Lecture : Biology Ch 9 Notes
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Humans, like most other large animals, practice sexual reproduction two parent pass chromosomes to their offspring. Why are the genetic and physical characteristics different between siblings: meiosis, daughter cells received the haploid number of chromosomes in varied combination. Meiosis serves two major functions: 1. Shuffling the chromosomes and genes to produce genetically different gametes (sperm and eggs) We cannot predict which sperm fertilizes a given egg. Introduces a level of genetic variation: so, each offspring is unique and has a different combination of chromosomes (and genes) than either parent. Chromosomes can be visualized by taking a picture of sorts (karyotype) Chromosomes come in pairs: because we inherit one from each parent. Both males and females normally have 23 of chromosomes: 22 sets of autosomes, 1 set of sex chromosomes. 2 different types of sex chromosomes: x - larger chromosomes, y - smaller chromosomes. 23 pairs of chromosomes (46 total) constitute the diploid - (2n) number.
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Related Questions
Which statements pertaining to genetic variability are correct? Check all that apply (note that wrong answers will be deducted from right answers)!
Crossing over is defined by the exchange of chromosome pieces during metaphase one of meiosis. |
If a germ cell (i.e. parent cell before meiosis) had only two pairs of homologous chromosomes (i.e. 4 chromosomes total) there are 2 possible combinations of maternal and paternal chromosomes in gametes. |
Siblings produced by sexual reproduction are different because sperms are different from one another and eggs are different from one another, and the combination of an egg and sperm is basically unique. |
Random fertilization means that all possible combinations of eggs and sperm are equally likely, i.e. it is pure chance which sperm fuses with which egg. |
Individual chromosomes contain thousands of genes. This means that during each crossing over event, more than one gene is exchanged between paternal and maternal chromosomes. |