Biology 1001A Lecture Notes - Lecture 11: Meiosis, Chromosome, Gametophyte

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4 Dec 2015

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Sexual recombination: zygotes bringing dna from two different parents into the, recombination during meiosis cuts and pastes dna same cell backbones. This is a mutation change in the double stranded sequence in chromosome. Homologous chromosomes carry the same genes but different allels. Known as reductional division for meiosis (reduces chromosome number: cells at the end of meiosis ii, cells divide to give products with 1 x c amount of dna. Products of meiosis are gametes only for humans and. A lot of other lifeforms don"t make gametes by other animals meiosis. In animal life cycles, the zygotes divides by mitosis. In plant life cycles the zygote and the spores divide by mitosis: products of meiosis in plants are spores. Spores divide by mitosis to make a multicellular gametophyte by mitosis. In some fungi/algae, the zygote divides by meiosis: zygotes are single cells go through meiosis to make single.

Related Questions

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.

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The bacterium E. coli, which is a major model system for the study of genes and DNA, has a singular circular chromosome of about 4x106 bp. In contrast, human diploid cells have __1__ chromosomes, of __2__ different types (donât forget that the X Â¹ Y!). The total amount of DNA found in a haploid cell such as a sperm or egg is called the organismâs âC-valueâ; the human C-value is __3__.

Also in contrast to the E. coli circular chromosome is the fact that eukaryotic chromosomes are not circular, but instead are __4__. Eukaryotic chromosomes are complexed heavily with protein to form a DNA-protein complex generically called __5__. The proteins found can be considered to fall into two general classes: __6__ and __7__. The first class is made up of 5 major proteins called __8__, __9__, __10__, __11__, and __12__. On a weight to weight basis, these proteins make up about __13__% of the total mass of a chromosome. Since these proteins must associate relatively non-specifically with DNA, they are rich in the basic amino acids __13__ and __14__, which gives the proteins a net __15__ charge.

One goal of packaging the DNA into chromatin is to compact the genome so it will fit into a nucleus. The basic unit of chromatin structure is the __16__, which has __17__ base pairs of DNA wrapped around a âcore particleâ composed of __18__ copies each of the core histones. Each nucleosome is separated by a stretch of âlinkerâ DNA so that the repeating unit is approximately 200 bp. Lets do a little arithmetic: If we consider that the nucleosome is approximately __19__ nm in diameter, that there is about 200 bp in this structure, and that 200 bp of DNA would normally occupy __20__ nm if stretched out straight (recall that each base is spaced about 0.34 nm from the next), we can see that the nucleosome alone allows for a __21__-fold compaction ratio.

The nucleosome structure is further compacted by histone __22__, which is not a part of the core particle. Instead, this histone __23__ (does what?) to cause the nucleosomal 10 nm fiber to condense into a higher-order structure referred to as the __24__ nm fiber. In the nucleus, chromosomes do not just float around freely: they are tethered to a proteinaceous structure called the __25__ at specific DNA regions called âSARsâ, which stands for __26__. SARs are rich in topoisomerases, to allow the winding and unwinding of the DNA that accompanies replication and transcription to occur, despite this constraint.

The 30 nm fiber discussed above is the form in which transcriptionally active DNA is believed to exist in the nucleus; however, further condensation leads to a highly condensed inactive form called __27__; in this terminology, the active form is referred to as __28__. The inactive condensed form can be divided into two types: one type is essentially invariant between cell types, and since it is âon all t timeâ, it is referred to as __29__. The other type comes and goes, depending on the expression of the genes present in that region of the chromosome; it is referred to as __30__.

Eukaryotic chromosomes carry the genes, of course, but also have other functional regions. One such region is the place where the spindle apparatus attaches during mitosis and meiosis; this region of the chromosome is called the __31__. Another important part of the linear eukaryotic chromosome is the ends; these are called __32__. In humans, the end of each chromosome is composed of many repeats of the short sequence __33__. One more type of functional region on each chromosome is the place where DNA replication starts; in humans, each chromosome has several of these __34__. Thus, eukaryotic chromosomes carry several different types of functional sequences, which together allow for their __35__ during S phase, __36__ during mitosis and meiosis, and the __37__ of their genes

Chromosome Mapping (determining the relative positions of genes on a chromosome) - This is a two point cross since it involves two loci on a chromosome.

Follow the directions for the crosses below involving 2 traits located together on the same chromosome (Drosophila Chromosome IV): eyeless and shaven bristles. Please only typed answer, no hand-written work or screen shots please.

1. a. Perform a monohybrid cross between a female fly with the eyeless mutation and a male fly with shaven bristles. Show results for the F₁ offspring. (NOTE: You will use an F₁ female in the next cross.)
ENTER DATA HERE:

Question: Are the phenotypes of the F₁ offspring what you would have predicted for this cross: why or why not?

Question: After looking at your F₁ offspring, which allele is dominant: wild-type eyes or eyeless? How can you tell?

Question: After looking at your F₁ offspring, which allele is dominant: wild-type bristles or shaven bristles? How can you tell?

Draw the Chromosome IV pair of an F₁ offspring: (HINT: One chromosome was inherited from the mother, with the eyeless allele at the eye shape location (locus) and the wild-type allele at the bristles locus. The second chromosome was inherited from the father, with the wild-type allele at the eye shape locus and the shaven bristle allele at the bristles locus.)

1. b. Perform a testcross between an F₁ female offspring from the previous cross and a new male with both the eyeless and the shaven bristle traits to produce an F₂ generation.
ENTER DATA HERE:

Question: What phenotypes are found in the F₂ offspring?

Question: Are the phenotypes of the F₂ offspring what you would have predicted for this cross: why or why not?

Draw the 2 different Chromosome IV pairings you expected in an F₂ offspring: (HINT: The F₁ female will donate one or the other of the chromosomes you drew above to each offspring. The new male with both the eyeless and the shaven bristle traits can only donate one type of chromosome, with both mutations.)

Question: What are the 2 phenotypes that would result from the 2 different chromosome pairings you just drew?

Question: What are the other 2 phenotypes that you obtained in your F₂ offspring? What process, which occurred during meiosis, was responsible for the creation of these recombinant phenotypes?

Draw a map that shows the map distance (in map units or centimorgans) between the locus for the shaven bristle allele and the locus for the eyeless allele. (NOTE: You need to add the proportion of SV;EY flies to the proportion of wild flies OR add the number of SV;EY flies and wild flies and then divide by the total number of flies. Then multiply either number times 100.)âSHOW ALL CALCULATIONS BELOW

CALCULATIONS:

CHROMOSOME MAP:

There are several different ways to draw maps of the chromosomes. You can draw a simple line graph using a free online graphing tool, such as:

http://www.onlinecharttool.com/

http://nces.ed.gov/nceskids/createagraph/

Or you can simply use your keyboard to create a line with the dash or underline, with the abbreviations for the genes inserted, and then put the map units below, such as:

___________A_____________________B_________

50 map units

Biology 1001A Lecture Notes - Lecture 11: Meiosis, Chromosome, Gametophyte

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