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Biology 3/4 2025 > Unit 3 AOS 1 Nucleic Acids and Proteins > Flashcards

Unit 3 AOS 1 Nucleic Acids and Proteins Flashcards

1
Q

What are amino acids?

A

Monomers that are the building blocks to proteins

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2
Q

What are proteins?

A

One of the four types of biomacromolecules that serve a variety of functions

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3
Q

What does an amino acid consist of?

A
  • A central carbon bonded to a hydrogen
  • A carboxyl group
  • An amino group
  • A variable R-group
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4
Q

What is a polypeptide?

A

Amino acids (monomers) that are bonded together (polymer)

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5
Q

What does a condensation reaction do?

A

Bonds amino acids into polypeptides

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6
Q

What does the primary structure of proteins involve?

A

The sequence of amino acids in a polypeptide chain

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7
Q

What does the secondary structure of proteins involve?

A

Polypeptide chains folding and coiling into alpha helices and beta pleated sheets

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8
Q

What does the tertiary structure of proteins involve?

A

Overall functional 3D shape of a protein
- A protein must at least have a tertiary structure for it to be functional

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9
Q

What does the quaternary structure of proteins involve?

A

When two or more polypeptide chains with tertiary structure bond together

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10
Q

What is gene expression?

A

The process of reading genetic information to create a functional product (typically a protein)

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11
Q

Where does transcription occur in eukaryotes and why?

A

Nucleus as that is where DNA is stored

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12
Q

Where does transcription occur in prokaryotes and why?

A

In the cytosol as DNA is free-floating due to an absence of a nucleus

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13
Q

What is the product of transcription?

A

Pre-mRNA

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14
Q

What is pre-mRNA?

A

Product of transcription
- Requires modifications before it can undergo translation

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15
Q

What is the purpose of RNA polymerase within transcription?

A

-Unwinds DNA
-catalyses transcription by joining complementary RNA nucleotides

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16
Q

What occurs in transcription?

A

-RNA polymerase binds to promoter region in DNA, causing it to unwind as it moves along
-RNA polymerase catalyses transcription by adding RNA nucleotides that are complementary to the template strand
-Transcription of pre-mRNA occurs in a 5’ to 3’ direction until termination sequence

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17
Q

What is the purpose of RNA-processing?

A

Modifies pre-mRNA into mRNA so that it can be translated

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18
Q

What occurs in RNA processing?

A

-Introns are removed from pre-mRNA and exons are spliced together, creating mRNA
-Addition of 5’ methyl-G cap and 3’ poly-A tail to mRNA
-Alternative splicing may occur

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19
Q

What kind of organisms does RNA processing occur in and why?

A

Eukaryotes as their genes have both introns and exons, whereas prokaryotes only have exons

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20
Q

What is the purpose of translation?

A

Reading and converting information carried by the mRNA into a polypeptide chain

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21
Q

Where does translation occur?

A

In ribosomes

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22
Q

What occurs in translation?

A

-mRNA leaves nucleus into cytoplasm
-5’ end of mRNA binds to ribosome and is read until start codon is recognised
-tRNAs with complementary anticodons deliver specific amino acids to ribosome
-tRNAs leave ribosome to pick up another amino acid
-amino acids bind via polypeptide bonds to create a polypeptide chain
-ribosome reached stop codon, ending translation

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23
Q

What is a bacteriophage?

A

A virus that infects prokaryotes (e.g. bacteria)

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24
Q

How do bacteriophages infect prokaryotes?

A

By inserting viral DNA or RNA into the bacterium, in order for the cell to produce their own proteins

25
What is CRISPR-Cas9?
A complex used by bacteria as a protection against viruses
26
What do Cas1 and Cas2 do?
-Cut out short section of viral DNA known as a protospacer -They put the protospacer into the CRISPR gene as a spacer
27
What is a spacer?
Short sequence of viral DNA that are added into the CRISPR sequence
28
What is a protospacer adjacent motif (PAM)?
A sequence of nucleotides that is found next to the DNA targeted by cas9 -signals Cas1-Cas2 and Cas9 where to cut
29
What is a protospacer?
A short sequence of DNA extracted from a bacteriophage by cas1-cas2, not yet incorporated into the CRISPR gene
30
What is gRNA?
RNA which has a specific sequence determined by CRISPR to guide Cas9 to a specific site -Transcribed genetic information from CRISPR
31
What does gRNA do?
Binds to Cas9 to form CRISPR-Cas9 complex
32
How does the CRISPR-Cas9 defence system work?
-Viral DNA inserted by a bacteriophage into bacteria is read by Cas1-Cas2 and cuts the DNA into a protospacer (recognised by PAM) -Protospacer is inserted into CRISPR and becomes a spacer -CRISPR is transcribed and becomes gRNA -gRNA binds to Cas9 to become CRISPR-Cas9 -CRISPR-Cas9 searches for viral DNA by reading PAM sequence -When DNA is found that is complementary to gRNA Cas9 cleaves the DNA to inactivate the virus -Mutations within virus prevents it from repairing
33
What is the purpose of CRISPR-Cas9 in prokaryotes?
To attack and destroy invading viral DNA
34
What is the purpose of CRISPR-Cas9 in gene editing?
To induce mutations to alter genomic DNA
35
How is gRNA produced in prokaryotes?
Naturally through the transcription and post-transcriptional modifications of the CRISPR gene
36
How is gRNA produced in gene editing?
Synthetically produced in a laboratory (sgRNA)
37
What happens after Cas9 cuts viral DNA?
DNA repair mechanisms often induce a mutation that inhibits viral function
38
What happens after the DNA is cut in gene editing?
DNA can mutate to knock out, enhance, or otherwise change the function of genes
39
How does CRISPR-Cas9 work in gene editing?
-sgRNA + Cas9 is injected into the cell -sgRNA identifies mutated DNA -Cas9 cuts out the mutated sequence, causing a double break in the strand -The faulty gene can be replaced by corrected DNA or a new gene altogether (gene knock-in) OR -The cell's attempt to repair the break effectively silences the targeted gene (gene knockout)
40
Define gene knockout
The expression of a target gene is prevented
41
Define gene knock-in
Nucleotides are substituted or added to a gene
42
What are the limitations of CRISPR-Cas9 in gene editing?
-Gene knock-in is not consistently successful ETHICAL: -Some people are concerned that scientific research on embryos does not protect the sanctity of human life -Potential harm to pregnant women and unborn babies
43
Name the properties of genetic code
-Universal -Unambiguous -Degenerate -Non-overlapping
44
Describe the properties of genetic code
Universal- Nearly all living organisms use the same codons to code for specific amino acids Unambiguous- Each codon is only capable of coding for one specific amino acid Degenerate- Amino acids may be coded for by multiple different codons Non-overlapping- Each triplet or codon is read independently, without overlapping from adjacent triplets or codons
45
What is the purpose of the protein secretory pathway?
To export proteins out of the cell to be used elsewhere
46
What is the process where proteins are exported out of a cell via a secretory vesicle?
Exocytosis
47
What organelles are involved in the protein secretory pathway?
-Ribosome -Rough endoplasmic reticulum -Transport vesicle -Golgi apparatus -Secretory vesicle
48
What are the functions of the organelles involved in the protein secretory pathway?
Ribosomes: Synthesise proteins Rough Endoplasmic reticulum: Folds and transports proteins (ribosome w/ protein attached) Transport vesicle: Transports proteins Golgi Apparatus: Modifies and packages proteins into secretory vesicle Secretory vesicle: Transports proteins to plasma membrane for exocytosis
49
What is the purpose of polymerase chain reaction (PCR)?
To amplify DNA
50
Describe the steps of PCR
Denaturation: DNA is heated to 90-95 degrees, causing the hydrogen bonds between double stranded DNA to become two single strands Annealing: DNA is cooled to 50-55 degrees, primer bind to complementary sequences on single stranded DNA Elongation: DNA is heated to 72 degrees, which allows taq polymerase to bind to the primers and begin synthesising a new complementary strand of DNA Steps are repeated to make multiple copies of DNA
51
What is gel electrophoresis?
Laboratory technique used to measure the size of DNA fragments
52
Describe the steps of gel electrophoresis
Step 1: DNA samples are placed in wells at one end of the gel, with a standard ladder being loaded into one well. Gel is immersed in a buffer solution to help carry an electric current Step 2: Electric current is passed through. Negative electrode at the wells end, positive electrode at the opposite end (DNA is negatively charged) Step 3: Smaller DNA fragments move further (and quicker) than large fragments, separating them based on size. DNA fragments settle into bands Step 4: Gel is stained with a fluorescent dye that makes it visible under UV light
53
What can gel electrophoresis be used for?
- Genetic testing - DNA profiling - Parentage testing
54
What are the 8 types of protein functions?
Enzymes Structural Transport Hormones Motor Receptors Defence Storage
55
What are four of the functions of proteins?
Enzymes: Speed up chemical reactions Transport: controls the entry and exit of substances from a cell Structural: support cell and tissue shape Hormones: chemical messengers used to communicate and induce changes in a cell
56
What are restriction endonucleases?
Enzymes responsible for cutting specific recognition sites
57
What are blunt ends?
DNA that has been cut straight, with no overhanging nucleotides
58
What are sticky ends?
DNA with a staggered cut that leaves overhanging, unpaired nucleotides
59
What are recognition sites?
A specific target sequence of DNA where restriction endonucleases act

Biology 3/4 2025 (2 decks)

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