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Biology A level > (8) DNA, RNA and protein synthesis > Flashcards

(8) DNA, RNA and protein synthesis Flashcards

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1
Q

describe the dna in eukaryotic cells (chromosomes)

A

it is long and linear, in the form of chromosomes, found in the nucleus
has to be wound up to fit in the nucleus- wound around proteins called histones

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2
Q

how is the dna of mitochondria and chloroplasts in eukaryotic cells different to the normal dna

A

circular and shorter than nuclear dna (more similar to prokaryotic dna) and not associated with histone proteins

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3
Q

what are the features of prokaryotic dna

A

dna molecules are shorter and circular, not wound around histones, it supercoils in order to fit into the cell

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4
Q

define gene

A

a sequence of dna bases that codes for a polypeptide or functional RNA

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5
Q

what forms the primary structure of the protein

A

the sequence of amino acids

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6
Q

what is a triplet

A

a sequence of 3 bases in a gene

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7
Q

what is a cells proteome

A

the full range of proteins that that cell is able to produce

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8
Q

what is functional RNA

A

RNA other than mRNA that perform special tasks during protein synthesis eg tRNA and ribosomal RNA

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9
Q

what is an intron

A

sections that don’t code for amino acids within a gene

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10
Q

what are exons

A

all the sections of the gene that do code for amino acids

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11
Q

what is an allele

A

a different form of the same gene

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12
Q

how does the blood type gene produce type O, type A and type B

A

the blood type gene exists as 3 different alleles and they all code for slightly different versions of the same polypeptide

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13
Q

what is the function of mRNA

A

it carries the genetic code from the dna to the ribosomes where its used to make a protein during translation

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14
Q

what is the function of tRNA

A

carries the amino acids that are used to make proteins to the ribosomes

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15
Q

what is the structure of tRNA

A

single polynucleotide strand folded into a clover shape. hydrogen bonds between specific base pairs hold the molecule in this shape

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16
Q

what happens during transcription

A

an mRNA copy of a gene is made from dna

17
Q

where does transcription take place in prokaryotic and eukaryotic cells

A

in eukaryotic cells it takes place in the nucleus

in prokaryotic in the cytoplasm

18
Q

what is pre-mRNA

A

mRNA strands containing introns and exons

19
Q

what is splicing

A

introns are removed from pre-mRNA and the exons join together forming strands of mRNA

20
Q

how is mRNA produced in prokaryotes

A

directly from DNA without splicing

21
Q

what are the 1st and 2nd stages of protein synthesis

A

1) transcription

2) translation

22
Q

what does it mean by the genetic code being non-overlapping

A

base triplets don’t share their bases, each triplet is separate from the triplet before it and after it

23
Q

what does it mean by the genetic code being degenerate

A

more possible combinations of triplets than there are amino acids (20 amino acids but 64 possible triplets) meaning some amino acids are coded for by more than one triplet

24
Q

what does it mean by the genetic code being universal

A

the same specific base triplets code for the same amino acids in all living things

25
Q

define what the genetic code is

A

sequence of base triplets (codons) in mRNA which code for specific amino acids

26
Q

what is a homologous pair in terms of chromosomes

A

2 chromosomes that carry the same genes but not necessarily the same alleles of the genes

27
Q

what is a codon

A

the sequence of three bases on mRNA that codes for a single amino acid

28
Q

how does the mRNA leave the nucleus in order to act as a template for protein synthesis

A

through pores in the nuclear membrane

29
Q

what is an anticodon

A

a sequence of 3 adjacent nucleotides on a molecule of tRNA that is complementary to a particular codon on a mRNA molecule

30
Q

what are the 5 steps of transcription

A

1) enzyme acts on a specific region of the dna causing the 2 strands to separate and expose the nucleotide bases
2) the nucleotide bases on one of the 2 dna strands is the template strand and pairs with the complementary nucleotides from the pool in the nucleus. RNA polymerase moves along the strand and joins the nucleotides to form pre mRNA
3) the complementary bases bind (adenine links to uracil)
4) as the rna polymerase adds nucleotides one at a time to build pre mRNA the dna strands rejoin behind it so only 12 base pairs on dna are exposed at a time
5) when the rna polymerase reaches a particular sequence of bases on the dna that is recognises as a stop codon, it detaches and pre mRNA is produced

31
Q

what does the emdosymbiotic theory state

A

a bacterial cell was engulfed by a larger cell. explains the presence of dna in mitochondria and chloroplasts

32
Q

what is symbiosis

A

after the cell was engulfed, the bacterial and host cell formed a beneficial symbiotic relationship

33
Q

what does dna in chloroplasts encode

A

the enzymes for photosynthesis

34
Q

describe the ancestors of mitochondria and chloroplasts

A

free living bacteria that needed their own dna to survive. when the bacteria became incorporated into a host cell some of the dna remained

35
Q

what 2 molecules make up ribosomes

A

RNA and protein

36
Q

during which phase of the cell cycle are gene mutations most likely to occur

A

interphase because it is the longest phase and is when gene replication occurs

37
Q

how is the structure of an mRNA molecule different to a tRNA molecule

A

mRNA doesn’t contain hydrogen bonds/ base pairs

mRNA doesn’t have an anticodon or an amino acid binding site all of which a tRNA molecule does have

38
Q

what is the difference between pre-mRNA and mRNA

A

pre-mRNA contains exons and introns but mRNA only contains exons

39
Q

why is it likely that the mRNA needed to produce one polypeptide is created more quickly in a prokaryotic cell than a eukaryotic cell

A

in eukaryotic cells the dna must be dissociated from histone proteins before transcription can take place (mRNA made) also the pre mRNA made during transcription has to undergo splicing but in prokaryotic cells the dna is not associated with histones and doesn’t contain introns so the production of mRNA takes less time

Biology A level (20 decks)

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