genetics, biodiversity and classification Flashcards
What are the 3 components of nucelotides
A pentose sugar, phosphate group, an organic base
Describe the structure of DNA
Made up of a deoxyribose sugar, a phosphate group and one of the 4 organic bases (A,G,C,T). It is double-stranded and hydrogen bonds between the bases form a helix shape
Describe the role of DNA
Carries genetic information, determines our inherited characteristics
Describe the structure of RNA
Made up of a ribose sugar, a phosphate group and one of the 4 organic bases (A,G,C,U). It is single stranded
Role of RNA
Transfers genetic information from DNA to ribosomes for protein synthesis
Which bases are purine and which are pyramidine
purine (double ring) - adenine, guanine
pyrimidine (single ring) - cytosine, thymine, uracil
How is DNA in eukaryotic cells different from in prokaryotic cells?
Eukaryotic cells - found in nucleus, long and linear. Associated with histone proteins to form chromosomes. Mitochondria and chloroplasts contain prokaryotic-like DNA.
Prokaryotic cells - short and circular. not associated with proteins
What is the genetic code?
The order of bases on DNA. Consists of codons (triplets of bases that code for a particular amino acid)
Identify features of the genetic code
Non-overlapping - each triplet is only read once.
Degenerate - more than 1 triplet codes for the same amino acid (64 possible triplets for 20 amino acids)
Universal - same bases and sequences used by all species
What is a gene?
A sequence of bases on a DNA molecule that codes for a specific sequence of amino acids to make a polypeptide. Can also code for functional RNA
What is a locus?
The fixed position on a DNA molecule occupied by a gene
What is an allele?
Different versions of the same gene, found at the same locus on a chromosome
What are exons and introns?
Exons - regions of DNA that codes for amino acid sequences. Separated by 1 or more introns.
Introns - regions of DNA that do not code for anything
Where are introns found
between exons
within genes
What is a genome?
The complete set of genetic information contained in the cells of an organism
What is a proteome?
The complete set of proteins that can be produced by a cell
Describe the structure of messenger RNA?
A long, single strand. Its base sequence is complementary to the DNA It was transcribed from
Suggest advantages of using mRNA rather than DNA for translation
shorter and contains uracil - breaks down quickly so no excess polypeptide forms.
single-stranded and linear - ribosome moves along strand and tRNA binds to exposed bases.
contains no introns
Describe the structure of transfer RNA
A single strand of around 80 nucleotides that is folded over into a clover leaf shape. On one end is an anti-codon, on the opposite end is an amino acid binding site
what is produced by transcription
mRNA
where does transcription take place?
in the nucleus
Outline the process of transcription
DNA uncoils into 2 strands with exposed bases. One used as a template.
Free nucleotides line up next to their complementary bases, and are joined together by RNA polymerase
What happens to mRNA after transcription?
In eukaryotic cells, pre-mRNA must be spliced to remove introns, leaving only the coding regions. Then it moves out of the nucleus and attaches to a ribosome
What is produced by translation
proteins
Where does translation take place?
In cytoplasm (on ribosomes)
Outline the process of translation
The anticodon of tRNA attaches to complementary bases on the mRNA.
Amino acids bonded to tRNA form peptide bonds, continuing to form a polypeptide chain until a stop codon is reached.
This process requires ATP
What is a mutation?
An alteration to the DNA base sequence. Often arise spontaneously during DNA replication
Why might a mutation not lead to change in the amino acid sequence
Genetic code is degenerate so mutation may end up coding for same amino acid as the original triplet. Mutation may occur in intron
What is substitution mutation?
When a nucleotide in the DNA sequence is replaced by another. This is more likely to be a quiet mutation, meaning no change occurs in the amino acid sequence
What is a deletion mutation?
When a nucleotide in the DNA sequence is lost. This is more likely to be harmful and significant, as it leads to a frame shift which means the entire amino acid sequence will be different
What a mutagenic agent? Give examples of this
Factors that increase the rate of gene mutation. X-rays, UV light, gamma rays, certain chemicals (alcohol and tobacco)
What a polyploidy chromosome mutation?
Where an individual has 3 or more sets of chromosomes instead of 2
What is chromosome non-disjunction
When chromosomes fail to seperate correctly in meiosis, resulting in gametes with 1 more or less chromosome than normal
What is meiosis?
A form of cell division that produces 4 genetically different haploid cells (cells with half the number of chromosomes found in the parent cell) known as gametes
How does meiosis differ from mitosis?
Meiosis produces 4 genetically different cells with half the number of chromosomes as the parent cells.
Mitosis produces 2 genetically identical cells with the same number of chromosomes as the parent cells
Meiosis I
Homologous chromosomes pair to form bivalents. Crossing over (exchange of sections of genetic material) occurs at chiasmata.
Cell divides into 2. Homologous chromosomes seperate randomly. Each cell contains either maternal or paternal copy
meiosis II
Independent segregation of sister chromatids
Each cell divides again, producing 4 haploid cells
Define population
All the organisms of a particular species that live in the same place
What is an allele?
Different forms of a particular gene, found at the same locus (position) on a chromosome. A single gene could have many alleles
Define genetic diversity
The total number of different alleles in a population
What advantage does a high genetic diversity provide?
Ability to adapt to a change in environment; allows natural selection to occur
Explain how natural selection results in development of new characteristics
Random mutations result in new alleles. Some alleles provide an advantage, making an individual more likely to survive and reproduce. Their offspring receive the new allele, and frequency continues to increase over many generations
What is directional selection
Occurs when environmental conditions change. Individuals with phenotypes suited to the new conditions will survive and pass on their genes. Over time the mean of the population will move towards these characteristics
Give an example of directional selection
Antibiotic resistance. Bacteria with a mutation allowing them to survive in the presence of antibiotics will reproduce. Therefore, frequency of this allele will increase and the population will shift to have greater antibiotic resistance
What is stabilising selection?
Occurs when environmental conditions stay the same. Individuals closest to the mean are favoured, and any new characteristics are selected against. Results in low diversity
Give an example of stabilising selection
Birth weight; babies that weigh around 3kg are more likely to survive than those at lower or higher weights
Define a niche
The role of a species within its environment. Species sharing the same niche will compete with eachother
What are 3 types of adaptation? Give examples of each
Anatomical (changes to body structure) - early fur.
Physiological (changes to bodily processes) - venom production.
Behavioural (changes to actions) - hibernation
Define species
A group of organisms that can interbreed to produce fertile offspring
what are the advantages of courtship behaviour?
Individuals can recognise sexually mature members of their own species of the opposite sex, synchronise mating, form a pair bond, and successfully breed
Define classification
The process of arranging organisms into groups
Name the 8 groups an organism can be classified into, from largest to smallest
domain - kingdom - phylum - class - order - family - genus - species
what system is used to give species a universal name?
binomial naming system
what are the 2 components to a binomial name?
Generic name - the genus the organism belongs to. 2 closely related species will share the same genus.
Specific name - the species the organism belongs to
How are binomial names handwritten?
The first letter of the generic name should be capitalised, with the rest in lowercase. The whole name should be underlined
what is phylogenetic classification?
The process of arranging organisms into groups based on their evolutionary origins and relationships
How can we clarify evolutionary relationships between organisms?
Analyse their molecular differences. Advances in immunology/genome sequencing provide clear pictures of how related 2 organisms are
Explain hierarchial classification
Groups within groups.
No overlap between groups.
What is biodiversity?
The variety of living organisms. it can be measured in terms of species diversity (number of species in a community), ecosystem diversity (range of different habitats) and genetic diversity
Define community
All the different species that live in one area and interact with eachother
How do you calculate index of diversity?
d= N(N-1) / sum of n(n-1)
N= total number of organisms of all species.
n= total number of organisms of each species
What impact does farming have on species diversity?
decreases species richness.
farmland is typically used for only 1 species (monoculture)
use of pesticides/herbicides
What impact does farming have on genetic diversity?
decreases.
farmers select for certain characteristics, which reduces number of different alleles in the population
How can biodiversity be increased in areas of agriculture?
- use hedgerows instead of fences.
- Grow different crops in the same area, or rotate crops around after a season.
- Limit use of pesticides and herbicides
Name 4 ways we can compare genetic diversity between organisms
- Frequency of observable characteristics.
- Base sequence of DNA
- Base sequence of mRNA
- Amino acid sequence
What is meant by gene technology
Sampling DNA or mRNA in order to read and compare the base sequence of organisms. Alternatively, the amino acid sequence can be studied as this will also provide information on the organisms mRNA and DNA sequences
Why do scientists prefer to use gene technology instead of observation?
Simply inferring DNA differences by observing an organisms characteristics is not reliable; the characteristics could be coded for by more than 1 gene, or could be influenced by the environment
What is meant by interspecific and intraspecific variation?
interspecific - differences between individuals of different species
intraspecific - differences between individuals of the same species
What is sampling?
Selecting a group of individuals to measure that will represent the whole target population
How can a random sample be achieved?
Create a grid for your sample area, and then randomly generate coordinates where a quadrat or transect can be placed. Repeat until required sample size is reached
how is pre-mRNA and mRNA different?
pre-mRNA has introns and exons whereas mRNA only has exons because of splicing
