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Molecular Genetics Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

whats a nucleotide made of (3)

A

nitrogenous base
Pentose sugar
phosphate group

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2
Q

What links nucleotide

A

Phosphodiester bond

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3
Q

What makes up the sugar phosphate backbone

A

Alternating sugars and phosphate grps

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4
Q

What does sugar phosphate backbone do

A

provides structural support to molecule

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5
Q

What is joined to the base pairing to stabilize it

A

Hydrogen bonds

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6
Q

Process of DNA replication

A 
1. Both strands of a DNA molecule 
separate 
2. Both strands act as templates for the  synthesis of two new daughter 
strands. 
3. Formation of Phosphodiester bonds catalysed by DNA polymerase.
4. The sequence of DNA on the newly 
synthesised strands is determined by 
complementary base pairing.
5. Hydrogen bonds form between the 
bases of one old and one new strand 
to form a complete DNA molecule.
6. Each daughter cell inherits a DNA 
molecule that is a hybrid, consisting 
of one old and one new strand
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7
Q

Where transcription happen

A

nucleus

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8
Q

Where translation happen

A

cytoplasm

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9
Q

Transcription (5)

A 
1. The enzyme RNA polymerase attaches 
to DNA and starts to unwind and 
separate the DNA double helix.
2. One DNA strand acts as template.
3. RNA nucleotides base-pair one by one 
with DNA bases on the template DNA 
strand via complementary base 
pairing. 
4. RNA polymerase connects RNA 
nucleotides into a polynucleotide chain
by catalyzing the formation of 
phosphodiester bonds (between RNA 
nucleotides).
5. As RNA polymerase moves along the 
DNA, it unwinds and exposes more of 
the template DNA strand for base pairing with RNA nucleotides
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10
Q

start codon

A

AUG

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11
Q

Stop codons

A

UAA UAG UGA

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12
Q

Does stop and start codons code for amino acid

A

STatrt codon codes for amino acid

stop codon doesnt

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13
Q

Define translation

A

Conversion from the nucleic acid language to the

protein language

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14
Q

What do codons do

A

sequence of codons Determine type and sequence of amino acids in polypeptide chain

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15
Q

What is the role of TrNA (1) and what must they do in order to achieve this main role (2)

A

match amino acids to the correct codons to form a
polypeptide

– attach to specific amino acid
– recognise the matching correct codon(s) in the mRNA

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16
Q

What do the two ends of TRna do (2)

A 
1) One end of 
tRNA molecule is 
attached to a 
specific amino acid
2) Another end of 
tRNA molecule has 
3 exposed RNA 
nucleotides 
forming an 
anticodon
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17
Q

How does TRNA attach itself to SPECIFIC Amino Acids

A

The anticodons are
complementary to the codons on
mRNA

18
Q

What is a Ribosomal RNA made up of (2)

A

 The smaller unit binds mRNA.

 The larger unit has 2 tRNA sites.

19
Q

What does ribosomal RNA do

A 
• Ribosomes coordinate the binding of 
tRNA to mRNA.
• Ribosomes also catalyse formation of 
peptide bonds between amino acids 
to form polypeptide.
20
Q

Translation (5)

A

• The anticodon on each tRNA complementary base-pairs with a codon on the
mRNA.
• mRNA and tRNA are held together by the ribosome.
• As translation proceeds, in the ribosome there is always
– one tRNA carrying a growing polypeptide chain
– another incoming tRNA carrying the next amino acid to be added
• The ribosome links the growing peptide chain to the new amino acid from the
incoming tRNA (peptide bond formed).
• When ribosome reaches the stop codon, translation stops.

21
Q

What does DNA cloning do

A

it produces

many identical copies of the target DNA for use

22
Q

Why are bacteria used as host cells to clone DNA/ genes?

(2)

A

• Bacteria have very short doubling time or high
rates of reproduction (via binary fission)
• Growing recombinant bacteria results in very
high numbers of bacteria with the target gene in
a very short period of time.

23
Q

how is recombinant plasmid form

A

Bacterial plasmids are joined to target DNA

24
Q

WHats a bacterial plasmid

A

small, double stranded DNA molecules

25
Q

Why do scientists join target DNA to bacterial plasmid instead
of bacterial chromosome (4)

A

plasmid …
• can easily incorporate foreign DNA
• is readily taken up by bacteria
• often contain genes coding for antibiotic resistance
o Easy to identify bacteria that had taken up the
recombinant plasmid from those that didn’t
• can self-replicate and so is present in one or more
copies in one bacterium → greater yield of target DNA

26
Q

How does recombinant plasmids increase the yield of target DNA for use

A

• Recombinant plasmid self-replicate to produce multiple copies
in each bacterium.
• When the bacterium divides, recombinant plasmid is also
replicated and passed on to its descendants.
• Rapid reproduction of bacteria AND self-replication of
recombinant plasmid together produces large number of
copies of the target DNA

27
Q

What must restriction sites be

A

Palindromic

28
Q

how are Restriction enzymes precise in digesting DNA

A

Restriction enzyme cut BOTH strands of the DNA double helix at
specific points in the restriction site which is palindromic

29
Q

How do restriction
enzymes cut/ cleave
the DNA?

A 
Restriction enzymes 
cleave the sugar
-phosphate backbone
of DNA by catalysing 
the breaking of the 
phosphodiester 
bonds.
30
Q

What happens when plasmid and gene are cut using same restriction enzyme

A 
This will 
produce the same sticky ends that 
are complementary. the exposed nucleotides on sticky 
ends can undergo complementary 
base-pairing and  hydrogen 
bonding. to form recombinant plasmid
31
Q

What is the use of DNA Ligase

A

DNA ligase is used to repair the sugar-phosphate backbone (catalysing the
formation of phosphodiester bond) to form an unbroken recombinant plasmid
with an intact sugar phosphate backbone.

32
Q

Is Complementary base pairing catalysed by dna ligase

A

no

33
Q

2 rules to choosing restriction enzyme to use for dna cloning

A

Rule #1: Both plasmid and target DNA must be cut with the same
restriction enzyme to produce complementary sticky ends.
HENCE, both must have the restriction site sequence of the chosen
enzyme in their DNA sequence
Exception: When using restriction enzymes that produce blunt ends
Rule #2: The restriction site sequence of the chosen restriction enzyme
must not be found within the target DNA’s sequence. (Restriction sites
should be flanking left AND right of the target DNA.)

34
Q

transformation

A

Transformation is to make host bacteria (usually E. coli) take up the
recombinant plasmid. This step is often not efficient.
• Bacteria that took up the plasmid is termed transformed bacteria
• To identify transformed bacteria, plasmids MUST have a selectable
marker. This marker is usually an antibiotic resistance gene.
• Bacteria that is successfully transformed will take up plasmid with
antibiotic resistance gene.

35
Q

Selection

A

bacteria is grown on nutrient medium
containing the antibiotic. This step is known as Selection.
• Transformed bacteria will survive and divide to form colonies but
non-transformed bacteria will be killed by the antibiotic.

36
Q

Whats MCS

A

Multiple Cloning Site (MCS) contains
a few unique restriction
sites only found here on the plasmid.

Point of insertion for target DNA.

37
Q 
Q: How to decide if a particular 
restriction enzyme “X” can be used to 
clone target gene “Y” into plasmid “Z”?
✓ Does enzyme “X” cut at the MCS of 
plasmid “Z”? Ans: 
✓ Does enzyme “X” cut at sites flanking 
both ends of target gene? 
✓ Does enzyme “X” cut within target 
gene? 
✓ Does enzyme “X” produce sticky 
ends?+
A 
Q: How to decide if a particular 
restriction enzyme “X” can be used to 
clone target gene “Y” into plasmid “Z”?
✓ Does enzyme “X” cut at the MCS of 
plasmid “Z”? Ans: Must be YES
✓ Does enzyme “X” cut at sites flanking 
both ends of target gene? Ans: Must 
be YES
✓ Does enzyme “X” cut within target 
gene? Ans: Must be NO
✓ Does enzyme “X” produce sticky 
ends? Ans: Preferably yes
38
Q

How does a DNA complementary abse pairing help it fulfil its function

A

A DNA molecule is double stranded / made up by two polynucleotide chains that are held by complementary base pairing between A and T nucleotides as well as G and C nucleotides.

How does it relate to function?
Complementary base pairing allows DNA to replicate itself accurately for transfer of genetic information from generation to generation.

39
Q

What gene and chromosome and Relationship between gene and chromosome

A

A gene is a sequence of DNA nucleotides that codes for a specific polypeptide by specifying the order in which amino acids must be joined together. AND
A chromosome is a long double-stranded DNA molecule that is highly coiled and folded. – 1m

Each chromosome contains many genes. – 1m

40
Q

What is complementary base pairing for

A

· Complementary base pairing (adenine pairs with thymine; guanine pairs with cytosine) allows the accurate copying / conservation of the base sequence of DNA during DNA replication. – 1m

How?
· As DNA replication is semi-conservative, both strands of a DNA molecule act as template for complementary base pairing to form new strands.
· The new strands formed are complementary to their template strands but also identical to the other template.
2 pts – 1m
(Hence, the resultant two DNA molecules are identical to each other / have the same base sequence.)

41
Q

Describe how human insulin formed (7m)

A
  1. The human insulin gene is obtained from the chromosome by cutting it with a
    restriction enzyme that produces sticky ends;
  2. The plasmid vector is cut with the same restriction enzyme, producing
    complementary sticky ends;
  3. The plasmids are mixed with the DNA fragments and complementary base-pairing
    between the sticky ends of the insulin gene and the plasmid DNA occurs;
  4. DNA ligase is added to the mixture to join / splice the cut ends of the DNA to form
    a continuous / unbroken recombinant plasmid;
  5. The recombinant plasmids are mixed with E.coli bacteria and plasmids enter the
    bacteria;
  6. Transformed bacteria containing the recombinant plasmid is selected on growth
    medium containing antibiotics;
  7. Only transformed bacteria will survive to transcribe and translate the insulin gene
    on the recombinant plasmid into human insulin protein.
42
Q

natural function of restriction enzyme

A

Its natural function is to hydrolyze/ digest/ cut viral DNA + to protect bacteria from invading viruses

Biology (9 decks)

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