Chapter 13 study guide PDF

Preview

Summary

Download Chapter 13 study guide PDF

Description

Chapter 13 Study Guide

Palmtag Bio 1010C

1. What type of organisms have no known sexual life cycle, in other works which type of organism has never been observed to undergo meiosis? Organisms that reproduce asexually. Athlete's foot, yeast infection, Penecilum notatum, and brie. 2. Are there any organisms that are capable of reproducing both sexually and asexually? If so describe how mitotic cell division and meiotic cell division are used for either example. Yes certain fungi as well as protists display this. In the fungus life cycle during sexual reproduction a zygote undergoes meiosis creating haploid gametes which then undergo fertilization creating a diploid zygote. On the asexual side spore producing structures create spores that undergo mitosis, and further develop. 3. What types of organisms reproduce exclusively through sexual reproduction? Do they employ meiotic or mitotic cell division to do this? Humans and plants reproduce exclusively through sexual reproduction. Gametes (sperm and eggs) are created through meiosis in the gonads. The sperm and egg undergo fertilization, which is where the two gametes nuclei fuse. This creates the zygote, which then undergoes rounds of mitosis for further development. 4. Describe and explain how the following terms relate to mitosis and meiosis, also determine whether each term represents a diploid (2n) or haploid (n) cell (if applicable): gonads, testes, ovary, gametogenesis, germ cells, mitosis, gametocytes, meiosis, gametes, sperm, egg (ovum). Gonads and testes (diploid 2n) is where gametogenesis takes place or where gametes (haploid n) are formed through meiosis. Gametes are also referred to as sperm and egg (haploid n). A diploid germ cell undergoes mitosis creating a diploid gametocyte which then undergoes meiosis creating 4 haploid gametes. 5. What does a chromosome look like before the S-phase of Interphase? What does it look like after the S-phase of Interphase? What constitutes a pair of homologous chromosomes? If an organisms genome consists of 2n = 4, how many pairs of homologous chromosomes does the organism have? How many of those chromosomes are maternal and paternal? Is a paternal chromosomes matched with a maternal or paternal chromosome in one homologous pair? G1 is before the S phase. The chromosome is a single strand and the cell is preparing for the S phase where it will double itself. After the S phase, the DNA has doubled and there are now two sister chromatids or one homologous pair, attached at the centromere. There is still only 1 chromosome. A pair of homologous chromosomes 1

pair of sister chromatids. 2n=4 would indicate that there are two pairs of homologous chromosomes. 1 is maternal and 1 is paternal. A maternal is matched with a paternal. 6. Describe how each of the following terms relates to an organism’s genome: chromosomes, homologous pairs of chromosomes, DNA, locus, gene, and allele. An organism's genome can be defined, as it's genetic material. A chromosome is a cellular structure located in the nucleus that carries an organism's genetic information. A homologous pair of chromosomes is a pair of chromosomes that are the length, have the same centromere position, and posses genes for the same characteristics at the same loci (locus- location on the chromosome where you find a certain gene). One homolog is inherited from the father and one from the mother. DNA is a double helix structure that contains genes that are blueprints for making proteins. A gene is a unit of hereditary information that is found in DNA. An allele refers to any alternate version of a gene producing different phenotypic effects. 7. In a mammalian (human) life cycle; why is it stated that “fertilization always alternates with meiosis”? In order for fertilization to occur, meiosis is necessary to create the sexual reproduction cells (gametes). 8. How many chromosomes does one human cell contain? How many homologous pairs? How many individual chromosomes and homologous pairs are autosomes? What is an autosome? How many individual chromosomes and homologous pairs are sex chromosomes? What are the varieties of sex chromosomes, how do they determine sex, why is there a 50% chance that an offspring will be either a male or female? How many autosomes and sex chromosomes are in a sex cell? There are 46 chromosomes in one human cell with 22 homologous pairs. There are 44 chromosomes and 21 pairs of autosomes. Autosomes are all of the chromosomes except for the sex chromosomes X and Y. There are 2 sex chromosomes in one human sex cell. One X and one Y in males, and two X’s in females. The chances of an offspring being male or female is 50% because a male and female is the only way sexual reproduction may occur, after crossing XX with XY on a punnet square, the outcome will always be XX, XY, XX, XY or 50% male and 50% female.Sex cells contain half the amount of chromosomes as an autosome cell and no homologous pairs, therefore they contain 22 autosomes and 1 sex chromosome.

9. In one or two sentences describe how the end result of mitotic cell division is different from the end result of meiotic cell division? Be sure to use the terms diploid and haploid in your sentence(s).

The end result of mitosis is two genetically identical diploid cells, and the end result of meiosis is four haploid gametes each genetically distinct from one another and the parent cell. 10. Describe and explain in detail the differences between mitotic cell division and meiotic cell division. In your descriptions (or diagrams); focus on the status of the chromosomes at each individual phase. Start with G1 of interphase, be sure to include whether the cell is diploid or haploid at each phase, and whether a chromosome is duplicated or singular at each phase. In both Meiosis and Mitosis Interphase is the first step: G1 phase (Growth) diploid- The cell goes through rapid growth and metabolic activities. S phase (synthesis) diploid- the middle stage of interphase where the cell’s DNA is copied exactly. Which means that the chromatin replicates to create a second identical set of DNA. After the replication, the two identical chromosomes- sister chromatidsare joined at the centromere. G2 phase (growth 2) diploid- during the replication in S phase, the cell consumed a large amount of energy, therefore this stage allows the cell to regenerate energy for division. As well, the cell manufactures proteins and other molecules to make structures required for division of the nucleus and cell.

11. In gametogenisis when one female gametocyte undergoes meiosis how many gametes does it produce, how many are viable? When one male gametocyte undergoes meiosis how many gametes are produced, how many are viable? After going through meiosis, 4 gametes (eggs) are produced with only one being viable for females. Once male gametocytes go through meiosis, 4 gametes (sperm) are created and all 4 are viable.

12. Describe independent assortment, at what point in meiosis does it occur, how does independent assortment contribute to genetic recombination in offspring.

Independent assortment is how genetic variation is derived due to the random orientation of homologous pairs, and it occurs during metaphase I. Its expressed through the daughter cells as all of the possible outcomes of combinations of the parent cells. 13. If an organism has a diploid number of 24, how many combinations of chromosomes could a gamete potentially have? When this organism reproduces, how many combinations of chromosomes could the offspring potentially have? If an organism has a diploid number of 24 to calculate the number of chromosome combinations you would take the haploid number (12) and raise it to 2, which would give you 2096 combinations. To find the possible combinations of the offspring, you would take 212 x 212, which would give you 16,777,216 possible combinations. 14. Describe crossing over, at what point in meiosis does it occur, how does crossing over contribute to genetic recombination in offspring. Does it increase or decrease the possibility of genetic recombination in an offspring? Crossing over is the reciprocal exchange of genetic material between non-sister chromatids during prophase I of meiosis. Crossing over creates recombinant chromosomes which are individual chromosomes derived from different parents, and greatly increases the possibility of genetic recombination in an offspring. 15. Describe how genetic recombination contributes to the process of evolution. It continuously creates more and more genetic variation. 16. How does alternation of generation observed in plants differ from the life cycle of mammals (humans)? In humans, gametes are the only haploid cells. Once these gametes are produced they experience no further development until fertilization when two haploid gametes fuse to create a diploid zygote that then undergoes mitosis to further develop. Inalteration of generations both haploid and diploid stages of the plants life is consistently undergoing mitosis and developing. Part of the plants life is is a haploid gametophyte and once fertilized, it then moves into the diploid phase becoming a sporophyte....