Genetics Flashcards
Prokaryotes
Bacteria and archaea
Lack a nucleus, one circular chromosome
No histones
70S ribosomes
No organelles
Peptidoglycan cell walls most bacteria (archaea cell walls are not PG)
Divide by binary fission
Eukaryotes
Fungi, protozoa, algae, helminths
True nucleus, several linear chromosomes
Histones
80S ribosomes
Organelles
Divide by mitosis
DNA in eukaryotes
In eukaryotes, linear DNA is found in long strands with associated proteins and is found in the nucleus. It’s wound around histone proteins. DNA and the histones are coiled to form chromosomes.
DNA in prokaryotes
In cytoplasm. Shorter and circular. Supercoiled to fit into the cell.
What is a gene?
A section of DNA which codes for polypeptides and RNA. There is a specific sequence of bases which code for particular polypeptides and RNA. Genes are found at a locus.
Alleles
Diff versions of the same gene
Homologous pairs
Pairs of chromosomes which contain the same genes at same locus but different alleles.
A degenerate code
Multiple codons can code for the same amino acid
Genome
The complete set of genes in a cell.
Proteome
The full range of proteins which a cell is capable of producing.
What are exons?
Sections of DNA which code for amino acids.
What are introns?
Sections which do not code for amino acids.
Does prokaryote DNA have introns?
No
Non-coding multiple repeats
Areas between genes in the genome that repeat over and over. Used in DNA fingerprinting.
What is mRNA?
A copy of a gene your body wants to make a protein for. Made during transcription and taken to ribosomes to be decoded and make proteins. In mRNA 3 bases adjacent to eachother is called a triplet.
Where is transcription in prokaryotes?
Cytoplasm
Where is transcription in eukaryotes?
Nucleus
Transcription
DNA helicase breaks h bonds between bases in DNA and causing it to unwind and separate into 2 strands and 1 strand acts as a template. RNA nucleotides attract to exposed bases by complementary base pairing.RNA polymerase joins RNA nucleotides together. Pre-mRNA spliced.
What begins transcription?
Promoter sequence
What ends transcription?
Terminator sequence
What is pre-mRNA?
MRNA containing introns and exons.
What is splicing?
Introns removed and exons are joined making mRNA. Takes place in nucleus.
Process of translation
MRNA attaches to ribosomes
TRNA anticodons bind to complementary mRNA codons
TRNA brings a specific amino acid
Amino acids join by peptide bonds with use of ATP
TRNA released
Ribosomes moves alone mRNA to form polypeptide
What is genetic code?
DNA is made of a code which can be read by ribosomes to build polypeptides. Ribosome reads a triplet at the same time. Base triplets do not share bases so the code is non-overlapping.
What is a diploid?
2n.
All cells in the body except gametes. Cells have chromosome pairs. Each pairs are homologous pairs.
Haploid
Only contains one of each of the homologous pair.
Meiosis
Type of cell division in eukaryotes that produces gametes. Cells start as a diploid to become a haploid.
Prophase 1 (1st division)
Each DNA strand shortens and becomes a condensed chromosome. Is visible. 2n
Prophase 1 continued
Each chromosome makes a copy of itself joined at the centromere.
Metaphase 1
Pairs of chromosomes line along the middle of the cell.
Anaphase 1
The pairs of chromosomes separate to opposite sides of the cell.
Telophase 1
Cell splits down the middle
Prophase 2
New nuclear membranes form and now two haploid cells.
Metaphase2
All chromosomes become arranged in a line down the middle of the cell.
Anaphase 2
Sister chromatids separate at the centromere and move to the opposite sides of the cell.
Telophase 2
Cell splits down the middle
End of 2nd division
Two haploid cells have been made from one of the first division cells.
What is crossing over?
In first division, chromatids from each chromosomes wind around eachother. Alleles can swap between chromosomes.
Indépendant segregation
When chromosomes separate it is random which daughter cells get which chromosomes
What is a mutation?
A sequence of DNA nucleotides are changed
Deletion
One or more bases are deleted.
Will always produce a change in the sequence of amino acids as it will cause a shift in the triplets being read.
Substitution
One base is substituted with another.
Not all will result in a diff amino acid (degenerative nature)
Addition
One or more bases are added.
Duplication
One or more bases is repeated
Inversion
A sequence of bases is reversed
Translocation
A sequence of bases is moved from one location in the genome to another in either the same chromosome or a different one.
Consequences of mutations
could code for a diff amino acid and synthesise a different protein.
Mutagenic agents
Increase the chances of mutations happening. Eg radiation or chemicals (benzene)
Can alter bases, act as a base or change the structure of DNA
Chromosome non-disjunction
Chromosomes do not separate properly. Mutations can lead to inherited conditions.
Genetic diversity
The number of different alleles for a characteristic within a population. A large number of diff alleles for a characteristic = high genetic diversity which is important as the population is more able to adapt to change in the environment and cope with disease.
What increases genetic diversity?
Mutations and migration
Genetic bottlenecks
Caused by an event which causes a dramatic reduction in population size so there are less alleles in the gene pool. Reduces genetic diversity. Survivors reproduce.
Founder effect
A small number of individuals start a new population and there is only a small number of alleles to start the initial gene pool. The frequency of alleles in the new colony may be diff to the original one.
Natural selection
Random mutations may occur within a population producing a new allele. If this allele is harmful it disappears quickly. Some mutations produce beneficial alleles eg better protein synthesis.
What are examples of behavioral adaptations?
Mating rituals
Possums playing dead when threatened
Huddling when it is too hot or cold
What are examples of physiological adaptations?
Processes happening inside an organisms body:
Hibernation
Antibiotics (some bacteria produce their own antibiotics to kill other species of bacteria).
What are examples of anatomical adaptations?
Structure of an organism:
Blubber to keep them warm
Streamlining to help them catch prey or evade predators.
2 types of natural selection
Directional selection and Stabilising selection
Directional selection
When individuals in a population have alleles for an extreme characteristic which makes the more likely to survive and reproduce in response to environmental change.
Eg In a population of bacteria there may be individuals which are more resistant to a certain antibiotic then others in a population. If the population is exposed to that antibiotic then the non-resistant bacteria will die and leave only the resistant individuals to survive, reproduce and pass on the resistant allele.
Stabilising selection
When individuals with alleles for characteristics in the middle range are more likely to survive and reproduce. Occurs when the environment is not changing so it reduces the range of characteristics.
Eg Human babies have a range of birth weights. Low birth weight babies struggle to maintain body temp as they have a high surface area to volume ratio. This puts pressure of their respiratory and cardiac systems and can be fatal. Large birth weight babies are more likely to die due to complications in birthing.
What is phylogeny?
The study of how organisms have evolved from other organisms. Tells us which species are related to which others and how closely related they are. A phylogenetic tree shows their relationships.
Taxonomy
Putting organisms into groups and naming them based on the groups they are in.
Taxa
8 levels of hierarchy and each level is a taxon
Domains
Bacteria
Archaea
Eukarya
Binomial name
Genus + species
Variation
The difference in alleles. Can be variation with and between species. Diff species have diff genes. Individuals within the same species have the same genes but diff alleles.
Random sampling
Must represent whole population and ensures sample is not biased.
Normal distribution
When values are spread around the mean symmetrically.
Standard deviation
Tells you how much the set of data points range around the mean.
Index of biodiversity formula
N(N-1)/sum of n(n-1)
N=total no of organisms of all species n=total number of organisms of one species
Courtship
Specific to a particular and only members of that species will respond.
Closer related species have similar courtship behaviour.
Simple courtship
Releasing chemicals eg male bumble bees release pheromones to attract females to the territory
Sound eg male deer roaring
Visual displays eg male birds puffing out their chests
Complex courtship
Dancing eg blue footed babies do a complex dance to show their blue feet
Building eg bowerbirds construct elaborate nests
Genome sequencing
Advances in mapping the genome means the entire base sequence for a species can be known. DNA sequence of one organism can be compared to the sequence of another organism.
Amino acid sequencing
Proteins are made of amino acids which are coded in organism DNA. Related organisms have similar amino acid sequences and DNA.
Immunological
Similar proteins will bind to the same proteins.
Biodiversity
The variety of different organisms in an area
Habitat
The place where an organism lives
Community
All the populations of different species in an habitat.
