4. Genetics, Variation & Interdependence Flashcards
1
Q
What is an ecosystem?
A
An ecosystem is a self sustaining system in which organisms interact with each other (Biotic factors) and their physical environment (Abiotic factors)
2
Q
What are histones and their function?
A
They are proteins that DNA is wound around so it can fit into the nucleus, it supports the DNA to coil up repeatedly into compact chromosome.
3
Q
What is the name of the process used by prokaryotic cells to condese DNA to fit in the cell
A
Supercoiling
4
Q
When are introns removed from DNA sequence in eukaryotes?
A
During protein synthesis
5
Q
Give 3 way DNA in prokaryotic cells are different to eukaryotic cells
A
Prokaryotic are short and circular whereas eukaryotic is long
No introns
Not associated with Justine
6
Q
What is used to code for an amino acid?
A
A codon aka. triplet (sequence of 3 bases)
7
Q
What is a gene?
A
A sequence of DNA base that codes for either a polypeptide or functional RNA
8
Q
What is functional RNA? with examples x
A
RNA molecules other than mRNA which perform special tasks during protein synthesis - tRNA & rRNA
9
Q
What do genes that don’t code for a polypeptide code for instead?
A
Functional RNA
10
Q
What word fits this description - The full range of proteins that the cells is able to produce.
A
Protenome
11
Q
Define genome
A
The complete set of genes in a cell
12
Q
Describe what introns and exons are
A
They are base sequence of a gene, Exons code for amino acid sequences and Introns dont
13
Q
What are pairs of matching chromosmes called?
A
Homologous pairs
14
Q
Where will alleles coding for the same charcteristic be found on each chromosome in a homologous pair?
A
At the smae fixed position (Locus) on each chromosome
15
Q
Describe the the two main stages of protein synthesis
A
Transcription- Where DNA is copied into a molecule called mRNA
Translation- Where mRNA joins with an organelle called a ribosome and the code it carries is used to synthesize a protein
16
Q
What is RNA ?
A
A single polynuclotide strand that contains Uracil instead of thymine
17
Q
When is mRNA made and what is its function?
A
It is made during transcription and its function is to carry the genetic code from the DNA to the ribosomes
18
Q
What are 3 adjacent bases called in mRNA ?
A
Codons or triplets
19
Q
Describe the function of tRNA and its structure
A
tRNA is involved in translation, it carries the amino acids that are used to make proteins to the ribosomes. It is a single polynucleotide strand that is folded into a clover shape because hydrogen bonds between specific bases hold it in their position. It has a specific sequence of 3 bases at one end called an anticodon. It has an amino binding site at the other end
20
Q
Describe the nature of the gentic code (3)
A
Degenerate- an amino acid can be coded for by more than one base triplet
Non overlapping- Adjacent bases do not overlap
Universal- The same triplets code for the same amino acids in all organisms
21
Q
What is the function of triplets
A
To CODE for amino acids
22
Q
What is a gene?
A
A gene is a sequence of DNA (nucleotide) bases that codes for a polypeptide or functional RNA
23
Q
What is an exon?
A
A base squence of a gene coding for amino acid sequences
24
Q
Describe the two main stages of protein synthesis
A
Transcription- mRNA is produced from DNA in the nucleus
Translation- Polypeptides produced from the sequence of codons carried by mRNA at ribosomes
25
Compare and contrast the structure of tRNA and mRNA
-They are both single polynucleotide strands
tRNA is folded into a clover leaf shape whereas mRNA is linear
-tRNA has hydrogen bonds between paired bases mRNA dosent
-tRNA has an anticodon, mRNA has a codon
-tRNA has an amino binding site, mRNA dosent
-tRNA is a shorted fixed length whereas mRNA is a longer, variable length
26
Describe how mRNA is formed by transcription in eukaryotic cells
Hydrogen bonds between DNA bases break. One DNA strand is used as a template. Free RNA nuclotides align next to their complementry bases on the template strand. Uracil used in place of thymine. RNA polymerase joins adjacent RNA nuclotides. This forms phosphodiester bonds via condensation reactions. pre- mRNA is formed and dpliced to remove introns forming mature mRNA. Uses ATP as energy for the reaction
27
Describe how production of mRNA in eukaryotic cells is different from prokaryotic.
Pre-mRNA produces in E cells whereas mRNA directly produced in P cells
Genes in P cells dont contain introns so no splicing involved
28
Describe how translation leads to the production of a polypeptide
mRNA attaches to a ribosome nd the ribosome moves to start a codon. tRNA brings a specific amino acid, the tRNA anticodon binds to complementary mRNA codon. THe ribosome moves along to the next codon and another tRNA binds so 2 amino acids can be joined via condensation reaction to form a peptide bond. (uses energy from hydrolysis of ATP) tRNA released after amino acid joined polypeptide. Ribosme moves along mRNA to form the polypeptide until a stop codon is reached.
29
Describe the role of ATP in translation.
Hydrolyis of ATP to ADP an pi releases energy so amino acids join to tRNAs and peptide bonds form between amino acids
30
Describe the role of tRNA in translation
Attaches to/ transports a specific amino acid
tRNA anticodon complemetary base pairs to mRNA codon forming hydrogen bonds
2 tRNA bring amino acid so peptide bond can form
31
Describe the role of ribosmoes in translation
mRNA binds to the ribosome, with space for 2 codons
Allows tRNA with anticodons to bind
CAtalyses formation of peptide bond between amino acids
Moves along mRNA to the next codon
32
Why can you not say tRNA brings amino acids in an exam?
You have to say it brings 'specific amino acids' to get the mark
33
What does RNA polymerase do in transcription?
Joins adjacent RNA nuclotides forming phosphodiester bonds
34
What is a gene mutation and when does it occur?
It is a change in the base sequence of DNA and can aruse spontaneoulsy during DNA replication
35
What is a mutagenic agent and give an example?
A factor that increases rate of gene mutation e.g UV light or alpha particles.
36
Explain how a mutation can lead to the production of a non functional enzyme/protein
A mutation can change sequence of base triplets in a gene so changes sequence of codons on mRNA. This changes amino acids in the polypeptide. The position of hydrogen/ionic/disulfide bond changes. Alters tertairy structure of protein changing the enzymes active site so substrate cant bind to dorm enzyme-substrate complex.
37
Explain the possible effects of a substitution mutation
Base/Nucleotide in DNA replaced by a different base/nuclotide
THis changes one triplet so changes on mRNA codon
One amino acid in polypeptide changes so tertiary structure might change if podition of H/I/D bond change or amino acid dosent change due to degenerate nature of genetic code or if the mutatuon is an intron
38
Explain the possible effects of a deletion mutation
One nucletotide/base removed from DNA sequence
This changes changes sequences of DNA triplets from point of mutation and changes the mRNA codons after point of mutation. This changes sequences of amino acids in primary structure of polypeptide. Changes position of H/I/D bonds in tertiary structure of protein. Changes tertiary stuctire of protein.
39
Describe the difference between between diploid and haploid cells
Diplod has 2 complete sets of chromosmes representd as 2n
Haplois has a single set of unpaired chromosmes presented n
40
Describe how a cell divide by meiosis
In interphase DNA replicates to make 2 copies of each chromosme (sister chromatids) joined tg by a centromere. Then we have Meiosis 1 which is the first nuclear division, this seperates homologus chromosmes as there is crossing over between homologus chromosmes leading to independent segregation of homologus chromosomes. Meisosi II is the second nuclear divisionwivh seperates chromatids
41
Explain why the number of chromosmes is halevd during meiosis
Homologous chromosomes are separated during meiosis I (first divison)
42
Explain how crossing over creates genetic variation
Homologus pairs of chromosmes form a bivalent. Chiasmata form which is a point of non contact between non sister chromatids. Alleles chromatids are exchanged between chromosmes. This creates new combinations of alleles ln chromosmes.
43
Explain how independent segregation creates genetic variation
Homologus pairs randomly align at the equator so random chromosomes from each apir get in the daughter cell, this creates different combinations of maternal and paternal chromosomes/ alleles in daughter cells.
44
Other than mutation and meiosis, how is genetic variation in a species increased>
Random fertilisation/ fusion of gametes and creating new alleles and chromosme combinations
45
Compare and explain the different outcomes of meiosos and mitosis
Mitosis produces 2 daughter cells whereas meiosis produces 4 daughter cells as there is 1 divison in mt and 2 in ms.
Mitosis maintains the chromosme no. so goes from diploid to diploid or haploid to haploid whereas in meiosis chromosome no. halves.
Meiosis produces genetically varied daughter cells wheraes mitosis produces identical cells
Crossing over and independent variation are only in meiosis.
46
Explain the importance of meiosis for reproduction
Two divisions create haploid hametes so diploid number is restored at fertilisation and chromosmes no. is matained between generations. In addition, independent segregation and crossing over creates genetic variation
47
How can you recognise where meiosis and mitosis occur in a life cycle?
Mitosis occurs between stages where chromosme numer is maintaines and meiosis occurs between stages where chromosome no. halves
48
Descibe how mutations in chromosmes can arise
Spontaneously by chromosome non-disjunction during meiosis
Homologous chromosomes or sister chromatids fail to seperate during meiosis so some gametes have an extra copy of a particular chromosme whilst others have none.
49
Suggest how the number of possible combinations of chromosomes in daughter cells following meiosis can be calculated
2n (n in squared position) where n = number of pairs of homologous chromosomes (half the diploid number)
50
Suggest how the number of possible combinations of chromosomes following random fertilisation of two gametes can be calculated
(2n)2 (small n and 2) where n = number of pairs of homologous chromosomes
51
What does crossing over do in meiosis?
Creates new combinations of maternal and paternal alleles on chromosomes
52
What is genetic diversity?
Number of different alleles of genes in a population
53
What are alleles and how do they arise?
Alleles arise by mutation and are variations of a particular gene that have same locus but different DNA base sequence
54
What is a population?
A group of interbreeding individuals of the same species
55
Explain the importance of genetic diversity
It enables natural selection to occur
New alleles or gene may benefit possesor
Change in the polypeptide coded for that positvely changes its properties
This gives possesor selective advantage by increasing chance of survival
56
What is evolution?
A change in allele frequency over many generations in a population that occurs throught the process of natural selection
57
List and explain the 5 priciples of natural selection in the evolution of populations
Mutation-Randon gene mutations result in new alleles of a gene
Advantage- In certain environments, new allele benefit possesor so organism has selective advantage
Reproductive success- Possesors more likely to survive and have increased reproductive succes
Inheritance-Advantage allele inherited by offspring
Allele frequency-Over many generations allele increases in frequency in population
58
Describe the 3 types of adaptations living things can develop
Anatomical- Structural/physical features that increase chance of survival
Physiological- Processes/ chemical reactions that increase chance of survival
Behavioural- Ways in which an organism acts that increase chance of survival
59
Explain the two types of selection with examples
Directional selection - Antibiotic resistance in bacteria- Organisms with an extreme variation of a trait have selective advantage that chages in environment. The curve moves towards extreme trait as there is an increased frequency of organisms for those w extreme trait
Stabilising selection-Human birth weight- Organisms with an average/modal variation of a trait and do not change in environment-increased frequency of organisms with alleles for avergae trait so distribution curve shows less variation around the mean
60
Explain how exposure to antibiotics is 'selection pressure'
Exposure to antibiotics is the selection pressure as it causes non-resistant bacteria to die and allowing resistant bacteria with the mutation to survive and reproduce.
61
Why is saying antibiotic resistance is when bacteria becomes immune wrong?
Bacteria dont have immune systems, they become resistant to the effect not 'immune'
62
Give and explain 5 aspetic techniques that can be used to investigate microbial growth
-Wash hands with soap and disinfect surfaces to kill microbes and prevent contamination (KM & PC)
-Sterilise pipette to KM and PC
-Flame the neck of the bottle of bacteria to KM and PC
- Keep bunsen burner close as it causes upward current of air drawing airborne microbes away PC
-Lift lid of petri dish only slightly to minimeise entry of microbes and PC
63
Decribe a method to investigate the effect of antimicrobial substances on microbial growth
Prepare are using aspetic techniques. Use a sterile pipette to transfer bacteria from broth to agar plate. Use a sterile spreader to evently spread bacteria over agar plate. Use sterile forceps to place smae sized discs soakes in different trypes/conc of microbails for same length of time onto agar plate at equal distance. Ligltly tape lid not fully sealed and incubate at 25 " for 48hrs
Measure zone of inhibition around each disc and calculate area using formula
64
Why is it important to mantain a pure culture of bacteria when investiating?
BActeria may outcompete bacteria being tested making it more harmfuk
65
Why hold the lid with 2 peices of tape rather than seal completely?
Oxygen prevents groth of anaerobic bacteria which is more likely to be harmful to humans
66
Why is perti disk incubated upside down?
Condensation drips onto lid rather than surface of agar
67
Suggest what a student can do if their results for zone of inhibiton are irregular?
Repeat reading in different positions and calculate a mean
68
When investigating the effect of antimicrobials on microbial substances, why are high conc of antimicrobials not used?
More bacteria will be killed so clear zones may overlap
69
Why are the petri dishes incubated at 25 degrees or less?
It is below human body temp to prevent growth of pathogens
70
What is a locus?
The fixed position of a gene on a particular DNA molecule
71
How can genetic diversity be meausred within or between species?
Comapring frequenct of measurable/observable traits.
Comparing base sequence of DNA
Comparing base sequence of mRNA
Comparing amino acid sequence of a specific protein encoded by DNA and mRNA
72
Explain how comparing DNA, mRNA and amino acid sequences can indicate relationships between organisms within a species and between species
More differences in a sequence indicate more distantly related/ earlier common ancestor . As mutations build up over time, there are more chnages in amino acids sequences
73
Explain how over time methods of investigating gentic diversity have changed?
Estimates made by inferring DNA differences from measurable of observable characteristics, however many of these were influenced by the environment and not genes and also some gens coded for by more than one gene so it was difficukt to distinguish one from the other, but gene technology allowed this to be replaced by direct investigation of DNA sequences
74
What is a species?
A group of organisms that can interbreed to produce fertile offspring
75
Suggest why two different species are unable to produce fertile offspring
Different species have different chromosme numbes and their offspring may have odd chromosome numbers, therefore homologus pairs cannot form and meiosis cannot occur to produce gametes
76
Explain why courtship behaviour is a necessary precursor to succesful mating
I t allows recognition of memebers of the same species so fertiel offspring in produced, It allows attraction of opposite sex. It indicates sexual maturity & fertility. It also establishes a pair bond to raise young
77
Descibe a phylogenic classification system
Species are arranged into groups called taxa based on their evolutionary origins and relationships. It uses a hierachy where smaller groups are [laced within larger groups and there is no overlap between groups
78
Name the taxa in the hierachy of classification
Domain (largest / broadest) → kingdom → phylum → class → order → family → genus → species (smallest)
79
Name the taxa in the hierachy of classification
Domain (largest / broadest) → kingdom → phylum → class → order → family → genus → species (smallest)
80
How is each species universally identified?
A binomial consisting of the name of its genus and species.
81
Suggest an advantage of binomial naming
Universal so no confusion as many organisms have more than one common name
82
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 → more distantly related / earlier common ancestor
● As mutations (change in DNA base sequences) build up over time
2. Advances in immunology → allowing comparison of protein tertiary structure (eg. albumin)
● Higher amount of protein from one species binds to antibody against the same protein from
another species → more closely related / more recent common ancestor
● As indicates a similar amino acid sequence and tertiary structure
● So less time for mutations to build up
83
What is biodiversity?
A variety of living organisms, can relate to a change of habitats from a small local habitat to the Earth
84
What is a community?
All population of different species that live in an area
85
What is species richness?
A measure of the number of different species in a community
86
What does an index of diversity do?
Describe the relationship between the number of species in a community and the individuals in each population
87
Why is index of diversity more useful than species richness?
It also takes account the number of individuals in each species so it therefore takes into account that some species may be present in small or high number
88
Describe how index of diversity values can be interpreted
High → many species present (high species richness) and species evenly represented
Low → habitat dominated by one / a few species
89
Explain how some farming techniques reduce biodiversity
Removal of woodlands/ monoculture/ using herbicides to kill weeds reduces variety of plants so there a fewer habitats and less variety of food sources. In addition use of pesticides to kill pests reduces predator population of the pest
90
Explain the balance between conservation and farming
Conservation required to increase biodiversity, but when implemented on farms, yields can be reduced, reducing profit / income for farmers Eg. by reducing land area for crop growth, increasing competition, increasing pest population
● To offset loss, financial incentives / grants are offered
91
Give examples of how biodiversity can be increased in areas of agriculture
Reintroduction of field margins and hedgerows (where farmers only grow one type of crop)
Reduce use of pesticides
Growing different crops in the same area (intercropping)
Using crop rotation of nitrogen fixing crops instead of fertilisers
92
What is the students T test used for?
Comparing means of data between populations (similarities or differences)
93
Why are there zones of inhibition
Because antibiotics diffuse out of paper onto the agar
