UNIT 4 - RNA,DNA,Protein synthesis and Diversity Flashcards
what is prokaryotic DNA like
single, circular chromosomal DNA
plasmids containing a few genes like antibiotic resistance
not associated with histones
what is Eukaryotic DNA like
-long condensed chromosomal DNA
- associated with histones
- has introns
what is mitochondrial DNA like
circular, shorter no associated with proteins
what is chloroplast DNA like
small, circular pieces of DNA
what is a gene
a base sequence of DNA that codes for a specific amino acid sequence to form a polypeptide strand or a functional RNA molecule
what is the Loci
the position of a gene on a chromosome is its locus
what is a codon
a sequence of three bases coding for an amino acid
what does degenerate mean
more possible combinations of triplets than amino acids
what does universal mean
every organism uses the same code and this means that the same codons code for the same amino acid in all living things
what does non-overlapping mean
DNA is read in triplets so no bases are read again
what is the genome
the complete set of genes in a cell
what is the proteome
the full range of proteins that a cell is able to produce
what are homologous chromosomes
chromosomes that are the same size and have the same gene but different alleles
what is mRNA
a single stranded molecule that is made of a sugar phosphate backbone and exposed unpaired bases U, A, C, G
what is the structure of tRNA
single stranded molecule with a folded shape due to hydrogen bonds
- has a specific anticodon complementary to specific codon
describe transcription
- The DNA unwinds and the hydrogen bonds break
- The exposed gene is used as a template and a complementary copy of the code from the gene is made called mRNA made from free RNA nucleotides with complementary bases to DNA sequence
- RNA polymerase bonds the RNA nucleotides together to form a sugar-phosphate backbone
- mRNA molecule then leaves the nucleus via a pore in the nuclear envelope
when, where and what happens in splicing
before the pre-mRNA leaves the nucleus splicing occurs which is the removal of introns and the coding sections called exons are joined together resulting in mRNA coding only for the genes
what is alternative splicing and what does it result in
when the exons of genes can be spliced in many ways to reproduce different mature mRNA molecules
a single eukaryotic gene can code for more than one polypeptide chain
what happens in translation
- mRNA molecule attaches to a ribosome and tRNA molecules carry amino acids to it and the amino acid bond with the tRNA molecule requires ATP
- a tRNA molecule with an anticodon that’s complimentary to the first codon on mRNA and they attach by complimentary base pairing
- the two amino acids attached to the tRNA molecules are joined by a peptide bond and the first tRNA molecule moves away leaving its amino acid behind
how do you calculate the number of amino acids in a protein
divide the number of coding nucleotides by 3 and minus one for the stop codon
what is a gene mutation
change in the sequence of base pairs in a DNA that occurs randomly that may results in an altered polypeptide
what are the three types of mutations
insertion mutations, deletion mutations and substitution mutations
what is an insertion mutation, what does it cause and what is changed in the big picture do to it
when a nucleotide is randomly inserted into the DNA sequence which changed the amino acid that is coded for as it creates a new different triplet of bases due to the knock off effect by changing the triplets further on in the DNA sequence.
what is a deletion mutation
mutation occurs when a nucleotide is randomly deleted from the DNA sequence which changed the amino acid that would have been coded for as there is a knock-on effect by changing the groups of three bases further on in the DNA sequence. This may dramatically change the amino acid sequence produced from this gene and therefore the ability of the polypeptide to function.
what is a substitution mutation
is when a base in the DNA sequence is randomly swapped for a different base. The mutation will only affect the amino acid triplet the substitution has happened in so there is no large knock-on effect
what are the three types of substitution mutations
Silent mutations which is when the mutations doesn’t alter the amino acid sequence.
Missense mutations is when the mutation alters a single amino acid.
Nonsense mutations is when the mutations creates a premature stop codon causing the polypeptide chain produced to be incomplete and therefore effecting the final protein structure and function.
what is a mutagenic agent and the examples
Mutagenic agents are environmental factors that increase the mutation rate of cells.
Examples of mutagenic agents are UV light, x-rays and toxic chemicals.
what is the mutation that happens in chromosome number called and when does it happen
Non-disjuction mutation
Non-disjunction occurs when chromosomes fail to separate during meiosis and this occurs spontaneously.
what do mutations in the chromosome number cause in haploids and what are the consequences of this
The gametes may end up with one extra copy of a chromosome or no copies of one and this means the gametes will have a different number of chromosomes then the haploid number.
If the abnormal gamete, then takes part in fertilization, then a chromosome mutation occurs.
what happens in prophase 1 in meiosis
- DNA condenses to form double armed chromosomes which are joined by a centromere and becomes visible. DNA replication has already occurred, so each chromosome consists of two sister chromatids joined together by a centromere.
- Chromosomes are arranged side by side in homologous pairs. A pair of homologous chromosomes is called a bivalent.
- Crossing over of non-sister chromatids may occur in the chiasma.
- Centrioles migrate to opposite poles and spindle fibre is formed.
- Nuclear envelope breaks down and nucleolus disintegrates.
what happens in metaphase 1 in meiosis
- Homologous chromosome pairs line up along the equator of the spindle with the spindle fibres attached to the centromeres.
what happens in anaphase1 in meiosis
- Homologous pairs of chromosomes are separated as the microtubules pull whole chromosomes to opposite ends of the spindle and random assortment happens due to the random lining up of homologous chromosomes in metaphase.
what happens in telophase 1 in meiosis
- Chromosomes arrive at opposite poles.
- Spindle fibres start to break down.
- Nuclear envelopes form around the two groups of chromosomes and nucleoli reform.
what happens in cytokenisis
Cell organelles get distributed between the two developing cells.
In animal cells the cell surface membrane pinches inwards creating cleavage in the middle of the cells which contracts dividing the cytoplasm in half.
In plant cells the vesicles from the Golgi apparatus gather along the equator of the spindle and they merge to form a new cell surface membrane and secrete a layer of calcium pectate which becomes the middle lamella which layers of cellulose are laid upon.
what happens in prophase II
1.Nuclear envelope breaks down
2.Chromosomes condense
3.Spindle forms at a right angle to the original
what happens in metaphase II
- Chromosomes line up at the equator of the spindle.
what happens in anaphase II
- Centromeres divide and individual chromatids are pulled to opposite poles of the cell creating four groups of chromosomes that have half the number of chromosomes compared to the original parent cell.
what happens in telophase II
- Nuclear membrane reforms around each group of the chromosomes
what happens in cytokinesis in meiosis II
Cytoplasm divides as new cell surface membranes are formed creating 4 new haploid cells.
what mechanisms in meiosis cause genetic variation and how
- crossing over as the sister chromosomes pair up and the chiasma causes stress on the DNA so some sections will break and rejoin the other chromosomes and this swapping of alleles results in a new combination on the two chromosomes
- independent assortment in the production of different combinations of alleles in daughters cells due to the random alignment of homologous pairs along the equator and randomly pulled to the poles of the cell
what is a chiasma
the crossing over bit of sister chromatids
what causes genetic variation
- crossing over in meiosis
- independent assortment in meiosis
- random fertilisation in reproduction
what is genetic variation
Genetic variation is the small differences in DNA base sequences between individual organisms within a species population that is transferred from one generation to the next
what is genetic diversity
Genetic diversity is the number of different alleles of genes in a population
why is genetic diversity important for populations
Genetic diversity is important as if a population has a low genetic diversity it might not be able to adapt to change in the environment and the whole population could be wiped out by a single event like disease.
what is genetic diversity in a population increased by
Genetic diversity is increased by:
Mutations in DNA forming new alleles
Different alleles being introduced into the population when individuals from another population migrate into it and reproduce, and this is called gene flow
what is reproductive success
Reproductive success is the passing of genes onto the generation in a way that to can pass on those genes
what 3 things can happen in a population that affect the allele frequency
founder effect, genetic drift and bottleneck effect
what is the founder effect
when a small number of individuals from a large population start a new population and as the population is made from a few individuals only some of the total alleles from the parent population will be present so not all the gene pool is present, so the allele frequencies occur in a different direction for the new population than the parent population.
what is genetic drift
when a population is significantly small chance can affect which alleles get passes onto the next generation and over time some alleles can be lost due to chance and there is a gradual change in frequencies in a small population due to chance and not natural selection then genetic drift is occurring
what is the bottleneck effect
when a previously large population suffers a fall in numbers dramatically and this is turn reduces the genetic diversity in the population as alleles are lost and the surviving individuals end up breeding and reproducing with close relatives.
what is natural selection and how does it happen
- Random mutation can produce a new allele of a gene
- Many mutations are harmful or neutral but under certain environmental conditions the new alleles may benefit their possessor leading to an increased chance of survival an increased reproductive success
- The advantageous allele is then passed onto the next generation making them more likely to survive and pass the allele on
- Over time the new allele will increase in frequency in the population
- Over generations this leads to evolution as the advantageous become more common in the population
- Natural selection happens in a population when the alleles that control the characteristics which help the organism to survive are selected
what are the three types of adaptations and what are they
- Behavioral adaptations: the way an organism behaves to increase chance of survival
e.g. possums sometimes play dead if they are being threatened by a predator - Physiological adaptations: processes inside an organism’s body that increase the chance of survival
e.g. brown bears hibernate to lower their metabolic rate over winter, so they don’t need to look for food in the months its scarce - Anatomical adaptations: structural features of an organism’s body that increase its chance of survival
e.g. otters have a streamlines shape to make it easier to glide through water ad makes it easier for them to catch prey and escape predators
what are the three types of selection
directional, stabilizing and disruptive
what is directional selection
where individuals with alleles for characteristics of an extreme type are more likely to survive and reproduce.
-Leads to a gradual change in allele frequencies
-This could be a response to an environmental change.
what is stabilizing selection
Individuals with alleles for characteristics towards the middle of the range are more likely to survive and reproduce
-Natural selection is natural selection that keeps allele frequencies relatively constant over generations
- it occurs when the environment isn’t changing, and it reduces the range of possible characteristics
what is disruptive selection
Natural selection favours the two extremes of phenotype
-Occurs in an environment that favours more than one phenotype
-Selection pressures against the average phenotype
what is evolution
Evolution is the change in adaptive features of a population over time as a result of natural selection
when does the same population of a species become 2 species
If two populations of one species are isolated from each other and become so different in phenotype that they can no longer interbreed to produce fertile offspring they have formed two new species
what is courtship and what is its importance
Courtship in animals is a behaviour that eventually results in mating and reproduction
Courtship can play a major role in species recognition and successful reproduction
what are the three domains
archea, bacteria, eukarya
what are archaea
Organisms within this domain are sometimes referred to as the extremophile prokaryotes, archaea were first discovered living in extreme environments, but not all archaea are Bacteria
what is the bacteria domain
These are organisms that have prokaryotic cells which contain no nucleus
what is the eukarya domain
Organisms that have eukaryotic cells with nuclei and membrane-bound organelles are placed in this domain
what is a binomial name and what does it consist of
Binomials are the scientific name of a species
It consists of the organism’s genus and species name in modern Latin
what 4 things can be used to investigate evolutionary relationships
DNA
mRNA
Amino Acids
Immunology
how do we use immunology in the investigation evolutionary relationships
Pure albumin samples are extracted from blood samples taken from multiple species
Each pure albumin sample is injected into a different rabbit
Each rabbit produces antibodies for that specific type of albumen
The different antibodies are extracted from the different rabbits and are then mixed with the different albumin samples
The precipitate (antibody-antigen complexes) resulting from each mixed sample is weighed
what do the results in immunology show us
The greater the weight of the precipitate, the greater the degree of complementarity between the antibody and albumin
what are the two ways of measuring biodiversity and explain them
species richness and species diversity
Species richness- the number of species within a community
Species diversity- looks at the number of different species in a community and the abundance of them
why is biodiversity in ecosystems important
Ecosystems with high species diversity are usually more stable than those with lower species diversity as they are more resilient to environmental changes
what is species diversity
The mix of different species that exist within a particular area or region can be measured to indicate levels of biodiversity
what is bad about using species richness aas a measurement of biodiversity
it can be misleading as it doesn’t consider the number of individuals in each species (the abundance)
what is index of diversity
The index of diversity looks at the number of different species in an area but also the evenness of abundance across the different species
An index of diversity is a measurement that describes the relationship between the number of species present and how each species present and how each species contributes to the total number of organisms that are present in that community
define biodiversity
variety of living organisms in an area
what are the ways that courtship behaviours increase successful mating
- recognise same species
- stimulates release of gametes
- recognition of opposite sex
- indication of sexual maturity
- formation of pair bond
