Term
|
Definition
| animal and plant reproductive cells that transmit genes from one generation to the next. |
|
|
Term
|
Definition
| all cells of the body except gametes |
|
|
Term
|
Definition
| a genes specific location on the chromosome |
|
|
Term
|
Definition
| a single individual is the sole parent and passes copies of all its genes to its offspring without the fusion of gametes, producing exact genetic copies of themselves |
|
|
Term
|
Definition
| the results of asexual reproduction |
|
|
Term
|
Definition
| two parents give rise to offspring that have unique combinations of genes inherited from both parents and is thus genetically different from their parents and siblings |
|
|
Term
|
Definition
| images of chromosomes arranged in pairs, starting with the longest chromosomes |
|
|
Term
|
Definition
| two non sister chromosomes composing a pair that have the same length, centromere position, and staining pattern. both are carrying genes controlling the same inherited characters, like eye color. |
|
|
Term
|
Definition
| X and Y, an exception to the general pattern of homologous chromosomes, they determine an individuals sex and only small parts of X and Y are homologous |
|
|
Term
|
Definition
| chromosomes that aren't sex chromosomes |
|
|
Term
|
Definition
| n=the number of chromosomes in a single set |
|
|
Term
|
Definition
a cell with two chromosome sets, has a diploid number = 2n
ex- for humans, the diploid number is 46, 2(23)=46 |
|
|
Term
|
Definition
gamates contain a single set of chromosomes. each has a haploid number = n
for humans ( n =23) so the haploid number is 23 |
|
|
Term
|
Definition
| union of gametes resulting in a fertilized egg |
|
|
Term
|
Definition
| the result of the fusion of two gamates creating a diploid containing two haploid sets of chromosomes from each parent |
|
|
Term
|
Definition
| creates gamets, a type of cell division that reduces the number of sets of chromosomes from two to one gamete, counterbalancing the doubling that occurs at fertilizatoin |
|
|
Term
| how are meiosis and fertilization related? |
|
Definition
| meiosis reduces the number of chromosomes creating haploid gametes while fertilization fuses these haploid cells together to restore the orginal chromosome count in the new individual |
|
|
Term
| alteration of generations |
|
Definition
| a type of life cycle present in plants and some algae. gametophytes create sporophyte which then create gametophytes, etc. |
|
|
Term
|
Definition
| a state during which homologs become physically connceted to each other along their lengths by a zipper-like protein structure. during this time, crossing over occurs |
|
|
Term
|
Definition
| a genetic rearrangement between non-sister chromatids involving the exchange of corresponding segments of DNA molecules |
|
|
Term
|
Definition
| x-shaded regions on a homologous pair where a cross over has occurred. appears as a cross becaus sister chromatid cohesion still holds the two original sister chromatids together, even in in regions beyond the crossover point where one chromatid is now part of the other homolog. |
|
|
Term
| what are three events unique to meiosis? |
|
Definition
1. synapsis and crossing over
2. homologus pairs at the metaphase plate
3. separation of homologs |
|
|
Term
| synapsis and crossing over |
|
Definition
| during prophase 1, duplicated chromosomes create sister chromatid pairs which in turn line up with other chromosomes to create homologus pairs. these pairs then overlap during synapsis and crossing over occurs |
|
|
Term
| homologous pairs at the metaphase plate |
|
Definition
| during metaphase I, chromosomes are lined up at the plate as pairs of homologs rather than individual chromosomes |
|
|
Term
|
Definition
| during anaphase 1, duplicated chromosomes move towards opposite poles but the sister chromatids remain attached. by contrast, in mitosis chromatids separate. |
|
|
Term
|
Definition
| chasmata was holding the homologs together, and during anaphase 1 the release of cohesion along sister chromatid arms allows homologs to separate. however, individual chromosomes are still held together trhough sister chromatid cohesion at the centromeres |
|
|
Term
|
Definition
| chromosomes are still being held together through sister chromatid cohesion at the centromeres, but during anaphase 2 these cohesion is broken and the siter chromatids separate |
|
|
Term
|
Definition
| each chromosome in a gamete is not exclusively maternal or paternal because crossing over produces recombinant chromosomes that carry genes derived from two different parents. |
|
|
Term
|
Definition
| begins early during prophase I as homologous chromosomes pair up along their lengths, aligning precisely with the corresponding gene on the other homolog. the DNA of two nonsister chromatids (one maternal and one paternal) is broken and the two segments beyond the cross over point are each joined to the other chromatid. thus the paternal chromatid is joined to a piece of the maternal chromatid beyond the crossover point |
|
|
Term
| advantages of asexual reproduction |
|
Definition
in a stable environment, asexual reproduction insures the perpetuation of successful combinations of alleles.
asexual reproduction is also less expensive energy-wise |
|
|
Term
|
Definition
| the entry of DNA from other members of the population or other species, not through sexual exchange |
|
|
Term
| _______ are the only haploid cells in animals |
|
Definition
| gametes are the only haploid cells in animals |
|
|
Term
| gametes fuse to from what? |
|
Definition
| gametes fuse to form a diploid zygote that divides by mitosis to develop into a multicellular organism |
|
|
Term
| either _____ or ____ cells cna divide by mitosis |
|
Definition
| either haploid or diploid cells can divide by mitosis, depending on the type of life cycle |
|
|
Term
| only ____ cells can undergo meiosis |
|
Definition
| only diploid cells can undergo meiosis |
|
|
Term
| what are the two stages of division after chromosomes duplicate? |
|
Definition
meiosis 1: reductional division, results in two haploid daughter cells with replicated chromosomes
meiosis II: equational division, sister chromatids separate of each the two haploid daughter cells creating 4 haploid daughter cells |
|
|
Term
|
Definition
| a pair of chromosomes, a group of four chromatids. usually consists of one or more chiasmata |
|
|
Term
|
Definition
occupies about 90% of the time required for meiosis
1. chromosomes begin to condense
2. homologous chromosomes enter synapsis
3. crossing over occurs
4. tetrads are formed |
|
|
Term
|
Definition
1. tetrads line up along the metaphase plate
2. microtubules attach to the kinetochore of one chromosome of each tetrad |
|
|
Term
|
Definition
1. cohesion at the chiasmata is broken allowing pairs of homologous chromosomes separate, but sister chromatids remain attached at the centromere
2. chromosomes move as a unite towards their respective poles |
|
|
Term
| telophase I and cytokinesis |
|
Definition
1. each half of the cell has a haploid set of chromosomes, still consisting of their sister chromatids
2. cytokinesis creates two daughter haploid cells |
|
|
Term
|
Definition
very similar to prometaphase of mitosis
1. no chromosomes are duplicated
2. spindle apparatuses are formed
3. chromosomes start to move towards metaphase plate |
|
|
Term
|
Definition
1. sister chromatids are arranged at the metaphase plate, but due to crossing over they're no long identical
2. kinetochores of sister chromatids attach to microtubules |
|
|
Term
|
Definition
1. cohesion at the centromere of the sister chromatids is severed and they separate
2. sister chromatids each move toward opposite poles |
|
|
Term
| telophase II and cytokinesis |
|
Definition
1. the chromosomes arrive at opposite poles
2. nuclei form and the chromosomes begin decondensing
3. cytokinesis separates the cytoplasm, creating four haploid daughter cells that are each genetically different from their siblings and parents |
|
|
Term
|
Definition
mitosis:
1. conserves the number of chromosome sets
2. produces identical daughter cells
3. only one division
4. creates 2 diploid cells
5. enables multicellular organisms to arise from a zygote, enables growth, repair, and asexual reproduction
meiosis:
1. reduces the number of chromosome sets from 2 (diploid) to one (haploid)
2. produces unique cells
3. consists of 2 divisions
4. synapsis of homologous chromosomes takes place during prophase 1
5. crossing over creates chiasmata
6. creates 4 haploids
7. creates gametes and increases genetic variablity |
|
|
Term
| what three events are unique to meiosis? |
|
Definition
1. synapsis and crossing over in prophase I
2. there are homologous chromosomes (tetrades) instead of individual replicated chromosomes at the metaphase plate during metaphase I
3. at anaphase I, homologous chromosomes instead of sister chromatids separate |
|
|
Term
| during what phase of meiosis do unique events take place? |
|
Definition
| events that are unique to meiosis occur during meiosis I |
|
|
Term
| three mechanisms that contribute to genetic variation |
|
Definition
1. independent assortment of chromosomes
2. crossing over
3. random fertilization |
|
|
