BIO SCI 93 Chapter Notes - Chapter 13.4: Zygote, Natural Selection, Mendelian Inheritance

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Origins of genetic variation among offspring: the behavior of chromosomes during meiosis and fertilization is responsible for most of the variation that arises in each generation, 3 mechanisms contribute to the genetic variation arising from sexual reproduction: In humans n = 23 223 = about 8. 4 million. Each gamete that you produce in your lifetime contains one of roughly 8. 4 million possible combinations of chromosomes. Crossing over: crossing over produces recombinant chromosomes. Factor in the variation brought about by crossing over, # of possibilities greatly increases. The dipole number for fruit flies is 8, and the diploid number for grasshoppers is 46. Mutations in a gene leads to the different versions (alleles) of that gene. W/o crossing over, independent assortment of chromosomes during meiosis i theoretically can generate 2n possible haploid gametes, and random fertilization can produce 2n x 2n possible diploid zygotes.

Related Questions

1). Explain the significance of the fact that gametes contain half of the chromosome complement of somatic cells. Tell me something about variation, if you have a sibling (if you don't imagine you do) - how is your sibling's genetic make-up similar and/or different from yours? What about your mom and dad?

2). Explain the terms reductional division and equational division. What is reduced or kept equal? To which nuclear divisions do these terms refer?

3). What is the diploid number (2n = ?) of an organism if it has
a) 12 chromosomes at Anaphase of Mitosis?
b) 12 chromosomes at Anaphase I of Meiosis?
c) 12 chromosomes at Anaphase II of Meiosis?

4). Compare/contrast Metaphase I of Meiosis with Metaphase of Mitosis.

5). What are the two mechanisms of variation in Meiosis, and during which stage(s) does each occur?

6). Draw a diagram of a bivalent and label the following parts: centromere, sister chromatids, non-sister chromatids, homologous chromosomes, chiasma.

7). A diploid cell has 1 pair of acrocentric chromosomes (Chromosome 1) and 1 pair of submetacentric chromosomes (Chromosome 2).
Â· Gene X is on Chromosome 1. Gene Y is on the short arm of Chromosome 2 and Gene Z is on the long arm of Chromosome 2.
Â· The maternal chromosomes have the X, y, z alleles, whereas the paternal chromosomes have the x, Y, Z alleles.
Draw these chromosomes, labeling ALL alleles, as they might appear in Metaphase I of Meiosis.

What type of daughter cells are produced during meiosis?

A. genetically distinct due to crossing over

B. genetically identical to the mother cell

C. genetically identical to each other

D. genetically aneuploids

What is NOT a benefit of asexual reproduction compared to sexual reproduction?

A. The offspring will be as successful in the habitat as the parent.

B. all members of the population can reproduce themselves

C. The only source of variation in the next generation is mutation.

D. They do not require another organism of the opposite sex.

In what phase of meiosis does Independent assortment of homologous chromosomes occur?

A. meiosis I

B. interphase

C. cytokinesis

D. meiosis II

In what phase of meiosis does Independent assortment of homologous chromosomes occur?

A. meiosis I

B. interphase

C. cytokinesis

D. meiosis II

Fill in the blank, each word can be used more than once.

word bank- crossing over, avoid predation, reproduce,independent assortment, phenotypes, frequencies, nucleotides,meiosis, protein, prophase, segregation, gene, allele, amino acids,fertilization, arrangement, chromosome.

A(n) _________ is one of multiple forms of the same gene.

These different forms of genes are in the same locus of a(n)_________, but they have slightly different sequences of________.

During ________ I of meiosis, genes of homologous chromosomesalign side-by-side.

Then in a process called _________, homologous chromosomesrandomly line up double-file at the center of the cell and thenseperate. Since alleles are randomly distributed, this processcreates variation among the gametes. After ________ with a gametefrom the other sex, variation among gametes will create variationamong the offspring.

Some offspring will have a more favorable combination of allelesthan others, and will therefore survive and ________ moresuccessfully, leading to more favorable alleles in the nextgeneration. However, sometimes conditions change, andonce-favorable phenotypes may becomes less favorable.

Scientists hope that they will soon be able to use biotechnologyto track the ________ of alleles over multiple generations, therebywatching evolution as it occurs.

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BIO SCI 93 Chapter Notes - Chapter 13.4: Zygote, Natural Selection, Mendelian Inheritance

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