Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

A-LEVEL BIOLOGY > DNA > Flashcards

DNA Flashcards

(52 cards)

Start Studying
1
Q

why does DNA replication occur before cell division?

A

so each new cell has a copy of DNA

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

describe DNA replication steps

A

1) DNA helicase unwinds/unwraps DNA double helix
2) exposed bases bind to free floating nucleotides in the nucleoplasm
3) DNA polymerase binds the complementary nucleotides to unpaired bases which reproduces the original DNA molecule exactly
4) replication is semi-conservative (1 old + 1 new strand)

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

what’s DNA helicase?

A

opens up double strand

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

what’s DNA polymerase?

A

enzyme that makes DNA polymers

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

where does DNA replication occur?

A

replication fork

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

what is RNA primer made of?

A

RNA primase

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

whose experiment proved semi-conservative replication with data?

A

meselson and stahl

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

define DNA replication

A

copying of DNA molecules to produce more DNA

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

describe meselson and stahl’s experiment

A
  • grew bacterium (E. coli) in the presence of radioactive 15N until a culture was obtained
  • the DNA was labelled 15N
  • subculture of the labelled bacterium was transferred for growth in the presence of normal 14N
  • the generation time of E. coli is known so it was possible to take samples of this growing subculture after each gen.
  • each sample’s DNA was extracted + isolated DNA was centrifuged in a caesium chloride sol. at 40,000 G for 20 hrs -> made DNA sediment out
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

describe meselson and stahl’s experiment THEORY

A
  • the heavier the DNA, the further down it moved in the centrifuge tubes
  • (15N DNA is heavier than 14N, so it moved to the lowest position)
  • after 1 gen. all DNA moved to intermediate position -> showed presence of mixed 14 + 15N -> DNA in the gen. had 1 strand of parent molecule and 1 new strand
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

why did meselson and stahl’s experiment disprove the conservative hypothesis?

A

if it was true, 2 DNA masses would’ve been visible -> 1 heavy, 1 light (not intermediate)
in the 2nd gen. half of the DNA was intermediate and the other half was light

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

describe DNA structure

A 
double stranded helix molecule
2 polynucleotide chains coiled
polymer with repeating monomers 
nucleotides
4 bases -> ATCG
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what bonds the sugar and phosphate in a nucleotide

A

phosphodiester bonds

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

what bonds bases together

A

H-bonds

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

how many hydrogen bonds between base pairs

A

AT -> 2

CG -> 3

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

state an easter linkage

A

O=C-O

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

define gene

A

section of DNA

sequence of 3 bases that code for a specific AA for a specific protein

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

define and give examples of purine bases

A

2 rings
A
G

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

define pyrimidine bases and give examples

A

1 ring
T
U
C

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what can phosphoric acid do?

A

substance that can libertine

H-ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

describe RNA structure

Study These Flashcards
A 
pentose sugar
single stranded
short -> (100-1000 nucleotides long)
ribose 
CG
AU
22
Q

how are nucleotides joined

Study These Flashcards
A

condensation reactions

23
Q

how are the 2 strands in DNA held together

Study These Flashcards
A

H-bonds between bases

24
Q

DNA replication steps

Study These Flashcards
A
  • before cell division so each new cell has a copy of DNA
  • DNA helicase unwinds DNA double helix and it opens up at replication fork
  • exposes bases bind to free floating nucleotides in nucleoplasm
  • DNA polymerase bonds complementary nucleotides to unpaired bases which reproduces original molecule exactly
  • replication is semiconservative (1 old 1 new strand)
  • SEE IMAGES*
25
describe transcription
- in nucleus - DNA used as template to make mRNA with RNA polymerase - initiation -> DNA helix unwinds - elongation -> RNA polymerase slides along template DNA strand, complimentary base pairing - nucleotides liked ro 3' end of growing RNA molecule - termination -> RNA polymerase reaches terminator portion of gene, RNA transcript = complete - mRNA + RNA polymerase + DNA strand dissociate from e/o
26
describe translation
- mRNA exits nuclear pore into cytoplasm - mRNA binds to small ribosomal sub-unit at start codon - AA's brought to ribosome by tRNA - complimentary base paring w/ mRNA codons + tRNA anticodons - charged tRNA binds to A site -> peptide bond forms between AA's at A + P site - whole complex shifts 1 down to the right - uncharged tRNA exits at E site - A site accepts next tRNA ->continues until stop codon - release factor binds to A site at stop codon - polypeptide released from tRNA at P site - whole complex dissociates
27
what determines the type of AA?
anticodon sequence of tRNA
28
define anticodon
sequence of 3 bases on tRNA that complimentary base pair with mRNA codons and fit with each other
29
how are mRNA + tRNA different?
mRNA -> 5' - 3' , length can change | tRNA -> fixed length
30
which codons dont code for AA's?
stop/start codons
31
define temp.
measure of KE of particles of a region
32
define heat
measure of total energy within | sum of KE + pot. energy
33
describe entry of substrate to active site
forces of attraction -> push + pull conformation change -> enzyme clamps down around substrate forms induced fit after reaction, active site returns to original shape
34
state an amine group
-NH2
35
state a carboxylic group
-COOH | O=C-OH
36
how many diff. AA's are there in normal proteins
20
37
how are peptide bonds formed?
condensation reactioms
38
state peptide bond linkage
O=C-N-H | *SEE IMAGE*
39
define catabolic reaction
when substances are broken down
40
describe protein primary structure
simplest level *AA seq. of protein in polypeptide chain peptide bonds link AA's each chain has own set of AA's assembled in particular order determined by DNA of coding gene
41
whats haemoglobin made of?
polypeptide chains
42
describe protein tertiary structure
- overall 3D structure due to interactions between R -groups of AA's that make up proteins - H-bonds contribute to structure - hydrophobic interactions -> AA's + non-polar - hydrophobic *R groups cluster inside protein - leaves hydrophylic AA's outside to interact with surrounding water molecules - fibrous proteins
43
define disulfide bonds? | whats their role?
covalent linkages between sulfur containing side chains | keep parts of a polypeptide attached to each other
44
describe protein secondary structure
3D organisation of main chain atoms of a protein (the atoms that all amino acids in a protein have in common) folded structures that form within polypeptides due to interactions between atoms of the *backbone parts of polypeptide chain take up certain shape after formation at ribosome -> fold/twist e.g. a-helix coils/b-helix zig-zag sheets held in shape by H-bonds
45
describe protein quaternary structure
some proteins made of many polypeptide chains twist -> subunits that come together e.g. haemoglobin has 4 sub units
46
how are polypeptides and proteins formed
AA monomers linked by peptide bonds by condensation reactions
47
globular proteins
``` round/spherical functional irregular AA seq. more sensitive to change (pH/temp) normally water soluble ```
48
fibrous proteins
polypeptides form long narrow chains parallel to e/o chains linked by disulphide cross bridges -> stable and strong structure repetitive AA seq. less sensitive to change (pH/temp) normally water INsoluble
49
define enzyme
biological catalysts that reduce E.act
50
why are globular proteins soluble in water?
- hydrophobic groups point into centre of molecule away from water - only hydrophilic groups are exposed outside the molecule so globular proteins are soluble
51
e.g. of globular proteins
``` HAVE ROLE ON METABOLIC REACTS. enzymes - catalyse metabolic reactions haemoglobin - binds to oxygen to transport it around body insulin immunoglobulin ```
52
e.g. of fibrous proteins
``` GIVE STRUCTURE keratin - skin/nails collagen - bone/cartilage/tendons/ligaments for tensile strength myosin fibrin actin elastin ```

A-LEVEL BIOLOGY (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions