Cellular Division and the Cell Cycle - Ch. 8 Flashcards
What happens during anaphase in mitosis?
Sister chromatids separate and move towards opposite poles of the cell. Each is now considered a full-fledged daughter chromosome.
What are the three stages in interphase?
- G1- 1st gap sequence growth; carrying out “cellular duties” 2. S Phase- chromosome duplication; DNA in nucleus is doubled 3. G2- 2nd gap sequence. Preparing for mitosis. Each chromosome in the cell consists of two identical sister chromatids.
Are gametes haploid or diploid cells?
Haploid (n). They have only 1 set of chromosomes.
homologous pair
matching pair of chromosomes that carries the same sequence of genes controlling the same inherited characteristics
During which phase of meiosis does “crossing over” occur?
Prophase I
What phase is this?
Meiosis- Telophase I
What happens during metaphase in mitosis?
Chromosomes line up single-file along the metaphase plate
What phase is this?
Mitosis - Anaphase
What phase is this?
Meiosis- Telophase II
What are the four main stages of mitosis?
- Prophase 2. Metaphase 3. Anaphase 4. Telophase
tetrad
Occurs during Prophase I of meiosis; homologous pairs stick together forming a tetrad
What are chromosomes made up of?
Chromatin (DNA and proteins)
What phase is this?
Meiosis- Prophase II
How many copies of DNA does each chromosome contain at the beginning of mitosis?
TWO copies. This is because of replication.
gene
specific region of DNA that codes for a specific trait
The first part of the cell cycle (where the cell spends 90% of its time) is called ______
interphase, which is the period of cell growth; the cell makes new molecules and organelles.
What phase is this?
Mitosis - Telophase
What phase is this?
Meiosis- Metaphase II
What happens during telophase in mitosis?
- Nuclear envelope begins to reform 2. Centrosomes disappear 3. Spindle fibers disappear 4. Nucleoli reform 5. Chromosomes decondense back into chromatin
What phase is this?
Meiosis- Anaphase II
autosomes
the pairs of chromosomes that are the same in males and females. In humans, chromosomes #1 - #22
sister chromatids
chromsome consisting of two copies
What does mitosis produce?
2 identical diploid (2 sets of chromosomes) daughter cells. There is NO change in chromosome number. Chromosomes are in unduplicated form.
What phase is this?
Meiosis: Anaphase I
What phase is this?
Meiosis- Metaphase I
What does meiosis produce?
4 haploid daughter cells containing half the number of chromosomes as the parental nucleus.
During which phase of meiosis does “independent assortment” occur?
Metaphase I
What’s the haploid number for humans?
23
sex chromosomes
In humans, it is chromosome #23. Females = XX Males = XY
meiosis
formation of gametes (reproductive cells, e.g. eggs and sperm, ovules and pollen)
centromere
the narrow “waist” that sister chromatids are joined together at
What happens during prophase in mitosis?
- Nuclear envelope disappears 2. Chromatin condenses to form chromosomes, each consisting of two sister chromatids 3. Mitotic spindle forms 4. Centrosomes move towards opposite poles 5. Nucleoli disappear
What happens during cytokinesis in mitosis?
Cytokinesis usually occurs with telophase. It is the division of the cytoplasm. In animals, a cleavage furrow pinches the cell in two, producing two daughter cells. In plants, vesicles move to middle of cell and produce a cell plate, and a new cell wall is created.
asexual reproduction
one individual produces offspring and those offspring directly inherit the genes of the parent
Why do cells go through mitosis?
Reproduction (asexual) Growth and development Repair and regeneration
What is mitosis?
The division of a cell, resulting in daughter cells that are genetically identical to the parent cell.
What phase is this?
Meiosis- Prophase I
What phase is this?
Mitosis- Metaphase
What occurs during the S Phase in Interphase?
All of the chromosomes are replicated. Following replication, each chromosome now consists of two sister chromatids. Once DNA replication is complete the cell contains twice its normal number of chromosomes and becomes ready to enter the phase called G2.
Where are chromosomes located in eukaryotic cells?
Nucleus
No question here. Just look at this picture of duplicated, unduplicated, and homologous chromosomes.
In what stages of interphase, mitosis, and meiosis are chromosomes duplicated and unduplicated?
*Interphase: *
G1- Unduplicated
S Phase- Duplicated
G2- Duplicated
Mitosis:
Prophase- Duplicated
Metaphase- Duplicated
Anaphase- Unduplicated
Telophase- Unduplicated
Meiosis:
Prophase I: Duplicated
Metaphase I: Duplicated
Anaphase I: Duplicated
Telophase I: Duplicated
Prophase II: Duplicated
Metaphase II: Duplicated
Anaphase II: Unduplicated
Telophase II: Unduplicated
Just look at the photo.
Yay!
What’s a metaphase plate?
a plane in the equatorial region of the spindle in dividing cells, alongwhich the chromosomes become arranged during the metaphase
What three processes contribute to an increase in genetic variation in sexually reproducing organisms?
- Crossing Over
- Independent Assortment
- Random Fertilization
What is “crossing over”?
Arms of homologous chromosomes cross over and exchange genes. Leads to genetic variation.
What is nondisjunction and when does it occur?
Nondisjunction is when a chromosome pair (either sister chromatids or homologous pairs) fails to seperate at anaphase. It can occur during meiosis I or II.
What’s trisomy21?
Down Syndrome. There are 3 copies of autosome 21.
