Chapter 13
What is the difference between asexual and sexual reproduction?
Asexual reproduction involves one parent producing genetically identical clones through mitosis, allowing for rapid reproduction. Conversely, sexual reproduction requires two parents to create genetically unique offspring via meiosis and fertilization, promoting genetic diversity. Asexual is faster, while sexual is slower but enhances adaptation.
What is the difference between an allele and a gene?
A gene is a segment of DNA that determines a specific trait (e.g., eye color), while an allele is a specific variant or "flavor" of that gene (e.g., blue vs. brown eyes). Genes are inherited in pairs—one from each parent—and these paired alleles determine an individual's unique phenotype.
How can the alteration of chromosome number or structurally altered chromosomes (deletions, duplications, etc.) can cause genetic disorders?
Alteration of chromosome number or structure causes genetic disorders by disrupting the necessary dosage of genes needed for proper development. Numerical errors (aneuploidy) lead to too many or too few chromosomes, while structural alterations (deletions, duplications, translocations) break or rearrange genes, leading to severe developmental delays, mental disabilities, and physical disorders.
What are crossing over, independent assortment, and random fertilization?
Crossing over, independent assortment, and random fertilization generate immense genetic variability by shuffling and combining alleles during meiosis and fertilization. Crossing over (prophase I) exchanges DNA between homologous chromosomes, creating new allele combinations. Independent assortment (metaphase I) randomly distributes maternal/paternal chromosomes, producing unique gametes. Random fertilization then merges these diverse gametes, ensuring unique offspring.
What is the role of meiosis and fertilization in sexually reproducing organisms?
Meiosis and fertilization are essential for sexual reproduction because they maintain a constant chromosome number across generations and generate genetic variation. Meiosis reduces the chromosome count by half to produce haploid gametes, while fertilization restores the diploid number, creating a unique zygote that combines DNA from both parents.
Who the hell is Gregor Mendel?
A MONK! That's fun. But he also brought experimental and quantitative approach to genetics and bred pea plants for some reason?
What is mendel's law of inheritance?
Mendel's laws of inheritance, developed by Gregor Mendel in the 1860s through pea plant experiments, describe how traits are passed from parents to offspring. The three primary principles are the Law of Dominance, Law of Segregation, and Law of Independent Assortment, which collectively explain how discrete genes (alleles) determine phenotypes.
What is the source of genetic variation?
Random fertilization
What is the importance of homologous chromosomes to meiosis?
Homologous chromosomes, pairs of maternal and paternal chromosomes, are essential in meiosis for generating genetic diversity and ensuring proper chromosome reduction. They pair up (synapsis) and undergo crossing over in Prophase I, exchanging genetic material, and then separate to produce haploid gametes.
What are P, F1 and F2?
P (parental) generation = true breeding plants
F1 (first filial) generation = offspring
F2 (second filial) generation = F1 offspring
What is the law of dominance?
In a heterozygote, the dominant allele masks the recessive allele, determining the organism's trait.
What are phenotype and genotype?
A genotype is an organism’s underlying genetic makeup or specific combination of alleles inherited from parents. A phenotype is the observable, physical, or behavioral trait resulting from that genotype (e.g., blue eyes, purple flowers). Genotype is the blueprint, while phenotype is the expressed outcome influenced by genes and environment.
How is the chromosome number is reduced from diploid to haploid through the stages of meiosis?
Meiosis reduces chromosome number from diploid through one round of DNA replication followed by two sequential divisions (Meiosis I and II). Reduction occurs during Anaphase I, where homologous chromosome pairs separate, ensuring each daughter cell receives only one set of chromosomes rather than pairs.
What are dominant and recessive genes?
Dominant genes express their trait with only one copy present, masking the other (recessive) gene. Recessive genes require two copies—one from each parent—to be expressed. Dominant genes often produce functional proteins, while recessive genes often represent a nonfunctional or reduced version, determining traits like eye color, hair type, or disease risk.
What is the Law of Segregation? (RUDE)
During gamete formation (meiosis), the two alleles for a trait separate, ensuring each parent passes only one allele to the offspring.
How does genetic imprinting and inheritance of mitochondrial DNA are exceptions to standard Mendelian inheritance?
Genetic imprinting and mitochondrial DNA (mtDNA) inheritance violate Mendelian laws by showing parent-of-origin effects and maternal-only transmission, rather than biparental inheritance of equal allele probability. Imprinting involves differential methylation that silences one parent's allele, while mtDNA inherits solely from the egg cell, passing mutations to all offspring
What are important differences between mitosis and meiosis?
Mitosis produces two genetically identical diploid somatic cells for growth and repair, while meiosis produces four genetically unique haploid gametes (sperm/eggs) for sexual reproduction. Mitosis involves one division, whereas meiosis involves two, reducing the chromosome number by half to create genetic diversity.
What are homozygous and heterozygous traits?
A homozygous trait occurs when an individual inherits identical alleles for a gene from both parents or , while a heterozygous trait occurs when an individual inherits two different alleles Homozygous traits produce consistent offspring, whereas heterozygous traits often result in the expression of the dominant allele.
What is the Law of Independent Assortment?
Genes for different traits are inherited independently of one another. The inheritance of one trait does not affect the inheritance of another, provided the genes are on separate chromosomes.
How many chromosomes for each condition- Diploid, triploid, monosomic, trisomic?