Bio term 2 reivison 2024 Flashcards
- Purpose of Mitosis
o Mitosis is the process of cell division that results in two genetically identical daughter cells.
o Its primary purpose is growth, repair, and maintenance of multicellular organisms, as well as asexual reproduction in some single-celled organisms.
- Process and Outcomes of Meiosis
o Meiosis is a type of cell division that produces gametes (sperm and egg cells) with half the chromosome number of the parent cell.
o It involves two rounds of division, resulting in four haploid daughter cells, each genetically distinct from the parent cell and from each other.
- Two Different Alleles for a Single Trait
o An individual organism might have two different alleles for a single trait due to inheritance, where one allele is inherited from each parent.
o This genetic variation contributes to diversity within a population and can lead to different phenotypic expressions of the trait.
- Phenotypic Ratio of Offspring
o The expected phenotypic ratio of offspring from a cross between a heterozygous tall plant (Tt) and a homozygous short plant (tt) is 1:1, tall to short.
- Probability of Child with Autosomal Recessive Disorder
o If both parents are carriers of an autosomal recessive disorder, the probability that their next child will have the disorder is 25% or 1 in 4.
- Chromosomal Abnormality - Trisomy 21
o Trisomy 21, also known as Down syndrome, results from an extra chromosome 21, leading to developmental delays and distinct physical features.
- Blood Type Crosses
o A cross between blood type AB and O individuals can result in offspring with blood types A or B, depending on the specific alleles inherited from the parents.
- Complementary DNA Strand for: CGTACGTA
o GCAUGCAU (complementary bases: G-C, C-G, T-A, A-T)
- Punnett Square for Haemophilia Carrier
o Female (XHXh) × Male (XhY)
o Probability of having a haemophilic child: 50%
- Crossing Over in Meiosis and Genetic Diversity
o Crossing over during meiosis results in the exchange of genetic material between homologous chromosomes, leading to genetic recombination and increased genetic diversity among offspring.
- Homologous Structure Example
o Homologous structures are similar structures found in different species that share a common ancestor.
o Example: The forelimbs of vertebrates, such as the wings of bats, flippers of dolphins, arms of humans, and wings of birds, are homologous structures. They indicate common ancestry despite serving different functions.
- Structure Supporting Common Ancestry
o The presence of a notochord in early vertebrate embryos supports the theory of common ancestry.
o The notochord is a flexible rod-like structure found in the embryos of all chordates, including vertebrates, suggesting a shared evolutionary history.
- Process of Natural Selection
o Natural selection is the mechanism of evolution whereby organisms better adapted to their environment tend to survive and reproduce more successfully.
o Over time, this process leads to the accumulation of beneficial traits in a population, resulting in evolutionary change.
- Antibiotic Resistance Development
o Overuse or misuse of antibiotics can lead to the development of antibiotic-resistant bacteria.
o Bacteria can acquire resistance through mutations or by acquiring resistance genes from other bacteria through horizontal gene transfer.
- Mechanisms Contributing to Genetic Variation
o Two mechanisms contributing to genetic variation in populations are mutation and genetic recombination through processes like crossing over and independent assortment during meiosis.
