Biology 1001A Lecture Notes - Lecture 3: Spindle Apparatus, Sister Chromatids, G0 Phase

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magentacrocodile542

16 Aug 2017

School

Western University

Department

Biology

Course

Biology 1001A

Professor

Beth Mac Dougall Shackleton Tom Haffie

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Document Summary

Twigs on the end of a phylogenetic tree dna is passed along the line for 4 billion years. A genome is all of the dna sequence in one copy of an organism"s chromosomes in the nucleus. N represents one copy of all of an organism"s nuclear chromosomes (ie. one set of the chromosomes). C represents the amount of dna in one set of an organism"s nuclear chromosomes. Gametes are a set of chromosomes that you pass along to your offspring, that set is also one c. Where is there dna in a cell: there is dna in the nucleus, which is called nuclear dna or nuclear genome, mitochondrial dna or mitochondrial genome in the mitochondria, dna in the chloroplasts. It appears that life started off on earth as circular chromosomes. Eukaryotic lineage broke the circular chromosomes up into linear like sticks. Most of the time, most cells are not dividing.

Related Questions

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).

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

Question 1

The process by which RNA is synthesized using DNA as a template is â¦

Select one:

a. replication

b. transcription

c. translation

d. inspiration

Question 2

Which of the following occurs during meiosis but not mitosis?

Select one:

a. DNA condenses into chromosomes

b. nuclear envelop disappears

c. homologous chromosomes separate

d. sister chromatids separate

Question 3

Which part of the animal life cycle is haploid?

Select one:

a. gamete

b. zygote

c. sporophyte

d. spore

Question 4

Single celled eukaryotic organisms are â¦

Select one:

a. viruses

b. bacterial

c. archaea

d. protists

Question 5

Which type of cellular division results in the formation of diploid cells from a diploid parent cell?

Select one:

a. mitosis

b. meiosis

c. interphase

d. A and B but not C

e. all of the above

Question 6

A sequence of DNA that codes for a single protein is a â¦

Select one:

a. gene

b. ribosome

c. mRNA

d. none of the above

Question 7

Which of the following is characteristic of animals?

Select one:

a. heterotrophic

b. sexual reproduction

c. embryonic development

d. all of the above

Question 8

All genes have only two possible alleles.

Select one:

True

False

Question 9

The presence of membrane-bound organelles is characteristic of â¦

Select one:

a. prokaryotes

b. viruses

c. bacteria

d. eukaryotes

Question 10

What are the building blocks of proteins?

Select one:

a. fatty acids

b. amino acids

c. nucleic acids

d. all of the above

Question 11

During which phase of the cell cycle does DNA replication occur?

Select one:

a. Mitosis

b. Interphase

c. Meiosis

d. Replicosis

Question 12

Which of the following characteristic is shared among fungi and animals?

Select one:

a. autotrophic

b. heterotrophic

c. cell walls

d. absorb nutrients

Question 13

A error in DNA replication that goes unrepaired is a â¦

Select one:

a. chromosome

b. chromatid

c. mutation

d. none of the above

Question 14

Alternate forms of a gene are called ________.

Select one:

a. chromatids

b. chromosomes

c. ribosomal subunits

d. alleles

Question 15

The physical expression of a genotype is the phenotype.

Select one:

True

False

Question 16

In complete dominance, a heterozygous genotype results in â¦

Select one:

a. a recessive phenotype

b. a dominant phenotype

c. a third and unique phenotype

d. none of the above

Question 17

Which theory explains the evolution of eukaryotes from prokaryotes?

Select one:

a. phagocytosis

b. endosymbiosis

c. pinocytosis

d. none of the above

Question 18

Which scientist experimented with plants to describe patterns of inheritance?

Select one:

a. Mendel

b. Chase

c. Einstein

d. Watson

Question 19

Which cellular organelle contains aerobic cellular respiration?

Select one:

a. chloroplasts

b. mitochondria

c. nucleus

d. lysosome

Question 20

Which of the following statements is false?

Select one:

a. Haploid gametes are formed by meiosis

b. Mitosis forms genetically identical daughter cells

c. Mitosis results in the formation of four daughter cells from a single parent cell

d. Mitosis forms diploid daughter cells from a diploid parent cell

Question 21

The first forms of life on Earth were ________.

Select one:

a. plants

b. microorganisms

c. birds

d. dinosaurs

Question 22

Which of the following is used to separate chromosomes during nuclear division?

Select one:

a. cytoskeleton

b. microtubules

c. actin and myosin

d. amoeboid movement

e. all of the above

Question 23

Which generation is most dominant in more primitive plants?

Select one:

a. bryophyte

b. sporophyte

c. gametophyte

d. androphyte

Question 24

Which of the following is characteristic of plants?

Select one:

a. autotrophic

b. contain chloroplasts

c. multicellular

d. all of the above

Question 25

During which phase of mitosis do chromosome line up along the middle of the cell?

Select one:

a. prophase

b. metaphase

c. anaphase

d. telophase

Question 26

During which phase of mitosis does DNA condense into distinct chromosomes?

Select one:

a. prophase

b. metaphase

c. anaphase

d. telophase

Question 27

The process by which DNA is used as a template to make new DNA is â¦

Select one:

a. translation

b. replication

c. transcription

d. allocation

Question 28

Which of the following is characteristic of plant but not animal cells?

Select one:

a. chloroplasts

b. water vacuole

c. cell wall

d. all of the above

Question 29

Which meiotic division is most like mitosis?

Select one:

a. Meiosis I

b. Meiosis II

c. Meiosis III

d. Meiosis IV

Question 30

Which enzyme catalyzes replication?

Select one:

a. DNA polymerase

b. RNA polymerase

c. Ribosome

d. all of the above

Biology 1001A Lecture Notes - Lecture 3: Spindle Apparatus, Sister Chromatids, G0 Phase

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