Mitosis + Meiosis
Define Chromosome Set
All the chromosomes from one parent.
Define Zygote
A fertilized egg
Are the X and Y chromosomes completely homologous?
No
DNA is made up of what?
Nucleotides
What are the different nitrogen bases?
Adenine, Guanine, Cytosine and Thymine
What is a haploid cell
Any cell with one chromosome set1
Nonsister Chromatids
Any two chromatids in a pair of homologous chromosomes that are not sister chromatids
Define Homologous pair
One maternal and one paternal chromosome
Mitosis conserves what?
chromosome number
Define mitosis
it is the division of one cell into two new daughter cells which are identical to each other and to the parent cell from which it originated
What is a gene
A segment of one strand of the DNA molecule
What makes up a gene
A specific sequence of nucleotides
Is a zygote diploid or haploid?
Diploid
Is our somatic cells diploid or haploid?
Diploid
What are Purines
Double ringed structures
Images of chromosomes for karyotypes are best obtained during what phase
Metaphase
Describe Telophase
- 2 daughter nuclei begin to form - Nuclear envelope form around the 2 sets of chromosomes - Chromosomes become less condensed - Mitosis is now complete
Describe what happens in Telophase 1 and Cytokinesis
- At the beginning of telophase 1, each half of the cell has a complete haploid set of chromosomes, but each chromosome is still composed of 2 sister chromatids. - Cytokinesis takes place along with telophase. In animal cells, cytokinesis begins with the formation of a cleavage furrow. In plant cells, a cell plate grows outward until its membrane fuses with the plasma membrane - Nuclear envelopes form around the haploid sets of chromosomes - Chromosomes become less condensed
Describe what happens in Anaphase 2
- The sister chromatids separate and are now referred to as daughter chromosomes - The kinetochore microtubules shorten and pull the daughter chromosomes to the opposite poles - The non kinetochore microtubules elongate, thus lengthening the cell.
Each chromosome has how many DNA molecules?
1
Define Mitosis (the first part of the Mitotic phase)
the division of the nucleus and its chromosomes
What are homologous chromosomes
two chromosomes in a pair that have the same length, centromere position, and staining pattern
Describe the structure of Adenine and Guanine
two ringed structures. One six-membered ring attached to a five-membered ring
What is "Crossing Over"
when chromosome strands overlap each other and exchange pieces of chromosome
Define Chiasmata
where 2 chromosomes are held together in crossing over
What are the 3 main points in Meiosis 2
- Begins right after Meiosis 1 - The cells do not go through Interphase stage before Meiosis 2 - There is no duplication of chromosomes before Meiosis 2
Describe what happens in Anaphase 1
- Begins when the 2 homologous chromosomes of each pair separate. - the 2 homologues start moving towards the opposite ends of the cell. They are pulled towards the poles as the microtubules attached to their kinetochores shorten. - The sister chromatids remain attached at the centromere and move as a single unit towards the same pole. - The non-kinetochore microtubules elongate, thus lengthening the cell. - By the en, the 2 ends of the cell have an equal number of chromosomes
Describe the M Phase (Mitotic Phase)
- Cell division occurs - involves Mitosis and Cytokinesis
Describe the G2 Phase (Second Gap Phase
- Cell makes final preparations for division - it's a period of metabolic activity and growth - Nucleus is closed in nuclear envelope - Each nucleus contains 1+ nucleoli ad chromatin fibers - Chromosomes are duplicated but not condensed - 2 centromeres have formed from replication of a single chromosome
Describe Metaphase
- It is the longest stage of mitosis, lasting around 20 minutes - The centrosomes are now at the opposite ends of the cell - Chromosomes lie along the equator (metaphase plate) of the cell with the centromere on the equator - For each chromosome the kinetochores of the sister chromatids are attached to the kinetochore microtubules coming from the opposite poles - The microtubule apparatus is arranged in a spindle shape, hence called spindle fibers
Describe Anaphase
- It is the shortest stage of mitosis, lasting only a few minutes - It begins when 2 sister chromatids of each chromosome pair seperate and thus become independent chromosomes - The 2 chromosomes start moving towards the opposite ends of the cell. They are pulled towards the the poles as microtubules attached to their kinetochores shorten - The nonkinetochore microtubules begin to elongate, thus the cell lengthens - by the end, the 2 ends of the cell have an equal and complete set of chromosomes
Telophase 2 and Cytokinesis
- Nuclei and nucleoli begin to form, chromosomes begin de-condensing and cytokinesis occurs. - The mitotic division of 1 parent cell produces 4 daughter cells, each with a haploid set of chromosomes - Each of the 4 daughter cells is genetically distinct from the other daughter cells and the parent cell
Describe what happens in Metaphase 1
- The centrosomes are now at the opposite ends of the cell. - The pairs of homologous chromosomes, in the form of tetrads, lie along the metaphase plate. - Both the sister chromatids of a chromosome are attached to a single kinetochore microtubules. - the 2 homologous chromosomes in a pair are attached to kinetochore microtubules coming from the opposite poles.
Describe what happens in Metaphase 2
- The chromosomes lie on the metaphase plate - Because of crossing over in Meiosis 1, the 2 sister chromatids of each chromosome are not genetically identical. - The kinetochores of sister chromatids are attached to microtubules extending from opposite poles
Describe Cytokinesis in plants
- The division begins towards the end of telophase - Two daughter cells are formed shortly by the end of mitosis - Cytokinesis begins when vesicles containing cell wall material collect in the middle of the cell. The vesicles fuse forming a large sac called the cell plate. The cell plate grows outward until its membrane fuses with the plasma membrane, separating the two daughter cells. The cell plate's contents join the parental cell wall.
Describe Cytokinesis in Animal Cells
- The division of the cytoplasm begins towards the end of telophase - Two daughter cells are formed shortly by the end of mitosis - cytokinesis begins with the formation of a cleavage furrow. the cell is pinched in two, creating two identical daughter cells - Cleavage furrows are formed by actin microfilaments
Describe what happens in Prophase 2
- The mitotic spindles begin to form - It is made up of microtubules connected to the 2 centrosomes. An array of short microtubules that extend from the centrosomes are called Asters. - The centrosomes move away from each other as the microtubules lengthen - Chromosomes appear as 2 sister chromatids which may differ from each other
Describe what happens in late prophase 1
- The nuclear envelope fragments - The dis-assembly of the synaptonemal complex takes place. The tetrad structure is retained because the homologous chromosomes are held together at the chiasmata. - The kinetochore of each homologous chromosome attaches to a microtubule of the opposite pole
Describe Prophase
- The nucleoli disappear - Chromosomes condense and are visible - Duplicated chromosomes are joined together at a specialized region (centromere) and appear are 2 identical sister chromatids - Mitotic spindles begin to form. It is made up of microtubules connected to the 2 centrosomes. Arrays of short microtubules that extend from the centrosomes are called asters - the centrosomes move away from each other as the microtubules lengthen
Describe the G2 phase of Interphase
- The nucleus is enclosed in a nuclear envelope - Each nucleus contains 1 or more nucleoli - Chromosomes duplicated during the S phase are not condensed enough to be visible - Each replicated chromosome consists of 2 genetically identical sister chromatids connected at the centromere - 2 Centrosomes have formed from the replication of a single centrosome
Describe the S phase (DNA Synthesis phase)
-DNA replication occurs -. DNA molecules are packed into chromosomes - Each chromosome has 1 DNA molecule - In the beginning, each chromosome is single - At the end, each chromosome consists of two sister chromatids - Each chromatid contains an identical DNA molecule and are attached by adhesive proteins all along their lengths
Describe Mitosis (the first part of the Mitotic phase)
-Divided into 5 parts: Prophase, Prometaphase, Metaphase, Anaphase, Telophase
Describe what happens in Prophase 1
-Longest phase. It occupies more than 90% of the time required for meiosis - The nucleoli disappear - Mitotic spindles begin to form. It is made up of microtubules connected to the 2 centrosomes. An array of short microtubules that extend from the centrosomes are called asters. - the centrosomes move away from each other as the microtubules lengthen. - Chromosomes condense and become visible - Duplicated chromosomes are joined together and appear as 2 identical sister chromatids -Homologous chromosomes pair along their lengths, precisely aligned gene by gene - Homologous chromosomes physically connect along their lengths by a zipper-like protein structure to form the synaptonemal complex - Each chromosome pair is is seen as a group of 4 chromatids called a tetrad - the DNA molecules of non-sister chromatids break at the same locations. These broken DNA molecules then exchange places and join to the other DNA molecule. This process is called Crossing Over. - Each group has one or more regions where crossing over has occurred. These region are called chiasmata. The chaismata hold the homologous chromosomes together until anaphase 1
Describe Prometaphase
-Nuclear envelope fragments -Each of the 2 chromatids of the chromosomes now has a special protein structure in the centromere called the kinetochore -microtubules extend from the centrosomes to the middle of the cell - some microtubules attach to the kinetochoes and are called kinetochore microtubules - The nonkinetochore microtubules interact with those from the opposite pole of the spindle
Describe the G1 phase (First Gap Phase)
-This is the portion of the cell cycle just after division but before DNA synthesis -. The cell grows by producing proteins and organelles
Name two reasons why mitosis occurs
1. Multicellular organisms grow in size and complexity by making more cells 2. old and damaged cells are replaced
Each chromosome consists of what?
2 sister chromatids joined at the centromere
What is the haploid number in humans
23
How many chromosomes do we inherit from each parent?
23; one from each pair of chromosomes
How many daughter cells are formed by the end of Meiosis
4
How many nucleotides are there in DNA
4
What is the diploid number in humans?
46
What percentage of the Cell Cycle is Interphase?
90%
What is a karyotype
A display of condensed chromosomes arranged in pairs.
Define Locus (plural loci)
A gene's specific location along the length of a chromosome
What is each nucleotide made up of?
A phosphate group, a pentose sugar, and a nitrogen base
Define Synapsis
A process in which homologous chromosomes physically connect along their lengths by a zipper-like protein structure to form the synaptonemal complex
in Multicellular organisms, mitosis occurs in which cells?
Autosomal cells
All the non-sex chromosomes are known as what?
Autosomes
Cell wall is made up of what?
Cellulose
in 46 human chromosomes, there are 2 types of each ______
Chromosome
In DNA, Guanine pairs with what nucleotide?
Cytosine
What are the names of the cells formed by cell division
Daughter cells
What kind of sugar is in a nucleotide
Deoxyribose sugar
Define Gametes
Egg or sperm sex cell
If an individual has a homologous pair of X chromosomes (XX), is the individual a male/female
Female
What phases make up the cell cycle?
G1, S, G2, M
What phases does interphase contain?
G1, S, and G2
What are the only cells not produces by mitosis?
Gametes
Both chromosomes of each pair carry what?
Genes controlling the same inherited characters
Is our gamete cells (egg and sperm) diploid or haploid?
Haploid
What is another term for homologous chromosomes?
Homologues
Name a multicellular organism that reproduces asexually
Hydra
the 2 DNA strands are together by which bonds? What are these bonds between?
Hydrogen bonds, the paired bases
Where is the inheritable material located?
In the chromosome
What does Meiosis 1 result in?
It results in the separation of the homologous chromosomes and the division of 1 diploid nucleus into 2 haploid nuclei.
If an individual has a chromosome pair of X and Y, is the individual a male/female
Male
What are the steps of meiosis
Meiosis I and Meiosis II, Meiosis 1 and meiosis 2
Which one is larger: Purines or Pyrimidines
Purines
What are the X and Y chromosomes known as?
Sex chromosomes
What are the two ways organisms are reproduce?
Sexually and Asexually
What are Pyrimidines
Single ringed structures
Are the homologous parts of the X and Y chromosomes large or small?
Small
How the chromosomes are electronically arranged in a computer?
Starting with the longest
Define reproduction
The biological process by which new organisms are produced
Define Tetrad
The four chromatids in a pair of homologous chromosomes that come together as a result of synapsis during meiosis
Draw Prophase on a piece of paper and label everything. Then, compare it to the picture
Things you should've labeled: centriole, early mitotic spindle, Aster, centromere, plasma membrane, cytoplasm, nuclear membrane, nucleolus, chromosomes consisting of two sister chromatids, centrosome
In DNA, Adenine pairs with what nucleotide?
Thymine
True or False: No single chromosome has the entire DNA of an individual
True
Define fertilization
Union of egg and sperm and their nuclei
Draw Telophase on a piece of paper and label everything. Then, compare it to the picture
What you should've labeled: cleavage furrow, nucleolus forming, nuclear envelope forming, plasma membrane, cytoplasm, centrosome, centriole, chromosome, aster
Draw Metaphase on a piece of paper and label everything. Then, compare it to the picture
What you should've labeled: plasma membrane, centriole, centrosome, kinetochore microtubules, nonkinetochore microtubules, sister chromatids, chromosome, centromere with kinetochore proteins, cytoplasm, aster, centrosome at spindle pole, spindle, metaphase plate
Draw Anaphase on a piece of paper and label everything. Then, compare it to the picture
What you should've labeled: plasma membrane, centromere, centriole, kinetochore microtubules, cytoplasm, kinetochores, nonkinetochore microtubues, aster, daughter chromosomes
Draw Prometaphase on a piece of paper and label everything. Check your drawing with the one on pg 8 of Mrs. Patil's first packet.
What you shouldve labeled: fragments of the nuclear envelope, kinetochore, kinetochore microtubule, nonkinetochore microtubules, centrosome, centriple, cytoplasm, aster, plasma membrane, chromosome, sister chromatids
An unfertilized egg cell has which chromosome?
X
Which two chromosomes are an exception to the general pattern of homologous chromosomes in human somatic cells?
X and Y chromosomes
A sperm cell has which chromosome?
X or Y
Are the two strands of the double helix complementary to each other?
Yes
What is the structure of DNA
a double-helix
What is a somatic cell
a non-sex cell
What happens in asexual reproduction
a single individual is the sole parent and passes copies of all its hereditary material on to its offspring
A diploid cell has a) what # of chromosomes b) it is abbreviated as what?
a) diploid number b) 2n
A haploid cell has a) what # of chromosomes b) it is abbreviated as what
a) haploid number b) n
What is a diploid cell
any cell with two chromosome sets
is binary fission a sexual or asexual reproduction
asexual
what is binary fission
bacterial cell division
How does Hydra reproduce?
by budding
What are autosomal cells?
cells other than sex cells, non-sex cells
Where do the nucleotides differ?
in their nitrogenous bases
The number of chromosomes in a single set is represented by what?
n
Describe the structure of Thymine and Cytosine
one six-member ring of carbon and nitrogen atoms