Chapter 2: Chromosomes and Cellular Reproduction Flashcards
How does prokaryotic DNA differ from eukaryotic DNA?
- Prokaryote: DNA is floating within the cell
- Eukaryote: DNA is complexed with histone proteins to form chromatin; much more organized; packed tightly and compartmentalized within the nucleus
How does the cell diameter of prokaryotic cells differ from eukaryotic?
- Prokaryote: small (1 to 10 um)
- Eukaryote: large (10 to 100 um)
How does the genome of prokaryotic cells differ from eukaryotic?
- Prokaryote: one circular DNA molecule
- Eukaryote: multiple, linear DNA molecules
What structures are present in eukaryotic cells, but absent in prokaryotic?
- Membrane-bound organelles
- Cytoskeleton
Why aren’t viruses considered to be “alive”?
- Do not possess a plasma membrane
- Are extremely small
- Do not possess a sufficient number of genes to replicate without a host
- Do not possess metabolic factors
What is a virus?
- Protein coat surrounding a piece of nucleic acid
- They are neither cells, nor primitive forms of life, nor are they “alive”
What are the three fundamental events for cell reproduction?
1) Genetic information must be copied.
2) The copies of genetic information must be separated from each other
3) The cell must divide
Describe prokaryotic cell replication.
- The single circular chromosome replicates.
- The origins segregate to opposite sides.
- The origins are anchored to opposite sides of the cell.
- The cell divides (cytokinesis). Each new cell has an identical copy of the original chromosome.
- This process is called binary fission
Differentiate diploid and haploid organisms.
- Diploid organism: has two sets of chromosomes organized as homologous pairs
- Haploid organism: carries one set of genetic information
How are homologous chromosomes similar?
- Look alike
- Have the same length and centromere position
- Have a similar banding pattern when stained
Where are the members of a homologous chromosome inherited from?
- One from the male parent
- One from the female parent
Define alleles.
A location on one homologue contains genes for the same trait that occurs at this locus on the other homologue, although the genes may code for different variations of that trait
What are centromeres?
The attachment point for spindle microtubules and the constricted region where the kinetochores form
What are telomeres?
The tips of a linear chromosome; the stable ends of chromosomes
How do you determine the number of chromosomes?
Count the number of functional centromeres
How do you determine the number of sister chromatids?
The number of sister chromatids = the number of telomeres
What are the four major types of eukaryotic chromosomes (depending on the position of the centromere)?
- Metacentric
- Submetacentric
- Acrocentric
- Telocentric
What are the two important processes of cellular reproduction?
- Growth: involves the duplication of the cells’ DNA and contents (interphase)
- Cell division: involves the separation of the cells’ DNA and content into daughter cells (mitotic phase)
Define mitosis.
The division of the nuclear material (DNA)
Define cytokinesis.
The division of the cytoplasm and its contents
What are the six steps to mitosis?
- Interphase
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase
What happens during the G1 phase of interphase?
The cell grows; synthesis of proteins necessary for cell division
What is the G0 phase in interphase?
The cells may enter a non-dividing phase
What happens during the M phase of interphase?
Mitosis and cytokinesis can take place
What happens during the S phase of interphase?
The DNA duplicates
What happens during the G2 phase of interphase?
The cell prepares for mitosis
What is the G2/M checkpoint in interphase?
After the checkpoint, the cell can divide
What happens during the M phase of interphase?
Mitosis and cytokinesis can take place
What are the three fundamental events of cell reproduction?
- Genetic information must be copied.
- The copies of genetic information must be separated from each other.
- The cell must divide.
Why do the processes that lead to cell reproduction differ in prokaryotic and eukaryotic cells?
Because of their structural differences
How do prokaryotic cells reproduce?
Simple division
Define meiosis.
- Production of haploid gametes
- Meiosis reduces the chromosome number by half, and includes two cell divisions
Define fertilization.
Fusion of haploid gametes.
Genetic variation is the consequence of ________.
meiosis
What does meiosis form?
Forms gametes and reduces the chromosome number by half
What is interphase?
DNA synthesis and chromosome replication phase
What is meiosis I?
The separation of homologous chromosome pairs, and the reduction of the chromosome number by half
What is meiosis II?
The separation of sister chromatids, also known as equational division
How many cell divisions does meiosis include? Differentiate them.
- Two
1) Reduction division
2) Equational division
Why does a reduction division need to happen in meiosis?
- Because the progeny would receive too many chromosomes, if not
- 2n (46 chromosomes) become n (23 chromosomes)
What happens during equational division in meiosis II?
The number of chromatids decreases (2 sisters to 1), but the number of chromosomes is the same (23)
How many gametes does meiosis II produce?
4
Compare the cells at the end of mitosis and meiosis.
- Mitosis: two daughter cells (2n)
- Meiosis: four daughter cells (n) with unique combination of alleles
Compare the second meiosis process to mitosis.
- Fairly similar
- Mitosis: individual chromosomes align vertically
- Meiosis: individual chromosomes align horizontally
Compare meiosis I and mitosis.
- Prophase 1: crossing over
- Anaphase 1: pairs of chromosomes separate
- Prophase 1 and Anaphase 1 does not happen in mitosis
Which steps are responsible for genetic diversity in meiosis?
- Prophase 1
- Anaphase 1
What phase in DNA synthesis produces identical sister chromatids?
S phase
When does crossing-over occur? What happens?
- Prophase I
- Segments of non-sister chromatids are exchanged
What is cohesin?
- Protein that holds the chromatids together
- Is key to the behavior of chromosomes in mitosis and meiosis
What allows sister chromatids to separate?
- The breakdown of cohesin
- Cohesin keeps sister chromatids together
What is the difference between chromatid and chromatine?
- Chromatine: the DNA-protein complex that forms the structure of a chromosome
- Chromatid: each of the two threadlike strands into which a chromosome divides longitudinally during cell division. Each contains a double helix of DNA
Does cell division occur in mitosis, meiosis I, and meiosis II?
- Mitosis: yes
- Meiosis I: yes
- Meiosis II: yes
Does chromosome reduction occur in mitosis, meiosis I, and meiosis II?
- Mitosis: no
- Meiosis I: yes
- Meiosis II: no
Does genetic variation occur in mitosis, meiosis I, and meiosis II?
- Mitosis: no
- Meiosis I: yes
- Meiosis II: no
Does crossing over occur in mitosis, meiosis I, and meiosis II?
- Mitosis: no
- Meiosis I: yes
- Meiosis II: no
Does random distribution of maternal and paternal chromosomes occur in mitosis, meiosis I, and meiosis II?
- Mitosis: no
- Meiosis I: yes
- Meiosis II: no
What happens during metaphase in mitosis, meiosis I, and meiosis II?
- Mitosis: individual chromosomes line up
- Meiosis I: homologous pairs line up
- Meiosis II: individual chromosomes line up
What happens during anaphase in mitosis, meiosis I, and meiosis II?
- Mitosis: chromatids separate
- Meiosis I: homologous chromosomes separate
- Meiosis II: chromatids separate
Diploid cells have:
a. two chromosomes
b. two sets of chromosomes
c. one set of chromosomes
d. two pairs of homologous chromosomes
b. two sets of chromosomes
When does crossing over occur in meiosis?
Prophase I
A cell in G1 of interphase has 12 chromosomes. How many chromosomes and DNA molecules will be found per cell when this original cell progresses to the following stage: G2 of interphase.
- 12 chromosomes
- 24 DNA
A cell in G1 of interphase has 12 chromosomes. How many chromosomes and DNA molecules will be found per cell when this original cell progresses to the following stage: metaphase I of meiosis.
- 12 chromsomes
- 24 DNA
A cell in G1 of interphase has 12 chromosomes. How many chromosomes and DNA molecules will be found per cell when this original cell progresses to the following stage: prophase of mitosis.
- 12 chromosomes
- 24 DNA
A cell in G1 of interphase has 12 chromosomes. How many chromosomes and DNA molecules will be found per cell when this original cell progresses to the following stage: anaphase I of meiosis.
- 12 chromosomes
- 24 DNA
A cell in G1 of interphase has 12 chromosomes. How many chromosomes and DNA molecules will be found per cell when this original cell progresses to the following stage: anaphase II of meiosis.
- 12 chromosomes
- 12 DNA
A cell in G1 of interphase has 12 chromosomes. How many chromosomes and DNA molecules will be found per cell when this original cell progresses to the following stage: prophase II of meiosis.
- 6 chromosomes
- 12 DNA
A cell in G1 of interphase has 12 chromosomes. How many chromosomes and DNA molecules will be found per cell when this original cell progresses to the following stage: after cytokinesis following mitosis.
- 12 chromosomes
- 12 DNA
A cell in G1 of interphase has 12 chromosomes. How many chromosomes and DNA molecules will be found per cell when this original cell progresses to the following stage: after cytokinesis following meiosis II.
- 6 chromosomes
- 6 DNA
How do you determine the number of DNA molecules?
1) Determine if sister chromatids are present
2a) If they are, the number of DNA molecules is twice the number of chromosomes
2b) If they aren’t, the number of DNA molecules is the same as the number of chromosomes
How many chromosomes and chromatids are in prophase of mitosis?
- Chromosomes: 46
- Chromatids: 92
How many chromosomes and chromatids are in metaphase of mitosis?
- Chromosomes: 46
- Chromatids: 92
How many chromosomes and chromatids are in anaphase of mitosis?
- Chromosomes: 92
- Chromatids: 92
How many chromosomes and chromatids are in telophase of mitosis?
- Chromosomes: 92
- Chromatids: 92
How many chromosomes and chromatids are in prophase I of meiosis?
- Chromosomes: 46
- Chromatids: 92
How many chromosomes and chromatids are in metaphase I of meiosis?
- Chromosomes: 46
- Chromatids: 92
How many chromosomes and chromatids are in anaphase I of meiosis?
- Chromosomes: 46
- Chromatids: 92
How many chromosomes and chromatids are in telophase I of meiosis?
- Chromosomes: 46
- Chromatids: 92
How many chromosomes and chromatids are there are the end of meiosis I?
- Chromosomes: 23
- Chromatids: 46
How many chromosomes and chromatids are in prophase II of meiosis?
- Chromosomes: 23
- Chromatids: 46
How many chromosomes and chromatids are in metaphase II of meiosis?
- Chromosomes: 23
- Chromatids: 46
How many chromosomes and chromatids are in anaphase II of meiosis?
- Chromosomes: 46
- Chromatids: 46
How many chromosomes and chromatids are in telophase II of meiosis?
- Chromosomes: 46
- Chromatids: 46
How many chromosomes and chromatids are there at the end of meiosis II?
- Chromosomes: 23
- Chromatids: 23
How many chromosomes and chromatids are in the G1 phase of interphase of mitosis?
- Chromosomes: 46
- Chromatids: 46
How many chromosomes and chromatids are in the S phase of interphase of mitosis?
- Chromosomes: 46
- Chromatids: 92
What is the correct order of stages in the cell cycle? A) G1, S, prophase, metaphase, anaphase B) S, G1, prophase, metaphase, anaphase C) Prophase, S, G1, metaphase, anaphase D) S, G1, anaphase, prophase, metaphase
A) G1, S, prophase, metaphase, anaphase
Which of the following events takes place in metaphase I?
A) Crossing-over occurs
B) The chromosomes condense
C) Homologous pairs of chromosomes line up on the metaphase plate
D) Individual chromosomes line up on the metaphase plate
C) Homologous pairs of chromosomes line up on the metaphase plate
