terminator, it and the RNA transcript dissociate from the DNA.

25
Q

Direction of transcription

A

Direction of transcription and which DNA strand used varies among genes
In all cases, synthesis of RNA transcript is 5’ to 3’ and DNA template strand reads 3’ to 5’

26
Q

Eukaryotic transcription

A

Basic features identical to prokaryotes
However, each step has more proteins
Three forms of RNA polymerase:
RNA polymerase II – transcribes mRNA
RNA polymerase I and III – transcribes nonstructural genes for rRNA and tRNA
RNA polymerase II requires 5 general transcription factors to initiate transcription

27
Q

RNA Modification

A

Bacterial mRNAs can be translated immediately
Eukaryotic mRNAs are made in a longer pre-mRNA form that requires processing into mature mRNA
Processing:
Introns – transcribed but not translated
Exons – coding sequence found in mature mRNA
Splicing – removal of introns
Other modifications – addition of tails and caps

28
Q

Capping and Tailing
Capping

A

Modified guanosine attached to 5’ end
Needed for mRNA to exit nucleus and bind ribosome

29
Q

Poly A tail

A

100 to 200 adenine nucleotides added to 3’ end
Increases stability and lifespan in cytosol
Not encoded in gene sequence

30
Q

RNA splicing

A

Introns found in many eukaryotic genes
Most structural genes have one or more introns
Spliceosome – removes introns precisely
Composed of snRNPs (small nuclear RNA + proteins)
Alternative splicing – splicing can occur more than one way to produce different products
rRNA and tRNA are self-splicing
They are ribozymes – RNAs that can catalyze reactions

31
Q

Translation and the Genetic Code

A

Genetic code – sequence of bases in an mRNA molecule
Read in groups of three nucleotide bases or codons
Most codons specify a particular amino acid
Also Start and Stop codons
Degenerate code – more than one codon can specify the same amino acid

32
Q

Bacterial mRNA

A

Bacterial mRNA has 5’ ribosomal-binding site
Start codon usually AUG
Typical polypeptide is a few hundred amino acids in length
Stop codons (aka Termination or nonsense codons)
UAA, UAG or UGA

33
Q

Ribosomal-binding site

A

The site for ribosome binding.

34
Q

Start codon

A

A codon that specifies the first amino acid in a polypeptide sequence.

35
Q

Coding sequence

A

A series of codons from the start codon to the stop codon that determine the sequence of amino acids of a polypeptide.

36
Q

Stop codon

A

Specifies the end of translation.

37
Q

Codons and anticodons

A

mRNA
Codon – set of 3 RNA nucleotides
T of DNA substituted for U of RNA
tRNA
Anticodon – 3 RNA nucleotide part of tRNA molecule
Allows binding of tRNA to mRNA codon

38
Q

The machinery of translation

A

Requires many components:
mRNA
tRNA
ribosomes
translation factors
Most cells use a substantial amount of energy on translation

39
Q

tRNA

A

Different tRNA molecules encoded by different genes
tRNA Ser carries serine
Common features:
Cloverleaf structure
Anticodon
Acceptor stem for amino acid binding

40
Q

Aminoacyl-tRNA synthetase

A

Catalyzes attachment of amino acids to tRNA
One for each of 20 different amino acids
Reactions result in tRNA with amino acid attached (charged tRNA or aminoacyl tRNA)
Ability of aminoacyl-tRNA synthetase to recognize appropriate tRNA has been called the “second genetic code”

41
Q

Ribosomes

A

Prokaryotes have one kind of ribosome
Eukaryotes have distinct ribosomes in different cellular compartments
Here, we focus on cytosolic ribosomes
Composed of large (50S) and small (30S) subunits
Structural differences between prokaryotes and eukaryotes exploited by antibiotics to inhibit bacterial ribosomes only

42
Q

Ribosome structure

A

Overall ribosome shape determined by rRNA
Discrete sites for tRNA binding and polypeptide synthesis
P site – Peptidyl site
A site – Aminoacyl site
E site – Exit site

43
Q

Comparisons of Small Subunit rRNAs Among Different Species Provide a Basis for Establishing Evolutionary Relationships

A

Components for translation arose in the ancestor of all living species
All organisms have evolutionarily related translational components
Gene for small subunit rRNA (SSU rRNA) found in all genomes
Gene evolution involves changes in DNA sequences
Similar sequences are evolutionarily conserved
Sequences critical for function not able to change

44
Q

The Stages of Translation

A

Initiation
mRNA, first tRNA and ribosomal subunits assemble
Elongation
Synthesis from start codon to stop codon
Termination
Complex disassembles at stop codon releasing the completed polypeptide

45
Q

Initiation in eukaryotes

A

Two eukaryotic differences in initiation
Instead of a ribosomal-binding sequence, mRNAs have guanosine cap at 5’ end
Recognized by cap-binding proteins
Position of start codon more variable
In many cases, first AUG codon used as start codon

46
Q

Antibiotics that target bacterial infections

A

Antibiotics that inhibit bacterial translation can treat bacterial infections

The antibiotics were identified in microorganisms to inhibit the growth of other microorganisms

BIO 110 (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions