Chapter 13: Meiosis and Sexual Life Cycles

Question 1

Genes

Answer 1

hereditary units

Question 2

Gametes

Answer 2

reproductive cells

Question 3

Locus

Answer 3

gene’s location

Question 4

Asexual Reproduction

Answer 4

a single organisms passes on genetic information to its offspring in the form of an exact genetic copy of themselves

Question 5

Clone

Answer 5

the offspring of asexual reproduction, genetically identical individuals

Question 6

Sexual Reproduction

Answer 6

two parents have an offspring with genetic variability from unique combos of genes from both parents

Question 7

Karyotype

Answer 7

ordered display of chromosomes

Question 8

Homologs or homologous chromosomes

Answer 8

two identical chromosomes (same length, staining pattern, centromere position)

Question 9

Sex chromosomes

Answer 9

X and Y chromosomes

Question 10

Autosomes

Answer 10

All chromosomes except X and Y

Question 11

Sex celss

Answer 11

l

Question 12

Fertilization

Answer 12

union of gametes, fusing their nuclei (like sperm and egg)

Question 13

Zygote

Answer 13

diploid combo of gametes, the resulting fertilized egg

Question 14

Alternation of generations

Answer 14

the alteration of meiosis and mitosis in the sexual life cycle of plants. sporophyte produces the gametophyte, and the gametophyte produces the sporophyte

Question 15

Chiasmata

Answer 15

points of crossover during meiosis

Question 16

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

Answer 16

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.

Question 17

Humans have ____ chromosomes that make up ____ pairs of genes

Answer 17

46, 23

Question 18

Discuss the difference between mitosis and meiosis

Answer 18

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.

Question 19

List the 3 different sexual life cycles and describe each

Answer 19

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.

Question 20

Using the figures in your book and notes, be able to identify any phase of meiosis

Answer 20

.

Question 21

What 3 mechanisms of cell division contribute to genetic variability? Explain or describe each mechanism.

Answer 21

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.