4: Genetic information and Variation Flashcards

Question

What are the steps of translation?

Answer 1

**1. The mRNA attaches to a ribosome.** - Molecules of tRNA carry amino acids to the mRNA sequence. - The bond between the tRNA molecule and the amino acid is formed using ATP. **2.The first tRNA anticodon binds to a complementary codon on the mRNA.** - Codons and anticodons will form hydrogen bonds with one another. - The first tRNA molecule will always bind to the same codon. - This is called the start codon. In humans it is the sequence AUG. **3.A second tRNA anticodon will attach to the next codon on the mRNA.** - This will occur using the same mechanism as the first tRNA molecule. **4.A peptide bond will form between the neighboring amino acids that are being held by the tRNA molecules.** - The first tRNA molecule will then unbind, leaving its amino acid behind. **5.This cycle will continue, producing a primary chain of amino acids.** - This is the process of elongation. **6.Eventually, the complex will reach a stop codon.** - A stop codon does not code for an amino acid. - Instead it signals the protein to dissociate from the ribosome and move into a different region of the cell.

Answer 2

- a change in genetic material/ nucleic acid base - if a mutation occurs in a gene, the sequence of amino acids it codes for and the protein formed could be altered - if the base that has been changed still codes for the same amino acid, the protein that is coded for does not change, making it a **neutral mutation**

Answer 3

- **GENE:** substitution, deletion, insertion - **CHROMOSOMAL:** caused by errors in cell division, inversion - duplication - silent - neutral

Answer 4

This means that the DNA is misread during replication, causing problems with making specific proteins essential to that organism. Mutagenic agents can cause an INCREASE in the rate of mutations. e.g. - Ultraviolet Radiation causing skin cancer - Cigarette smoke (carcinogen chemicals) causing lung cancer - Viruses used in gene therapy (good mutations) - ionising radiation, chemicals and viruses | occur simultaneously

Answer 5

**one base is replaced with another** This means that the sequence for the amino acids has changed which means the sequence will either NOT make the protein the original sequence coded for, make a FAULTY protein, a completely DIFFERENT protein or in most cases, NO protein at all!

Answer 6

**a base is deleted from the sequence** This means that the sequence for the amino acids has changed which means the sequence will either NOT make the protein the original sequence coded for, make a FAULTY protein, a completely DIFFERENT protein or in most cases, NO protein at all!

Answer 7

**due to the genetic code being “degenerate”(some amino acids are coded for by more than one DNA triplet code.)** eg. TAT / TAC - both code for the amino acid Tyrosine (substitution) However, deletions will always lead to a change in base numbers present, which leads to a shift in the base triplets.This is called a **FRAMESHIFT**

Answer 8

A mutation that occurs when a nucleotide (with a new base) is randomly inserted into the DNA. - this changes the amino acid that would have been coded for by the original base triplet, as it creates a new, different triplet of bases - an insertion mutation also has a knock-on effect by changing the triplets (groups of three bases) further on in the DNA sequence **(frameshift mutation)** - This may dramatically change the amino acid sequence produced from this gene and therefore the ability of the polypeptide to function

Answer 9

chromosome mutations are caused by errors in cell division/ meiosis - In humans, when meiosis works properly then 4 gametes are produced with 23 chromosomes. - However, when things go wrong with meiosis , the cells produced contain variations in the numbers of whole chromosomes or pairs of chromosomes. - this is known as **non-disjunction** when the chromosomes fail to separate properly. - Chromosome mutations lead to inherited conditions because the error is present in the gametes. - Eg. Downs Syndrome (an extra 21 chromosome)

Answer 10

during crossing over in meiosis, the gene is cut in two places and then inserts “backwards” at 180 °. - This means a large portion of the gene is backwards, affecting a large proportion of amino acids, meaning non-functional protein could be coded for.

Answer 11

when awhole gene or section of a gene is duplicated so that two copies of the gene/section appear on the same chromosome - The original version of the gene remains intact and therefore the mutation is not harmful - Overtime, the second copy can undergo mutations which enable it to develop new functions - Duplication mutations are an important source of evolutionary change - Alpha, beta and gamma haemoglobin genes evolved due to duplication mutations | CAN BE ADVANTAGEOUS

Answer 12

A form of point mutation resulting in a codon that codes for the same or a different amino acid but without any functional change in the protein product

Answer 13

- Mutations have been responsible for antibiotic resistance in bacteria, sickle cell resistance to malaria, and immunity to HIV, among others. - An Ecuadorian community with the rare gene mutation known as Laron syndrome are protected against cancer and diabetes.

Answer 14

- Many other diseases, such as cancer, diabetes and asthma, are linked to genetic mutations. - Genetic disorders such as Down’s Syndrome, Prader-willi syndrome, Cystic fibrosis are all caused by chromosomal mutations or gene mutations.

Answer 15

the total no. of different alleles in a population, making it more or less likely that the individuals react to environmental change.

Answer 16

**population-** a group of individuals of te same species that live in the same place and can interbreed **species-** one or more population with the same genes that can produce fertile offspring

Answer 17

- environmental factors that affect the chance of survival of an organism - selection pressures increase the chance of individuals with a specific phenotype surviving/ reproducing over others

Answer 18

- individuals with favoured phenotypes have a higher fitness (higher ability to survive and pass on good alleles to offspring). - higher fitness= better suited to the environment

Answer 19

- a population with a large gene pool/ high genetic diversity has a strong ability to adapt to environmental change - if a population has a small gene pool/ very low genetic diversity then they are less able to adapt to environmental changes and are vulnerable to extinction

Answer 20

- large gene pool - high genetic diversity - more alleles - larger variety of phenotypes - better suited phenotype - positive selection pressure - more likely of surviving with advantageous characteristic - pass on characteristic to offspring

Answer 21

the mechanism of evolution where environmental features apply a selctive force/ pressure and where individuals with advantageous traits are more likely to survive and reproduce, passing on those traits to their offspring.

Answer 22

- **Charles Darwin** (1835) - visited Galapagos Islands - different mutations occur causing variation within specues - published 'the origin of species' in 1859 - the re-examining of the natural selection with modern day knowledge (e.g. genetics) is called **Neo-Darwinism**

Answer 23

1. random genetic mutations can create multiple alleles of genes within a population (gene pool) 2. genetic variation within a population createsn intraspecific competition 3. individuals with particular alleles are better able to face challenges imposed by the environment 4. individuals possessing alleles which code for advantageous characteristics will be more likely to survive as these characteristics may enable them ti better ibtain resources, grow more rapidly or have a greater response against disease 5. individuals that survive are more likely to reproduce and pass on the advantageous allele to the next generation 6. therefore, over time, the frequency of the advantageous allele increases in the population

Answer 24

- a type of cell division that produes 4 genetically varied haploid daughter cells - 2 parts (meiosis 1 and 2) - meisosis 1 has interphase, meiosis 2 doesnt - I (G1,S,G2),P,M,A,T

Answer 25

1. **Interphase** chromosomes present as chromatin, DNA replicates and new organelles/ macromolecules are manufactured ready for cell division 2. **Prophase I** chromosomes condense and become shorter. homologous chromosomes come to lie close together in synapsis (paired chromosomes are called bivalents). identical pairs of sister chromatids are the result of DNA replication that occur during interphase. each group of 4 methods is a tetrad held together by centromere chiasma form (2 chromatids crossed) over to crossover and exchange genetic material causing Gene variation 3. **Metaphase I** bivalents (tetrads) become aligned in the center of the cell and are attached to spindle fibers. the orientation of each pair of chromosomes on the spindle is a random event and provide a second source of genetic variation 4. **Anaphase I** Spindle activity separates homologous chromosome pairs and the homologous pairs of chromosomes migrates to opposite cell poles 5. **Telophase I** spindle fibres disintegrate and the nuclear membranes reform in animal cells membrane constricts down the middle of the cell and two identical daughter cells are formed in cytokinesis each daughter cell has one member from each homologous chromosome pair

Answer 26

1. **Prophase II** 2 cells have one member from each pair of homologous chromosomes and are diploid cells during late prophase 2 the nuclear membranes disintegrate again and spindle fibers begin to form 2. **Metaphase II** chromosomes (each with two sister chromatids) line up independently along the equator of the spindle meiosis 2 separates the sister chromatids and to distribute them into the four products of meiosis 3. **Anaphase II** centrioles replicate allowing chromatids to repel each other spindle activity pulls chromatids to opposite cell poles making them chromosome 4. **Telophase II** in animal cells there's a constriction across the middle and each cell then divides into two this results in four haploid daughter cells each possessing one member from each pair of the original chromosomes as a result 4 genetically different cells are produced

Answer 27

- CROSSING OVER- during prophase one of meiosis the non-sister chromatids are so closely associated they become intertwined forming positions of overlap (chiasmata) At these positions the non-sister chromatids break and exchange sections of genetic material - INDEPENDENT ASSORTMENT/ SEGREGATION Chromosomes are halved separating them making it completely random which chromosome from each pair ends up in which daughter cell at the end of meiosis - ORIENTATION OF CHROMOSOMES ON SPINDLE IN METAPHASE

Answer 28

S- DNA replicate so DNA content doubles M1- by the end of M1 homologous chromosome separated into different cells M2- by the end of M2 the DNA content is half of the original cell

Answer 29

**MITOSIS:** - Produces cells with the same number of chromosomes as the parent cell (diploid) - Genetically identical daughter cells - Produces two daughter cells - One division - No pairing or separating of homologous chromosomes - No independent segregation or crossing over of chromosomes **MEIOSIS:** - Produces cells with half the number of chromosomes as the parent cell (haploid) - Genetically different daughter cells - Producers four daughter cells - Two divisions - There is pairing and separating of homologous chromosomes - There is Independence segregation and crossing over of chromosome

Answer 30

- physiological- to do with chemical reactions of the body - behavioural- animal tendencies and behaviour - anatomical- physical/ structural features

Answer 31

Natural selection may affect allele frequencies within populations in several different ways The types of selection that operate within populations are: - Stabilising Selection - Directional Selection For continuously varying characteristics, these selection methods modify their frequency distributions in different ways

Answer 32

a selective force that favours the phenotypes closest to the mean value of a trait. - Stabilising selection acts against the extremes within va range of phenotypic variation - This type of selection leads to a reduction in the range of variation within the population without any change in the mode - Stabilising selection operates in an unchanging environment to maintain the best adapted genotypes within the population

Answer 33

a selective force favouring individuals with an extreme trait and selects against phenotypes at other extremes. - Directional selection operates in changing environments and acts for or against extremes of phenotype within the variable population. - This type of selection leads to a reduction in the range of variation within the population, together with a progressive shift in the mode

Answer 34

**the arrangement of organisms into groups of various sizes on the basis of shared features.** **taxonomy**- a form of classification that focuses on physical similarities between different species,for ease of naming and identification. **phylogeny-** the classification of organisms by these evolutionary relationships, so that every group shares a common ancestor.

Answer 35

**Taxonomy –** the science of classification (naming and organising into groups) – 8 levels of groups – called taxa, each group is a taxon –Arranged as hierarchy (organised into levels) –No overlap in levels –3 Domains – Eukaryota, Bacteria & Archaea –As you move down the hierarchy there are more groups but fewer organisms in each group –Ends in species – group of similar organisms that reproduce to give fertile offspring DOMAIN, KINGDOM, PHYLUM, CLASS, ORDER, FAMILY, GENUS, SPECIES

Answer 36

**Binomial nomenclature** – naming system used for classification (all organisms are give one internationally acepted name in Latin *Genus species* (genus with capital and all underlined or in italics)

Answer 37

**artificial classification-** classes organisms based on analogous characteristics where they have the same function we're not the same evolutionary origins. **phylogenetic classification-** Classifies groups based on shared features derived from their ancestors and arranges the groups into a hierarchy with no overlap

Answer 38

- pre-matics activities for stimulation, partner attraction and mating institution - acts carried out by organisms to attract a mate of the right species of the opposite sex - species specific (only members of the same species recognise each other, preventing inbreeding and causing more successful fertile offspring)

Answer 39

- females are often only receptive to mating for a short amount of time - this is when their eggs are ready for fertelisation - if females respond favourably to courtship, offspring are likely to be produced

Answer 40

- for species recognition - identification of a mate capable of breeding - to form a pair bond - insures stimulation and synchronisation of mating

Answer 41

- recognises members of their own species to ensure mating only occurs between the same species as only members of the same species to produce fertile offspring - identify a mate capable of breeding as both partners need to be sexually mature, fertile and receptive to mating - form a pair bond that will lead to successful mating/ raising offspring - synchronise mating so it takes place when there's maximum probability of the sperm and egg mating - become able to breed by bringing a member of the opposite sex into a physiological state allowing breeding to occur

Answer 42

- the more closely related the species, the more similar their courtship behaviour - same species have the same courtship behaviour | based on order and sequence of elements and moves

Answer 43

- **FIREFLIES-** give off pulses of light. The pattern of flashes is specific to each species. - **CRICKETS-** make sounds similar to morse code (the code is different for each species) - **MALE PEACOCKS-** show off their colourful tails, tail pattern only found in peacocks - **MALE BUTTERFLIES-** uses chemicals to attract females. only those of the correct species would respond.

Answer 44

the number and variety of living organisms in an area

Answer 45

**habitat-** a place where organisms live **species-** a group of similar organisms that are able to breed with each other and have fertile offspring. **population-** a group of organisms from the same species in a habitat **community-** all of the populations of the different species living in the same habaitat

Answer 46

- **species diversity-** the no. of different species and individuals in a community - **genetic diversity-** the variety of genes in a population of a species - **ecosystem diversity-** the whole range of different habitats on all scales

Answer 47

**species richness** (the no. of different species in a particular area at a time)

Answer 48

**d= N(N-1)/ ∈n(n-1)** N- total no. of organisms of all species d- index of diversity n- sum of no. of organisms of each species

Answer 49

- the higher the value, the greater the species diversity - calculating index of diversity is quantitative as it provides a no. that makes it easier to compare the variety in different habitats

Answer 50

- The species diversity can be used as a measure of health of an ecosystem - The **higher the species diversity index the more stable and ecosystem** is likely to be **Why?:** The more different species there are, the more likely some species will be able to tolerate a change in the environment

Answer 51

- Agriculture **reduces species diversity** - Natural ecosystems usually develop into complex communities with lots of different species - Ecosystems associated with agriculture are controlled by humans and are reduced to a few species

Answer 52

- Removing hedgerows - Overgrazing - Creating monocultures (replacing natural meadows with cereal crops) - Filling in ponds, draining wetland and marsh

Answer 53

- Use of pesticides & inorganic fertilisers - Effluent runoff of slurry (animal waste) into water - Not rotating crops/ lack of intercropping / growing two or more crops in the same space.

Answer 54

* **Maintain existing hedgerows at the most beneficial height and shape**. An A-shape provides better habitats than a rectangular one. * **Plant hedges rather than erect fences** as field boundaries. * **Maintain existing ponds** and where possible create new ones. * **Leave wet corners of fields** rather than draining them. * Plant native trees on land with a **low species diversity** rather than in species-rich areas. * **Reduce the use of pesticides** - use biological control where possible or genetically modified organisms that are resistant to pests. make food slightly more * Use organic, rather than inorganic, fertilisers. * **Use crop rotation** that includes a nitrogen-fixing crop, rather than fertilisers, to **improve soil fertility.** * Use **intercropping** rather than herbicides to control weeds and other pests. * Create natural meadows and use hay rather than grasses for silage. * Leave the cutting of verges and field edges until after flowering and when seeds have dispersed. * Introduce **conservation headlands** - areas at the edges of fields where pesticides are used restrictively so that wild flowers and is recognised that insects can breed.

Answer 55

- these practices will make food slightly more expensive to produce, - to encourage farmers there are a number of financial incentives from the Department for Environment, Food and Rural Affairs (DEFRA) and the European Union. - maintaining biodiversity is very important. - if biodiversity is reduced the global living system becomes increasingly unstable and we all rely on the global system for food and other resources.

Answer 56

- Traditionally, genetic diversity was measured by observing the characteristics of organisms. - This method is based on the fact that each observable characteristic is determined by a gene or genes (with environmental influences). - The variety within a characteristic depends on the number and variety of alleles of that gene (plus environmental influences).

Answer 57

- A large number of observable characteristics are coded for by more than one gene. - They are **polygenic**, meaning they are not discrete from one another but rather vary continuously. It is often difficult to distinguish one from another. - Characteristics can also be modified by the environment. Differences may therefore be the result of different environmental conditions rather than different alleles.

Answer 58

- Gene sequencing (or DNA sequencing) is the process of determining the exact order of nucleotide bases present in a gene, from a sample of DNA. - In these computerised systems, each nucleotide base can be tagged with a different coloured fluorescent dye -adenine (green), thymine (red), cytosine (blue) and guanine (yellow).

Answer 59

- We can measure the genetic diversity of a species by sampling of DNA sequence. Each coloured band the DNA of its members and sequencing it to produce a pattern of represents one of the four nucleotide bases. - Analysis of these patterns allows us to compare one species with another or one individual with another of the same species to determine how diverse they are.

Answer 60

- Mutations that occur during DNA replication alter the sequence of bases present in a gene - over time these differences accumulate. - As a result, we would expect species that are more closely related to show more similarity in their DNA base sequences than species that are more distantly related.

Answer 61

- The base sequences on mRNA are complementary to those of the strand of DNA from which they were made. - It follows that we can measure DNA diversity, and therefore genetic diversity, by comparing the base sequence of mRNA.

Answer 62

- The degree of similarity in the amino acid sequence of the same protein in two species will also reflect how closely related the two species are. - This can be done by counting either the number of similarities or the number of differences in each sequence.

Answer 63

- The proteins of different species can also be compared using immunological techniques. - The principle behind this method is the fact that antibodies of one species will respond to specific antigens on proteins, such as albumin, in the blood serum of another. - The response is the formation of a precipitate. - The greater the number of similar antigens, the more precipitate is formed and the more closely the species are related. - The fewer the number of similar antigens, the less precipitate is formed and the more distantly the species are related

Answer 64

Analysing individuals DNA base sequences to see what genes or specific alleles are involved.

Answer 65

**Short Tandem Repeats.** The DNA profile will produce coloured bands/ lines and these will be compared to see the similarities and differences between them.

Answer 66

**Interspecific Variation:** Variation between different species/ one species differs from another. **Intraspecific Variation:** Variation between members of the same species.

Answer 67

- May be caused by genetic or environmental factors. - Genetic – all members of the same species have the same genes, but have different forms of these genes (alleles). - Different alleles cause variations in the organism's phenotype. - Mutations may result in the change or loss of a protein.

Answer 68

- To investigate variation, biologists cannot make reliable conclusions by taking a single measurement. - Sampling involved taking a selection of individuals from the target population (the population being investigated) - These individuals will represent the population as a whole (in theory)

Answer 69

- **Sampling Bias –** The selection process may be biased. The investigators may be making unrepresentative choices, either deliberately or unwittingly. - **Chance –** Even if sampling bias is avoided, the individuals chosen, by pure chance, may not be representative.

Answer 70

**Random sampling:** aims to prevent bias and eliminate human involvement in choosing samples… - Divide the area of study into a grid. - Use a random number generator to choose coordinates. - Take samples from intersection ( where they cross over) of coordinates.

Answer 71

- **Use a large sample size**. More individuals selected, the smaller the probability that chance will influence the result/the less effect anomalies will have. Makes the data more reliable. - **Use of statistical tests to analyse the data**, determining the extent to which chance may have influenced the data.

Answer 72

**descriptive-** to measure spread data (e.g. range, standard deviation, standard error) **inferential-** allow us to use what we know to make inferences, used to test theory/ hypothesis

Answer 73

- A “thin” curve means that most values remain close to the average, and the standard deviation is small. A “fat” curve means that there is a wider spread of values about the mean, and the standard deviation is large.

Answer 74

- to do with frequencies/ counts og things in categories - looks at significance of difference between expected and observed frequencies (w/ numerical value) - if no. small, small difference, accept null hypothesis (and vice versa)

Answer 75

- correlation to access degree of association (different measurements in the same sample) - looking for positive vs negative correlation between 2 variables - stats used to identify if correlation really exists (closer to 1/-1, more likely the correlatin - need to calculate critical value first - represents borderline between accepting and rejecting null hypothesis

Answer 76

- looking for the difference beteen 2 means - know if differece is significant or not - before you interpret results, work out critical value - represents borderline between accepting/ rejecting null hypothesis

4: Genetic information and Variation Flashcards

(100 cards)