DNA and protein synthesis Flashcards
1
Q
What is a gene?
A
A section of genetic material that codes for a protein or characteristic e.g. eye colour, tongue rolling
2
Q
How many genes are we made up of?
A
Roughly 25,000
3
Q
What is an allele?
A
Variation in a gene (gene - eye colour, allele - brown/blue)
4
Q
What is a chromosome?
A
The structure on which genes are stored
There are 23 pairs in humans
5
Q
What does DNA stand for?
A
Deoxyribonucleic acid
6
Q
What is DNA?
A
It’s the chemical from which genes are constructed
7
Q
What is a chromatin?
A
DNA and associated proteins(histones) found in the nucleus
8
Q
What is a genome?
A
All the genes that comprise us/an organism
9
Q
What is a proteome?
A
All the proteins that can be made from the genome
10
Q
What are nucleic acids?
A
These are macromolecules built of up nucleotides e.g. RNA and DNA
11
Q
What is a DNA strand made up of?
A
It is a long strand (2m) comprised of nucleotides - this will form our double helix
12
Q
What is a nucleotide made up of?
A
A phosphate, deoxy ribose, nitrogenous base
13
Q
How many bases are used to make DNA?
A
There are a total of 5 bases - 4 are used to make DNA nucleotides
14
Q
What are the 4/5 bases?
A
Adenine, Thymine
Guanine, Cytosine
(uracil)
15
Q
How many different DNA nucleotides can we make?
A
4
16
Q
How many hydrogen bonds do adenine and thymine form?
A
2
17
Q
How many hydrogen bonds do guanine and cytosine form?
A
3
18
Q
What are adenine and guanine known as?
A
The purines - they have a double carbon ring
19
Q
What are thymine and cytosine known as?
A
The pyramidines - they have a single carbon ring
20
Q
How do we form nucleotides?
A
There are 2 condensation reactions
- nitrogenous bases + pentose = nucleoside + H2O
- nucleoside + phosphoric acid = nucleotide + H2O
21
Q
How do different nucleotides bond together?
A
The phosphate from one nucleotide bonds to carbon 3 on the other DNA nucleotide
22
Q
What is the bond between 2 nucleotides?
A
A phosphodiester bond
23
Q
What are 2 nucleotides bonded together called?
A
Dinucleotide
24
Q
What is the enzyme that helps phosphodiester bonds form?
A
DNA polymerase
25
What is the top end of the polynucleotide chain called?
5 ' carbon end
26
What is the bottom end of the polynucleotide chain called?
3 ' carbon end
27
In what way do the 2 polynucleotide strands run together?
They run anti parallel to each other
28
What are the 2 polynucleotide strands known as?
The coding strand and the non-coding strand
Or the sense strand and the non-sense strand
29
What is the DNA strand known as?
Polynucleotide strand
30
How do you describe a DNA strand?
2 polynucleotide strands join together to form a double helix
31
What provides DNA with stability?
The phosphate deoxyribose backbone
32
Why is it important that DNA has stability?
So it is stable enough to last the cell's whole life
So the order of the bases is not damaged
33
How do we ensure that DNA has stability?
The bases are on the inside of the molecule
34
Why is it better to have hydrogen bonds between strands rather than another type?
On mass, they provide strength and stability but individually they are weak so they can still be separated out during protein synthesis
35
Why is it important that DNA is a very large molecule?
It can hold a lot of genetic information
36
What is a RNA nucleotide made of?
Phosphate
Ribose sugar
Base (A, U, G, C) - Thymine is replaced with uracil
37
What are all RNA molecules?
Single stranded
38
How do we create a poly RNA nucleotide strand?
We have condensation reactions between carbon 3 and the phosphate
Phosphodiester bond formed
39
What is the enzyme that helps form poly RNA nucleotide strands?
RNA polymerase - once the complimentary copy of the coding strand has been created inside the original strand, this helps to join them together to from a poly nucleotide RNA strand
40
What are the 4 types of RNA?
Pre-messenger RNA
Messenger RNA
Transfer RNA
Ribosomal RNA
41
What are some of the characteristics of messenger RNA?
Long strand
Single helix - single stranded
Shorter than DNA (as it only contains the genes for a specific protein)
Contains the genetic code - sequence of mRNA nucleotide bases
42
What is a degenerate?
Both codons can hold the same amino acid
Most amino acids have more than one codon
43
Where is the mRNA code derived from?
The DNA code - a complimentary strand is formed
44
How is mRNA read?
In codons (3 bases) = 1 amino acid
45
What are stop codons?
There are 3 codons that tell the strand when to stop being formed
46
Are codons overlapping?
No
47
Are codons universal and what does this mean?
Yes - for all organisms, the same codon codes for the same amino acid
48
What does every single mRNA strand start with?
AUG
49
How is the mRNA formed?
Through transcription from DNA
50
How does mRNA leave the nucleus?
Via nuclear pores
51
What is mRNA associated with?
Ribosomes in cytoplasm
52
What does mRNA form?
The template from which proteins are built
53
Why is it important that mRNA is easily broken down?
It only exists when needed (we don't store amino acids) and no energy is wasted
54
What structure does tRNA have?
A clover leaf structure
55
What does tRNA have at the top?
Amino acid attachment site
56
What does tRNA have at the bottom?
3 bases known as the anti-codon
57
How many tRNA are there?
64
58
What does RNA stand for?
Ribonucleic acid
59
What do we do for protein synthesis within the nucleus?
We make a complimentary copy of the coding strand using RNA nucleotides - not the whole strand but rather just the section that codes for the specific protein that we want
60
What do we use to break the hydrogen bonds in between complimentary bases in the DNA strand?
DNA helicases
61
What happens after the hydrogen bonds in the DNA strand are broken?
The RNA nucleotides come and form a complimentary copy of the coding strand using base pair theory inside the original strand
62
What happens once the mRNA polynucleotide strand is formed?
It will move out from between the 2 DNA strands and an enzyme called DNA ligase will help hydrogen bonds reform between the 2 DNA strands
63
What are ribosomes made up of?
Amino acids and RNA
64
What does ribosomal RNA help do in ribosomes?
Helps make sites in ribosomes for assembling proteins from amino acids
65
What is ribosomal RNA?
It is a polynucleotide that is folded and attached to proteins to make ribosomes
66
What is there at the beginning of each gene?
A promoter region
67
What is there at the end of each gene?
A terminator region
68
What is the 1st step of protein synthesis?
We identify the gene in the DNA strand
69
What happens after we identify the gene in the DNA strand in protein synthesis?
The DNA helicase enzyme unwinds this section of the DNA strand breaking the hydrogen bonds between the complimentary bases
70
What happens after the DNA strand is unwound in protein synthesis?
The RNA nucleotides come between them and the RNA bases line up opposite the bases on coding strand in complimentary fashion
71
What do the RNA nucleotides form with the bases on the coding strand and why?
Hydrogen bonds to help fix them into place
72
How are the RNA nucleotides opposite the coding strand joined together?
RNA polymerase joins them forming phosphodiester bonds
73
What is formed when the RNA nucleotides opposite the coding strand are joined together?
Single-stranded pre-messenger RNA molecule (single helix)
74
What happens once the pre-messenger RNA molecule is formed?
It will move out from between the 2 DNA strands (hydrogen bonds between RNA and coding strand break)
75
What happens to the DNA strands after the pre-messenger RNA molecule moves out?
It recoils - hydrogen bonds, with DNA ligase, reform between complementary bases
76
What is the final thing to happen to pre-messenger RNA before it moves out of the nucleus?
Splicing
77
What is splicing?
This is where we cut out sections/RNA nucleotides from mRNA
78
What are the sections we cut out in splicing called?
Introns - these are non-coding sections within a gene
79
What are the sections that remain in splicing?
Exons
80
What happens after the introns are removed?
The exons join together to form a shorter mRNA strand
(this is now mRNA and not pre mRNA)
81
What happens after splicing has occurred?
mRNA leaves nucleus via nuclear pores into cytoplasm where we have ribosomes and tRNA
82
What does the mRNA attach to in the cytoplasm?
The ribosome - covers 6 bases (2 codons)
83
What happens after the mRNA attaches to the ribosome?
The tRNA with the complimentary anti-codon to the first codon sits on the mRNA
84
How is the anti-codon kept in place with the codon during translation?
The bases form hydrogen bonds
85
What will the tRNA sitting on the codon have?
A specific amino acid attached to its amino acid attachment site
86
What happens after the first tRNA attached to the mRNA strand?
tRNA with the complimentary anti-codon to the next codon is also attached (brings specific amino acid)
87
What happens once there are 2 amino acids on the ribosome?
They will form a peptide bond in a condensation reaction
88
What happens once the 1st peptide bond is formed during translation?
The amino acid dissociates from the tRNA
89
What happens to the tRNA once it dissociates from the amino acid?
It leaves the mRNA and ribosome and goes into the cytoplasm to attach another specific amino acid
90
How does the process of translation continue throughout?
The ribosome moves down the mRNA strand to cover the next codon and the process is repeated until we get to the end (ribosome leaves mRNA at a stop codon)
91
Can many ribosomes travel along the mRNA at the same time and what is this known as?
Yes - polysome
92
When might gene mutations arise?
During DNA replication - they occur spontaneously
93
What is a mutation?
The deletion, addition or substitution of bases
94
Why might not all mutations have an impact?
Due to the degenerate nature of the genetic code
95
What is a substitution mutation?
A DNA nucleotide is substituted for another
96
What kind of effect does a substitution mutation have?
A less damaging effect on the polypeptide, only changing one amino acid - but can sometimes cause quite a severe change
97
What is an addition substitution?
An extra DNA nucleotide may be added
98
How will an addition substitution affect the genetic code?
It will impact all the subsequent triplets - all the amino acids to the right of the addition (known as a frameshift to the right)
99
What is a deletion mutation?
A DNA nucleotide is removed
100
How will a deletion substitution affect the genetic code?
All subsequent triplets affected - frameshift to the left
101
What will happen to the polypeptide chain because of a frameshift?
It will have a different primary structure due to a different order of amino acids
102
What could frame shifts also change the position of?
The stop and start codons
103
What are point mutations?
They involve the change of 1 DNA nucleotide
104
How can the appearance of the mutations be increased?
By mutagens
105
Give examples of mutagens?
X-rays
High energy radiation
Chemicals in cigarette smoke
Chemicals in caffeine
UV light
106
What is a caryogram?
An image of chromosomes
107
What is a caryotype?
Number of chromosomes
108
What are chromosomes seen in pairs known as?
The diploid number - found in every adult cell - somatic cell - known as 2n
109
What are the first 22 chromosomes known as?
Autosomes - they are all the same regardless of gender - known as homologous pairs
110
Do homologous pairs contain the genes in the same position?
Yes
111
What is the locus of a gene?
It means the position of a gene
112
What are gametes?
Sex cells - they are haploid cells - they are n cells - only have 1 set of chromosomes - no homologous pairs
113
What do chromosomes normally form?
A network called a chromatin
114
Does the number of chromosomes double during replication?
No - a single strand is known as a chromosome and so is a double strand - a single strand can also be known as a chromatid
115
What does each eukaryotic chromosome contain?
- DNA
- Proteins (histone proteins, scaffold proteins, polymerases)
- Small amounts of RNA
116
What is a nucleosome?
The DNA wrapped around the histones
117
What is a supercoil?
The nucleosome continues to coil
118
What is a chromatin?
The supercoil coils into chromatins
119
What happens when DNA undergoes replication?
Chromatins coil around scaffold proteins to form chromosomes
120
How is the genetic material of viruses stored?
It can be RNA or DNA - it is single stranded
121
Does prokaryotic DNA have less content than eukaryotic DNA?
Yes - pro (less than 0.1 pg)
- eu (more than 1 pg)
122
Do organelles in prokaryotes have DNA?
No - some eukaryotic organelles do have DNA though (this DNA is circular)
123
What is nuclear DNA associated with and what is prokaryotic DNA associated with?
Histones - organelle DNA and prokaryotic DNA has no proteins and is circular
124
What is the shape of nuclear DNA?
Strand like
125
Do prokaryotic DNA have introns?
No - no splicing takes place
126
How much is non-functional DNA is present in prokaryotes and eukaryotes?
Prokaryotes - non functional DNA are fewer
Eukaryotes - non functional DNA is quite abundant
127
What are the similarities between prokaryotic and eukaryotic DNA?
- Both double-stranded
- Helix
- Complimentary base pairs
- Both have H bonds
- Both made of DNA nucleotides
- Both contain the genetic code
