AP Biology > Unit 6 > Flashcards

Unit 6 Flashcards

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1
Q

What are purines?

A

Double ring structures (A, G)

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2
Q

What is Chargaff’s Rule?

A

The amount of adenine is equal to the amount of thymine
The amount of guanine is equal to the amount of cytosine.

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3
Q

What are pyrimidines?

A

Single ring structures (C, U, T)

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4
Q

How many hydrogen bonds are there between Adenine and Thymine?

A

2

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5
Q

How many hydrogen bonds are there between Guanine and Cytosine?

A

3

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6
Q

What’s the backbone of DNA made of?

A

sugar-phosphate

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7
Q

What’s in the center of DNA?

A

Nucleotides pairing

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8
Q

What does it mean that DNA is antiparallel?

A

One strand runs 5’ to 3’, other strand runs in
opposite, upside-down direction 3’ to 5’

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9
Q

What does 5’ end and 3’ end mean?

A

5’ end: free phosphate group
3’ end: free hydroxyl group

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10
Q

What is the primary source of heritable information in some viruses?

A

RNA

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11
Q

What are plasmids?

A

Small, circular DNA molecules that are separate from the chromosomes

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12
Q

T/F: Plasmids replicate independently from the chromosomal DNA

A

TRUE

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13
Q

How are plasmids used in prokaryotes?

A

Contain genes that may be useful to the prokaryote when it is in a particular environment, but may not be required for survival

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14
Q

What are some key differences between RNA and DNA?

A

DNA is double stranded and adenine bonds to thymine. RNA is single stranded and adenine bonds to uracil

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15
Q

In what model does DNA replicate?

A

In a Semi Conservative model

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16
Q

Where does DNA replication begin?

A

At origins of replication

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17
Q

What unzips DNA strands at each replication fork?

A

Helicase

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18
Q

What is formed when proteins open the DNA?

A

A replication fork

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19
Q

What stops DNA from rebonding?

A

single strand binding proteins (SSBPs)

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20
Q

What prevents strain ahead of the replication fork?

A

Topoisomerase

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21
Q

What does primase do?

A

Adds RNA primers to DNA strands

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22
Q

In what direction does DNA polymerase read the template DNA strand?

A

3’ to 5’

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23
Q

In what direction is the newly synthesized strand made by DNA polymerase?

A

5’ to 3’

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24
Q

What does DNA polymerase do?

A

Reads primer on the template strand and adds nucleotides to new strand

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25
What does DNAP that moves towards the replication fork do?
Synthesizes leading strand smoothly with one primer
26
Since DNAP only moves from a 5' to 3' direction, what does DNAP moving away from the replication fork do?
Creates a lagging strand discontinuously in short fragments called Okazaki fragments requiring many primers
27
What does a different DNAP do with the RNA nucleotides?
Replaces them with DNA nucleotides
28
What is DNA ligase?
Joins Okazaki fragments into a continuous DNA strand
29
As we age, why does DNA become shorter and shorter?
DNAP can only add nucleotides to a 3 end and can't finish replication at a 5' end
30
What do telomeres do?
Forms a cap at the end of DNA
31
What happens when a DNA polymerase reads a error during replication?
Nuclease removes segments of nucleotides and DNA polymerase & ligase can replace the segments.
32
What are proteins?
polypeptides made up of amino acids
33
Define gene expression:
Process where DNA chooses and controls which proteins are made
34
What are the two phases of gene expression?
Transcription and translation
35
What is transcription?
The synthesis of RNA using information from DNA
36
Where does transcription occur in eukaryotes and prokaryotes?
Eukaryotes: The nucleus Prokaryotes: Cytoplasm
37
What are the 3 key types of RNA in transcription and translation?
Messenger RNA (mRNA) Ribosomal RNA (rRNA) Transfer RNA (tRNA)
38
What's the purpose of mRNA?
mRNA carries information from the DNA (at the nucleus) to the ribosomes in the cytoplasm
39
How many strands of DNA are used in transcription and what is it generally called?
1 strand / template strand
40
How is mRNA formed to the DNA
Antiparallel and complementary
41
Define codons:
Read by mRNA in groups of three nucleotides and codes for amino acids
42
How many different codon combinations are there?
64
43
How many code for amino acids, how many are "stop" codons, and which is the start codon?
61 codes for amino acids 3 stop codons AUG
44
What are the 3 steps of transcription?
1. Initiation 2. Elongation 3. Termination
45
How does transcription start in transcription?
RNA polymerase molecules attach to the promoter region of DNA
46
What is the promoter region of DNA?
Specific set of nucleotides that RNA polymerase binds to & starts at and is located upstream of the desired gene
47
How does RNA polymerase bind to the promoter in eukaryotes?
Promoter region often has a "TATA box" sequence and transcription factors must bind to promoter before RNA polymerase
48
How does RNA polymerase bind to the promoter in prokaryotes?
RNA polymerase can bind directly to promoter if first bound to sigma factor
49
What does RNA polymerase do to the DNA once bound?
It separates the DNA strands, forming a transcription bubble
50
In what direction does RNA polymerase move during elongation?
In the 3' to 5' direction
51
In what direction does the mRNA elongate?
5' to 3'
52
Does RNA polymerase open the entirety of the DNA at the same time?
No, in small sections only
53
Where does the mRNA go after adding complementary RNA to the nucleotides?
It peels away from DNA template strand and DNA double helix reforms
54
What happens in prokaryotes during the termination sequence?
RNA polymerase detaches and mRNA is released and proceeds to translation (needs no modification)
55
What happens in eukaryotes during the termination sequence?
- RNA polymerase transcribes a sequence of DNA called polyadenylation signal sequence which codes for a polyadenylation signal in RNA transcript
56
What happens when enzymes recognize the polyadenylation signal?
pre-mRNA is cleaved from RNA polymerase and undergoes modification
57
What are the 3 modifications pre-mRNA must go through before translation?
1. 5' cap 2. Poly-A tail 3. RNA splicing
58
What do the 5' cap and Poly-A tail help with?
Preventing degradation and makes mRNA more stable
59
What is RNA splicing?
Sections of pre-mRNA is removed (introns) and sections are joined together (extrons)
60
Why does splicing occur?
So that alternative splicing occurs and more than one kind of polypeptide can be formed by a single gene
61
What is translation?
The creation of a polypeptide using the data from mRNA
62
Where does translation occur?
At the ribosome
63
A nucleotide sequence becomes an ___________________.
Amino acid sequence
64
Which type of RNA is a important in translating mRNA into an amino acid sequence?
t(ransfer)RNA
65
What are two parts of a tRNA?
The anticodon region which is complimentary to the mRNA and the amino acid that the mRNA is supposed to code for.
66
What enzyme attaches amino acids to tRNA?
Aminoacyl-tRNA synthase
67
Ribosomes have how many subunits?
2 subunits
68
What are the different sizes of subunits in prokaryotes and eukaryotes?
- Prokaryotes: small subunit (30s) large subunit (40s) - Eukaryotes: small subunit (40s) large subunit (60s)
69
What are the 3 sites of a large subunit and what are their functions?
A = Amino acid site which holds the next tRNA P = Polypeptide site which holds the current tRNA adding an amino acid to the polypeptide chain E = exit site for the tRNA
70
What are the 3 stages of translation?
Initiation, elongation, and termination
71
What happens in the initiation stage of translation?
Small subunit of ribosome attaches first, tRNA carrying methionine attaches to start codon (AUG), then large subunit attaches
72
What are the 3 steps in elongation of translation?
1. Codon recognition 2. Peptide bond formation 3. Translocation
73
What happens in the termination stage of translation?
Stop codon reaches A site of the ribosome and polypeptide bond attached to P site is hydrolyzed, leading to polypeptide detaching.
74
What is gene expression?
The process of how the info in a gene is turned into a functional product like a protein.
75
T/F: All of the information of the gene will be expressed/turned on.
FALSE: The combination of genes and level of expression affects phenotype
76
What are the differences between genes that are constitutively expressed and those that are inducible?
Constitutively expressed means they are always expressed (usually for basic cellular functions) and inducible means they can be turned off or on.
77
Why do prokaryotes and eukaryotes need to regulate gene expression?
In order to save energy/resources, adapt to the environment, and to make different cell types (mainly eukaryotes)
78
Where does regulation occur in prokaryotes and eukaryotes?
Mainly in transcription (regulation can occur in many steps in eukaryotes)
79
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