10.3 Study Guide Flashcards
What is meiosis?
Meiosis is the division of a parent cell into four unique haploid daughter cells.
What are homologous chromosomes and sister chromatids?
Homologous chromosomes are pairs of chromosomes, one from each parent, that carry the same genes but different alleles. Sister chromatids are identical copies of a single chromosome (produced during cell division).
What are asexual and sexual reproduction?
Asexual reproduction is where one parent copies itself to form a genetically identical offspring. A mutation in the DNA could cause variation. Example: Mitosis
Sexual reproduction is where an organism combines the genetic information from each of its parents and is genetically unique. Mutations and crossing over may cause genetic variation. Example: Meiosis
What is fertilization?
Fertilization is the process where the haploid sperm and egg cells are combined to make the diploid zygote cell.
What is a gamete and a somatic cell?
Gamete: One of the four haploid cells created during meiosis. Each is unique. Example: Egg and sperm cells
Somatic Cells: The cells made during mitosis. They are the body’s cells, each is identical to each other.
What do haploid (n) and diploid (2n) mean?
Haploid (n): One copy of each chromosome
Diploid (2n): Two copies of each chromosome
What is a tetrad?
A tetrad is formed when homologous chromosomes are paired together during synapsis.
What is synapsis?
The pairing of homologous chromosomes.
What is crossing over?
Homologous chromosome pairs swap pieces of chromosome, creating new combinations of traits.
What is independent assortment?
The chromosomes combine differently, creating varied pairings, which leads to different combinations of the chromosomes in the gametes.
What is the order and what are the events of the stages in meiosis? What does the cell look like in each stage of meiosis?
Order: Interphase 1, Prophase 1, Metaphase 1, Anaphase I, Telophase 1, Prophase II, Metaphase II, Anaphase II, and Telophase II. Before the first round of meiosis, the chromosomes are copied during the synthesis stage. Then, the chromosome pairs condense. The homologous chromosomes pair together and condense while the nuclear membrane breaks down. They chromosome pairs may cross over, and swap pieces of chromosome. Then, they line up along the metaphase plate and the spindle fibers pull the pairs of homologous chromosomes apart, leaving pairs of sister chromatids. These pairs of sister chromatids go into two new daughter cells. Then, in each of these two new daughter cells, the pairs of chromosomes condense as the nuclear membrane breaks down. Then, they line up along the metaphase plate and the spindle fibers pull each sister chromatid apart into individual chromosome strands. Then, these chromosome strands go into new daughter cells. In the end, there are four unique daughter cells with different combinations of chromosomes.
When is the chromosome number reduced by half?
By the end of meiosis 1, the chromosome number is reduced by half in each cell.
What are the sources of genetic variation?
Independent assortment, crossing over, random fertilization, and mutations in the DNA.
Random fertilization: Any sperm plus any egg created trillions of varied combinations of chromosomes from different parents.
Mutations in the DNA result in different chromosomes being created, which leads to different chromosome combinations.
Compare/contrast mitosis and meiosis.
Similar: Both are types of cell division, both occur in multicellular organisms, parent cells are genetically identical, and daughter cells are produced. Both have prophase, metaphase, anaphase, and telophase. Genetic variation may be caused by mutations that occur during DNA replication.
Mitosis: Daughter cells are diploid cells, daughter cells are somatic cells, produces cells for growing and healing, parent cells are somatic cells. two identical cells made, divides one at a time, during Metaphase, sister chromatids line up, during anaphase, sister chromatids separate, mutation is only source of variation, type of asexual reproduction, little genetic variation between daughter cells.
Meiosis: Parent cells are germ cells, produces reproductive cells, daughter cells are haploid cells, daughter cells are gametes, Anaphase II: 1/2 the number of sister chromatids separated, four different cells are made, Metaphase II: 1/2 the number of sister chromatids line up, Anaphase I: chromosome pairs are separated, Metaphase I: Chromosome pairs line up,
divides two times, crossing over can rearrange genes on chromosomes, allows for recombination of DNA, produces cells for sexual reproduction, greater variety in offspring,
Compare/contrast asexual and sexual reproduction.
Similarities: Mutations in the DNA may result in genetic variation
Asexual: Little variation between daughter cells, mitosis is an example, mutation is the only source of genetic variation, offspring receive parent’s traits, does not require an organism of the opposite sex
Sexual: crossing over may result in genetic variation, gametes produced by meiosis are used, new combinations of DNA are a result, males do not reproduce themselves, so the population does not grow as quickly, more variation, which increases survival and chance for descendants.
