Genetic information, variation and relationships between organisms Flashcards
Definition of a gene?
A gene is a base sequence of DNA that codes for
- the amino acid sequence of a polypeptide
-a functional RNA (including ribosomal RNA and tRNAs)
What is the locus?
The fixed position a gene occupies on a DNA molecule
What is a triplet?
A sequence of three DNA bases coding for a specific amino acid.
The genetic code
Degenerate
More than one triplet can be coded for one amino acid
Universal
Triplet code is the same code for all living organisms in one amino acid
Non- overlapping
Each base is only part of one triplet codon
What are introns?
Non coding regions of a gene
What are exons?
Coding regions of a gene
DNA in prokaryotes
Short, circular and not associated with proteins.
DNA in eukaryotes
Long, linear and associated with proteins called histones. Together a DNA molecule and its associated proteins form a chromosome.
DNA of mitochondria and chloroplasts
Short, circular and not associated with proteins.
Genome
The complete set of genes in a cell
Proteome
The full range of proteins that a cell is able to produce.
Structure of chromosome
At start of cell division, they appear as two threads joint by a single thread (each thread known as chromatid). These are conjoined by a centromere.
DNA is held together by histones.
Chromosomes in humans
46
23 pairs
Chromosomes in gametes
23
Homologous chromosomes
A pair of chromosomes, one maternal and one paternal which have the same gene loci
What is an allele?
Different versions of the same gene
Gene mutation
A change in the base/ nucleotide sequence of DNA resulting in the formation of a new allele
Sources of DNA from organisms
Bone/ skin/ preserved remains
Reasons for low levels of genetic diversity
- Inbreeding
- Population started with small number of individuals
- Population may have been very small
RNA structure
A polymer forming a single strand.
- Pentose sugar ribose
- Nitrogen containing organic bases (adenine,guanine,cytosine, uracil)
- Phosphate group
The two types of RNA in protein synthesis
messenger RNA (mRNA)
transfer RNA (tRNA)
Structure of mRNA
Linear
Exons
Codon
Structure of tRNA
Clover leaf shape
Has specific amino acid binding site
Function of transcription
The process of making mRNA from DNA
Results of transcription
- prokaryotic cell
Transcription results directly in the production of mRNA from DNA.
Results of transcription
- eukaryotic cell
Transcription results in the production of pre-mRNA which is then spliced to form mRNA.
Function of translation
Translation as the production of polypeptides from the sequence of codons carried by mRNA.
RNA polymerase role
Ribosome role
Role of tRNA
Role of ATP
What is the process of splicing?
Introns are removed from the pre-mRNA by the spliceosome and exons are spliced back together.
What is a spliceosome?
Huge, multimegadalton ribonucleoprotein (RNP) complexes found in eukaryotic nuclei.
Meiosis stages
Prophase, metaphase, anaphase, telophase
- two stages process each stage occurring twice yet DNA only replicates once
Crossing over
Process by which non sister chromatids exchange alleles and DNA
Ways in which meiosis increases genetic variation?
- Exchange of genetic material between chromatids of maternal and paternal origin. (prophase)
- Orientation of each paire of chromosomes one spindle is a random event. (metaphase)
- Independant segregation
What is meiosis?
Meiosis is a type of cell division which results in four genetically varied daughter cells
Independant segregation
Separation of chromosomes, halving them resulting in four daughter cells with completely different combinations of maternal and paternal chromosomes.
- Completely random event
- Increases genetic variation
Mutations
Mutagenic agents
Base deletion
Base substitution
Genetic diversity
The number of different alleles of genes in a population.
Principles of natural selection
Random mutation can result in new alleles of a gene.
Many mutations are harmful but, in certain environments, the new allele of a gene might benefit its possessor, leading to increased reproductive success.
The advantageous allele is inherited by members of the next generation and over many generations, the new allele increases in frequency in the population.
Anatomical adaptations
Physiological adaptations
Behavioural adaptations
Courtship behaviour
What are groups called in phylogenetic classification?
Each group is called a taxon (plural is taxa).
Phylogenetic classification
Arrange species into groups based on their evolutionary origins and relationships. Using a hierarchy in which smaller groups are placed within larger groups with no overlap between groups.
What is the order of the heirarchy comprising the taxa?
Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.
Acronym for heirarchy of taxa
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Binomial classification
A formal system of naming species of living things by giving each a name composed of two parts, their Genus and Species
Definition of species
Groups of organisms which are able to produce fertile offspring
Definition of species richness
A measure of the number of different species in a community.
Index of diversity
The relationship between the number of species in a community and the number of individuals in each species.
Farming techniques which reduce biodiversity
Conservation
