8 - DNA, genes and protein synthesis Flashcards
1
Q
DNA helicase
A
- breaks hydrogen bonds between bases
- unwinds and separates two strands of DNA
2
Q
DNA polymerase
A
- joins together adjacent nucleotides
- forms phosphodiester bonds (in backbone)
3
Q
structure of ATP
A
- one adenine
- one ribose
- three phosphate group
4
Q
how does ATP store and release energy
A
- bond between phosphate groups UNSTABLE
- so low activation energy (easily broken)
- when bonds break they release energy
5
Q
terminal phosphate
A
furthest last phosphate
6
Q
ATP energy release equation
A
ATP + H2O → ADP + Pi + free energy
7
Q
features of DNA in relation to replication
A
- weak H bonds between bases (allow two strands to sepetate/ unzip)
- two strands (so both act as templates)
- complementary base pairing (accurate replication)
8
Q
evidence for DNA as polymer (1 mark)
A
repeating units of nucleotides
9
Q
A
A
adenine
10
Q
G
A
guanine
11
Q
T
A
thymine
12
Q
U
A
uracil
13
Q
C
A
cytosine
14
Q
complementary base pairing rules
A
A – T/U (2 Hydrogen bonds)
C – G (3 Hydrogen bonds
15
Q
formation of nucleotide
A
- pentose sugar and base join together (condensation reaction) = NUCLEOSIDE + water
- phosphate group + nucleoside (condensation reaction) with ester bond = NUCLEOTIDE + water
16
Q
formation of polynucleotide
A
- nucleotides join together (condensation reaction)
- phosphodiester bond between PHOSPHATE of one nucleotide and PENTOSE SUGAR of another nucleotide
17
Q
antiparallel direction
A
two DNA chains runs in opposite directions
18
Q
why is DNA a stable molecule?
A
- sugar phosphate backbone (protects chemically reactive bases inside)
- hydrogen bonds (stabilise the core of the molecule)
19
Q
why the replication of DNA is described as semi-conservative
A
- each strand acts as a template
- daughter DNA has one new strand and one original/ parent strand
20
Q
why is ATP a good immediate energy source
A
- only one bond hydrolysed to release energy
- releases less/ smaller more manageable quantities of energy
21
Q
processes that require energy
A
- metabolic processes
- movement
- active transport
- secretion
- activation of molecules
22
Q
what is a locus
A
a particular gene that is always found in the same position in a chromosome (THAT POSITION IS LOCUS)
23
Q
allele
A
one of a number of alternative forms for a gene
24
Q
centromere
A
region where sister chromatids join
25
three types of RNA
- messenger
- transfer
- ribosomal
26
what is a gene
- specific length of DNA bases
27
what is genetic code
sequence of DNA bases in a gene
28
genome
all of the genes in a cell (including those in mitochondria and chloroplast)
29
proteome
full range of proteins produced by the genome
30
codon
combination of three bases in mRNA that ALWAYS codes for the same amino acid
31
universal genetic code
in almost all living organisms, the same triplet (codon) codes for the same amino acid
32
degenerate genetic code
each amino acid is coded for by more than one triplet
33
non-overlapping genetic code
each base only forms part of one codon
34
coding strand
- aka. sense strand
- NOT USED as a template for transcription
- same sequence as mRNA (but U instead of T in mRNA)
35
template strand
- aka. antisense strand
- strand which mRNA is BUILT FROM
36
exons
nucleotide/ base sequence that codes of a sequence of amino acids that make up polypeptide
37
introns
- doesn't code for proteins
- doesn't exist in bacteria
38
splicing
process where introns are removed and functional exons are joined back together
39
central dogma
directional flow of information
40
antiparallel
- DNA strands run in opposite directions
41
describe how mRNA is produced and prepared for translation (5 marks)
1. hydrogen bonds broken in DNA strands
2. free RNA nucleotides bind via complementary base pairing to exposed DNA bases
3. thymine is replaced by uracil
4. RNA polymerase joins adjacent RNA nucleotides
5. by phosphodiester bonds
6. mRNA is spliced and introns are removed
42
describe how translation leads to the production of a polypeptide
1. mRNA binds to ribosome
2. ribosome finds the start codon
3. tRNA carries amino acid
4. tRNA has the specific anticodon complementary to codon so they bind
5. ribosome moves along to next codon
6. adjacent amino acids join by condensation reactions, peptide bonds between amino acids
43
how is phosphodiester bond formed between two nucleotides in DNA?
- condensation reaction between phosphate and deoxyribose
- catalysed by DNA polymerase
44
why does protein synthesis require energy?
condensation reaction between amino acids and formation of peptide bond USES ATP
