Podcast
Questions and Answers
In meiosis, the number of daughter cells produced is ______.
In meiosis, the number of daughter cells produced is ______.
4
Meiosis involves ______ divisions.
Meiosis involves ______ divisions.
2
In sexual reproduction, the offspring are ______ to either parent.
In sexual reproduction, the offspring are ______ to either parent.
not identical
Oogenesis is the production of ______ in the ovaries.
Oogenesis is the production of ______ in the ovaries.
Signup and view all the answers
Spermatogenesis results in the production of ______ sperm cells.
Spermatogenesis results in the production of ______ sperm cells.
Signup and view all the answers
External fertilization typically occurs in ______ and fish.
External fertilization typically occurs in ______ and fish.
Signup and view all the answers
Parthenogenesis refers to the development of an unfertilized ______ into an adult animal.
Parthenogenesis refers to the development of an unfertilized ______ into an adult animal.
Signup and view all the answers
Meiosis is a type of cell division in which the daughter cells receive only half the number of ______ present in the parent cells.
Meiosis is a type of cell division in which the daughter cells receive only half the number of ______ present in the parent cells.
Signup and view all the answers
Homologous chromosomes are pairs of similar chromosomes that carry ______ for the same trait.
Homologous chromosomes are pairs of similar chromosomes that carry ______ for the same trait.
Signup and view all the answers
Humans have a total of ______ chromosomes, which include 22 pairs of homologous chromosomes and one pair of sex chromosomes.
Humans have a total of ______ chromosomes, which include 22 pairs of homologous chromosomes and one pair of sex chromosomes.
Signup and view all the answers
Diploid cells contain the full number of chromosomes represented as ______.
Diploid cells contain the full number of chromosomes represented as ______.
Signup and view all the answers
Gametes are specialized sex cells, with female gametes known as ______ cells.
Gametes are specialized sex cells, with female gametes known as ______ cells.
Signup and view all the answers
During prophase I, synapsis results in four chromatids joining together to form a ______.
During prophase I, synapsis results in four chromatids joining together to form a ______.
Signup and view all the answers
In anaphase I, disjunction refers to the separation of tetrads into ______ chromosomes.
In anaphase I, disjunction refers to the separation of tetrads into ______ chromosomes.
Signup and view all the answers
At the end of telophase II, ______ haploid cells are produced.
At the end of telophase II, ______ haploid cells are produced.
Signup and view all the answers
Study Notes
Meiosis and Sexual Reproduction
- Meiosis is a cell division process where daughter cells receive half the chromosomes of the parent cell.
- Homologous chromosomes are pairs of similar chromosomes (same size, shape) carrying alleles (genes) for the same trait.
- Humans have 46 chromosomes (22 pairs of homologous chromosomes and one pair of sex chromosomes).
- Autosomes are chromosomes other than sex chromosomes (somatic/body cells).
- Diploid cells contain the full number of chromosomes (2n).
- Haploid cells (gametes) contain half the number of chromosomes (n) and lack homologous pairs.
- Gametes are specialized sex cells.
- Female gametes are egg cells/ova (ovum is singular).
- Male gametes are sperm cells.
- Fertilization is the fusion of sperm and ovum nuclei to form a zygote.
- Meiosis is a "reduction division" in specialized cells for reproduction, preparing sex cells. The process follows IPMATPMAT.
Stages of Meiosis
-
Prophase I:
- Each chromosome has already replicated and consists of two chromatids.
- Synapsis results in four chromatids joining to form a tetrad.
- Homologous chromosomes line up close together and become attached at their centromeres (Synapsis).
- Crossing over occurs (exchange of segments between chromatids) as tetrads form.
-
Metaphase I:
- Centromeres are attached to spindle fibers.
- Tetrads line up at the equatorial plane.
-
Anaphase I:
- Disjunction - separation of tetrads into homologous chromosomes.
- Non-disjunction - the failure to separate homologous chromosomes.
-
Telophase I:
- Cytokinesis (division of cytoplasm) forms daughter cells.
- Nuclear membranes reappear around the nuclei.
- No further chromosome replication; the rest of the process resembles mitosis.
-
Prophase II: Both daughter cells divide.
-
Metaphase II: Homologous chromosomes line up on the equator.
-
Anaphase II: Homologous chromosomes separate.
-
Telophase II: 4 different haploid cells (gametes) are produced.
Mitosis vs. Meiosis
-
Mitosis:
- 2 daughter cells
- 1 cell division
- Chromosome number same as parent
- Daughter cells identical to parent cells
- Asexual reproduction
-
Meiosis:
- 4 daughter cells
- 2 cell divisions
- Chromosome number half of parent
- Daughter cells different from parent cells
- Sexual reproduction
Sexual Reproduction Advantages
- Offspring are not identical to either parent.
- Variations in offspring increase adaptability in a changing environment.
- Individuals can move into new environments.
- A diverse population increases the likelihood of species survival.
Sexual Reproduction in Simple Organisms
-
Conjugation: Allows recombination of hereditary material to create new varieties of organisms.
- Spirogyra: Cell material flows between two cells through a conjugation tube, forming a zygospore.
- Paramecium: A protoplasmic bridge forms between two cells, enabling material exchange. Mating types (e.g., positive/negative) and isogametes are involved.
- Bacteria: Similar mechanisms of genetic exchange exist.
Sexual Reproduction in Animals
-
Gonads: Specialized organs producing gametes.
- Ovaries: Produce ova (egg cells).
- Testes: Produce sperm cells.
- Hermaphrodites: Contain both ovaries and testes.
Gametogenesis
-
Oogenesis: Production of ova in the ovaries.
- Meiotic division produces 3 polar bodies and one mature ovum.
-
Spermatogenesis: Production of sperm in the testes.
- Meiotic division produces 4 sperm cells.
Comparison of Egg and Sperm
- Egg cells contain yolk and are larger than sperm.
- Sperm are motile, eggs are sessile.
Fertilization
- Fusion of sperm and egg nuclei to form a zygote.
- Diploid (2n) chromosome number is restored.
- External fertilization: Takes place outside the body (e.g., amphibians, fish). More eggs are produced relative to internal fertilization.
- Internal fertilization: Takes place inside the body (e.g., mammals, birds). Fewer eggs are produced relative to external fertilization.
Parthenogenesis
- Development of an unfertilized egg into an adult animal.
- Occurs in some species of bees, ants, and aphids.
Karyotype
- A visual representation of an organism's chromosomes. Humans have 23 pairs, including 22 autosomes and a pair of sex chromosomes.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
