genes and diversity Flashcards
What is genetic diversity?
The total number of different alleles in a population.
Define a gene mutation.
A change in the base sequence of DNA resulting in a new allele.
What is the role of histones in eukaryotic DNA?
Histones support DNA by allowing it to be coiled tightly into chromosomes.
Explain the structure of mRNA.
mRNA is a single-stranded, linear chain that corresponds to the genetic sequence of a gene with unpaired bases.
What is the significance of the genetic code being universal?
It provides indirect evidence for evolution as the same triplet code is used across all organisms.
Describe the process of transcription in eukaryotes.
- DNA hydrogen bonds break; 2. One DNA strand is a template; 3. Free RNA nucleotides align by complementary base pairing; 4. Uracil pairs with adenine; 5. RNA polymerase joins nucleotides by phosphodiester bonds; 6. Splicing removes introns, forming mature mRNA.
How does crossing over during meiosis increase genetic diversity?
Homologous chromosomes exchange alleles during prophase I at chiasmata, producing new allele combinations.
What is the purpose of using a t-test in genetic diversity studies?
A t-test assesses if the differences between two means are significant by calculating a p-value.
How do mutagenic agents increase the mutation rate?
Agents like UV radiation or chemicals induce changes in DNA, increasing gene mutation rates.
Describe stabilising selection with an example.
In stabilising selection, individuals with intermediate traits are more likely to survive, such as medium-sized human babies who have a higher survival rate than very large or small babies.
Explain the concept of a genetic bottleneck.
A bottleneck event drastically reduces population size, leading to reduced genetic diversity in the gene pool of the survivors.
List factors that can increase genetic diversity within a population.
Migration, mutations, and large population sizes.
Define ‘founder effect’ in population genetics.
When a few individuals establish a new population, reducing allele variety compared to the original population.
Explain why the genetic code is described as degenerate.
Multiple triplet codons can code for the same amino acid, reducing the effect of base substitutions.
Describe the role of ATP in translation.
ATP provides energy for forming peptide bonds between amino acids during polypeptide synthesis at the ribosome.
Define ‘index of diversity’ and explain its importance.
A measure of species richness and abundance, indicating biodiversity; higher values reflect more diverse ecosystems.
How does directional selection affect a population?
It increases the frequency of alleles for an extreme trait, e.g., antibiotic resistance in bacteria.
What adaptations allow species to survive in diverse environments?
Anatomical (e.g., blubber in whales), physiological (e.g., hibernation), and behavioral adaptations (e.g., possums playing dead).
What aseptic techniques are used to prevent contamination in microbiology?
Sterilizing equipment, working near a Bunsen flame, and using proper handling of cultures to avoid contamination by unwanted microorganisms.
Explain the process of meiosis in producing genetically diverse gametes.
In meiosis I, homologous chromosomes are separated, with crossing over and independent assortment introducing variation. Meiosis II separates sister chromatids, creating four unique haploid cells.
What is a phylogenetic classification system?
A system grouping organisms based on evolutionary relationships, with hierarchy from domain to species.
How does courtship behavior increase species survival?
By allowing species recognition and synchronization of mating, increasing chances of successful reproduction.
What is the difference between eukaryotic and prokaryotic DNA?
Eukaryotic DNA is linear, associated with histones, and located in the nucleus, while prokaryotic DNA is circular, not associated with histones, and found in the cytoplasm.
Explain the role of mRNA in protein synthesis.
mRNA carries the genetic code transcribed from DNA to ribosomes, where it guides the sequence of amino acids in protein synthesis.
How is genetic variation introduced during meiosis?
Through crossing over in prophase I and independent assortment of chromosomes in metaphase I.
What is the function of tRNA?
tRNA carries specific amino acids to the ribosome, where its anticodon pairs with mRNA codons during translation.
Define ‘species’ in terms of taxonomy.
A group of similar organisms that can interbreed and produce fertile offspring.
What is the role of ribosomes in translation?
Ribosomes facilitate the binding of tRNA to mRNA and catalyze the formation of peptide bonds between amino acids to form a polypeptide chain.
Describe the process of DNA replication.
- DNA helicase unwinds the DNA double helix, 2. Each strand acts as a template, 3. Free DNA nucleotides pair with complementary bases, 4. DNA polymerase joins nucleotides to form a new strand.
Explain the concept of codominance.
In codominance, both alleles in a heterozygote are fully expressed, resulting in a phenotype that shows both traits distinctly.
What is the function of an exon?
Exons are sequences within a gene that code for amino acids in the final protein product.
How does non-disjunction cause chromosomal disorders?
Non-disjunction during meiosis results in gametes with abnormal numbers of chromosomes, leading to disorders like Down syndrome (trisomy 21).
Define ‘polygenic inheritance’.
Polygenic inheritance occurs when multiple genes determine a single trait, such as height or skin color.
