DNA and RNA nucleic acid Flashcards
1
Q
what are the types of nucleic acid?
A
Deoxyribonucleic acid
Ribonucleic Acid
these are both pentose sugar
2
Q
why are they known as macromolecules?
A
they contain polymers and polynucleotides (made of smaller sub units : nucleotides)
3
Q
what are nucleotides?
A
monomers of nucleic acid made of 3 components
4
Q
what are the 3 components?
A
phosphate group
pentose sugar
nitrogen - containing base (organic)
5
Q
how many types of N containing bases are there?
A
5 types, they are purine bases and pyrimidine bases
6
Q
what are the purine Bases?
A
Adenine and Guanine
7
Q
what are the Pyrimidine Bases?
A
Thymine, cytosine and uracil
8
Q
what are the bases in DNA?
A
- Adenine 2. Thymine 3.Cytosine 4. Guanine
9
Q
what are the bases in RNA?
A
1.Cytosine 2. Guanine. 3.Adenine 4.Uracil
10
Q
where is DNA found?
A
in eukaryotic in the nucleus it is a double stranded polynucleotide
11
Q
how do nucleotides join?
A
by condensation reaction between deoxyribose sugar and phosphate group of nucleotides known as sugar-phosphate back bone
12
Q
why way do nitrogen containing base point?
A
sideways
13
Q
where do the 2 strands go?
A
they run opposite to each other (anti parallel) held by H bonds between bases.
14
Q
where must purine bases be?
A
always opposite a pyrimide base
15
Q
what are some complementary base pairs?
A
Adanine:Thymine
Cytosine:Guanine
16
Q
what is RNA?
A
it is single stranded it has uracil instead of Thymine
17
Q
what are types of RNA?
A
mRNA
rRNA
tRNA
18
Q
how is mRNA formed?
A
single strand formed into a helix
19
Q
where is mRNA made?
A
in the nucleus passes into the cytoplasm then moves to the ribosomes
20
Q
where is rRNA made?
A
in the nucleolus
21
Q
where is rRNA found?
A
in the cytoplasm
22
Q
what is rRNA used for?
A
to form ribosomes made of rRNA and protein
23
Q
what is tRNA?
A
a clover leaf shape, one end attaches to specific amino acid other end has triplet of bases (anticodon) used in protein synthesis
24
Q
what is tRNA used for?
A
to transfer information
25
how is DNA formed?
2 DNA strands run antiparallel. deoxyribose nucleic acid anti parallel strands twist into a double helix, joined by complementary base pairs.
26
what happens when cells divide?
each new cell must have copy of the same genetic material, DNA must replicate itself, this happens in the interphase
27
what happens in DNA replication?
two strands of DNA unwind and split H bonds break. then free nucleotides line up against DNA strands.
28
how are nucleotides activated?
by phosphate group.
29
why does the enzyme DNA polymerase join?
forms 2 new DNA molecules, known as semi conservative theory,
30
what does each new DNA have?
an original strand and a new one this creates two identical sister chromatids
31
what were the 3 theories in 1950s?
conservative replication
dispersive replication
semi conservative replication
32
who provided the evidence?
meselsohn + stah replication theory was accepted
33
what did the evidence show?
each new DNA strand was a template for the synthesis of the new strand
34
how was this proved?
they used E.coli and nitrogen isotopes N14 (light) and N15(heavy)
35
what was the experiment?
E.coli was grown on N15 for first generation, all nitrogen bases were N15
36
what happened to the resulting DNA?
it was split in a centrifuge and 1 heavy band was obtained
37
where was this heavy band transferred to?
to N14 medium and allowed for 3 generation of replication . the DNA was split from each generation
38
what controls the cells activities?
chemical reactions all of these are controlled bye enzymes and therefore proteins
39
what makes up protein molecules?
sequences of DNA bases and therefore DNA controls cell activities
40
what is the name for one sequence of bases that code for one protein?
gene
41
what are proteins made of?
amino acids
42
what does protein shape depend on?
folding which depends on sequence of amino acids - primary structure
43
what does the sequence of bases in DNA control?
the sequence that amino acids join when a protein is made on ribosomes
44
how many amino acids are there?
20
45
how are amino acids coded for?
by sequence of 3 bases on DNA molecules
46
what is a set of 3 bases known as?
codon or triplet code
47
what is particular about sequence on a DNA molecule?
it is read in a certain direction
48
why is one of the two strands used?
it is a template
49
why three bases?
genetic code 64 triplets of nucleotides. DNA has 4 bases to code for 20 amino acids, meaning each base cant code for one amino acid. 3 bases makes 64 codes more than enough for 20 amino acids
50
how triplet code determined?
by series of RNA experiments
51
what is degenerate code?
it is more than one triplet code for amino acids
52
what was discovered about 3 codons?
they do not code for amino acids - stop codons
53
what is usually a start codon?
AUG
54
what is special about the code?
it is non overlapping
55
what are all codons?
universal same for all organisms
56
what does part of DNA molecule code for?
polypeptide and it is a gene
57
how many do humans have?
140,000 human genome has been mapped
58
how is info sent from DNA to cytoplasm?
by transcription
59
what is info in DNA used for?
to build molecules of RNA
60
what does mRNA do?
takes message from DNA to ribosomes in cytoplasm
61
what is the first stage of transcription?
DNA double helix unwinds and unzips, H bonds between base pairs break.
62
what is the second stage of transcription?
Free RNA nucleotides align with exposed DNA, on one strand of the DNA
63
what is this strand?
the template or coding strand
64
then what happens in stage 3?
RNA polymerase links RNA nucleotides a single strand of mRNA forms the DNA helix forms behind it
65
what does mRNA contain?
codons
66
what does mRNA do?
it is small enough to leave through nuclear pores attaches to ribosome
67
what is tRNA ?
chain of nucleotides
68
what is the structure of tRNA?
clover leaf shape
Hairpin Bend
H bonds to hold it in shape
anticodon - different for each amino acid amino acid binding structure
69
what happens translation?
mRNA molecule attaches to ribosome, tRNA molecules bind with exposed mRNA bases. then ribosomes hold two amino acids together as polypeptide bond.
70
how is this catalysed?
by an enzyme
71
what happens next?
ribosomes moves along mRNA read next codon, tRNA is released passes back to cytoplasm to get another amino acid.
72
how far does the polypeptide chain grow?
until stop codon is and new protein molecule is formed
73
why do organism show variation?
species have similar characteristics but aren't identical, have same genes different alleles
74
why are there variations in phenotype?
due to environment and genotype
75
what are 4 cause of variation?
crossing of non sister chromatids during prophase 1 meiosis
independent assortment of bivalents in meta phase 1 meiosis
random fusion of gametes during sexual reproduction
DNA mutation - chromosome and gene
76
what is mutation?
change in composition of DNA
77
what is chromosome mutation?
change in chromosome structure number of chromosomes
78
what is gene mutation?
change in base sequence of gene
79
what can gene mutation lead to?
a new allele if allele has selective advantage it can transfer to off spring
80
what is translocation?
when section of chromosome lost to other chromosomes
81
what is polysomy?
whole chromosomes are duplicated chromosomes fail to separate in anaphase 1
82
what is polyploidy?
set are chromosomes are duplicated
83
what do mutations do?
change the order of DNA bases in gene
84
what are 3 ways it can occur?
Substitution
Addition
Deletion
85
what is substitution?
nucleotide is replaced by different one (sickle cell anemia)
86
what is Addition?
extra nucleotides are added
87
what is deletion?
nucleotides are lost ( cystic fibrosis)
88
what do addition and deletion do?
alter amino acid sequence change protein structure
89
what is nonsense mutation?
it is caused by substitution and makes a stop codon causing protein to be smaller
90
what is missense mutation?
caused when substitution base makes protein with different amino acid sequence
91
what is silent mutation?
when base codes for the same amino acid
92
name 2 mutagens that increase chance?
radiation- xray
| chemicals - benzopyrene in smoke
93
what is a carcinogen?
is a mutagen that mutates genes which controls mitosis leading to uncontrolled cell division (cancer)
94
what is sickle cell anaemia?
globular protein with quaternary structure, it has 4 polypeptide chains per molecule, 2 alpha chains and 2 beta chains.
95
what does each chain contain?
a haem group each of these has Fe2+ ion
96
what binds to haem group?
O2 molecule, 4O2 molecules transported per haemoglobin molecule, reversible O2 binding, it has an s shaped binding curve
97
what is Phenylketonuria?
the phenylalanine hydroxylase hepatic enzyme is affected
98
what is phenylalanine converted to?
to the amino acid tyrosine, phenylalanine concentration increases
99
why are people pale?
low tyrosine levels
| babies are tested - High PKU prevent normal brain development
100
why use genetic diagrams?
allows us to predict characteristics of offspring from 2 parents
101
what is monohybrid inheritance?
genetic diagrams involving a single gene, it can show dominant and recessive inheritance e.g. tall + short pea plants, tall allele dominant to dwarf
102
what else can be shown?
codominance inheritance e.g. in white + red salvia plants produce pink
103
pea plant experiment?
cross breeding pure tall and dwarf produces tall in first generation, crossing of F1 always produced 3 tall plants to 1 dwarf
104
what are the rules of genetic diagrams?
identify - tall plant is dominant
give alleles symbols tall= T dwarf t
always letters that look different.
105
what are the 3 blood groups?
Ia Ia and Ib are codominant
Ib
Io
106
what is sex linkage?
refers to genes carried on sex chromosomes
| X chromosome bigger than Y, X carries more genes
107
where is sex linkage found?
on X chromosomes not on Y it can have a recessive allele which leads to a particular condition, condition is more likely to occur in women
108
what is haemophilia?
if one of the genes has a recessive allele that causes the condition then it is more common in males
109
symptoms of haemophilia?
bleeding into joints can be disabling
