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T4 genetics Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

definition of a gene

A

base sequence of DNA that codes for the amino acid sequence of a polypeptide or functional RNA mol

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2
Q

definition of a chromosomes

A

bundles of DNA coiled around histones (proteins) that keep their structure. humans have 23 pairs.

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3
Q

definition of genome

A

an organisms complete set of genes

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4
Q

definition of proteome

A

all of the proteins a cell is ABLE to make

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5
Q

definition of allele

A

a different version of the same gene - eg. blue/brown eye colour gene

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6
Q

definition of homologous chromosome

A

pair of matching chromosomes
-have same shape, size, genes
-could have different alleles
-alleles coding for the same characteristic will be found on the same locus (location on chromosome).

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7
Q

features of Eukaryotic DNA

A

-long, linear DNA mols
-found in nucleus
-found as chromosomes
-wound around histones (proteins)
-has introns

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8
Q

features of prokaryotic DNA

A

-shorter, circular DNA mols
-found in cytoplasm
-found as coiled chromosomes or plasmids
-not associated w proteins
-no introns

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9
Q

3 features of the genetic code + explanations

A
  1. non-overlapping - each base triplet is completely separate from the triplet before and after - dont share bases
    2.degenerate - more possible combinations of triplets than amino acids that can be produced
    3.universal - same base triplets code for the same amino acid in all living things
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10
Q

what is an intron

A

NON-coding DNA found between genes as non-coding multiple repeats (contain same base sequences repeated multiple times)

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11
Q

what are exons

A

coding DNA

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12
Q

what is splicing

A

-introns removed from pre-mRNA and exons joined together to form mRNA which can be translated into protein

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13
Q

what is alternative splicing

A

selectively including/excluding certain exons, creating different mRNA sequences from a single gene. This means that a different protein isoform is produced.

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14
Q

features of mRNA

A

-long, single polynucleotide strand in a linear structure
-no h bonds
-no amino acid binding site
-made during transcription
-has codons (base triplets)

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15
Q

features of tRNA

A

-smaller, single polynucleotide strand folded into a clover leaf shape
-has H bonds (hold cloverleaf structure together)
-has amino acid binding site (at top)
-involved in translation
-has anticodons (base triplets, at bottom)

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16
Q

process of transcription

A
  1. DNA helix unwinds as H bonds break to expose the bases to act as a template (only one chain is template)
  2. free mRNA nucleotides in the nucleus align opposite exposed complementary DNA bases
    3.the enzyme RNA polymerase bonds together the RNA nucleotides, forming phosphodiester bonds to create a new pre-mRNA polymer chain. one entire gene is copied
  3. splicing then occurs to the pre-mRNA, where introns are removed and exons are joined together to create mRNA.
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17
Q

why does mRNA need to be made to leave the nucleus

A

-mRNA is much shorter than DNA, so it is able to fit out of the nuclear pore to carry the genetic code to the ribosome in the cytoplasm
-there are enzymes in cytoplasm that may damage DNA

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18
Q

process of translation

A
  1. mRNA attaches to a ribosome in the cytoplasm at the start codon
    2.a tRNA mol w the complementary anticodon to the start codon on mRNA aligns opposite, held in place by the ribosome.
    3.the ribosome moves along the mRNA mol to enable the rest of the tRNA mol to align w the codons on the mRNA.
  2. the two amino acids that have been aligned by the tRNA are joined by peptide bonds using ATP and an enzyme
  3. this continues until the stop codon is reached and the ribosome detaches. a polypeptide chain has been produced.
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19
Q

definition of genetic mutation

A

change in the DNA base sequence which may result in an altered or non-functional polypeptide.
occur spontaneously during DNA rep (S)

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20
Q

what is a mutagenic agent + example

A

something that increases the mutation rate of cells eg. UV light, ionising radiation

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21
Q

2 types of mutation (yr 12)

A
  • substitution mutation
    -deletion mutation
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22
Q

what is a substitution mutation

A
  • a single nucleotide base is replaced by another
    -this only affects the amino acid for the triplet in which the mutation occurs and will NOT have a knock-on effect.
    -can take 3 forms:
    1.silent
    2.missense
    3.nonsense
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23
Q

what is a nonsense mutation

A

-type of substitution mutation
-mutation that creates a premature STOP codon, causing the polypeptide chain produced to be incomplete and therefore affecting the final protein structure and function

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24
Q

what is a silent mutation

A

-type of substitution mutation
-mutation that doesn’t affect the amino acid (due to the degenerative nature of the genetic code)

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25
Q

what is a nonsense mutation

A

-type of substitution mutation
-mutation that causes a premature stop codon

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26
Q

what is a deletion mutation

A
  • a nucleotide base is deleted from the DNA sequence
    -this changes the amino acid that would have been coded for and has a knock-on effect for the rest of the triplets after by causing a frame shift
    -this may dramatically change the amin acid sequence produced and therefore the ability of the polypeptide to function
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27
Q

what happens in prophase 1

A

-chromosomes condense and become visible
-spindle fibres form from centrioles at opposite poles of the cell
-nuclear envelope breaks down
-HOMOLOGOUS chromosomes wrap around each other and exchange alleles and DNA (crossing over)

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28
Q

what happens in metaphase 1

A

-pairs of HOMOLOGOUS chromosomes line up at the equator of the cell
-spindle fibres attach to centromeres

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29
Q

what happens in anaphase 1

A

-spindle fibres shorten
-HOMOLOGOUS chromosomes move towards opposite poles of the cell
-independent assortment occurs - homologous chromosomes are randomly organised on either side of the equator

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30
Q

what happens in telophase 1

A

-chromosomes have reached opposite poles of the cell
-nuclear envelope reforms
-chromosomes uncoil

31
Q

what happens in cytokinesis (in meiosis 1)

A

-cytoplasm splits dividing into 2 haploid cells (as there is just one of each pair of the homologous chromosomes)

32
Q

what happens in meiosis 1 (brief)

A

-separation of homologous chromosomes

32
Q

what happens in meiosis 2 (brief)

A

-separation of sister chromatids
-produces 4 genetically different, haploid cells

33
Q

how does meiosis introduce variation (brief)

A
  1. crossing over
  2. independent segregation/assortment
34
Q

what is crossing over

A

-introduction of genetic variation in meiosis
-when 2 homologous chromosomes wrap around each other, getting loci for same gene close and exchanging sections of DNA
-may exchange alleles, which leads to variation

35
Q

what is independent assortment

A

-random organisation of homologous chromosomes on either side of the equator.

36
Q

what are non-disjunction mutations

A

-when chromosomes fail to separate correctly during meiosis, meaning gametes end up w an abnormal number of chromosomes (anueploidy)

37
Q

how does chromosome no change during fertilisation

A

doubles

38
Q

how does chromosome no change during mitosis

A

stays the same

39
Q

how does chromosome no change during meiosis

A

halves

40
Q

def of genetic diversity

A

-number of DIFFERENT alleles of genes in a pop

41
Q

def of species

A

-similar groups of organisms that can reproduce to make FERTILE offspring

42
Q

def of allele frequency

A

-incidence of a gene variant within a pop (how often does a certain allele appear)

43
Q

def of reproductive success

A

-passing on of genes to next gen in a way that allows them to also pass those genes on (fertile offspring)

44
Q

def of evolution

A

-gradual change in a species over a long period of time

45
Q

how is genetic diversity increased

A

-mutation - increase size of gene pool
-gene flow - individuals from another pop migrate into a pop and reproduce

46
Q

stages of natural selection

A

-random mutations create new alleles in a pop that may be beneficial to organism
-individuals w most advantageous alleles will survive and be reproductively successful
-advantageous allele passed onto next gen, increasing allele frequency for this allele
-over many gens, this will lead to survival and evolution of this species

47
Q

what is a genetic bottleneck

A

-factor affecting allele frequency
-event occurs that causes large reduction in pop (eg. natural disaster, disease) that reduces no of different alleles in gene pool, reducing genetic diversity and making pop more vulnerable
-can cause inbreeding in pops as surviving individuals end up reproducing w close relatives, increasing genetic diseases in pop

48
Q

what is the founder effect

A

-factor affecting allele frequency
-occurs when small no of individuals from large pop start a new pop
-small no of alleles from larger pop will be present, reducing gene pool
-can lead to higher incidence of genetic disease

49
Q

3 types of adaptation, explanation and example

A
  1. anatomical - physical/structural
    eg. white fur on polar bears
  2. physiological - bio process within organism
    eg. hibernation
    3.behavioural
    eg. penguins huddling
50
Q

def of courtship behaviour

A

-series of behaviours that attract other members of a species to mate and reproduce successfully
-helps in species recognition

51
Q

examples of simple courtship behaviour

A

-sounds
-releasing pheromones (chemicals)
-visual displays

52
Q

examples of complex courtship behaviours

A

-building
-dancing

53
Q

4 ways courtship behaviours increase probability of successful reproduction

A

-attracts members of same species
-stimulates release of gametes
-indication of sexual maturity/fertility
-recognition of opposite sex

54
Q

def of taxonomy

A

-practice of biological classification - each individual grouping called a taxon (plural taxa) and arranged in a hierarchy

55
Q

what is a hierarchy

A

-shows smaller groups within larger groups
-no overlaps

56
Q

def of phylogeny

A

-classification based on evolutionary origins (see how closely related 2 organisms are)

57
Q

what are the 3 domains and who defined them

A
  1. archaea - prokaryotic cells that usually live in extreme environments
  2. eukarya
  3. bacteria
    -carl woese
58
Q

carl linnaeus taxa

A

-kingdom
-phylum
-class
-order
-family
-genus
-species

59
Q

what is the binomial name

A

-genus + species

60
Q

how is genome sequencing used to establish evolutionary relationships

A

-can use DNA, mRNA and amino acids sequences
-related organisms will have more similar DNA base sequences, which make mRNA sequences and amino acid sequences

61
Q

immunology method

A
  1. human blood serum (blood proteins, no cells) injected into animal eg. rabbit
  2. rabbit forms antibodies specific to proteins
  3. sample of rabbit blood taken and antibodies extracted
  4. anti-human antibodies added to blood samples from other species to see how well they recognise proteins of different species
  5. the more similar the blood proteins to human proteins, the greater the reaction (more precipitate formed)
62
Q

DNA hybridisation method

A
  1. take DNA from 2 species and radioactively label 1 so they can be identified
  2. 2 species DNA mixed and heated to break H bonds and separate strands
  3. mixture cooled to allow strands to recombine w other strands w complementary base sequence
  4. some double strands that reform will be hybrids if DNA is similar
  5. to measure degree of similarity, hybrid DNA heated in stages. higher temp before it splits = more H bonds created, so more similar DNA
63
Q

def of biodiversity

A

-range and variety of genes, species and habitats within a region

64
Q

def of species richness

A

-number of different species in a community

65
Q

how to work out species richness

A

-random sample of community
-divide into grid
-random no generator to pick co-ordinates
-count no of diff species

66
Q

def of species diversity

A

-no of diff species in a community and the EVENESS of abundance

67
Q

ways of maintaining biodiversity

A

-breeding programmes for endangered species
-protection and regeneration of rare habitats
-reintroduction of field margins and hedgerows
-reduction in deforestation and CO2 emissions
-recycling
-green spaces in urban areas

68
Q

direct impacts of agriculture on biodiversity

A

-selective breeding = fewer species and fewer alleles within a species
-removing hedgerows
-woodland clearance
-over grazing
-pesticides/herbicides

69
Q

indirect impacts of agriculture on biodiversity

A

-effluent runoff into water
-not rotating crops/monoculture
-use of pesticides kills local animals that feed on pests

70
Q

what is directional selection + example

A

-individuals w alleles of an extreme type are selected for
-produces gradual change in allele frequency over several gens
-could be in response to env change
-eg. antibiotic resistance in bacteria

71
Q

what is stabilising selection + example

A

-average phenotype is selected for and extremes selected against
-keeps allele frequency relatively constant over gens
-occurs when env is not changing
-reduces range of possible characteristics
-eg. human birth weights

72
Q

what is disruptive selection + example

A

-natural selection favours two extremes of a phenotype
-maintains high frequencies of 2 diff sets of alleles
-occurs in env that favours more than 1 phenotype
-selection pressures select against average phenotype
-eg. Atlantic Salmon - good to be big (fight) and tiny (fit in small gaps)

Biology (6 decks)

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