4-Genetric Info, Variation, Relationships Flashcards
What are DNA molecules like in prokaryotic cells
Short, circular, not associated with proteins
Whats DNA like in eukaryotic cells
Long, linear, associated with proteins called histones
DNA molecule with a protein forms a chromosome
What is the DNA in chloroplasts and mitochondria of eukaryotes diffrent
Short, circular, not associated with proteins
What is a gene
A base sequence of DNA which codes for the amino acid sequence in a polypeptide or a functional RNA like rRNA
What’s a locus
A specific position a gene occupies on a DNA molecule
What’s a triplet and what does it do
A sequence of 3 DNA bases, codes for a specific amino acid
Why is the genetic code universal
A triplet can code for the same amino acids in all organisms
Why is the genetic code non overlapping
Each base in the sequence is read once
Eg 123,456 not 123,234,345,456
Why is the genetic code degenerate
An amino acid can be coded for by more than one triplet
What are exons and introns
Exons, Coding sequences for amino acids/rRNA/tRNA
Introns, non coding sequences
Exons are separated by introns
What’s a genome
Complete set of genes in a cell
What’s a proteome
Full range of proteins a cell is able to produce
What’s the structure of mRNA
Long, single helix
Contains uracil instead of thymine
Contains codons (3 bases complimentary to a DNA triplet)
What’s the structure of tRNA
Small, single stranded chain in a clover leaf shape one side is longer than the other (where amino acids attach)
Anticodon is complimentary to codons
What does transcription in prokaryotes result in
Direct production of mRNA from DNA
What does transcription in eukaryotes result in
Pre-mRNA which is spliced to form mRNA
What happens in transcription
Enzyme (DNA helicase) break H bonds separating the two DNA stands exposing the nucleotide bases
Nucleotide bases on one DNA strand, the template strand pair with complimentary nucleotides from the pool in the nucleus
Adenine and uracil are complimentary, cytosine and guanine are complimentary
RNA polymerase moves along the strand joining the adjacent nucleotides together by a phosphodiester bond forming pre-mRNA
When RNA polymerase reaches a terminator sequence it detaches and production of pre-mRNA finishes
During transcription how are eukaryotes spliced
DNA in eukaryotic cells have introns and exons, non coding introns would prevent the synthesis of a polypeptide
In pre-mRNA complimentary bases of the introns are removed leaving the exons to join together
What happens during translation
A ribosome attaches to a start codon on mRNA
tRNA molecule with an anti codon pairs up with the codon on mRNA using the base pair rule, adenine and uracil are complimentary, guanine and cytosine are complimentary
tRNA carries a specific amino acid to the ribosome
The tRNA with a complimentary anticodon pairs with the next mRNA codon carrying another amino acid
Two amino acids on tRNA are joined by a peptide bond using an enzyme and ATP, process repeats
When the ribosome reaches a stop codon the ribosome, mRNA and tRNA molecules seperate
Whats a gene mutation
Change in the base sequence of chromosomes
What happens during a base substitution mutation
A base is swapped with a different base, if it causes the amino acid to change the bonds between them change, the protein formed and it’s shape changes so it can’t function properly
However DNA is degenerate so if a base is substituted and still forms the same amino acid no change occurs
What happens during a base deletion mutation
A nucleotide is lost from the DNA sequence, all bases shift left changing all the triplet codes after, different amino acid, different protein that can’t function
What increases the rate of gene mutation
Mutagenic agents
How can a mutation in the number of chromosomes during meiosis be caused
Spontaneously arise by chromosome non disjunction, chromosomes fail to seperate
Process of meiosis
Describe crossing over and independent segregation
- DNA is replicated
- Two rounds of division occur
- First division, meiosis 1, homologous pairs separate randomly (independent segregation), and sections cross over (non sister chromatids exchange alleles)
new combinations of maternal and paternal alleles, creates genetic variation
Homologous pairs separate - Second division, meiosis 2, sister chromatids move apart, 4 daughter cells formed
Products of meiosis
Daughter cells genetically different from each other
How does meiosis produce haploid cells from a single diploid cell
Chromosomes duplicated, two sets of divisions so each cell will contains one set of chromosomes and thus are haploid
How to calculate the number combinations of chromosomes in each daughter cell
2^n
n is the number of homologous pairs
Meiosis vs mitosis
Meiosis
2 nuclear divisions, produces haploid cells, introduces genetic variation
Mitosis
1 nuclear division, produces diploid cells, produces genetically identical cells
How do identify meiosis in a lifecycle
Where a diploid cell (2n) become a haploid cell (n)
How is genetic variation increased further in humans
Random gametes fuse therefore the number of combinations is (2^n)^2
What’s genetic diversity
A factor (the number of different alleles of genes in a population) enabling natural selection to occur
Principals of natural selection causing populations to evolve
Random mutation results in new alleles of a gene
Many mutations are harmful but can also benefit increasing reproductive success
Advantageous allele inherited by offspring
Over generations allele increases in frequency in population
What adaptations may occur due to natural selection
Anatomical (structure), longer beak
Physiological (chemical reactions), special enzymes
Behavioural, survival instincts
What’s directional selection
A specific extreme trait has a selective advantage due to a change in environment
eg antibiotic resistance, as antibiotics are used more (change in environment) bacteria with allele for resistance to antibiotics thrive and reproduce passing on allele
What’s stabilising selection
The modal trait remains the same as environment stays the same, causes extreme traits to be lost
eg human birth weight, having a healthy weight provides best chances of survival, pass on allele to offspring
How to know if two organisms are pet of the same species
Able to produce fertile offspring
Whats courtship behaviour
A necessary precursor for successful mating
How does courtship allow for species recognition
Recognition of members from their own species, ensure mating only occurs between members of the same species, produce fertile offspring
Identify a male capable of breeding, partners need to be sexually mature fertile and receptive to mating
Forming a pair bond, successful mating and raising of offspring
Synchronise mating, occurs when the best chance of the egg meeting the sperm is
Ability to breed, member of opposite sex brought into a physiological state allowing for breeding
What’s a phylogenetic classification system
Arranges species into groups based on their evolutionary origins, relationships
Use of a hierarchy, smaller groups placed into larger groups, no overlap between groups
Each group is a taxon
What hierarchy do the taxa represent
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
How is each species universally identified
By a binomial
Name of genus (capital letter) species (lowercase)
How are evolutionary relationships between organisms clarified nowadays
Immunology and genome sequencing has advanced
What’s biodiversity
A range of habitats, can be small and local or earth
What’s the richness of species
Measure of the number of different species in a community
What’s an index of diversity and the equation
Relationship between number of species in a community and number of individuals in each species
d= N(N-1)/sum of n(n-1)
N= number of organisms of all species
n= number of organisms of each species
Higher value, higher species diversity
Which farming techniques reduce biodiversity, how to balance this with farming
Removal of hedgerows, plant hedgerows rather than erect fences as field boundaries
Creating monocultures, create natural meadows and use hay for silage
Filling in ponds, maintain ponds and create new ones
Overgrazing of land, leave cutting of verges until after flowering when seeds have dispersed
How can you investigate diversity by comparing observable characteristics and disadvantages
Observable characteristics are determined by genes and environmental influences. The variety of characteristics depends on the number of alleles of the gene
Characteristics are polygenic and altered by environment, inferring DNA differences from observable characteristics has been replaced with observing DNA itself
How can you compare genetic diversity by base sequence of DNA
Base sequence of DNA can be read and compared to that of another organism, similar DNA base sequence shows similar features between organisms showing a close evolutionary relationship, due to mutations a new species will have a different DNA base sequence
How can diversity be investigated by comparing the base sequence of mRNA
Base sequence on mRNA is complimentary to DNA, genetic diversity can be measured by comparing DNA between organisms and thus mRNA
How can diversity be investigated by comparing the amino acid sequence of proteins encoded by DNA/mRNA
Amino acid sequence is determined by mRNA which is determined by DNA, similarity between amino acid sequences of two different organisms can show genetic relation
