Meiosis and genetics Flashcards
(34 cards)
What is meiosis?
A two-billion-year-old process of cell division forming the basis of sexual reproduction, producing genetically unique haploid cells.
What is the purpose of meiosis in sexual life cycles?
To reduce chromosome number by half and ensure genetic diversity in gametes (reproductive cells)
How many chromosomes do human somatic cells have?
46 chromosomes in 23 homologous pairs, one from each parent.
What is the difference between meiosis I and II?
Meiosis I separates chromosomes; Meiosis II separates sister chromatids.
What happens during prophase I?
Chromosomes condense, homologous chromosomes pair via synapsis, crossing over occurs, and spindle fibers form.
What is synapsis?
Synapsis is the pairing of homologous chromosomes
What occurs during metaphase I and anaphase I?
Tetrads (4 chromatids) align at metaphase plate; homologous chromosomes are separated and pulled to opposite poles.
How is meiosis II similar to mitosis?
Sister chromatids separate in anaphase II, leading to four genetically different haploid cells.
What are the key differences between mitosis and meiosis?
Mitosis produces identical diploid cells ( 2 set of chromosomes) ; meiosis creates four genetically varied haploid cells (one set) .
What three events are unique to meiosis I?
Synapsis and crossing over, alignment of homologous pairs, and separation of chromosomes.
What did Gregor Mendel study?
Inheritance using pea plants, identifying concepts like dominant/recessive traits and segregation.
What is Mendel’s law of segregation?
Alleles separate during gamete formation so each gamete receives only one allele.
What is a gene?
Gene: heritable factor
What is a test cross?
Breeding a dominant-phenotype organism with a homozygous recessive to determine genotype.
What is the law of independent assortment?
Alleles of different genes assort independently during gamete formation.
What is incomplete dominance?
A blend of parental traits in heterozygotes (e.g., pink flowers from red and white).
What is codominance?
Both alleles in a heterozygote are fully expressed (e.g., AB blood type).
What is pleiotropy?
One gene affects multiple traits (e.g., sickle-cell disease).
What is epistasis?
one gene affects the expression of another gene (e.g., coat color in Labradors).
What is polygenic inheritance?
Multiple genes affect a single trait (e.g., skin color, height).
How does environment affect phenotype?
Phenotype is influenced by both genes and environmental factors (nature and nurture).
What are recessively inherited disorders?
require two copies of a mutated gene, one from each parent, to manifest the condition
What is cystic fibrosis?
A recessive disorder causing defective chloride channels and mucus buildup in organs.
What is sickle-cell disease?
A recessive disorder causing misshaped red blood cells, with heterozygote advantage in malaria regions.
