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BIOLOGY 1113 Lecture Notes - Lecture 25: Homologous Chromosome, Cell Division, Sexual Reproduction

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jadesheep597
17 Oct 2018
School
Ohio State University
Department
Biology
Course
BIOLOGY 1113
Professor
Eric Danhart

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BIOLOGY 1113 Lecture Notes - Lecture 24: Sister Chromatids, Chromatid, Centromere

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BIOLOGY 1113 Lecture Notes - Lecture 25: Homologous Chromosome, Cell Division, Sexual Reproduction

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BIOLOGY 1113 Lecture 26: Lecture #26 Bio Notes

Document Summary

All images are credit to freeman biology 6th edition. Cell division- new cell creation by division of old cells. Embryo- beginning stage of development, however, after fertilization/zygote formation. Meiosis(reduction division)- sexually reproducing organisms, diploid parent cell(2n) produces haploid cells(n)(gametes), creating half of chromosome number. Gamete- reproductive cell, haploid, fuses w/ other haploid cell to form zygote(diploid). Sperm- male gamete, reproductive cell, egg- female gamete, reproductive cell. Fertilization- fusion of nuclei of 2 gametes(haploid), forming zygote w/ nucleus(diploid). Each organism has a certain # of chromosomes(humans = 46). Sex chromosomes- chromosomes differ in shape/# in males/females. Homologous chromosomes(not identical, alleles)- diploid organisms, member of pair of chromosomes that are same size, shape, and gene content. Homologs- same type of chromosomes in diploid/polyploid organism. Homologous pair- diploid organisms, pair of chromosomes same size, shape, gene, in same position along chromosomes. Gene- segment of dna, found in specific place, influencing hereditary trait. Allele- distinct version of gene, different forms of genes.

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Related Questions

Match the terms to the definitions provided.

Question 1 options:

gamete

somatic cells

zygote

sexual reproduction
1.

Reproductive life cycle that involves an alternation between haploid and diploid cells
2.

A single cell with a diploid number of chromosomes resulting from the fusion of an egg and a sperm.
3.

Cells (egg or sperm) resulting from a meiotic division of germ-line cells
4.

The non-reproductive cells found in embryos and mature individuals

Question 2 (5 points)

Match the terms to the definitions provided.

Question 2 options:

syngamy

haploid

meiosis

diploid

germ-line cells
1.

The cells that will eventually undergo meiosis to produce gametes.
2.

The number of chromosomes found in gametes (eggs or sperm).
3.

The process by which two haploid gametes fuse to form a new diploid cell.
4.

A specialized reduction division that produces cells with half the normal number of chromosomes.
5.

Two sets of chromosomes present in the somatic cells of adult individuals.

Ploidy refers to the number of complete sets of chromosomes (genes) present in a cell. The number of chromosomes in a complete set is a fixed characteristic of a species. Humans are diploid with two sets of 23 chromosomes. Fruit flies are diploid with two sets of 4 chromosomes. Sexually reproducing organisms are diploid, each somatic cell of an organism has two complete sets ("di" is a prefix indicating 2.). To complete a life cycle and reproduce new members of a species, mating is required. Mating brings a donation from a male and a donation from a female together. However, if the male and female cells remain diploid, the fertilization will result in a tetraploid zygote. In general, these are not viable. A mechanism is needed to form special haploid cells, gametes. The diploid set is split precisely into two complete haploid sets. That mechanism is meiosis.

The complete set of chromosomes of a species is also the complete set of genes of a species, the genome. (Yes, there is a minor contribution from mitochondria and chloroplasts. Inheritance of this information is "cytoplasmic".)

Please answer the following questions:

1. How many chromosomes in a brain cell of a fruit fly? How many chromosomes are in a liver cell of a human? Explain both answers.

2. How many chromosomes are in a fruit fly unfertilized egg? How many chromosomes are in a human egg? Explain both answers.

3. Why is meiosis necessary for sexually reproducing organisms? How many chromosomes are in a human zygote? Relate the two answers.

4. What is a gene allele? Suppose there is a gene called "bingo" and it is present once in a complete haploid set. How many alleles of "bingo" does a diploid individual have? How many copies or versions of the gene "bingo" are present in a diploid individual?

5. Modern DNA sequencing clearly identifies alleles by showing the different DNA sequence of each allele. These alleles may be termed structural alleles (I coined the term for this problem.). Classical genetics only dealt with phenotypes or visible traits. As a result, alleles of genes were identified by functionality, usually normal or non-functional. Using your knowledge of gene structure and gene expression, postulate a relationship between structural alleles and functional alleles. (include relative amounts; more, less, or equal).

What is a genome? What is a genome made of? Describe the bacterial genome. How do bacteria reproduce? What is binary fission? Distinguish between a chromosome and chromatin. Where are chromosomes located in eukaryotic cells? What is the chromosome made of? What is a centromere? What is the centromere's role? What are sister chromatids and how do they arise? Distinguish between somatic cells and germ (gametes) cells. Describe the cell cycle. What are the different phases? What occurs during S phase? What is interphase? How is the cell cycle controlled?

Describe mitosis. What are the phases of mitosis? What occurs in each of the phases of mitosis? What is cytokinesis? How does this differ between plant and animal cells? What is a kinetochore? Where does it form? What is its role? What is the role of microtubules in mitosis? What is a centriole and what is it composed of? What is a centrosome and what is its role in mitosis? What is the metaphase plate and why is this important? What is the mitotic spindle, its role and its makeup? What defines a diploid cell? How many copies of each chromosome is in a diploid cell? What about a haploid cell? Why do the daughter cells of mitosis always have the same complement of chromosomes?

Describe meiosis. What are the phases of meiosis? What occurs in each of the phases of meiosis? Distinguish between meiosis I and meiosis II and describe how each of these processes compare to mitosis. Why do animal cells undergo meiosis? What is a gamete? What is a zygote? What are recombination, crossing-over, and chiasma? When and why does this occur? What is meant by 'homologous pair of chromosomes'? Why don't the daughter cells of meiosis have the same genetic makeup? What controls the segregation of chromosomes into the gametes?

What are genetic characters? What are genetic traits? What is an allele? What is a locus? How many alleles at each locus would a human cell have and why? Distinguish between genotype and phenotype. What is meant by a dominant gene? What is meant by a recessive gene? How do these differ? What is the genotype of a homozygous dominant organism? What is its phenotype? What is the genotype of a homozygous recessive organism? What is its phenotype? What is the genotype of a heterozygous organism? What is its phenotype? What is a genetic cross? Distinguish between the P, F1, and F2 generations. What is a true-breeding line? What is the genotype and phenotype of a cross between homozygous dominant and homozygous recessive parents? If the F1 progeny are crossed, what would be the genotype and phenotype of the F2 generation? What would be the phenotypic ratio? What would be the genotypic ratio? Be ready to generate Punnet square tests or probability analyses of crosses involving more than one genetic locus. Describe a dihybrid cross where two alleles are homozygous dominant in one parent and homozygous recessive in the other. What would be the phenotypic ratio of the F2 generation from this dihybrid cross? What is meant by independent assortment? Be prepared to calculate probabilities resulting from different crosses.

Distinguish between complete and incomplete dominance. How would incomplete dominance alter the results of a hybrid cross? What would the resulting F2 generation phenotype and genotype ratios be? What is codominance? How does this affect the results of crosses? Be prepared to determine likely blood types of parents based on the blood types of their offspring. What is a polygenic trait? What is a carrier state for a genetic disease? What is meant by linked genes? How does this affect expected outcomes of genetic crosses? How is gene linkage used for chromosomal mapping? Distinguish between autosomes and sex chromosomes. What sex chromosomes are found in women? What sex chromosomes are found in men? What are sex-linked traits? Be prepared to give the results of crosses that involve sex-linked recessive traits. What is the process of nondisjunction? What are the likely results? Why is this important? What is a Barr body? Recognize the genetic abnormality of Downs Syndrome, Turner's Syndrome, and Klinefelter's Syndrome.