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BIO Exam I - Stack 1
Meiosis and life cycles
| Question | Answer |
|---|---|
| Offspring acquire genes from parents by ___. | inheriting chromosomes |
| ___ and ___ alternate in sexual life cycles. | Fertilization / meiosis |
| Meiosis ___ the number of chromosome sets from ___ to ___. | reduces / diploid / haploid |
| ___ produced in sexual life cycles contributes to evolution. | Genetic variation |
| heredity (inheritance) | the transmission of traits from one generation to the next |
| What is variation? Why is there variation among siblings? | -Variation is differences between members of the same species. -Variation is due to crossing over and independent assortment. |
| genetics | the scientific study of heredity and hereditary variation |
| gene | a discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA; many different kinds |
| What are gametes and what do they have to do with heredity? | -Gametes are reproductive cells that transmit genes from one generation to the next. -They are the vehicles that carry out heredity. |
| somatic cells | -all cells of the body except for the gametes and their precursors -do not undergo meiosis -humans have 46 chromosomes in each somatic cell |
| chromosomal locus | a gene's specific location along the length of a chromosome |
| asexual reproduction | a single individual is the sole parent and passes copies of all its genes to its offspring without the fusion of gametes |
| sexual reproduction | two parents give rise to offspring that have unique combinations of genes inherited from the two parents |
| clone | a group of genetically identical individuals; the offspring produced by asexual reproduction |
| karyotype | a display of the chromosome pairs of a cell arranged by size and shape |
| homologous chromosomes / "homologs" | two chromosomes composing a pair that have the same length, centromere position, and staining pattern |
| What are autosomes? How many do humans have? | -chromosomes that are not involved in determining sex -22 pairs, or 44 |
| What are sex chromosomes? How many do humans have? | -chromosomes that determine an individual's sex -1 pair, or 2 (XX or XY) |
| What is a diploid cell? What is the diploid number for humans? | -any cell with two chromosome sets; has a diploid number of chromosomes abbreviated "2n" -46 (so, 2n=46) |
| What is a haploid cell? What is the haploid number for humans? | -any cell with a single set of chromosomes; each has a haploid number of chromosomes abbreviated "n" -23 (so, n=23) |
| What is fertilization? What is the result of it? | -the union of gametes (each haploid), culminating in the fusion of their nuclei -a fertilized egg, or zygote (diploid) |
| How are the sexual life cycles of animals, plants/algae, and fungi/protists similar? Different? | -meiosis and fertilization alternate in all 3 -the cycles differ in the timing of meiosis and fertilization |
| synapsis | when paired homologous chromosomes become physically connected to each other along their lengths (by a zipper-like protein structure, the synaptonemal complex) |
| chiasmata | the x-shaped regions where crossing over has occurred between homologous nonsisiter chromatids; they become visible after synapsis |
| What is crossing over? Where does it occur? When does it begin? When does it end? | -a genetic rearrangement between nonsister chromatids involving the exchange of corresponding segments of DNA - occurs at chiasmata -begins during pairing and synaptonemal complex formation -completed while homologs are in synapsis |
| What happens during prophase I of meiosis? | - [PRO = BEFORE ... so prophase before the other stages] - chromosomes condense - homologs come together as pairs (tetrads) - synapsis - crossing over - nuclear envelope breaks down |
| What happens during metaphase I of meiosis? | - [META = AFTER ... so metaphase after the 1st stage] - homolog pairs arrange at metaphase plate - law of segregation, independent assortment |
| What happens during anaphase I of meiosis? | - [ANA = BACK ... the chromatids move back] - homolog pairs separate and move towards opposite poles of the cell - sister chromatids move as a unit |
| What happens during telophase I (and cytokinesis) of meiosis? | - [TELO = END ... this, along with cytokinesis, is the end of meiosis I] - nuclear envelopes form - chromosomes decondense - cell splits and forms 2 haploid cells |
| What happens during prophase II of meiosis? | - chromosomes condense - nuclear envelope breaks down - NO CROSSING OVER |
| What happens during metaphase II of meiosis? | - chromosomes align at equatorial/metaphase plate - the 2 sister chromatids are NOT genetically identical |
| What happens during anaphase II of meiosis? | - sister chromatids separate and move to opposite poles as individual chromosomes |
| What happens during telophase II (and cytokinesis) of meiosis? | - nuclear envelopes form - chromosomes decondense - cells split for a total of 4 haploid cells - each daughter cell is genetically distinct from each other and parent cell |
| What mechanisms contribute to the genetic variation arising from sexual reproduction? | independent assortment of chromosomes, crossing over, and random fertilization |
| What does the synaptonemal complex do? | - makes sure the breaks in chromatids are aligned - mediates chromosome pairing, synapsis, and recombination |
| What are chiasmata? What occurs there? | - the x-shaped regions where crossing over has occured between homologous nonsister chromatids; they are visible after synapsis - where crossing over occur; recombinant chromosomes produced |
| What are recombinant chromosomes? Why are they special? | - individual chromosomes that carry genes (DNA) derived from two different parents - variation...these chromosomes are ones that have never existed before |
| independent assortment | - when allele pairs separate independently during the formation of gametes; traits are transmitted to offspring indep. of each other - ex: if a cell has 2 pairs of chrom.s, it's random which way they will orient at metaphase I; 2 diff ways, 4 diff combos |
| random fertilization | - describes the concept that the probability of any set of genes has an equal likelihood of combining to form the offspring - a zygote represents the combination of parental probabilities |
| The number of different types of gametes that are possible as the result of independent assortment of parental chromosomes is: | - 2^n - where n = the number of chromosome PAIRS - (this does not count for crossing over) |
| What are the chances that two people will have a second child who is genetically identical to their first child? | - 2^23 is about 8 million - so, 8 mil x 8 mil = 64 tril possible combinations in zygotes |
| What is natural selection? What does natural selection act on? | - the process in which individuals what have certain inherited traits tend to survive and reproduce at higher rates than other individuals BECAUSE of those traits - acts on phenotypic traits (think, heterozygote wont express rec. disorder) |
Created by:
jessica.gvc
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