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a level biology topic 4 > a level biology topic 4 > Flashcards

a level biology topic 4 Flashcards

1
Q

give 2 similarities of DNA in eukaryotic cells and prokaryotic cells

A

made of DNA nucleotides containing deoxyribose sugar, phosphate group and nitrogenous base.

DNA nucleotides joined together by phosphodiester bonds to make polymer chains.

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2
Q

give 3 differences between DNA in eukaryotic cells and prokaryotic cells

A

in eukaryotic dana is longer in prokaryotic is shorter

in eukaryotic dana is linear in prokaryotic it is circular

in eukaryotic DNA is ascoatiated with histones to makes chromosomes . no histones associated with prokaryotic cells

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3
Q

how is DNA in the chloroplast and mitochondria in eukaryotic cells similar to DNA in prokaryotic cells

A

shorter, circular, no histones

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4
Q

what is a gene

A

a gene is a base sequences of DNA that codes for amino acid sequence of a protein and functional RNA

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5
Q

what is a triplet

A

sequence of three DNA bases

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6
Q

what do triplets do

A

code for a specific amino acid

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7
Q

three features of genetic code

A

degenerate
universal
non overlapping

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8
Q

define degenerate

A

multiple triplets are able to code for the same amino acid

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9
Q

how is this advantageous

A

if there is a point mutation in a triplet it may still code for the same amino acid.

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10
Q

universal meaning

A

the same triplets of DNA codes for the same amino acid in all organisms

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11
Q

non overlapping meaning

A

each base in a gene is only one part of one triplet so each base is read as a discrete unit

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12
Q

advantage of this

A

if point mutation occurs only one codon(triplet) is affected therefore only one amino acid

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13
Q

what are introns and are they found in eukaryotic or prokaryotic

A

section of DNA that does not code for protein , found in eukaryotic only.

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14
Q

exons definition

A

section of DNA codding for proteins

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15
Q

what do you call triplets on mRNA

A

codons

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16
Q

so what are codons full definition

A

triplets found on mrna that codes for specific amino acid

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17
Q

what is a start codon

A

codons found at start of every gene that initiate translation

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18
Q

what ate stop codons

A

codons found at end of every gene that cause ribosomes to detach stopping translation

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19
Q

genome definition

A

full set of dna in an organism including all genes

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20
Q

proteome

A

full set of proteins that a that cells are able to produce

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21
Q

should the genome ever change

A

no

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22
Q

why may proteome of organism need to change

A

organism may need to produce different proteins at different times

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23
Q

what is mrna

A

type of single stranded rna involed in protein synthesis

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24
Q

when is it formed

A

during transcription

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25
where is it copied from and due to this what is complementory to
copied from dna in transciption so it is complementary to the dna sequences
26
what is trna and what is its role. what does contain ,full explanation
role is involved in translation it carries amino acids to ribosomes. single polynucleotide strand that is folded in clover shape. h bonds between dna base pairs. trna molecules has three bases called anticodon. these are complementary to codnon on mrna. SPECIFIC TO ONE AMINO ACID.
27
ORDER OF 2 PROCESSES OF PROTEIN SYNTHESIS
transcription translation
28
explain fully the process of trancription
1)the DNA helix unwinds catalysed by DNA helicase. one stand of DNA acts as template. 2)DNA helicase breaks the hydrogen bonds between bases 3)mrna nucleotides align opposite to complementary DNA bases 4) enzyme rna polymerase joins together rna nucletodides to create new rna polymer chain. on entire gene is copied.
29
what does mrna leave the nucleas via after trancription
nuclear pores
30
when is pre mrna made and what is it
made after transcription . its is mrna that still has introns.
31
what are spliceosomes and what are there role
proteins that splice out introns out of pre-mrna
32
in one simple sentence what is trancription
process in which dna copy is copied into mrna
33
explain the process of translation fully
1) modifies mrna attaches to ribosomes in cytoplasm. then the ribosome attaches to start codon. 2) the trna molecule with the complementary anticodon to the start codon aligns opposite to the mrna held together by ribosome. 3) the two amino acids that have been delivered by trna molecule are joined by peptide bond. this is catalysed by enzyme atp. 4) this countinues until ribosomes reach stop codon. which causes ribosomes to detach ending translation 5) new polypetide chain is created.
34
what is a gene mutation
random change in base sequence of DNA that occur during dna replication
35
what is the name given to all factors that make mutation more likely to occur
matagenic agents
36
examples of mutagenic agents
carcinogens ionising radiation high energy radiation
37
why is a substition likely to be less harmfull than other forms of mutations that cause a framshift
subsition of one base is may not affect gene as genetic code is degenerate. however a framshift changes the sequence of amino acids sequence, which lead to non functional polypetides
38
what is non disjunction
when chromosomes do not split equally during anaphase
39
two ways non disjunction can alter chromosomes
change whole set of chromosomes(polyploidy) change in individual number of chromes(aneuploidy)
40
how many daughter cells does meiosis produce, how many cell divisions. genetically identical or not
produces 4 daughter cells genetically unidentical two nuclear divisions
41
two mechanism in meiosis that cause cell division and in what stage of round of meiosis do they occur
independent segration and crossing over both first round
42
what is the the behaviour of homologous chromosomes in cell during meiosis
they line up at opposite ends of the equator
43
what is independent segregation
random separation of homologous chromosomes during meiosis
44
result of this
large number of possible combinations of chromosomes of daughter cells created meiosis. called by 2 to the power n
45
what is crossing over full explanation
chromatids get twisted around each other causing tension causing them to break. chromatid recombine with other chromatids . resulting in new combinations of alles
46
three differences between meiosis and mitosis
meiosis- 2 cell division meiosis- genetically unidentical cells meiosis- one set of chromosomes- haploid mitosis diploid
47
tip- in meiosis diploid cells are dividing to become haploid cells
ok
48
what is genetic diversity
number of different alles of genes in a population
49
when can natural selection occur
when there is genetic diversity within a population
50
what is natural selction
the process at which species change over time to adapt to environment(evolution) . changes allele frequency.
51
explain how natural selection works through survival of fittest in terms of allele frequecy
random mutation causes a new alles for a gene. if these allelles are advantages then the organisms with alles with survival and pass down advanatageous alles to offspring. then this offspring will survive and advantageous allelle frequency will increas
52
name two types of selection
direction and stabilsing
53
what is direction selection. is there a change in envrioment? does modal trait change
extreme characteristics is favourable . change in environment. modal trait changes
54
what is stabilising section
favours average trait . no change in environment . modal trait stays the same
55
what make organisms the same species
if they are able to reproduce toegether
56
what is courtoship behaviour
actions that organism perform to attract mate to reproduce
57
how are species arranges in phylogenic classifiacation and what does it tell us
arranges species into groups according to evolutionary origins and ancestors. it tells us how closely related organisms are.
58
importnat of couroship behaviour
helps organism recognise mating pattners to ensure organism reproduce so species survives help organism choose healthy and strong pattner
59
what is hierarchy
system that organizing organism based on similarites.
60
in binomial naming what does the first name represent
the genus ( class or group)
61
second name
species

a level biology topic 4 (3 decks)

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