Chapter 13: Meiosis and Sexual Life Cycles Flashcards
Genes
hereditary units
Gametes
reproductive cells
Locus
gene’s location
Asexual Reproduction
a single organisms passes on genetic information to its offspring in the form of an exact genetic copy of themselves
Clone
the offspring of asexual reproduction, genetically identical individuals
Sexual Reproduction
two parents have an offspring with genetic variability from unique combos of genes from both parents
Karyotype
ordered display of chromosomes
Homologs or homologous chromosomes
two identical chromosomes (same length, staining pattern, centromere position)
Sex chromosomes
X and Y chromosomes
Autosomes
All chromosomes except X and Y
Sex celss
l
Fertilization
union of gametes, fusing their nuclei (like sperm and egg)
Zygote
diploid combo of gametes, the resulting fertilized egg
Alternation of generations
the alteration of meiosis and mitosis in the sexual life cycle of plants. sporophyte produces the gametophyte, and the gametophyte produces the sporophyte
Chiasmata
points of crossover during meiosis
Explain the following to your friend:
“In a literal sense, children don’t inherit particular physical traits from their parents, it is the genes that are actually inherited
The physical traits derived from our genes are called phenotype. We don’t inherit phenotypes from our parents. We inherit genes and genotypes from our parents. Both of my parents have hazel eyes. I did not inherit my parents hazel eyes. Neither did any of my sisters. The reason we didn’t inherit these physical traits is because our DNA doesn’t code for the phenotype “hazel eyes”. Both my parents have the gene for brown eyes, and because of this my siblings all have brown eyes. We inherit genes that in turn determine our physical traits.
Humans have ____ chromosomes that make up ____ pairs of genes
46, 23
Discuss the difference between mitosis and meiosis
Mitosis is the process of somatic cell division. Loose chromosomes that were duplicated in interphase wind up tightly, pair up and join at their centromere, align at the metaphase plate, attach to spindle fibers, split up, and form new nuclei. Let’s call the P.M.A.T. (Prophase, Anaphase, metaphase, Telophase.) The result of this is an exact replica of the cell before. Mitosis produces 2 daughter cells. They have the exact same genetic make-up.
Meiosis is the process of sex-cell division. It follows the same structure of mitosis, with a very distinct difference, it performs 2 rounds of P.M.A.T. Meiosis takes the 46 chromosomes (which is actually 96 chromotids, wow!) and goes through P.M.A.T one time. During Prophase 1, chromosomes perform something called “Cross Over”. They still do their normal function of winding and pairing, but they also cuddle up to each other and swap alleles. This “Crossing over” will give each daughter cell genetic variance. The next distinct difference is in Metaphase 1 when the chromosome align at the metaphase plate, instead of a single file line, there are two lines. The rest of the process remains the same as before. Then we move into P.M.A.T. round 2. The daughter cells (both of them) undergo P.M.A.T again, without all the cool Cross Over stuff. And because there’s only the normal amount of 46 chromosome (and 46 chromatids) there’s only one line at the metaphase plate. So, it’s pretty much normal P.M.A.T stuff. However, now we have a total of FOUR genetically unique cells (eggs, sperm), that might help form very unique humans in the future.
List the 3 different sexual life cycles and describe each
Sexual life cycles all happen by meiosis and fertilization, the timing of these things vary the life cycles between animals, plants, and fungi.
In animals, the gametes are the only haploid cells. Meiosis occurs during the production of gametes, which don’t divide anymore because they’re haploid. THen they move to fertilization, creating a diploid zygote. The zygote divides by mitosis, creating another animal.
Plants undergo alteration of generations. The original multicellular organism is called the sporophyte, and produces not gametes, but haploid spores, by meiosis. Those spores embed and divide mitoticallly to make a whole new organism, gametophyte. The gametophyte undergoes mitosis, as well, producing gametes, still haploid. These gametes fertilize, creating a diploid zygote that will develop into our sporophyte.
Fungi also produce differently. After forming a diploid zygote, meiosis occurs without producing a multicellular diploid offspring. Meiosis produces haploid cells that divide by mitosis, producing unicellar organisms or haploid multicellular organism. The haploid organism undergoes mitosis, producing gametes. The only diploid stage of fungi’s sexual life cycle is the zygote.
Using the figures in your book and notes, be able to identify any phase of meiosis
.
What 3 mechanisms of cell division contribute to genetic variability? Explain or describe each mechanism.
Independent assortment of chromosomes- chromosomes align randomly at the metaphase plate which when separated form new daughter cells that offer genetic variability.
Crossing over- two sister chromatids swap genetic information at chiasma. (Sister hood of the Traveling Genes)
Random Fertilization- in humans, each member produces about 8.4 million (2^23) different combos of our genes in our gametes, when fertilized that’s 70 trillion different possible combos (2^23x2^23). Fertilization is random. You aren’t just one in a million. You are a 1/70Trillion.
