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biology > 4a DNA, RNA and Protein synthesis > Flashcards

4a DNA, RNA and Protein synthesis Flashcards

1
Q

what is the same in dna of all organisms

A

the structure of DNA

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2
Q

nuclear eukaryotic DNA

A

Linear, associated with proteins

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3
Q

what do eukaryotic cells contain

A

linear DNA molecules that exist as chromosomes

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4
Q

chromosomes

A

thread like structures, each made up of one long molecule of DNA

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5
Q

where are chromosomes found

A

in the nucleus

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6
Q

Why does a DNA molecule have to be wound up to fit into the nucleus

A

because they are really long

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7
Q

What is the DNA molecule wound around

A

proteins called histones

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8
Q

histone proteins

A

help to support the DNA

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9
Q

how does DNA make a compact chromosome

A

it is coiled up very tightly with the protein

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10
Q

which cell organelles have their own DNA in eukaryotic cells

A

mitochondria and chloroplasts

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11
Q

what is the DNA in mitochondria and chloroplasts similar to

A

Prokaryotic DNA because its circular and shorter than DNA molecules in the nucleus. not associated with histone proteins

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12
Q

DNA in prokaryotes

A

molecules are shorter and circular

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13
Q

How do prokaryotes carry DNA

A

as chromosomes

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14
Q

what is different in prokaryotic chromosomes

A

The DNA isn’t wound around histones, it condenses to fit in the cell by supercoiling

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15
Q

gene

A

sequence of DNA bases that codes for either a polypeptide or functional RNA

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16
Q

what does the sequence of amino acids in a polypeptide do

A

forms the primary structure of a protein

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17
Q

what do different polypeptides have

A

have a different number and order of amino acids

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18
Q

what does the order of bases in a gene determine

A

the order of amino acids in a particular polypeptide

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19
Q

triplet

A

sequence of 3 bases that codes for a certain amino acid

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20
Q

first stage of protein synthesis

A

DNA is copied into messenger mRNA

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21
Q

what happens to genes that dont code for polypeptides

A

they code for functional RNA instead

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22
Q

functional RNA

A

RNA molecules other then mRNA which perform special tasks during protein synthesis e.g. tRNA and ribosomal RNA which forms part of ribosomes

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23
Q

introns

A

sections of DNA that don’t code for amino acids

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24
Q

exons

A

the sections of DNA that do code for amino acids

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25
when are introns removed
during protein synthesis
26
why are introns removed
so they dont affect the amino acid order
27
do prokaryotic cells have introns?
no
28
what do eukaryotic cells also contain
multiple repeats outside of genes
29
non-coding repeats
DNA sequences that repeat over and over, but dont code for amino acids
30
how can genes exist
in more than one form
31
alleles
the different forms a gene can exist in
32
why is the order of bases slightly different in each allele
so they code for slightly different versions of the same polypeptide
33
example of alleles
gene that determines blood type, exists as three alleles one determines type o, another type A and the other type B
34
in a eukaryotic cell nucleus how is DNA stored
as chromosomes
35
how many pairs of chromosomes do humans have
23 pairs, 46 in total
36
homologous pairs
pairs of matching chromosomes - same size and have the same genes although they could have different alleles
37
where will alleles coding for the same characteristic be found
at the same fixed position (locus) on each chromosome in a homologous pair
38
two stages of protein synthesis
transcription and translation
39
RNA
polynucleotide strand
40
what base does RNA have instead of thymine
uracil
41
what does uracil pair with during protein synthesis
adenine
42
when is mRNA made
during transcription
43
role of mRNA
carries the genetic code from the DNA to the ribosomes, where its used to make proteins during translation
44
mRNA
single polynucleotide strand
45
codons
group of three adjacent bases in mRNA
46
role of tRNA
translation. it carries the amino acids that are used to make proteins to the ribosomes
47
structure of tRNA
single polynucleotide strand thats folded into a clover shape. hydrogen bonds between specific base pairs hold the molecule in this shape. They have an anticodon at one end and an amino acid binding site on the other
48
anticodon
specific sequence of three bases at one end of a tRNA molecule
49
what happens during transcription
an mRNA copy of a gene is made from DNA
50
where does transcription take place in eukaryotic cells
the nucleus
51
where does transcription take place in prokaryotic cells
the cytoplasm as they do not have a nucleus
52
transcription step 1
starts when RNA polymerase attaches to the DNA double helix at the beginning of a gene
53
transcription step 2
the hydrogen bonds between the two DNA strands in the gene are broken by DNA helicase attached to the RNA polymerase. this separates the strands and the DNA molecule uncoils at that point exposing some of the bases.
54
transcription step 3
one of the strands is then used as a template to make an mRNA copy
55
transcription step 4
the RNA polymerase lines up free RNA nucleotides alongside the exposed bases on the template strand. the free bases are attracted to the exposed bases. specific complimentary base pairing means that the mRNA strand end up being a complementary copy of the DNA template strand
56
transcription step 5
once the RNA nucleotides have paired up with their specific bases on the DNA strand, they are joined together by RNA polymerase, forming an mRNA molecule
57
transcription step 6
the RNA polymerase moves along the DNA, separating the strands and assembling the mRNA strand
58
transcription step 7
the hydrogen bonds between the uncoiled strands of DNA reform once the RNA polymerase has passed by and the strands coil back into a double helix
59
transcription step 8
when RNA polymerase reaches a particular sequence of DNA called the stop signal it stops making mRNA and detaches from the DNA
60
transcription step 9
mRNA then moves out the nucleus through a nuclear pore and attaches to a ribosome in the cytoplasm, where the next stage of protein synthesis takes place.
61
eukaryotes protein synthesis
introns and exons are both copied into mRNA during transcription. (pre mRNA).
62
splicing
when introns are removed and exons are joined together in the nucleus
63
prokaryotes protein synthesis
mRNA is produced directly from the DNA
64
second stage of protein synthesis
translation
65
where does translation occur
at the ribosomes in the cytoplasm
66
what happens during translation
amino acids are joined together to make a polypeptide chain following the sequence of codons carried by the mRNA
67
translation step 1
the mRNA attaches itself to a ribosome and tRNA molecules carry amino acids to it. ATP provides the energy needed for the bond between the amino acid and the tRNA molecules to form
68
translation step 2
a tRNA molecule carrying an amino acid with an anticodon thats complementary to the first codon on the mRNA attaches itself to the mRNA by specific base pairing
69
translation step 3
a second tRNA molecule attaches itself to the next codon on the mRNA the same way
70
translation step 4
the two amino acids attached to the tRNA molecules are joined by a peptide bond. the first tRNA molecule moves away leaving its amino acid behind
71
translation step 5
a third tRNA molecule binds to the next codon on the mRNA. its amino acid binds the first two and the second tRNA molecule moves away
72
translation step 6
the process continues producing a chain of linked amino acids (a polypeptide chain) until theres a stop signal on the mRNA molecule
73
translation step 7
the polypeptide chain moves away from the ribosome and translation is complete
74
genetic code
the sequence of base triplets in mRNA which code for specific amino acids
75
how is each base triplet read in genetic code
it is read in sequence, seperate from the triplet before it and after it
76
why is genetic code non overlapping
base triplets dont share their bases
77
why is genetic code degenerate
there are more possible combinations of triplets then there are amino acids (20 AA but 64 possible triplets) this means that some amino acids are coded for by more than one base trplet
78
how many amino acids are there
20
79
start and stop signals
triplets used to tell a cell when to start and stop production of the protein, found at the beginning and end of the mRNA
80
how is genetic code universal
the same specific base triplets code for the same amino acids in all living things
81
how can you work out the sequence of amino acids from some mRNA
break down the genetic code into codons then use the information in the table to work out what amino acid they code for

biology (6 decks)

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