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Genetic Information, Variation And Relationships Between Organisms Flashcards

1
Q

What is a gene?

A

a section of DNA that codes for polypeptides or RNA molecules

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2
Q

What do genes code for?

A

polypeptides
functional RNA, rRNA, tRNA

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3
Q

What is degenerate code?

A

-multiple triplets code for the same amino acid

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4
Q

What is a start code?

A

the amino acid that signifies the beginning of the polypeptide

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5
Q

What is a stop code?

A

does not code for amino acids and ends the polymer
tells ribosomes the amino acid chain is done

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6
Q

What is non- overlapping code?

A

each base is only read once

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7
Q

What is universal code?

A

almost all triplets code for the same amino acids across living organisms

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8
Q

What are exons and introns?

A

Exons are called coding sequences of DNA that are used to form polypeptides
Introns allow for a single gene to encode many transcriptions
Exons are separated by introns- non-coding sequences of bases that are removed when making mRNA

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9
Q

What are chromosomes?

A

-often not individually visible
-observed in cell division
-two chromatids
-joined in the middle at the centromere

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10
Q

What are homologous chromosomes?

A

-46 individuals arranged in 23 pairs
-each pair contains one chromosome from mother and one from father= homologous pairs
-homologous chromosomes contain genes at the same loci, in each pair you have 2 alleles

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11
Q

What is a proteome?

A

sometimes used to refer to the proteins made by a cell in specific conditions

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12
Q

What is a complete proteome?

A

the full range of proteins coded for in the genome and made by a cell.

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13
Q

Properties of RNA.

A

-made up 60% of ribosomes
-made in nucleus, extra nuclear pores
-function= protein synthesis
-catalyses peptide bonds

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14
Q

Properties of mRNA

A

-single stranded helix
-1000s of nucelotides
-CG,AU
-made in nucleus, DNA as template

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15
Q

Structure of tRNA

A

acceptor stem
= where amino acid attaches
hydrogen bonds
= between base pairs
variable arm
=unique to each tRNA
=used for recognition
unpaired bases
=not paired to complementary base pairs
anticodon
=corresponds to the codon of mRNA
=matches up to form complementary pairs
=ensure correct amino acid is brought to the polypeptide in the correct order

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16
Q

what is the function of mRNA

A

-made un the nucleus via transcription of DNA
-exists via a nuclear pore to enter the cytoplasm
-used by ribosomes as template for protein synthesis
-sequence of codons determines sequence of amino acids in primary structure of polypeptide

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17
Q

what is the function of tRNA

A

=anticodon complementary to mRNA codon
=brings the correct amino acid for that codon
=facilitates the peptide bond to join the amino acids into a polypeptide

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18
Q

what happens during transcription

A

-DNA helicase breaks H bonds to expose nucleotides
-free nucleotide pair up with the complementary bases on template strand
-RNA polymerase moves along one strand (template strand) to join the nucleotides
-forms pre-mRNA
-DNA polymerase rejoins hydrogen bonds after RNA polymerase passes by
-only 12 of DNA base pair are exposed at any one time
-terminator sequence detaches RNA polymerase

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19
Q

what happens during translation

A

-mRNA is attracted to the ribosome
-attaches at the start codon
-moves along ‘reading’ codons
-tRNA attached to amino acid matches to complementary base strand
-temporarily bonds to mRNA , 2 bond at any one time
-peptide bond forms between 2 amino acids
-bond between tRNA and amino acid breaks and tRNA leaves empty
-ATP needed for peptide bonds to form between amino acids
-ATP needed to form bonds between tRNA and amino acid
-ribosome moves along moleculeof mRNA until it reaches a stop codon
-detaches then repeates process if necessary
-can be more than one ribosome
-each ribosome creates separate polypeptide chains
-created primary structure

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20
Q

what are the two causes of genetic mutation?

A

spontaneous
-1 or 2 per 100,000 genes per generation
-varies between species
-no outside influence

mutagenic agent
(outside factors that can increase the basic mutation rate**
-high energy ionisation radiation, disrupts DNA structure
-chemicals, niitrogen diocide interferes with transcription, benzopyrene, inactivates a tumour-suppressor gene and increases likelihood of cancer

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21
Q

what are the different types of genetic mutation

A

substitution
deletion
addition
duplication
inversion
translocation

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21
Q

what is substitution and its after effects?

A

where one base is substituted and swapped for another base

effects:
-codes for same amino acid= no effect (degenerate code)
-codes for different amino acid that has no structural role= not much problem
-codes for different amino acid that has a structural role= could affect tertiary structure
-create stop codon= large difference in polypeptide

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22
Q

what is deletion and its after effects?

A

a base on DNA that has been removed causes the rest to move along and join up leaving no gap (frame shift)

effets:
-frame shift= codons after mutation shifted and could code for all different amino acids
-could form non-functional protein which may affect phenotype
-deletion at start= every codon altered along gene= significant impact
-deletion at end= some codons altered, protein may shift

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22
Q

what is addition and its after effects?

A

another base will be added to pairing strand= frame shift

effects:
-single/double additon= frame shift
-no frame shift= different polypeptide formed but may still function depending on how much/where it was added

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23
what is duplication and its after effects?
part of DNA molecule has been copied/ duplicated effects: -any number of bases can be duplicated so if not a multiple of 3 then frame shift occurs -if 1 amino acid gets repeated in primary structure of polypeptide it is likely to still function -more duplication= greater impact
24
what is inversion and its after effects?
part of DNA structure has flipped around and re-attached itself effects: -may have no effect (degenerate code) -may only affect one or two amino acids -may from stop codon-high impact
25
what is translocation and its after effects?
part of 1 gene is removed and stuck into another gene, happens between non-homologous chromosomes (dont have same pair or same gene) effect: -significant effects on gene expression -cancers more likely -reduced fertility
26
what is polyploidy and non-disjunction and their effects?
polyploidy= organisms that have an ectra set of chromosomes, mostly in plants non-disjunction= pairs fail to separate in meiosis giving the gamete one too many or one too little, if this gamete takes part in fertilisation a child may be born with turner's syndrome or down syndrome effects: -genetic diversity for natural selection and speciation -less well suited to environment -cancer
29
what is genetic diversity
the number of different alleles in a population
30
what is a gene pool
the collection of all genes and alleles in a population
31
what is allele frequency
the proportion of organisms within the population carrying a particular gene
32
what is natural selection
the process that leads to evolution within a population
33
what is the process of natural selection
-random mutations occur within a population -intruduces genetic variation within a population -provides organism with an advantage -new allele provides a reproductive selective advantage, individual with allele is more likely to reproduce and pass the allele onto offspring -over manhy generations there will be an increase in theb frequency of this allele within the population
34
what is stabilising selection
the middle trait has the selective advantage and therefore continues to be the most frequent in the population
35
what is an example of stabilising selection
HUMAN BIRTH WEIGHT -a middling bith weight is the selective advantage as extremely low birth weigths may be disadvangtageous to survival due to undervelopment of the baby and an extremely large birth weifght may lead to complications at birth
36
what is directional selection
when one of the extreme traits has the selective advantage
37
what is an example of directional selection
ANTIBIOTIC RESISTANCE -random mutation creates an allele that provides bacteria in a population resistance to an antibiotic, those with the resistant allele will survive others will die
38
what is a genetic bottleneck
an event that causes a big reduction in a population, reducing the amount of different alleles in the gene pool and so reduces genetic diversity
39
why is genetic diversity important
no genetic diversity= might not be able to adapt to a change in an environment and the whole population could be wiped out by a single event
40
describe how the production pf mRNA in a eukaryotic cell is different from the production of mRNA in a prokaryotic cell
pre-mRNA produced in eukaryotic cells whereas mRNA is produces directly in prokaryotic cells as genes in prokaryotic cells dont contain introns so no splicing in prokaryotic cells
41
What are the 3 domains
Eukarya Bacteria Archae
42
43
describe the role of ATP, tRNA and ribosomes in translation
ATP hydrolysis of ATP to ADP + Pi releases energy amino acids join to tRNAs and peptide bonds from between amino acids tRNA attaches to / transports a specific amino acid in relation to its anticodon tRNA anticodon complementary base pairs to mRNA codon, forming hydrogen bonds 2 tRNAs bring amino acids together so peptide bond can form Ribosomes mRNA binds to ribosome, with space for 2 codons allows tRNA with anticodons to bind catalyses formation of peptide bond between amino acids moves along
44
what is a gene mutation
a change in a base sequence of DNA on chromosomes can arise spontaneously during DNA replication
45
what is a mutagenic agent
a factor that increases rate of genetic mutation e.g UV
46
how can a mutation lead to the production of a non-functional protein or enzyme
-change sequences of base triplets in DNA so changes sequences of codons on mRNA -so changes sequence of amino acids in the polypeptide -so changes position of hydrogen/ ionic/ disulphide bonds between amino acids -so changes protein tertiary structure of protein -enzymes- active site changes shape so substrate cant bind, enzyme-substrate complex cant form
47
explain possible effects of a substitution mutation
base/nucleotide in DNA replaced by a different base/nucleotide changes one triplet so changes one mRNA codon one amino acid in polypeptide changes -tertiary structure may chage if position of hydrogen/ionic/ disulphide bonds change or amino acid doesnt change - due to degenerate nature of genetic code or if mutation is in an intron
48
explain the possible effects of a substitution mutation
one nucleotide/base removed from DNA sequence changes sequence of DNA triplets from point of mutation (frameshift) changes sequence of amino acids in primary structure of polypeptide changes position of hydrogen/ ionic/ disulphide bonds in tertiary structure of protein chnages tertiary structure of protein
49
what is a diploid cell
has 2 complete sets of chromosomes, represented as 2n
50
what is a haploid cell
has a single set of unpaired chromosomes, represented as n
51
what are homologous chromosomes
a pair of chromosomes, one maternal and one paternal, that have the same gene loci and therefore determine the same features
52
describe how a cell divides by meiosis
interphase- DNA replicates, 2 copies of each chromosome, joined by a centromere **meiosis I** (first nuclear division) separates homologous chromosomes -chromosomes arrange into homologous pairs -crossing pver between homologous chromsomes -**independent segregation** of homologous chromsomes **meiosis II** (second nuclear division) separates chromatids
53
why is the number of chromosomes halved during meiosis
homologous chromosomes are separated during meiosis I
54
how does crossing over creates genetic variation
homologous pairs of chromosomes associate point of contact between non-sister chromatids forms alleles / equal lengths of non-sister chromatids exchanged between chromosomes creating new combinations of maternal and paternal alleles on chromosomes
55
how does independent segregation create genetic variation
homologous pairs randomlhy align at equator- so random which chromosome from each pair goes into each daughter cell creating different combinatio0ns of maternal and paternal chromosomes
56
other than mutation and meiosis, explain how genetic variation within a species is increases
random fertilisation/ fusion of gametes creating new allele combinations/ new maternal and paternal chromosome combinations
57
explain the different outcomes of mitosis and meiosis
mitosis produces 2 daughter calls, meiosis produces 4 daughter cells as there is one division in mitosis, whereas 2 divisions in meiosis mitosis maintains the chromosome number as homologous chromomsomes separate in meiosis but not mitosis mitosis produces genetically idetical daughter cells whereas mitosis produces genetically varied daughter cells as crossing over and independent segregation happen in meiosis but not mitosis
58
explain the importance of meiosis
- two divisions creates haploid gametes (halves number of chromosomes) -so diploid number is restored at fertilisation - chromosome number maintained between generations - independent segregation and crossing over creates genetic variation
59
describe how mutations in the number of chromosomes arise
spontaneously by chromosomes non-disjunction during meiosis homologous chromosomes or sister chromatids fail to seperate during meiosis so gametes have an extra copy of a particular chromosome and others have none
60
how can the number of possible combinations of chromosomes in daughter cells following meiosis be calculated
2^n n= number of pairs of homologous chromosomes
61
how can the number of possible combinations of chromosomes following random fertilisation of two gametes be calculated
(2^n)^2 n=number of pairs of homologous chromosomes
62
what is genetic diversity
number of different aleles of genes in a population
63
what are alleles and how do they arise
variations of a particular gene (same locus) - different DNA base sequence arise by mutation
64
what is a population
a group of interbreeding individuals of the same species
65
explain the importance of genetic diversity
enables natural selection to occue in certain enviornments, a new allele of a gene might benefit its possessor giving possessor a selective advantage, increased reproductive success and chances of survival
66
what is evolution
change in allele frequency over many generations in a population occuring through the process of natural selection
67
explain natural selectiom
random gene mutations can result in new alleles of a agen in certain environmkents the new allele might benefit its possessor and organism has a selective advantage possessors are more likely to survive and have increased reporoductive success advanjtageous allele is inherited by members of the nect generation over many generations allele increases in frequency in popualtion
68
explain directional selection
-organisms with an extreme variation of a trait have a selective advantage. -there is usually a change in environment -increases frequency of organisms with / alleles for extreme trait -normal distribution curve shifts towards extreme trait example: antibiotic resistance in bacteria
69
explain stabilising selection
-organisms with an average / modal variation of a trait have a selective advantage -there is no change in environment, it usually remains stable -there is an increased frequency of organisms with / alleles for average trait -normal distribution curve similar, less variation around the mean example: human birth weight
70
what are examples of aseptic techniques that could be used to investigate the effect of antimocrobial substances on microbial growth
wash hands with **soap** / **disinfect** surfaces which kills **microbes** / prevents **contamination** **sterilise pipette** which kills microbes / prevents contamination **flame neck** of bottle of bacteria to kill microbes / prevent contaminations **bunsen burner** close to equipment - upward current of air draws air- borne microbes away to prevent contamination lift lid of petri dish slightly - **prevent entry** of microbes/ **contamination**
71
describe a method to investigate the effect of antimocrobial substances on microbial growth
1. Prepare area using aseptic techniques 2. use a sterile pipette to transfer bacteria from broth to agar plate using aseptic techniques 3. use a sterile spreader to evenly spread bacteria over agar plate 4. use sterile forceps to place same suze discs that have been soaked in differfent types of antimicrobials for same length of time, onto agar plate at equal distance 5. lightly tape lid onto plate, invert and incubate at 25 ^C for 48 hours 6. measure diameter of inhibiton zone around each disc and calculate area using (pi x r^2)
72
why is it important to maintain a pure culture of bacteria
- bacteria may outcompete bacteria being investigated - or could be harmful to humans
73
why hold lid with two pieces of tape instead of sealing it completely
- allows oxygen in preventing growth of anaerobic bacteria - which are more likely to be pathogenic / harmful to humans
74
why use a paper disc with no antimicrobial agent
-acts as a control - ensuring antimicrobial prevented growth, not paper disc
75
why incubate upside down
condensation drips onto lid rather than surface of agar
76
what if inhibition zones are irregular
repeat readings in different positions, calculate a mean
77
why incubate at 25^C or less
below human body temo to prevent growth of pathogens
78
explain the presence and absence of clear zones
clearn zones = antimicrobial diffuses out of disc into agar, killing / inhibiting growth of bacteria large clear zones= more bacteria killed = more effective antimicrobial no clear zones = if antibiotic used, bacteria may be resistant or antibiotic may not be effective agaisnt that specific bacteria
79
what is a species
a group of organisms that can interbreeed to produce fertile offspring
80
suggest why 2 different species are unable to produce fertile offspring
-different species have **different chromosome numbers** = offspring may have **odd chromosome number** -**homologous pairs** cannot form = **meiosis** cannot occur to produce gametes
81
explain why courtship behaviour is a necessary percusor to successful mating
- allows recognision of members of the same species so fertile offspring produced - allows recognition / attraction of opposite sex - stimulates / synchronises mating - indicates sexual maturity / fertility - establishes a pair bond to raise young
82
name the hierachy of classification
domain kingdom phylum class order famiky genus species
83
suggest an advantage of binomial naming
universal so no confusion as many organisms have more than one common name
84
describe two advances that have helped to clarify evolutionary relationships between organisms
advances in genome sequencing- allowing comparison of DNA base sequences -more differences in DNA base sequences so more distantly relagted - as mutations build up over time advances in immunology- allowing comparison of protein tertiary structure -higher amount of protein from one species binds to antibody against the same protein from another species so more closely related - as indicates a similar amino acid sequence and tertiary structure - so less time for mutations to build up
85
what is biodiversity
- variety of living organisms - can relate to a range of habitatas, from a small local habitat to the earth
86
what is a community
all populations of different species that live in an area
87
what is species richness
a measure of the number of different species in a community
88
what does an index of diversity do
describe the relatioship between -the number of species in a community -the number of individuals in each species
89
suggest why index of diversity is more useful than species richnes
-takes into account number of individuals in each sopecies -takes into accoundt that some species may be present in small or high numbers
90
what is the formula for index of diversity?
d = N(N-1) / thesumof n(n-1)
91
how can index of diversity values be interpreted
high value - many species present (**High species richness**) and species evenly represented low value - habitat dominated by one/ a few species
92
explain how some farming techniques reduce biodiversity
removal of **woodland** and **hedgerows** - reduces variety of plants - fewer habitats - less variety of food sources monoculture (growing one type of crop) - reduces variety of plants - fewer habitats - less variety of food sources use of herbicides to kill weeds - reduces variety of plants - fewer habitats - less variety of food sources use of pesticides to kill pests - predator population of pest decreases
93
explain the balance between conservation and farming
conservation required to increase biodiversity when implemented on farms, yields can be reduced, reducing profiit / income for farmers to offset loss, financial incentives / grants are offered
94
give examples of how biodiversity can be increased in areas of agriculture
- reintroduction of field margins and hedgerows - reduce use of pesticides - growing different crops in the same area - use of crop rotation of nitrogen fixing crop instead of fertilisers
95
how can genetic diversity within or between species be measured?
- comparing frequence of measurable or observable characteristics - comparing base sequence of DNA - comparing base sequence of mRNA - comparing amino acid sequence of a specific protein encoded by DNA and mRNA
96
explain how comparing DNA, mRNA and amino acid sequences can indictae relationships between organisms within a species and between species
- more differences in sequences = earlier common ancestor / more distantly related - as mutations build up over time - more mutations cause more changes in amino acid sequences
97
explain the change in methods of investigating genetic diversity over time
early estimates made by inferring DNA differences from measurble or observable characteristics -many coded for by more than one gene - difficult to distinguish one from another - many influences by environment - deifferences due to environment not genes gene technolobgies allowed this to be replaced by direct investigation of DNA sequences
98
explain the key considerations in quantitative investigations of variation within a species
-collect data from random samples - removes **bias** - use large sample sizes - **representative** of whole population - ethical samplig - must not harm organism / allow release unchanges calclate a mean value of collected data and standard deviation of that mean -S.D shows spread of values about the mean - **higher S.D = higher variation** -if standard deviation overlap, causing values of two sets of data to be shared, any difference between the two may be **due to chance** / **not significant** -use statistical test - analyse whether there is a **significant** differennce between populations
99
how does the binomial system work
Genus at the start, species at the end Genus starts with **capital letter** whole name **underlined** if written, italics if typed
100
What is the meaning of hierarchy
Groups within groups with no overlap between the groups
101
explain the role of independent segregation in meiosis
to provide genetic variation allows different combinations of maternal and paternal chromosomes
102
what is the difference between species richness and index of diversity
species richness only measures the number of species

Biology (8 decks)

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