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topic 3 - genetics Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what is DNA

A

genetic blueprint which codes for and determines the characteristics of an organism

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2
Q

what is a gene

A

sequence of DNA that encodes for a specific trait

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3
Q

what is a locus

A

position of a gene on a particular chromosome

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4
Q

what is an allele

A

alternate form of a gene that codes for the different variations of a specific trait

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5
Q

what is an example of a gene and its potential allelic variations?

A

eye colour

brown, blue, green, grey

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6
Q

what is a gene mutation

A

change in the nucleotide sequence of a section of DNA coding for a specific trait

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7
Q

what is formed as a product of mutation?

A

new alleles

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8
Q

what are the three types of gene mutations

A

beneficial (missense mutations, new variations of a trait)
detrimental (nonsense mutations, abrogate the normal function)
neutral (silent mutations, have no effect on the functioning)

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9
Q

what is an example of a disorder caused by a gene mutation?

A

sickle cell anemia

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10
Q

what is sickle cell anemia caused by

A

base substitution (single base is changed in the gene sequence)

6th codon position for the beta chain of hemoglobin is changed

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11
Q

sickle cell anemia changes to DNA, mRNA, and polypeptide chain?

A

DNA: GAG –> GTG
mRNA: GAG –> GUG
Polypeptide: glutamic acid –> valine

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12
Q

what are the consequences of sickle cell anemia?

A
  • alters hemoglobin structure (forms insoluble strands)
  • cannot transport oxygen effectively (causes fatigue)
  • red blood cells adopt a sickle shape (may form clots)
  • sickle cells are destroyed at a higher rate (causes anemia)
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13
Q

what is the genome

A

totality of genetic information of a cell, organism or organelle (includes all genes)

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14
Q

what does the human genome consist of

A

46 chromosomes
3 billion base pairs
21,000 genes

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15
Q

what is the Human Genome Project (HGP)?

A

international cooperative venture established to sequence the human genome (showed that humans share the majority of their sequence)

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16
Q

where is the genetic material found in prokaryotes?

A

cytoplasm, in the nucleod

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17
Q

differences between prokaryotic and eukaryotic DNA?

A

prokaryotic DNA:

  • single circular molecule made of naked DNA
  • may have additional plasmids

eukaryotic DNA:

  • multiple linear NA molecules packaged with histones
  • no plasmids (unless genetically modified)
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18
Q

what are plasmids

A

circular DNA molecules

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19
Q

what do homologous chromosomes share

A
  • the same structural features (ex. same size, same branding pattern)
  • the same genes at the same loci positions
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20
Q

what are homologous chromosomes

A

paired chromosomes inherited from both parents (maternal + paternal) in sexually reproducing animals

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21
Q

diploid vs haploid?

A

diploid: 2 sets of chromosomes (i.e. body cells, as they receive genetic material from both parents)
haploid: 1 set of chromosomes (organisms only pass on half of their genetic material to reproduce)

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22
Q

what happens when haploid sex cells fuse?

A

diploid cell, grows into an organism

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23
Q

how is sex determined in humans?

A

sex chromosomes

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24
Q

what sex chromosomes do females possess? males?

A

females: XX
males: XY

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25
Q

what is the Y chromosome responsible for?

A

development of the male sex characteristics

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26
Q

what happens when there is no Y chromosome?

A

female sex organs develop

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27
Q

why is the father responsible for determining the sex of the offspring?

A

if the sperm contains a Y chromosome, embryo = boy

X chromosome = girl

the female egg will always have an X chromosome

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28
Q

what are the remaining chromosomes in the organism (not sex chromosomes)

A

autosomes

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29
Q

how many homologous autosomes do humans have

A

22 pairs

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30
Q

what are karyotypes?

A

number and types of chromosomes in a eukaryotic cell

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31
Q

what is a karyogram

A

shows the chromosomes of a cell in homologous pairs of decreasing length

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32
Q

when and why is karyotyping usually used?

A

occurs prenatally to…

  • determine the gender of the unborn child
  • test for chromosomal abnormalities
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33
Q

what is Down Syndrome?

A

condition whereby the individual has three copies of chromosome 21 (i.e. trisomy 21)

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34
Q

how does autoradiography work

A
  • radioactive thymidine is incorporated into a cell’s DNA
  • chromosomes were fixed to a photographic surface and treated with AgBr
  • radiation converts silver ions into insoluble grains that is visible via electron microscopy when a film is developed
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35
Q

what is the point of autoradiography?

A

to measure the length of DNA molecules while uncoiled

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36
Q

who pioneered autoradiography?

A

John Cairn

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37
Q

can organisms with different diploid numbers interbreed?

A

unlikely as they cannot form homologous pairs in zygotes

when they do breed, offspring are infertile

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38
Q

what is chromosome number a characteristic feature of (?)

A

members of a particular species

ex. horses (diploid = 64)

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39
Q

summary of meiosis I?

A
  • reduction division
  • separates homologous chromosomes
  • crossing over may occur during Prophase I
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40
Q

summary of meiosis II?

A
  • akin to mitotic division
  • separates sister chromatids
  • occurs b/c DNA is replicated in interphase to create chromosomes with sister chromatids
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41
Q

what is meiosis?

A

reduction division of a diploid cell to produce four haploid cells (gametes) that are genetically distinct

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42
Q

what are the two cellular divisions of meiosis?

A

meiosis I - separates pairs of homologous chromosomes

meiosis II - separates sister chromatids

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43
Q

what are sister chromatids?

A

identical DNA molecules produced in the S phase of interphase held together by a centromere

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44
Q

what happens during prophase i?

A

chromosomes condense, nuclear membrane dissolves, homologous chromosomes form bivalents, crossing over occurs

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45
Q

what happens during metaphase i?

A

spindle fibres connect to bivalents + align them along the middle of the cell

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46
Q

what happens during anaphase i?

A

spindle fibres contract + split bivalent, homologous chromosomes move to opposite poles of the cell

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47
Q

what happens during telophase i?

A

chromosomes decondense, nuclear membrane may reform, cytokinesis

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48
Q

what happens during prophase ii?

A

chromosomes condense, nuclear membrane dissolves, centrosomes move to opposite poles (perpendicular to before)

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49
Q

what happens during metaphase ii?

A

spindle fibres from opposing centrosomes attach to chromosomes at centromere and align them along cell equator

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50
Q

what happens during anaphase ii?

A

spindle fibres contract + separate the sister chromatids, chromatids move to opposite poles

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51
Q

what happens during telophase ii?

A

chromosomes decondense, nuclear membrane reforms, cytokinesis

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52
Q

what is the final outcome of meiosis?

A

four haploid daughter cells

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53
Q

what are chiasmata

A

points where the homologous chromsomes are held together

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54
Q

what is synapsis

A

homologous chromosomes pairing up to form a bivalent

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55
Q

what is recombination

A

new gene combinations formed on chromatid

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56
Q

what are recombinants

A

nonsister chromatids that have exchanged DNA

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57
Q

number of possible gamete combinations?

A

2^n where n = haploid number

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58
Q

T/F: the orientation of pairs of homologous chromosomes is not random

A

F, random

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59
Q

what would happen if chromosome number was not halved in gametes?

A

polyploidy as the total chromosome numbers would double each generation

60
Q

what are the three main sources of genetic variation arising from sexual reproduction?

A
  • crossing over (prophase i)
  • random assortment of chromosomes (metaphase i)
  • random fusion of gametes from different parents
61
Q

what is non-disjunction

A

chromosomes failing to separate correctly

62
Q

what does nondisjunction result in

A

gametes w/ one extra or one missing chromosome

63
Q

what is the effect of the age of parents on the chances of nondisjunction?

A

strong correlation between maternal age and occurence of non-disjunction events

64
Q

what is DISCO PUG? (mitosis/meiosis differences)

A 
Divisions (1 vs 2)
Independent Assortment (N vs Y)
Synapsis (N vs Y)
Crossing over (N vs Y)
Outcome (2 cells vs 4 cells)
Ploidy (dip --> dip, dip --> hap)
Use (body cells vs sex cells)
genetics (identical vs genetic variation)
65
Q

what is a genotype

A

allele combination for a specific trait

66
Q

what is a penotype

A

physical expression of a specific trait

67
Q

what are phenotypes determined by

A

genotype + environmental factor

68
Q

what are the three possible types of allele combinations?

A

homozygous (both alleles are the same)

heterozygous (alleles are different)

hemizygous (only one allele, ex. X/Y gene in males)

69
Q

what did Gregor Mendel’s pea experiment establish

A

principles of inheritance

70
Q

what were the findings of Mendel’s pea experiment?

A

organisms have heritable factors

parents contribute equally to inheritance by supplying one version of the gene each

gametes contain only one allele of each gene

fusion of gametes results in zygotes with two alleles of each gene

71
Q

what are gametes

A

haploid sex cells formed by meiosis

72
Q

what are the two main modes of inheritance?

A

complete dominance

co-dominance

73
Q

what is complete dominance? how is it expressed?

A

one allele is expressed over another

dominant is expressed in heterozygote (capitale)
recessive is masked in heterozygote (lower case)

74
Q

can recessive phenotypes be expressed in heterozygotes?

A

no, only homozygotes as heterozygotes display the dominant phenotype

75
Q

what is codominance

A

both alleles are equally expressed in the phenotype

76
Q

what is an example of codominance?

A

ABO blood system

77
Q

how is codominance expressed?

A

superscripts for the different co-dominant alleles (recessive still lower case)

78
Q

how are human red blood cells categorized into different blood groups?

A

structure of a surface glycoprotein (antigen)

79
Q

A,B, and O alleles are all controlled by a single gene. Which allele is recessive and which two are co-dominant?

A

A + B alleles = codominant

O = recessive

80
Q

what does a monohybrid cross determine

A

allele combinations for potential offspring for one gene only

81
Q

monohybrid cross steps?

A

designate letters to represent alleles

identify genotype / phenotype of parents

determine genotype of gametes

work out gamete combination with punnett grid

identify ratios of offspring

82
Q

why were Mendel’s results questioned

A

too close to the exact ratios predicted to be genuine

83
Q

what causes genetic diseases

A

mutations to a gene / genes

84
Q

what type of allele (recessive, dominant, codominant) is responsible for the most common type of genetic diseases (????0

A

recessive

85
Q

what is autosomal dominance?

A

both parents are affected by a trait but any offspring is not - trait is DOMINANT (parents are heterozygous)

86
Q

what is autosomal recessive?

A

neither parents is affected by the trait but any offspring is, the trait must be RECESSIVE (parents must be heterozygous)

87
Q

who is a carrier

A

heterozygous individuals that possess one copy of the faulty allele but do not develop disease symptoms

88
Q

how many copies of a faulty allele does an autosomal recessive genetic disease require?

A

both alleles

89
Q

how many copies of a faulty allele does an autosomal dominant genetic disease require to cause the disorder?

A

one copy

90
Q

how many copies of a faulty allele does a genetic disease caused by co-dominant alleles require to occur

A

one copy

91
Q

example of an autosomal recessive genetic disease?

A

cystic fibrosis

92
Q

example of an autosomal dominant genetic disease?

A

huntington’s disease

93
Q

example of a genetic disease caused by co-dominant alleles?

A

sickle cell anemia

94
Q

what is cystic fibrosis + what is it caused by?

A
  • caused by mutated CFTR gene (chromosome 7)

- produces thick mucus that clogs airways and causes respiratory issues

95
Q

what is huntington’s disease + what is it caused by?

A
  • caused by mutated HTT gene (chromosome 4)

- amplification of CAG repeats leading to neurodegeneration

96
Q

what is sickle cell anemia + what is it caused by?

A
  • mutated HBB gene (chromosome 11)

- leads to anemia + other complications

97
Q

why are many genetic diseases rare?

A

any allele that adversely affects survival is unlikely to be passed on to offspring as the capacity to reproduce is unlikely

98
Q

what is sex-linkage

A

gene controlling a characteristic is located on a sex chromosome

99
Q

why are sex-linked conditions usually X-linked?

A

Y chromosome is much much shorter than the X chromosome and contains less genes

100
Q

why can only females be carriers?

A

heterozygote for the recessive disease condition, males cannot be heterozygous carriers

recessive trait can be masked

101
Q

what are two examples of X-linked recessive conditions?

A

red-green colour blindness

haemophilia

102
Q

T/F: for recessive X linked conditions, affected mothers must have affected sons

A

T

103
Q

T/F: for dominant X linked conditions, affected fathers MUST have affected daughters

A

T

104
Q

what is a gene mutation

A

change to the base sequence of a gene that can affect the structure and function of the protein it encodes

105
Q

what are spontaneous mutations

A

mutations caused by copying errors during DNA replication

106
Q

what are induced mutations

A

mutations caused by exposure to external elements

107
Q

what are three factors which can induce mutations?

A

radiation
chemical
biological agents

108
Q

what are mutagens

A

agents which increase the rate of genetic mutations

109
Q

what are carcinogens

A

mutagens which lead to the formation of cancer

110
Q

what are two major examples of radiation exposure

A

nuclear bombing of hiroshima

accident/meltdown in chernobyl

111
Q

what are some of the long-term consequences of radiation exposure?

A
  • increased incidence of cancer
  • reduced immunity (T cell count down)
  • congential abnormalities
  • organ specific health effects
112
Q

what is a pedigree?

A

chart of the genetic history of a family over several generations

113
Q

what are the symbols of a pedigree?

A 
males = squares
females = circles
affected individual = shaded
unaffected individual = unshaded
mating = horizontal line 
generations = roman numerals
age = left to right
114
Q

can sex linkage be confirmed with a pedigree?

A

NO but patterns are there!

115
Q

what is the polymerase chain reaction? (PCR)

A

artificial method of replicating DNA under laboratory conditions

116
Q

what is gel electrophoresis?

A

laboratory technique used to separate and isolate proteins or DNA fragments based on mass/size

117
Q

how does gel electrophoresis work?

A

samples placed in a block of gel + current is applied

smaller samples move faster through the gel (lower resistance)

samples move towards the anode

DNA is negatively charged (b/c of phosphate group)

proteins are treated with an anioinic detergent to impart a uniform negative charge on all molecules

118
Q

what is DNA profiling?

A

technique by which individuals can be identified and compared via their respective DNA profiles

119
Q

when is DNA profiling most commonly used?

A 
forensic investigations
paternity tests (offspring STRs are a combination of parents)
120
Q

what are STRs? (short tandem repeats)

A

different lengths of particular DNA segments

121
Q

how does DNA profiling work?

A

STR’s are amplified by PCR then separated by gel electrophoresis for comparison

unique profiles appear when multiple loci are compared

122
Q

what is a transgenic?

A

new organism created as a result of gene modification

123
Q

why an an organism potentially express a new trait if the appropriate gene is introduced into its genome?

A

genetic code is (almost) universal

124
Q

process of gene transfer?

A
  1. DNA extraction (amplified using PCR)
  2. digestion + ligation (specific restriction enzyme + DNA ligase)
  3. transformation and expression (plasmid inserted into host cell + antibitioc to select for successful transgetic cells)
125
Q

benefits of GM crops?

A
  • can grow in a wide range of environments
  • reduce farming costs + deforestation
  • reduces spoilage
  • improve nutritional standards
126
Q

risks of GM crops

A
  • unexpected health issues
  • restrict access due to patent protections
  • cross pollination with weeds
  • reduce biodiversity (competes w native plants)
127
Q

what is an example of GM crop + risks to wildlife?

A

Bt corn, incorporates insecticide producing gene which is toxic to monarch muterflies

128
Q

what are clones

A

groups of genetically identical organisms or a group of cells derived from a single original parent cell

129
Q

what does cloning multicellular organisms require

A

production of stem cells

130
Q

how can stem cells be artificially generated

A

somatic cell nuclear transfer (SCNT)

131
Q

how does somatic cell nuclear transfer work?

A

somatic cells are removed from donor + cultured

enucleated egg cell is fused with nucleus from donor to make a diploid egg

electric current stimulates egg to develop into embryo

embryo is implanted into surrogate

132
Q

what are animal cloning methods?

A

binary fission
budding
fragmentation
parthenogenesis

133
Q

what are plant cloning methods?

A

vegetative propogation

134
Q

what are human cloning mechanisms?

A

natural mechanisms (identical twins)

135
Q

what is binary fission

A

parental organism divides equally into two clones

ex. flatworms

136
Q

what is budding

A

cells split off from parent, generating smaller clones

occurs in hydra

137
Q

what is fragmentation

A

new organisms grow from separated fragment of parent

ex. annelid worm

138
Q

what is parthenogenesis

A

embryos formed from an unfertilized diploid ova

ex. fish

139
Q

what is vegetative propagation

A

small pieces of plant acn be induced to grow independently

140
Q

why are plants capable of vegetative propagation?

A

adult plants possess totipotent meristematic tissue

141
Q

what is a stem cutting

A

separated portion of a plant stem that is used to regrow a new clone

142
Q

difference between identical and nonidentical twins?

A

identical twins: fertilized egg splits into 2

nonidentical: nonfertilized egg splits into 2, fertilized by diferent sperm

143
Q

what are the two forms of artificial cloning

A

embryo cloning

adult cloning

144
Q

what is embryo cloning + how does it work

A

cloning from an embryo by separating the embryonic cells into groups

embyronic stem cells are pluripotent so each cell can potentially form a cloned off spring

145
Q

why can we not control the genetic features of potential clones in embryo cloning?

A

occurs after random fertilization

146
Q

what is adult cloning?

A

process of somatic cell nuclear transfer

SCNT

biology (11 decks)

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