4) Genetic Info, Variation And Relationship Between Organisms Flashcards
DNA – Structure related to function
- stable due to numerous hydrogen bonds so can be passed on from generation to generation;
- weak hydrogen bonds between strands are easily broken for DNA replication or protein synthesis;
- large so can carry a lot of genetic information;
- base pairs are contained within the helix and held in place by the strong sugar-phosphate backbone;
- complementary base pairs allow the synthesis of an identical daughter molecule;
- 2 strands so both can act as templates
- helical shape means that it can be coiled so compact for storage;
Degenerate and Non-
overlapping
- Degenerate: more than one (base) triplet for each amino acid;
- Non-overlapping: each base is part of only one triplet;
Comparing DNA and mRNA
- DNA double stranded/double helix and mRNA single-stranded;
- DNA (very) long and RNA short;
- Thymine/T in DNA and uracil/U in RNA;
- Deoxyribose in DNA and ribose in RNA;
- DNA has base pairing and mRNA doesn’t/ DNA has hydrogen bonding and mRNA doesn’t;
- DNA has introns/non-coding sequences and mRNA doesn’t;
Comparing mRNA and tRNA
- mRNA longer;
- mRNA is a straight molecule but tRNA is a folded molecule/clover-leaf shaped molecule;
- mRNA contains hydrogen bonds but tRNA has hydrogen bonds;
Which two molecules are ribosomes
made from ?
- One of RNA/ribonucleic acid(s)/nucleotide(s)/nucleic acid(s)/rRNA/ribosomal RNA/ribosomal ribonucleic acid;
- One of protein(s)/polypeptide(s)/amino acid(s)/ peptide(s)/ribosomal protein;
Describe transcription
- DNA strands separate by breaking hydrogen bonds; (dna helicase)
- (Only) one of the strands is used as a template (to make mRNA);
- Complementary base pairing so A to U, T to A, C to G, G to C;
- (RNA) nucleotides joined by RNA polymerase;
- Forms phosphodiester bonds
- Pre-mRNA formed;
- Splicing/ introns removed to form mRNA
Describe translation
- mRNA binds to ribosome;
- ribosome moves to start codon/AUG
- Idea of two codons/binding sites;
- (Allows) tRNA with anticodons to bind/associate with codon on mRNA;
- tRNA brings specific amino acid;
- mRNA moves along to the next codon;
- (Catalyses) formation of peptide bond between amino acids (held by tRNA molecules);
Role of ribosome in translation
- mRNA binds to ribosome;
- Idea of two codons/binding sites;
- (Allows) tRNA with anticodons to bind/associate;
- (Catalyses) formation of peptide bond between amino acids (held by tRNA molecules);
- Moves along (mRNA to the next codon)/translation described;
Role of tRNA in translation
- anticodon complementary to codon/reads message on mRNA;
- specific amino acid;
- carried/transferred (to ribosome);
- correct sequence of amino acids along polypeptide;
Meiosis – Causes of Variation
- Homologous chromosomes pair up;
- Chiasmata formed
- Independent segregation;
- Maternal and paternal chromosomes are re-shuffled in any combination;
- Crossing over leads to exchange of parts of (non-sister) chromatids/alleles between homologous chromosomes;
- (Both) create new combinations of alleles;
Meiosis – Process of Crossing Over
- Homologous pairs of chromosomes associate / form a bivalent;
- Chiasmata(ta) form;
- (Equal) lengths of (non-sister) chromatids / alleles are exchanged
- Producing new combinations of alleles;
How does mutation
cause change in enzyme function?
- Change in amino acid / (sequence of) amino acids / primary structure;
- Change in hydrogen / ionic / disulphide bonds alters tertiary structure / active site (of enzyme);
- Substrate not complementary / cannot bind (to enzyme / active site) / no enzyme- substrate complexes form;
How does mutation
cause change in protein (receptor)
structure
- Change in DNA base (sequence);
- Change in amino acid (sequence)/primary structure;
- Alters (position of) hydrogen/ionic/disulfide bonds;
- Change in tertiary structure (of receptor);
Mutation leading to
evolutionary changes/phylogenetic
relationships
- Mutations change base / nucleotide (sequence);
- (Causing) change in amino acid sequence;
- Mutations build up over time;
- Few(er) mutations / differences (in amino acid / base / nucleotide sequence / primary structure) in closely related species;
- Closely related species have recent common ancestor;
Why it is courtship song important for species recognition
- (acts as) sign stimulus/releaser (= the essential feature of a stimulus, which is necessary to elicit a response);
- responds only to species-specific sound;
- Song characteristic of species / differs between species;
- Song linked to courtship
The importance of courtship behavior
- enables male I female to recognise opposite sex;
- enables recognition of own species;
- synchronises mating behaviour
How does courtship behaviour increase probability of mating
- Attracts mate of the same species;
- Indication of sexual maturity / fertility / synchronises mating;
- Stimulates release of gametes;
- Formation of a pair bond / bond between two organisms (to have / raise young)
Why are hybrids unable to reproduce.
- Females not attracted to call of male / does not recognise male;
- Because of differences in song/sign stimulus;
- Necessary precursor to mating;
- Hybrids are sterile
Define species richness
The number of different species in a community
Effect on biodiversity with larger fields
- Larger fields have more centre / less hedge / fewer species;
- Biodiversity decreases
Farming Techniques – Pros and
Cons to farmer for Planting Hedges
Pros -
1. Greater (bio)diversity so increase in predators of pests
2. Increase in predators of pests so more yield/income
3. Increase in pollinators so more yield/income
Cons -
1. Reduced land area for crop growth/income
2. Greater (bio)diversity so increase pest population
3. Increase pest population so less yield/income
4. Increased competition so less yield/income
