Bio Study Guide ch. 9
Explain the steps in Prophase 2
- DNA supercoils - nuclear membrane breaks down - spindle fibers form attaching centrosomes to centrioles
Explain the steps in Telophase 2
- DNA uncoils - spindle fibers break down - nuclear membrane forms
Explain the steps in Metaphase 2
- chromosomes line up in the middle
Explain the steps in Anaphase 2
- chromosomes pull apart
Explain the steps in Cytokinesis 2
- division of plasma membranes
Explain the steps in Anaphase 1
- homologous chromosomes are pulled apart
Explain the steps in Telophase 1
- same events as in mitosis - EXCEPT: now the daughter cells are haploid
Explain the steps in Prophase 1
- tetrads form - homologous chromosome pairs - cross over occurs - homologous chromosomes exchange part of their chromatin. produces new gene combos - all other events same as mitosis's prophase
Explain the steps in Metaphase 1
- tetrads line up randomly on the metaphase plant. increases variation
What two differences should you know when talking about what is divided?
-homologous chromosomes -sister chromatids
# of cells produced: mitosis
2
How many chromosomes are in an egg cell?
23
How many homologous pairs do humans have?
23
How many pairs of homologous chromosomes?
23
What is the haploid number?
23
How is the amount of chromosomes represented?
2n=46
Down syndrome is a common nondisjunction. How is down syndrome scientifically recognized?
3 chromosomes at pair 21
# of cells produced: meiosis
4
How many haploid gametes do males produce?
4
In Telophase/ Cytokinesis 2, how many final cells are there? Are they haploid or diploid?
4 haploid daughter cells
How many chromosomes are in a brain cell?
46
How many chromosomes are in a skin cell?
46
How many chromosomes do humans have?
46
What is the diploid number?
46 (2x haploid)
Define monosomy.
A cell that only has one copy of chromosomes
What is a karyotype?
A display of the 46 chromosomes of an individual.
What would happen if meiosis did not occur?
Cells involved with fertilization would produce new organisms having twice the number of chromosomes as those in the previous generation.
How are homologous chromosomes related?
Each in a pair carries the same sequence of genes controlling the same inherited characteristics.
T/F: Does meiosis 2 have an interphase?
F; cells go right from telophase 1/ cytokinesis to prophase 2
Why is fertilization necessary?
Fertilization is the fusion of the nucleus of a haploid sperm cell and the nucleus of a haploid egg cell, forming a zygote.
When is the number of chromosomes split in half during cell division of meiosis?
First cell division
What are the only cells in humans that are haploid?
Gametes- sex cells that have a single set of chromosomes one from each homologous pair
Human chromosomes contain about 28K genes. What other kinds of genes would you expect to find on these chromosomes?
Genes for hair, skin color, height and genes for special chemicals produced by the body
How does meiosis differ from mitosis?
Meiosis is a type of cell division that produces 4 cells, each with half the number of chromosomes as a parent cell. Mitosis produces 2 cells with 46 chromosomes.
In Anaphase 2, what moves to either poles here?
Sister chromatids
When crossover occurs, what is being exchanged between what?
Sister chromatids of tetrads exchange some genetic material
T/F: Does meiosis 1 have an interphase?
T
What is the purpose of meiosis?
The purpose of meiosis is to reproduce the normal diploid cells to haploid cells and to make egg and sperm.
What if the purpose of mitosis?
The purpose of mitosis is to create two new perfectly identical cells when either there is a need to replace old or damaged cells and to reproduce asexually by making new cells.
How do you think doctors and scientists can use the information displayed in a karyotype?
They can make sure that the individual has the appropriate number of chromosomes and that there are no deletions or additions to individual chromosomes that might cause a change in a person's genes.
Define nondisjunction.
When chromosomes fail to separate during meisosis
When do eggs have more problems dividing and nondisjunction is more likely?
When the female is at an older age.
What is a tetrad?
a chromosome pair, consisting for four chromatids
Type of cell: Mitosis
body cell
What separates in Meiosis 1?
cell divides
How is a diploid different? Hint: Diploids in mitosis
contains a pair of each chromsome, have 2x
How are haploids different? Hint: meiosis
contains only one of each chromsome, has half
beginning cell: meiosis
diploid 2n
beginning cell: mitosis
diploid 2n
ending cell: mitosis
diploid 2n
What is the difference between a haploid and a diploid cell?
diploid: a cell that contains 2 homologous sets of chromosomes haploid: a cell with a single set of chromosomes- produced through meiosis
How many chromosomes in a cell produced by mitosis?
diploid=46
Explain the steps in Meiosis 2
exactly like Mitosis; sister chromatids separate
What gender is XX?
female
What is different chromosomally between males and females?
females: 46 chromosomes have 23 homologous pairs males: 2 chromosomes of 1 pair do not look alike
# of chromosomes: meiosis
half as parent cell
In telophase/ Cytokinesis 1, are the two cells produced here haploid or diploid?
haploid
What separates in Meiosis 2?
haploid daughter cells from meiosis 1 divide
ending cell: meiosis
haploid n
How many chromosomes in a cell produced by meiosis?
haploid=23
What separates during Anaphase 1?
homologous chromosomes
Why does meiosis NOT stop at telophase 1?
it has to produce double the cells
What gender is XY?
male
What are the 2 major ways meiosis is different than mitosis?
meiosis produces 4 new offsprings, versus the 2 offspring cells from mitosis. meiosis involves the exchange of genetic material between homologous chromosomes.
Does age have an effect on sperm in males?
not necessarily, only slows down around 80s and 90s
Where does each chromosome originally come from during fertilization?
one from mom and one from dad
How many haploid gametes do females produce?
one haploid and three "polar bodies"
# of chromosomes: mitosis
same as parent cell
Type of cell: meiosis
sex cell
Define zygote.
the cell produced by the union of two gametes, before it undergoes cleavage.
Purpose: Meiosis
to make egg and sperm
Purpose: Mitosis
to make more body cells
Define homologous chromosomes.
two chromosomes, one of paternal origin, the other of maternal origin, that are identical in appearance and pair during meiosis
