Chapter 2: Chromosomes and Cellular Reproduction

Ch 2 video assignments, homework, & adaptive quiz

What are the two major phases of the cell cycle?

interphase and M phase

During which phase of the cell cycle would each cell be undergoing biochemical events required to prepare for cell division, and each chromosome consist of two identical chromatids?

G₂

In which portion of the cell cycle do chromosomes begin to condense and the spindle fibers begin to form from the centrosomes?

prophase

If a cell normally has 12 chromosomes, how many chromosomes are present in the G₂ phase of the cell cycle?

12

A cell starts out in G₂ phase with 12 chromosomes, but after mitosis, each of the daughter cells has only 11 chromosomes in G₁ phase. What event provides the most likely explanation for this scenario?

During prometaphase in the original cell, one of the chromosomes failed to attach to a spindle fiberor was improperly segregated during mitosis.

If a cell starts out in G₂ phase with 12 chromosomes, how many chromosomes would you expect in each of the daughter cells if one of the chromosomes failed to separate in anaphase?

One daughter cell will have 11 chromosomes, and the other will have 12

In which phase of meiosis do homologous chromosomes initiate pairing?

prophase I

During which phase of meiosis do homologous chromosomes separate?

anaphase I

During which type of cell division does each daughter cell contain half the amount of DNA as did the cell just prior to cell division?

meiosis I, meiosis II, and mitosis

If a cell normally has 12 chromosomes, how many chromosomes would be present in each cell at the end of meiosis II if a single pair of homologous chromosomes failed to separate during anaphase I?

2 daughter cells will each have five chromosomes and two daughter cells will each have seven chromosomes.

During which phase of meiosis does independent assortment occur?

metaphase I

Which process results in sister chromatids that are no longer identical?

crossing over

During which phase of meiosis does crossing over occur?

prophase I

What are the two processes in meiosis that create genetic differences among cells?

independent assortment and crossing over

In female animals, the cell capable of being fertilized is the ___________

ovum

All of the following make meiosis different from mitosis EXCEPT ___________

a) meiosis comprises two divisions

b) chromosome number is reduced by half in meiosis

c) resulting cells from meiosis are genetically different from the parent cell

d) meiosis lacks a preceding S phase

e) pairing of homologous chromosomes usually occurs only in meiosis

meiosis lacks a preceding S phase

Which event of meiosis explain genetic variation among the gametes?

a) crossing over

b) random assortment of maternal and paternal chromosomes

c) distribution of differing numbers of chromosomes to daughter cells

d) both a and b

e) all of the above

both a and b

unicellular, no membrane- bound organelles

eubacteria and archaea

prokaryotes

both unicellular and multicellular with membrane-bound organelles

yeast

eukaryotes

what’s the difference between prokaryote and eukaryote DNA?

prokaryote - not complexed with histones in bacteria and not as organized; usually one circular DNA molecule

eukaryote - complexed with histones to help with sorting; has multiple linear DNA molecules

neither prokaryotic nor eukaryotic with an outer protein coat surrounding nucleic acid

viruses

simple division

has an origin of replication and high rate of replication

prokaryotic cell reproduction

separation of replicated circular chromosome

simple division

goes through a cell cycle, has homologous pairs and structures of chromosomes, and has genetic consequences of the cell cycle

eukaryotic cell reproduction

cells carry two sets of genetic information

aka somatic cells (mitosis)

diploid (2n)

cells carry one set of genetic information

aka gametes (meiosis)

haploid (n)

two version of a gene encode a trait

allele

two sets of chromosomes (2 versions of same genes)

homologous pairs

tips/ends of a linear chromosome

protective capes so as replication occurs, genes don’t degrade

telomeres

attachment point for spindle microtubules (how cells pull chromosomes apart with spindle fibers)

centromere

where the DNA attaches to the spindle

kineochore

submetacentric

metacentric

telocentric

acrocentric

an extended period between cell divisions, DNA synthesis, and chromosome replication phase

cell is growing and getting ready to split

interphase

mitotic phase (splitting)

M phase

key transitions points in the cell cycle

phase checkpoint

cell is growing and doubles in size; proteins necessary for cell division are synthesized

G₁

DNA synthesis (double the DNA)

S phase

checkpoints before M phase; biochemical preparation of cell division

G₂

nuclear and cellular division (separation of sister chromatids)

M phase/mitosis

actual split of cells/ separation of cytoplasm

cytokinesis

regulated decision point (cell can sit in this phase, go through apoptosis, or go on)

G₁/S checkpoint

only passed if DNA is fully replicated undamaged

G₂/M checkpoint

mitosis: not condensed chromosomes

interphase

mitosis: condensed chromosomes and developing spindle

prophase

mitosis: break nuclear envelope and interact with spindle fibers

prometaphase

mitosis: chromosomes line up down the middle and attach to spindle fibers

metaphase

mitosis: break sister chromatids apart

anaphase

mitosis: make nuclear envelope and dissolve spindle fibers

telophase

stable; nondividing period of variable length

G₀ phase

What are the genetic consequences of the cell cycle?

produces 2 cells that are genetically identical to each other and with the original cell. Each new cell contains a full complement of chromosomes and about half the cytoplasm and organelle content of the original parental cell

the production of haploid gametes

meiosis

the fusion of haploid gametes

fertilization

consequences of meiosis

genetic variation

meiosis: DNA synthesis and chromosome replication

interphase

meiosis: separation of homologous chromosome pairs, and reduction of the chromosome number by half

meiosis I

meiosis: separation of sister chromatids, also known as equational division

meiosis II

Prophase I: close pairing of homologous chromosomes

synapsis

Prophase I: closely associated four chromatids of two homologous chromosomes

tetrad

Prophase I: exchange of genetic information of chromosome segments from non-sister chromatids within the synapsed chromosome

crossing over

random alignment of homologous pairs of chromosomes along the __________ plate

metaphase I

separation of homologous chromosome pairs, and the random distribution of chromosomes into two newly divided cells — second mechanism of generating genetic variation in the newly formed gametes

anaphase I

nuclear envelope back

telophase I

the period between meiosis I and meiosis II

interkinesis

If 8 chromosomes in metaphase II, then how many chromosomes in _______

a) prophase of mitosis

b) metaphase of meiosis I

c) anaphase of mitosis

d) anaphase II of meiosis

e) anaphase I of meiosis

f) after cytokinesis that follows mitosis

g) after cytokinesis that follows meiosis II

a) 16 chromosomes, 32 DNA molecules

b) 16 chromosomes, 32 DNA molecules

c) 32 chromosomes, 32 DNA molecules

d) 16 chromosomes, 16 DNA molecules

e) 16 chromosomes, 32 DNA molecules

f) 16 chromosomes, 16 DNA molecules

g) 8 chromosomes, 8 DNA molecules

what are the 3 sources of genetic variation in meiosis?

four cells are produced from each original cell

chromosome number in each new cell is reduced by half

newly formed cells from meiosis are genetically different from one another and from the parental cell

which genetic diseases or disorders result from errors in mitosis or meiosis?

down syndrome - extra chromosome 21

turner syndrome - single X

cancers - errors in mitosis

how do errors in mitosis or meiosis bring about these diseases and disorders?

abnormal separation of chromosomes so that cells have too many or too few chromosomes

comparison of mitosis, meiosis I, and meiosis II: cell division

yes

comparison of mitosis, meiosis I, and meiosis II: reduction in chromosome number

no, yes, no

comparison of mitosis, meiosis I, and meiosis II: genetic variation produced

no, yes, no

comparison of mitosis, meiosis I, and meiosis II: crossing over

no, yes, no

comparison of mitosis, meiosis I, and meiosis II: random distribution of maternal and paternal chromosomes

no, yes, no

comparison of mitosis, meiosis I, and meiosis II: metaphase

individual chromosomes line up

homologous pairs ling up

individual chromosomes line up

comparison of mitosis, meiosis I, and meiosis II: anaphase

chromatids separate

homologous chromosomes separate

chromatids separate

a protein that holds the chromatids together

key to the behavior of chromosomes in mitosis and meiosis

controls separation of chromatids and chromosomes in mitosis and meiosis

cohesin

protects cohesin at the centromeres from the action of separase, so the sister chromatids remain together

shugoshin in anaphase I

breaks down and the centromeric cohesin is cleaved by separase, so the sister chromatids separate

shugoshin during anaphase II

male gamete production

spermatogenesis

female gamete production

oogenesis

The fruit fly Drosophila melanogaster has four pairs of chromosomes, whereas the housefly Musca domestica has six pairs of chromosomes.

How many different combinations of chromosomes are possible in the gametes of the fruit fly?

How many different combinations of chromosomes are possible in the gametes of the house fly?

Based on chromosome number, in which species would you expect to see more genetic variation among the progeny?

16

64

the house fly

Suppose a scientist measures the amount of DNA per cell of a particular diploid species at various stages of meiosis. She finds that the meiotic cells contain 3.7 pg, 7.3 pg, or 14.6 pg of DNA.

What stages of the cell cycle would correspond to the different amounts of DNA contained within a cell at that stage?

3.7 pg - after cytokinesis of meiosis II

7.3 pg - metaphase II, G₁

14.6 pg - prophase I, telophase I before cytokinesis, G₂

Identify the images as a cell in metaphase of mitosis, meiosis I, or meiosis II. All cells come from from an organism that has a diploid (2n) chromosome number of eight.

mitosis, meiosis I, meiosis II

Identify the stages of meiosis.

The given chromosomes are derived from a diploid cell.

Which set of terms describes the chromosomes labeled A and B?

The chromosomes labeled A are sister chromatids and the chromosomes labeled B are nonhomologous chromosomes.

Suppose a diploid European wild raspberry is completely heterozygous at all 14 of its chromosomes (2n = 14).

How many different combinations of gametes can be produced by this European wild raspberry, assuming no homologous recombination between chromosomes? (*remember gametes are haploid when using the 2ⁿ formula*)

128

The somatic cell of a cat contains 38 chromosomes (2n = 38). How many chromosomes and how many DNA molecules would the secondary spermatocyte of this cat have?

Using the formula 2ⁿ, where n equals the number of chromosome pairs, the answer is:

19 chromosomes

38 DNA molecules

Label each phase of the cell cycle with the appropriate name.

Identify each stage of M phase.

prophase, metaphase, anaphase, telophase, cytokinesis

Cell division by mitosis is a mechanism of cell replication. Some single-celled organisms reproduce by cell division, and cell division enables multicellular organisms to grow and to repair damaged cells.

What is a product of cell division by mitosis?

two cells genetically identical to the original cell

A cell has a circular chromosome and histone proteins associated with its DNA but lacks a nuclear membrane.

Choose the domain of the cell with the best justification.

The cell belongs to Archaea because it has histone proteins, which are present in Archaea and Eukaryota, but absent in Eubacteria.

Match the relationships to the best corresponding concepts.