Term
|
Definition
| Is the scientific study of heredity and hereditary variations |
|
|
Term
|
Definition
Parent endow their offspring with coded information in the form of hereditary units (genes).
*** Inherited information is passed onion the form of each genes specific sequence of DNA nucleotides |
|
|
Term
|
Definition
Reproductive cells, are vehicles that transmit genes from one generation to the next.
The only cells in the human body not produced by mitosis |
|
|
Term
|
Definition
| All cells of the body except gametes and their precursors |
|
|
Term
|
Definition
| A specific place along the length of the chromosome where a given gene is located. |
|
|
Term
|
Definition
A single individual is the sole parent and passes copies of all it's genes to its offspring without fusion of gametes.
***Only organisms that reproduce asexually have offspring that are exact genetic copies of themselves.
Offspring are derived by mitosis.
Any change in DNA is called a mutation |
|
|
Term
|
Definition
A group of genetically identical individuals.
Offspring that are the result of asexual reproduction are called clones |
|
|
Term
|
Definition
| Two parents give rise to offspring that have unique combinations of genes inherited from the two parents. |
|
|
Term
|
Definition
| Is the generation to generation sequence of stages in the reproductive history of an organism, from conception to the production of its own offspring |
|
|
Term
|
Definition
| A display of chromosome pairs of a cell arranges in size and shape |
|
|
Term
|
Definition
Two chromosomes composing a pair, have the same length, centromere position, and staining pattern.
***X and Y are important exceptions. (females have a pair of X chromosomes while males have an X and a Y chromosome). Only a small portion of the X and Y are homologous. |
|
|
Term
|
Definition
| Determines an individuals sex... They are the X and Y chromosomes |
|
|
Term
|
Definition
| All chromosomes except sex chromosomes. |
|
|
Term
|
Definition
Any cell with two chromosome sets. It has a diploid of chromosomes abbreviated 2n.
For humans, the diploid number is 46...that is the number of chromosomes found in somatic cells |
|
|
Term
|
Definition
A cell that contains a single set of chromosomes (gametes)
Each haploid cell has n chromosomes (for humans, n=23, consists of 22 autosomes and one sex chromosome). |
|
|
Term
|
Definition
| When a haploid from the father fuses with the haploid of the mother. This fusion of gametes, culminating in fusion of their nuclei. |
|
|
Term
|
Definition
| The product of fertilization, is diploid since it contain one set from the mother and one set of chromosomes from the father. |
|
|
Term
|
Definition
| Located in the gonads (ovaries for females and testes for males) are the cells that produce gametes |
|
|
Term
|
Definition
A modified type of cell division in sexually reproducing organisms consisting of two rounds of cell division but only one round of DNA replication. It results in cells with half the number of chromosomes sets as the original cell.
Occurs in the germ cells during production of gametes, which undergo no further cell division prior to fertilization.
Only diploid cells can undergo meiosis. |
|
|
Term
| Alternation of generations |
|
Definition
A second type of life cycle in some plants and algae.
A life cycle in which there is both a multicellular diploid form, the sporophyte, and a multicellular haploid form, the gametophyte.
The sporophyte undergoes meiosis to produce spores. These spores divide mitotically, producing a multicellular haploid gametophyte. These gametophytes give rise to gametes by mitosis. At this point, fertilization can occur.
The name of alternation of generations comes from the fact that the sporophyte create the gametophyte, which then lead to the creation of sporophyte. |
|
|
Term
|
Definition
The first division of a two stage process of cell division in sexually reproducing organism that result in cells with half the number of chromosomes sets as the original cell.
Consists of:
Prophase I
Metaphase I
Anaphase I
Telophase I and cytokinesis |
|
|
Term
|
Definition
The second division of a two stage process of cell division in sexually reproducing organism that result in cells with half the number of chromosomes sets as the original cell.
Consist of:
Prophase II
Metaphase II
Anaphase II
Telophase II and cytokinesis |
|
|
Term
|
Definition
| Different versions of genes at corresponding loci. |
|
|
Term
|
Definition
1. Chromosomes begin to condense, and homologs loosely pair along their lengths aligned gene by gene
2. Paired homologs become physically connected to each other along their lengths by a zipper like protein structure (the synaptonemal complex), this state is called synapsis.
3. Cross over; a genetic arrangement between non sister chromatids involving the exchange of corresponding segments of DNA molecules, begins during pairing and synaptonemal complex formation, and is completed while homologs are in synapsis.
4. Synapsis has ended with the disassembly of the synaptonemal complex and the chromosomes in each pair have moved apart slightly.
5. Each homologous pair has one or more X shaped regions called chiasmata. A chiasma exists at a point where crossover has occurred. It appears as a cross because sister chromatid cohesion still holds the two original sister chromatids together, even in regions beyond the crossover point, where one chromatid is now part of the other homolog.
6. Centrosome movement, spindle formation, and nuclear envelope breakdown occurs as in mitosis.
7. Microtubules from one pole or the other attach to the two kinetochores, protein structures at the centromeres of the two homologs. The homologous pairs then move towards the metaphase plate. |
|
|
Term
|
Definition
1. Pairs of homologous chromosomes are now arranged at the metaphase plate, with one chromosome in each pair facing each pole.
2. Both chromatids of one homolog are attached to kinetochore microtubules from one pole; those of the other homolog are attached to microtubules from the opposite pole. |
|
|
Term
|
Definition
1. Breakdown of proteins responsible for sister chromatid cohesion along chromatid chromatid arms allows homologs to separate.
2. The homologs move toward opposite poles, guided by the spindle apparatus.
3. Sister chromatid cohesion persists at the centromere, causing chromatids to move as a unit toward the same pole. |
|
|
Term
| Telophase I and cytokinesis |
|
Definition
1. At the bringing of telophase I, each half of the cell has a complete haploid set of duplicate chromosomes. Each chromosome is composed of two sister chromatids; one or both chromatids include regions of non sister DNA.
2. Cytokinesis (division of the cytoplasm) usually occurs simultaneously with telophase I, forming two haploid daughter cells.
3. In animals cells like these, a cleavage furrow forms. In plant cells, a cell plate forms.
**In some species, chromosomes decondense and nuclear envelopes form***
IMPORTANT, no chromosome duplication occurs between meiosis I and meiosis II. |
|
|
Term
|
Definition
1. A spindle apparatus forms.
2. In late prophase II, chromosomes, each still compose of two chromatids associated at the centromere, move toward the metaphase II plate |
|
|
Term
|
Definition
1. The chromosomes are positioned at the metaphase plate as in mitosis.
2. Because of crossing over in meiosis I, the two sister chromatids of each chromosome are not genetically identical.
3. The kinetochores of sister chromatids are attached to microtubules extending from opposite poles. |
|
|
Term
|
Definition
| 1. Breakdown of proteins holding the sister chromatids together at the centromere allows the chromatids to separate. The chromatids move toward opposite poles as individual chromosomes. |
|
|
Term
| Telophase II and cytokinesis |
|
Definition
1. Nuclei form, the chromosomes begin decondensing and cytokinesis occurs.
2. The meiotic cell division of one parent cell produces four daughter cells, each with a haploid set of chromosomes.
3. The four daughter cells are genetically distinct from one another and from the parent cell. |
|
|
Term
Mitosis vs Meiosis
-DNA replication |
|
Definition
In mitosis, it occurs during interphase before mitosis begins
In meiosis, occurs during interphase before meiosis I begins |
|
|
Term
Mitosis vs Meiosis
- Number of cell divisions |
|
Definition
In mitosis... One, including prophase, prometaphase, metaphase, anaphase, and telophase.
In meiosis.... Two, each including prophase, metaphase, anaphase, and telophase. |
|
|
Term
Mitosis vs Meiosis
- Synapsis of homologous chromosomes |
|
Definition
In mitosis, it does not occur.
In meiosis, occurs during prophase I along with crossing over between non sister chromatids; resulting chiasmata hold pairs together due to the sister chromatid cohesion. |
|
|
Term
Mitosis vs Meiosis
- Number of daughter cells and genetic composition |
|
Definition
In mitosis...Two daughter cells, each a diploid and genetically identical to the parent cell.
In meiosis.... Four, each haploid, containing half as many chromosome as the parent cell; genetically different from one another and from the parent cell |
|
|
Term
Mitosis vs Meiosis
-Role in the animal body |
|
Definition
In mitosis... Enables multicellular adult to arise from zygote; produces cells for growth, repair, and in some species, asexual reproduction.
In meiosis..... Produces gametes; reduces the number of chromosomes set by half and introduces genetic variability among the gametes |
|
|
Term
| 3 events unique to meiosis that occur in meiosis I |
|
Definition
1. Synapsis and crossing over
2. Homologous pairs at the metaphase plate
3. Separation of homologs |
|
|
Term
|
Definition
Since each pair of homologous chromosomes is positioned independently of the other pairs at metaphase I, the first meiotic division results in each pair sorting its maternal and paternal homologs into daughter cells independently of every other pair.
***when aligning on the metaphase plate, its a fifty fifty chance that a certain homologous pairs will be facing a certain direction.***
In humans, since n=23, there are about 8.4 million different possible chromosome arrangements by independent assortment (2^23). |
|
|
Term
|
Definition
Produces recombinant chromosomes (individual chromosomes that carry genes, DNA, derived from two different parents.
**In humans, an average of 1-3 crossover events occur per chromosome pair. Depends on the size of the chromosome and position of their centromeres. |
|
|
Term
|
Definition
The fusion of a male gamete with a female gamete during fertilization will produce a zygote will an unique set of chromosomes.
Think about it, by independent assortment, each sperm and egg can have a one in 8.4 million configuration. 8.4 million multiplied by 8.4 million, is about 70 trillion. Once crossing over is factor in, the true number of configurations is astronomical. |
|
|
