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106 Cards in this Set
- Front
- Back
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What kind of coding is DNA coding? |
Triplet code/ degenerate code |
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What is transcription? |
The process of turning a gene into a strand of mRNA |
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Describe the process of DNA transcription |
DNA strand unwinds and unzips, H bonds break Activated free nucleotides line up against complementary base pairs on the template strand Sugar phosphate backbone forms between free nucleotides using RNA polymerase |
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What is translation? |
The process of translating a strand of mRNA into a polypeptide chain |
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What happens after an mRNA strand is formed in the nucleus? |
Leaves through a nuclear pore Attaches to a ribosome Translation begins |
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What happens when mRNA has left the nucleus? |
Attaches to a ribosome- 6 bases at a time are exposed to the large subunit of the ribosome Process of translation begins |
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Describe the process of translation |
tRNA molecules carry amino acids to the ribosome- the first amino acid is always methionine. The tRNA's UAC anticodon is complementary to the first mRNA codon (AUG). Using ATP energy and an enzyme, the tRNA molecule hydrogen bonds to the mRNA molecule. A second tRNA molecule with a different amino acid binds to the second exposed codon with its complementary anticodon. A peptide bond forms between the two adjacent amino acids using an enzyme in the small ribosome subunit. The ribosome moves along the mRNA strand and the process continues until it reaches a stop codon |
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What is a stop codon? |
A codon that doesn't code for an amino acid |
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What is always the first amino acid in a polypeptide chain and what is it's codon? |
Methionine, AUG |
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How are some proteins activated by cAMP? |
cAMP alters their 3D shape so that they are a better fit to their complementary molecules |
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What is an anticodon? |
A sequence of 3 RNA bases that are specific to a certain amino acid and complementary to a codon on the mRNA molecule |
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What enzyme catalyses the formation of peptide bonds in the ribosome? |
Peptidal transferase |
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What is a silent mutation? |
A mutation where the bases change but it still codes for the same amino acid |
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What is a mis-sense mutation? |
A mutation where the bases change and the amino acid it codes for is altered |
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What is a non-sense mutation? |
A mutation where the bases change and change it to a stop codon, so it no longer codes for an amino acid |
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What is a mutation? |
A random change to the sequence of bases |
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What are the two fundamental types of mutation? |
DNA mutation Chromosome mutation |
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What are the types of chromosome mutation? |
Deletion, inversion, inversion, translocation |
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What can cause chromosome mutations? |
Tar found in tobacco, UV light, X-Rays, gamma rays |
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When do mutations occur? |
During DNA replication |
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What is the difference between mutations in meiosis and in mitosis? |
Mutations in meiosis are called somatic mutations and can be passed on to offspring Mutations in mitosis are non-somatic mutations and can't be passed on |
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What are the types of DNA mutations? |
Point mutations, Insertion mutations, Deletion mutations |
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What can insertion and deletions cause? Explain what it is. |
Frameshift The bases all shift up or down by a certain number, causing the codons all the way along the DNA to be changed |
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What is sickle cell anemia caused by? |
A point mutation on a gene for the beta polypeptide chains in haemoglobin, causing the wrong amino acid to be coded for (mis-sense), valine in the place of glutamic acid |
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What is sickle cell anaemia? |
A disease caused by a genetic mutation that causes the red blood to become rigid and shaped like a crescen so that they can no longer fit through the narrow blood capillaries |
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What causes cancer? |
Growth-promoting genes called protooncogenes can be changed to oncogenes by a point mutation which stops the gene being able to be turned off. This causes unregulated cell division which leads to a tumour. |
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What causes Huntington disease? |
A stutter in the genetic code- a repeat of three nucleotides. |
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What is Huntington disease? |
A disease caused by a genetic mutation, the symptoms of which manifest later in life and include dementia and loss of motor control |
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Give 3 examples of diseases caused by genetic mutations |
Huntington disease, sickle cell anaemia, cystic fibrosis |
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What is cystic fibrosis usually caused by? |
A deletion of a triplet of base pairs, which deletes one amino acid in a sequence of thousands in the normal polypeptide |
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Explain how a mutation can be beneficial using the example of skin colour in humans |
Dark skin protects from damaging effects of UV light in Africa, and the sun is intense enough to allow them to synthesise enough vitamin D A mutation causes some humans to have paler skin- these humans would have died in Africa because they would be burnt by the sun and suffer from skin cancer. However, when humans migrated to colder climates, those with dark skin could not synthesise enough vitamin D and died in childbirth from narrow hips from the deficiency. Those with pale skin could synthesise enough vitamin D and survived more easily. |
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Why have inuit people not lost their dark skin, despite living in a less bright environment?
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They can get a lot of vitamin D from the seal meat and blubber they have in their diet |
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Why is genetic mutation essential? |
Without it, evolution would not be possible |
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What are structural genes? |
Genes which code for protein with specific functions, aided by their structure |
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What are regulatory proteins? |
Proteins that regulate transcription of DNA |
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Name the components of the lac operon |
Regulatory gene (far away along the DNA) (not part of lac operon) Promoter region Operator region Repressor Structural gene for beta galactosidase Structural gene for lactose permease (PROGG) |
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What does E-Coli usually use to respire? What can it also use? |
Glucose, can use lactose using the lac operon |
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Describe how E-coli can use lactose in respiration |
Normally, a repressor protein is bound to the operator region on the lac operon, and this also overhangs and obstructs the promoter region. This stops RNA polymerase binding to the promoter region so the structural proteins aren't synthesised. When lactose diffuses into E-coli, it binds to another site on the repressor protein and changes its shape so it falls away from the operator region. RNA polymerase can now bind, and beta galactosidase and lactose permease are synthesised. These respectively break down lactose into glucose and galactose, and increase cells' permeability to lactose so more can be broken down. Therefore lactose are said to be the inducer. |
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What are homeobox genes? |
Genes that control the development of the body plan of an organism, including where the head and tail go (polarity) and positioning of the organs |
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In which organisms are homeobox genes found? |
ALL of them! |
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Why should pregnant women avoid too much vitamin A in early pregnancy? |
It contains a substance that interferes with the morphogens (substances that control the pattern of tissue development) which can cause birth defects including cranial deformities |
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What is apoptosis? |
Programmed cell death that occurs in multicellular organisms, leading to tidy an controlled cell death |
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What is necrosis? |
An untidy and damaging cell death that occurs after trauma, releasing hydrolytic enzymes |
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Outline the sequence of events for apoptosis |
Enzymes break down the cell cytoskeleton The cytoplasm becomes dense The cell surface membrane changes and small blebs form Chromatin condenses and nuclear envelope breaks DNA breaks into fragments Cell breaks into vesicles which are phagocytosed |
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How is apoptosis controlled? |
A range of different types of cell signalling including cytokines, hormones and nitric oxide |
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How does nitric oxide induce apoptosis? |
Makes the inner mitochondrial membrane more permeable to hydrogen ions and dissipating the proton gradient |
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How is polydactyly caused? |
Lack of apoptosis- joints are all joined by skin during limb development, and should be separated by apoptosis before birth, but sometimes this doesn't happen |
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Describe the events in Prophase I |
Homologous chromosomes pair up, form bivalents Maternal and paternal chromosomes cross over, forming a chiasma |
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What is a chiasma? |
A chromosome with a new combination of alleles, created in crossing over |
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Describe what happens in Metaphase I |
Homologous pairs of chromosomes line up on the equator There is an independent/random assortment of homologous pairs (maternal/paternal chromosomes could be on either side of the equator) |
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Describe what happens in metaphase II |
Chromosomes line up on the equator There is an independent/random assortment of chromatids (chiasmata could be on either side of the equator) |
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explain why meiosis is two stage process
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It needs to halve the number of chromosomes. The chromosomes are two chromatid at first , first stage separates the homologous pairs of chromosomes and last stage separates the sister chromatid |
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Which stages in meiosis cause variation? |
Prophase I, metaphase I, metaphase II Can also be variation caused by chromosome mutation- if they don't split in anaphase II |
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How is fertilisation random? |
Random mating Random fusing of sex cells |
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Why are there twice the divisions in meiosis? |
The sex cells need to have half as many chromosomes so that they can be used in fertilisation and sexual reproduction, and so that the zygote has a full set of chromosomes |
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What is an allele? |
An alternative version of a gene |
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What is a phenotype? |
An observable characteristic of an organism |
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What is a genotype? |
The particular alleles present within the cells of an organism, for a particular organism, for a particular characteristic |
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What is a locus? |
The specific position on a chromosome, occupied by a specific gene |
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What is meant by dominant? |
An allele that will be expressed in the phenotype whether it occurs in the homozygous or the heterozygous condition |
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What is meant by codominant? |
When two alleles are expressed equally in the phenotype |
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What is meant by recessive? |
An allele that will only be expressed in the phenotype when homozygous |
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What is sex-linked inheritance? |
When genes are on the sex chromosome (X or Y) and so are only inherited if the chromosome is inherited |
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What is haemophilia? |
A sex-linked genetic disease which causes blood to not clot |
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How can you check the genotype of a phenotype? |
Do a test cross with one that has the recessive phenotype |
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What is epistasis? |
When different genes at different loci interact to affect one phenotype. One gene is epistatic (first locus) and suppresses the hypostatic gene (second locus) |
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How does recessive epistasis work? |
The epistatic gene will suppress the hypostatic gene if the allele is in the homozygous recessive genotype. It does this because the homozygous recessive genotype causes a functional protein such as an enzyme inhibitor or a repressor protein |
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How does dominant epistasis work? |
The epistatic gene will suppress the hypostatic gene if the epistatic allele is in the dominant form. It can be hetero or homozygous. The dominant allele will cause a functional protein to be produced which changes the phenotype. |
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What does a 9:3:4 ratio suggest?
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Recessive epistasis |
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What does a 12:3:1 ratio suggest?
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Dominant epistasis
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What does a 13:3 ratio suggest? |
Dominant epistasis |
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What does a 9:7 ratio suggest? |
Complementary epistasis |
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How does complementary epistasis work? |
The dominant allele for the first gene will cause a functional protein to be produced which will produce an intermediate compound (it might be colourless, or have a pigment). The intermediate compound will be converted into a different pigment if there is also a dominant allele for the second gene. E.G. if the final pigment was purple, the genotype would have to be A_B_ |
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What does the chi squared test test?
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The null hypothesis |
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What is the null hypothesis?
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There is no significant difference between the observed and expected numbers, and any difference is due to chance
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What is the chi squared test?
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A statistical test to find out of the difference between observed categorical data and expected data is small enough to be due to chance |
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When can the chi squared test be used? |
For categorical data Where there is a strong biological theory that we can use to predict expected values Large sample size No zero scores |
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How do you calculate the degrees of freedom?
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Number of categories-1 |
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What is the critical value in a chi squared test? |
The level at which we are 95% certain that the result is not due to chance
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Compare continuous and discontinuous variation |
Continuous varies between limits, non-continuous has no intermediates Continuous is plotted as a normal distribution curve, non-continuous is plotted as a bar chart Continuous is quantitative, non-continuous is qualitative Continuous alleles have small additive effects, non-continuous different alleles have large effects Many alleles and genes involved in continuous (polygenic), fewer alleles and one gene in non-continuous |
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Give examples of continuous variation
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Height, weight, fur length |
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Give examples of discontinuous variation
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Eye colour, fur colour, blood group
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A mathematical model to calculate allele frequencies in populations |
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What assumptions does the Hardy Weinberg principle make? |
-The mating in the population is random -There is no selective advantage for any genotype -There is no mutation, migration or genetic drift |
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What is the equation for finding frequency of genotypes? |
p^2 + 2pq + q^2 = 1 |
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What is the equation for finding frequency of alleles? |
p + q = 1 |
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What is meant by population? |
A group of individuals of the same species that can interbreed |
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What is a gene pool? |
The set of genetic information carried by a population |
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What can cause a population to become unstable? |
Selection pressures, genetic drift, inbreeding |
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What is a selection pressure? |
An environmental factor that gives greater chances of survival to reproductive age to some members of a population |
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What is genetic drift? |
The change in allele frequency in a population, as some alleles pass on to the next generation and some disappear. This causes some phenotypic traits to become rarer or more common |
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What are the types of isolating mechanisms? |
Seasonal (temporal) barriers such as climate change throughout a year Reproductive mechanisms (incompatible genitals, breeding seasons, courtship behaviours) |
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What is stabilising selection?
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When natural selection keeps things the way they are, because those organisms with mutations don't survive
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What is directional selection? |
When those organisms with a mutation are better adapted and natural selection causes an increase in the frequency of a phenotype in a population
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What is the biological species concept?
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A species is a group of similar organisms that can interbreed and produce fertile offspring
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What is the phylogenetic species concept? |
A species is a group of organisms that have a similar morphology (shape), physiology (biochemistry), embryology (stages of development) and behaviour, and occupy the same ecological niche Two organisms are members of the same species if the differences in these factors are small enough to just be phenotypic variation within a species |
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What is a monophyletic group?
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A group that contains an ancestral organism and all of its descendent species |
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What is cladistics? |
The hierarchal classification of species, based on their evolutionary ancestry. It uses DNA and RNA sequencing, computer programmes and molecular analysis to classify species |
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What is a paraphyletic group? |
A group that includes the most recent ancestor but not all of its descendants |
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What is polyploidy? What can it be used for? |
Used to create hybrid species like bread wheat, which is bigger because it has more chromosomes, so bigger nuclei, so bigger cells |
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give an example of a molecule that control gene expression by binding directly to the DNA |
A homebox produces a protein, this polypeptide is a transcription factor as this protein binds to DNA and starts transcription so regulating gene expression, genes that control body plan. or Repressor protein changes shape when bound tolactose and lifts off operator allowing allowing the binding of RNA polymerase to promoter so transcription can proceed . without lactose the protein binds to the operator stopping, transcription / gene expression. |
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Benefits of asexual reproduction and disadvantages |
- quick, rapid reproduce -completed w/out sexual reproduction -all genetic info suits environments# disadv: - no genetic variety - all equally susceptible
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how to make basal sprout grow |
-damage the trunk - cut trunk - remove h20-- stress |
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describe the two type of artificial vegetative propagation |
1)cutting - cut the stem between nodes -treat with hormones 2) grafting -a shoot section of plant is joined to root-stock |
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describe the production of artificial clones of plants from tissue culture |
- small piece of tissue taken from the shoot tip ( explant) - explant is put into a nutrient growth medium - they divide but do not differentiate ( callus) - callus placed in another growing medium containing shoot growth hormone - then growing shoot placed in a growing medium containing root growth hormone -growing plant transferred to greenhouse, then transferred to field |
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discuss the advantage and disadvantage of plant cloning agriculture |
- quick - farmers can choose desirable features e.g high yield disadvantage : no genetic variety - all susceptible to disease or change in environment |
