Praxis (5236) - Biology > 3A2 Transfer of Genetic Material > Flashcards

3A2 Transfer of Genetic Material Flashcards

Describe DNA replication and the role of RNA in protein synthesis. Understand gene regulation and use gene charts. (97 cards)

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1
Q

What does the central dogma of genetics describe?

A

The flow of genetic information in cells: DNA to RNA to protein.

Coined by Francis Crick in 1958 to describe the directional flow of genetic information.

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2
Q

What enzyme allows for the creation of DNA by copying RNA?

A

Reverse transcriptase

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3
Q

What is the replication of RNA from existing RNA called?

A

RNA-dependent RNA replication, typically seen in RNA viruses.

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4
Q

What is the enzyme responsible for copying the gene’s nucleotides into an RNA molecule?

A

RNA polymerase

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5
Q

What is the first step of gene expression?

A

Transcription

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6
Q

What occurs during the process of transcription?

A

DNA sequence information is converted to RNA.

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7
Q

What is the process of translation?

A

Sequence encoded in the RNA molecule is decoded and converted into an amino acid sequence.

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8
Q

What cellular structure translates RNA sequence information into an amino acid sequence?

A

Ribosome

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9
Q

What are codons in the context of translation?

A

Codons are sequences of three RNA nucleotides that instruct the ribosome to add a specific amino acid during protein synthesis.

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10
Q

Differentiate between transcription and translation processes.

A
  • Transcription: DNA to RNA conversion
  • Translation: RNA to protein conversion
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11
Q

What does the semiconservative model of DNA replication entail?

A

The two strands of the parental molecule separate, and each strand functions as a template for synthesis of a new, complementary strand.

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12
Q

What is DNA replication?

A

The process of duplicating the parent cell’s genetic material to ensure the correct amount of genetic material is present between daughter cells.

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13
Q

What is the site of initial unwinding in DNA replication called?

A

Origin of replication

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14
Q

When does DNA replication occur?

A

Prior to cell division during the S phase of the cell cycle.

Stages of the cell cycle are: G1, S, G2, M-Phase

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15
Q

What is the function of helicase in DNA replication?

A

To break the hydrogen bonds holding the double strand together to unwind and expose the single strands to promote replication.

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16
Q

What type of energy does helicase require for its action?

A

Adenosine triphosphate

(ATP)

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17
Q

What is the directional nature of helicase?

A

Unidirectional

Once helicase begins unwinding he DNA it will only move in one direction- forward.

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18
Q

What shape does the DNA molecule form as a result of DNA helicase action?

A

Replication fork

The Y-shaped structure created by DNA helicase separating the two sides of the parental DNA.

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19
Q

What is the genetic code in DNA?

A

The sequence of nitrogen-containing bases that directs protein synthesis.

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20
Q

What is the rule that dictates which nucleotides pair with each other during DNA replication?

A

Rule of complementary base pairing.

Adenine (A) will always pair with Thymine (T).
Cytosine (C) will always pair with Guanine (G).

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21
Q

Why does DNA replication start at many different places on the parental strand?

A

To quickly replicate DNA.

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22
Q

What does DNA polymerase do during DNA replication?

A

Adds nucleotides from the 5’-3’ direction to the leading strand and synthesizes the lagging strand in little fragments called Okazaki fragments.

Produces double-stranded DNA during DNA replication.

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23
Q

What is the primary function of RNA in gene expression?

A

RNA carries genetic information from DNA and helps assemble proteins during translation at the ribosome.

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24
Q

How does RNA polymerase begin transcription?

A

It binds to a region in DNA called the promoter sequence, which guides RNA polymerase on where to bind to DNA.

Produces a single stranded RNA during gene expression.

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25
What is the role of **topoisomerase** in DNA replication?
It **untangles the DNA molecule** by cutting the phosphodiester bonds comprising the backbone of the DNA structure to allow unwinding during DNA replication (and sometimes transcription).
26
What is the function of **RNA primase** in DNA replication?
It attaches a short RNA molecule called a primer to the DNA sequence to help DNA polymerase attach to the single strand of DNA. ## Footnote RNA primers are typically about 10 nucleotides long. After 10 nucleotides, DNA polymerase will begin adding DNA nucleotides.
27
What base does RNA primase lay down instead of thymine when building the RNA primer?
Uracil
28
What is the outcome if DNA polymerase mispairs a base during replication?
Mutation
29
What is the **main function** of **RNA polymerase** in transcription?
Synthesize a strand of RNA called **messenger RNA**.
30
Where does DNA replication occur in **eukaryotic** cells?
In the nucleus.
31
Where does DNA replication occur in *prokaryotic* cells?
In the nucleoid region of the cytoplasm.
32
What is the role of **single strand binding proteins** in DNA replication?
Covering unwound strands to prevent reannealing.
33
What is the function of **exonucleases** in DNA replication?
Removing RNA primers and replacing them with DNA.
34
What is the function of **DNA ligase** in DNA replication?
Connects Okazaki fragments. ## Footnote This process is known as ligation.
35
What is the role of **Telomerase** in DNA replication?
Extends the telomeres by adding **repetitive sequences** to the ends of chromosomes.
36
List the main steps of **DNA replication**.
1. Initiation 2. Primer binding 3. Elongation 4. Primer Removal and Replacement 5. Ligation 6. Termination ## Footnote **Initiation**: Helicase unwinds the DNA, SSBs stabilize the strands, and topoisomerase prevents overwinding. **Primer Binding**: Primase synthesizes short RNA primers to provide a starting point for DNA synthesis. **Elongation**: DNA polymerase III synthesizes the leading strand continuously and the lagging strand in Okazaki fragments. **Primer Removal and Replacement**: DNA polymerase I removes RNA primers and replaces them with DNA nucleotides. **Ligation**: DNA ligase joins the Okazaki fragments by forming phosphodiester bonds between them. **Termination**: Replication ends when the entire molecule has been copied, and the newly formed DNA strands are proofread and corrected as needed.
37
What did Reiji Okazaki discover about DNA replication and antiparallel strands?
DNA polymerase builds a strand of DNA that runs 5' to 3', which posed a challenge for the other parent strand running in the 5' to 3' direction.
38
What is the name of the **parent strand that runs in the 3' to 5' direction** toward the replication fork and is replicated continuously by DNA polymerase?
Leading strand
39
What is the name of the **parent strand of DNA that runs in the 5' to 3' direction** toward the fork and is replicated discontinuously?
Lagging strand
40
How does DNA polymerase replicate the lagging strand of DNA?
By making short lengths known as **Okazaki fragments**, in a discontinuous fashion.
41
What does **mRNA** stand for, and what is its function?
It stands for 'messenger RNA,' and it **serves as a messenger** to carry genetic information from the nucleus to the cytoplasm.
42
What occurs during the **initiation stage of transcription**?
1. Binding of RNA polymerase to the promoter region 2. Formation of transcription initiation complex 3. Unwinding of DNA for access to template DNA
43
What are the sense strand and antisense strand during transcription?
* **Sense strand** (Coding strand): This strand resembles the mRNA sequence (except mRNA has uracil instead of thymine). It is not used as a template during transcription. * **Antisense strand** (Template strand): This strand serves as the template for transcription. RNA polymerase reads this strand to create a complementary mRNA strand.
44
What are the three stages of **transcription**?
1. Initiation 2. Elongation 3. Termination ## Footnote **Initiation**: * RNA polymerase binds to the promoter region of the DNA. * The DNA strands unwind, and RNA polymerase begins synthesizing RNA at the start site. **Elongation**: RNA polymerase moves along the DNA template strand, adding RNA nucleotides in the 5′ → 3′ direction, forming a growing mRNA strand. **Termination**: * RNA polymerase reaches a termination sequence or signal. * The enzyme detaches, and the newly synthesized RNA strand is released.
45
What are the **three major types of RNA** produced during transcription?
* Ribosomal RNA (rRNA) * Messenger RNA (mRNA) * Transfer RNA (tRNA)
46
Where does transcription and translation occur in prokaryotes and eukaryotes?
* In prokaryotes, transcription and translation are coupled and occur simultaneously in the cytoplasm. * In eukaryotes, transcription and translation occur separately in the nucleus and cytoplasm and/or endoplasmic reticulum.
47
What is the role of the **promoter** in transcription?
Marks where transcription should begin and signals the RNA polymerase to start transcription at that point.
48
What is the phase of transcription where RNA polymerase **transcribes the gene into a strand of mRNA**?
Elongation ## Footnote During transcription, RNA polymerase synthesizes a complementary mRNA strand using the DNA template.
49
What happens at **termination** in translation?
Once a stop codon (terminator) reaches the ribosome, translation stops, or terminates. ## Footnote At termination, the polypeptide is freed from the ribosome, and tRNAs stop bringing the amino acids in. All of the components come apart from one another, and translation is done. The result is a brand new free-floating polypeptide.
50
What are introns and exons?
* **Introns** are non-coding regions of DNA or RNA * **Exons** are coding sequences in DNA or RNA
51
Where does **RNA transcription** occur in eukaryotes?
Within the nucleus
52
Where does **RNA splicing** occur in eukaryotes?
In the nucleus
53
What are **spliceosomes** and their role in RNA splicing?
They are composed of protein and small RNA molecules that remove introns from RNA and join the ends of adjacent exons together during RNA splicing.
54
How does the spliceosome identify the correct places for the removal of introns?
They look for **starting and ending points** of an intron. ## Footnote Starting and ending points are marked by GT-AG dinucleotides or AU-AC dinucleotides.
55
What is **Alternative Splicing**?
A process where a **single RNA transcript is spliced in different ways** to produce different functional proteins. ## Footnote Alternative splicing allows the organism to regulate different cellular activities by combining exons to form multiple proteins from the same gene.
56
What are the **potential errors** in RNA splicing?
* Removal of wrong intron * Exon cutting by a spliceosome ## Footnote Splicing errors can lead to the production of non-functional or disease-producing proteins.
57
What is unique about RNA processing in eukaryotes compared to prokaryotes?
Eukaryotes undergo an RNA processing step right after transcription and before translation, while prokaryotes do not have this additional step.
58
What is the purpose of **introns** in gene expression?
They play a role in gene expression by allowing different combinations of exons to be spliced together, leading to alternative splicing and the production of multiple proteins from a single gene.
59
Describe **pre-mRNA**.
An RNA transcript that is found in Eukaryotic cells, that is awaiting processing to become mRNA.
60
What are the three main processes that comprise pre-mRNA processing?
* Splicing * Capping * Tailing
61
Where does **RNA capping and tailing** occur?
Inside the **nucleus**, right after transcription and RNA splicing.
62
What is the purpose of **RNA splicing**?
To remove introns and join exons to form mature RNA capable of producing functional proteins.
63
How are amino acid chains linked together in genetic translation?
By peptide bonds
64
What is the significance of **peptide bonds** in protein synthesis?
They are covalent bonds between two amino acids that form long chains of amino acids known as **polypeptides**.
65
What is the function of **tRNA** molecules during translation?
They **carry amino acids** and use their anticodon to match the corresponding mRNA codon during translation.
66
Where are **ribosomes** located in a cell?
On the rough endoplasmic reticulum (RER) surrounding the nucleus of a cell and freely floating in the cytoplasm.
67
What is the process by which **peptide bonds are formed** between amino acids?
Dehydration synthesis ## Footnote When two amino acids line up, one releases a hydrogen molecule, and the other releases an oxygen and a hydrogen, forming a water molecule. The water leaves, and the amino acids are bonded together.
68
Describe the structure of a ribosome **during translation**.
A ribosome is made of **two subunits that sandwich the mRNA strand**. The mRNA is threaded through the middle of the ribosome. Inside, the ribosome is not solid but contains molecules that allow RNA strands to move in and out.
69
Where does **translation** occur in the cell?
At the ribosomes, either on the rough ER or in the cytoplasm. ## Footnote Ribosomes are tiny organelles on the rough endoplasmic reticulum.
70
What is the **role of ribosomes** in translation?
They decode mRNA and link amino acids to form polypeptides.
71
What marks the **termination** of the translation process?
The presence of **stop codons**. ## Footnote UAA, UAG, and UGA are known as stop codons.
72
What happens to the **polypeptide chain** once the translation process is terminated?
It drifts out of the ribosome and floats freely in the cytoplasm.
73
What recognizes the **stop codon** in mRNA?
Release factors ## Footnote Release factors are proteins that identify the stop codon in the mRNA sequence.
74
What is the **start codon** in translation?
AUG ## Footnote AUG is the start codon that initiates the translation process.
75
What is the definition of **translation**?
The **synthesis of a polypeptide** using the genetic code found in mRNA.
76
What is gene repression and induction?
* **Gene repression** is when genes are **turned off** during gene expression by repressor proteins. * **Gene induction** is when genes are **turned on** during gene expression by inducer or activator proteins.
77
What is **gene expression**?
The process of **turning on or off** different genes in a cell to create proteins necessary for various cellular functions.
78
How is gene expression **regulated**?
Through internal signals from internal proteins or DNA condition, as well as external signals like nutrients, hormones, and physical properties. These signals can activate or repress proteins needed for gene expression. ## Footnote Eukaryotes are regulated through transcription factors. Prokaryotes are regulated by RNA polymerase binding to the promoter region of a gene to create mRNA.
79
What is the role of the **catabolite activator protein (CAP)** site in the lac operon?
The **CAP site binds the CAP-cAMP complex** when glucose levels are low. ## Footnote Binding of the CAP-cAMP complex enhances RNA polymerase binding to the promoter, increasing transcription of the lac operon when lactose is present.
80
What is the function of the **promoter** region in the lac operon?
It is where RNA polymerase binds to initiate transcription of the structural genes needed to metabolize the sugar lactose, containing structural genes for lactose metabolism.
81
How is gene expression **turned off** in prokaryotes?
Through the **binding of the repressor** to the operator, blocking RNA polymerase from reading the DNA.
82
What does the **allolactose** do in the lac operon?
**Binds to the repressor protein**, causing it to change conformation and cease binding to the operator.
83
What are **operons**, and how are they related to gene expression in prokaryotes?
They are clusters of related genes found in prokaryotes. They are translated together, allowing for the coordinated production of proteins involved in the same cellular function.
84
What is the importance of **gene regulation** in cells?
It is crucial for cells to **produce only the necessary proteins at specific times**, which ensures energy efficiency and allows cells to respond appropriately to their environment.
85
What does the **degenerate** nature of the genetic code mean?
Multiple codons may code for the same amino acid.
86
Why is the genetic code considered **universal**?
Because nearly all organisms use the same genetic code, with very few exceptions (e.g., mitochondrial DNA).
87
What is a **codon**?
A sequence of **three nucleotides** which codes for one amino acid. ## Footnote Examples: UAG, CGA
88
What is **codon recognition?**
The process of **matching codons to the correct amino acids** during translation.
89
How many different codons are there?
64
90
What is a **codon chart**?
A chart of all the codons and the amino acids they stand for.
91
How do you **read** a **codon chart**?
Find the first, second, and third letter of the codon in question and use an abbreviation for which amino acid the codon codes for.
92
What is **prokaryotic transcription**?
The process of transcribing DNA into messenger RNA (mRNA) for translation.
93
What are the components of a typical operon?
* Promoter * Operator region * Regulator protein (repressor or activator)
94
What is **prokaryotic translation**?
The process of translating mRNA information into a series of amino acids to form a protein.
95
What is the function of **chaperone proteins** in protein synthesis?
To fold the polypeptide chain into the correct shape.
96
What nucleotide will **adenine** always bind with in DNA?
Thymine
97
What nucleotide will **guanine** always bind with in DNA?
Cytosine
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