Biology 3218F/G Lecture Notes - Lecture 4: Agaricus Bisporus, Basidium, Stemonitis

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bronzegrasshopper299

20 Sep 2016

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Life cycles centre on when and where and how you have meiosis. In this series of diagram, there is a bar in the middle that divides diploid on the bottom and haploid at the top. In this instance, we have zygotic meiosis b/c the zygote goes through meiosis and produces haploid cells. Haploid cells go through mitosis to form haploid individuals. Red and white ball forms a tube, and accumulation is the mycelium (one mycelium is a + type, the other is a type) At one point, after they"ve eaten enough, they form gametes which will fertilize and form a short-lived zygote; zygote goes through meiosis to reform haploid cells. Most common type of sexual reproduction in fungi. These can be more complicated as they can reproduce both sexually and asexually at the same time. Individuals are diploid; specialized cells go through meiosis to produce gametes; gametes get together to form a zygote; haploid is short-lived.

Related Questions

1. How does meiosis generate genetic diversity?

a) crossing over

b) random alignment at metaphase I

c) synapsis

d) both crossing over and random alignment at metaphase I

2. What would happen if crossing over occurred between sister chromatids?

a) Genetic diversity would decrease due to the loss of gene combinations.

b) Genetic diversity would increase due to the addition of gene combinations.

c) Gene rearrangement would lead to changes in gene expression.

d) Nothing would happen becasue sister chromatids are genetically identical or nearly identical.

3. Animals that sexually reproduce are _____ and produce _____ gametes. (haploid, diploid; haploid, haploid; diploid, diploid; diploid, haploid)

4. The F1 generation of a cross between two individuals, one that is homozygous dominant for a trait and the other that is homozygous recessive for the trait, will yield progeny with the same phenotype. (true or false)

5. Homologous chromosomes separate from each other in:

a) mitosis

b) meiosis I

c) meiosis II

d) They never separate from each other during any form of cell division

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2. A recessive nuclear gene in yeast causes respiratory deficiencies, resulting in small colonies, called petite. Strains with this type of defect are called segregational petites, because the trait segregates according to Mendelian patterns. Other strains of yeast form small colonies as a result of a defect in a mitochondrial gene. These are called neutral petites. Recall that yeast cells can grow in the haploid stage and in the diploid stage. They have two mating types, a and a, and are isogamous. You cross a haploid neutral petite strain with a haploid segregational petite strain.

a) What is the phenotype of the diploid F1?

b) When the diploid F1 goes through meiosis to form ascospores, what do you expect to see in the haploid strains that grow from the ascospores

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).

Biology 3218F/G Lecture Notes - Lecture 4: Agaricus Bisporus, Basidium, Stemonitis

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