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topic 4 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what does it mean if the genetic code is degenerate?

A

more possible combinations of triplets than amino acids

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2
Q

what does it mean if the genetic code is universal?

A

the same triplet of bases codes for the same amino acids in all organisms

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3
Q

what does it mean if the genetic code is non overlapping?

A

each base is only part of one triplet

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4
Q

what is a triplet made up of?

A

3 amino acids

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5
Q

what is a gene?

A

base sequence of DNA that codes for the amino acid sequence of a polypeptide

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6
Q

what is a start codon?

A

at the start of every gene to initiate translation

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7
Q

what is a stop codon?

A

at the end of every gene, causes ribosomes to detach and stop translation

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8
Q

what are introns?

A

non coding sections of DNA, only in eukaryotes, spliced out of mRNA

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9
Q

what are exons?

A

sections of DNA that code for amino acids

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10
Q

what is a genome?

A

an organism’s complete set of DNA which never changes

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11
Q

what is a proteome?

A

an organism’s full range of proteins which always changes

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12
Q

what is a locus?

A

the location of a gene on a chromosome

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13
Q

what is an allele?

A

an alternative form of a gene

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14
Q

what is a chromosome?

A

where DNA is stored

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15
Q

how many pairs of chromosomes are there in humans?

A

23

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16
Q

where is DNA stored?

A

in the nucleus of eukaryotic cells, and is circular in prokaryotic cells

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17
Q

what is the purpose of transcription?

A

a gene is copied into mRNA which can carry the genetic code to a ribosome so a protein can be made

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18
Q

what are the stages of transcription?

A

1) DNA helix unwinds to expose the bases and act as a template
2) a chain of DNA acts as a template
3) catalysed by DNA helicase
4) which breaks the hydrogen bonds between bases
5) free mRNA nucleotides in the nucleus align with exposed complementary bases
6) RNA polymerase bonds RNA nucleotides by phosphodiester bonds
7) pre mRNA is spliced to form mRNA
8) mRNA moves out of the nuclear pore and attaches to a ribosome in the cytoplasm

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19
Q

what is the purpose of translation?

A

to produce a new protein

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20
Q

what happens in translation?

A

mRNA joins with a ribosome, the tRNA brings along the specific amino acid

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21
Q

what are the stages of translation?

A

1) mRNA attaches to a ribosome at the start codon
2) tRNA has an anticodon complementary to the mRNA codon
3) tRNA brings along a specific amino acid
4) amino acids are joined by peptide bonds using ATP
5) tRNA is released
6) ribosome moves along mRNA to form a polypeptide
7) it detaches at the stop codon
8) and enters the golgi for folding and modification

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22
Q

what is RNA made of?

A

ribose, nitrogenous base, phosphate group

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23
Q

what are the bases for RNA?

A

adenine, guanine, cytosine, uracil

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24
Q

what is the structure of RNA?

A

a short, single polynucleotide strand

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25
Q

what is the job of RNA?

A

to copy and transfer the genetic code from the DNA in the nucleus to the ribosomes

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26
Q

what is mRNA?

A

a copy of a gene from DNA

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27
Q

where is mRNA created?

A

in the nucleus

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28
Q

where does mRNA go?

A

made in nucleus, leaves to carry a copy of the genetic code to a ribosome in the cytoplasm

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29
Q

why is mRNA less stable?

A

only temporarily needed to form a protein

30
Q

where is tRNA found?

A

in the cytoplasm

31
Q

what is the shape of tRNA?

A

a clover shape

32
Q

what does tRNA have instead of a codon?

A

an anticodon

33
Q

what is the size order of DNA/mRNA/tRNA?

A

DNA= largest, tRNA= smallest

34
Q

what is the stability order of DNA/mRNA/tRNA?

A

DNA= most stable, mRNA= least stable

35
Q

what happens in a substitution?

A

another base is substituted for another

36
Q

what happens during deletion?

A

nucleotide is lost by deletion and frameshift occurs

37
Q

what happens in a chromosome mutation?

A

changes in whole sets/number of individual chromosomes

38
Q

how many daughter cells are produced in mitosis/meiosis?

A

2 daughter cells= mitosis

4 daughter cells= meiosis

39
Q

how many chromosomes are produced in mitosis/meiosis?

A 
mitosis= same number of chromosomes 
meiosis= half the number of chromosomes
40
Q

what type of reproduction is mitosis/meiosis?

A 
mitosis= asexual 
meiosis= sexual
41
Q

is there variation in mitosis/meiosis?

A 
mitosis= no variation
meiosis= variation
42
Q

what happens in meiosis 1?

A

prophase 1) DNA replication, homologous chromosomes pair, DNA crosses over
metaphase 1) chromosomes align on the cell equator
anaphase 1) chromosome pairs separate
telophase 1) nuclear envelopes reform

43
Q

what happens in meiosis 2?

A

prophase 2) chromosomes move towards the cell equator
metaphase 2) line up on the equator, microtubules attach
anaphase 2) chromosomes pull apart at the centromere
telophase 2) new cell membranes and gametes form

44
Q

how does crossing over of chromatids create genetic variation?

A

chromatids cross over so alleles are exchanged

45
Q

how does independent segregation create genetic variation?

A

homologous pairs are separated- random which chromosome is in each daughter cell

46
Q

what is genetic diversity?

A

number of different alleles in a species or population

47
Q

how is genetic diversity increased?

A

by mutations, and gene flow which introduces different alleles into a population

48
Q

what happens in a genetic bottleneck?

A

large number of a population die, which reduces the population, and after reproduction there is reduced genetic diversity

49
Q

what happens in the founder effect?

A

a type of genetic bottleneck, but only has a small number of alleles in the initial gene pool

50
Q

what is the purpose of natural selection?

A

to increase advantageous alleles within a population

51
Q

what happens during natural selection?

A

not all individuals in a population are as likely to reproduce, different alleles increase an individual’s chance of survival, a greater proportion inherit the beneficial allele, so they are more likely to survive, reproduce and pass on useful genes

52
Q

what is phylogeny?

A

the history of organisms

53
Q

what is taxonomy?

A

the study of classification

54
Q

what is each group known as?

A

a taxon

55
Q

what is a hierarchy?

A

groups within groups, no overlap

56
Q

what is a species?

A

groups of similar organisms that can reproduce to give fertile offspring

57
Q

what is the order of classification?

A

kingdom, phylum, class, order, family, genus, species

58
Q

what does the binomial naming system use?

A

Genus, species, (italics)

59
Q

what is the purpose of courtship behaviour?

A

to attract a mate of the correct species

60
Q

what is genome sequencing?

A

comparing the entire base sequence of an organism’s DNA

61
Q

why do we compare amino acid sequences?

A

related organisms have similar DNA base sequences

62
Q

why do we use immunological comparisons?

A

similar proteins bind to the same antibodies

63
Q

what is biodiversity?

A

the variety of organisms living in an area

64
Q

what is a habitat?

A

the place where an organism lives

65
Q

what is a community?

A

the population of different species in a habitat

66
Q

what is species diversity?

A

the number of different species/organisms in a community

67
Q

what is genetic diversity?

A

the variety of genes within a population?

68
Q

what is ecosystem diversity?

A

the range of different habitats

69
Q

what is species richness?

A

the number of organisms in a particular area at a given time

70
Q

what is index of diversity?

A

species richness + population sizes

71
Q

what are examples of agricultural practices?

A

woodland clearances= increase the area of farmland
hedgerow removal= increases area by turning small fields into larger ones
pesticides= kill organisms that feed on crops
herbicides= chemicals that kill unwanted plants
monoculture= only one type of plant

biology updated (10 decks)

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