MEIOSIS AND SEXUAL LIFE CYCLES Flashcards
What are gametes?
Gametes are reproductive cells that act as vehicles that transmit genes from one generation to the next
What are the only haploid cells in the human body?
Gametes
How are gametes produced?
Gametes are the only cells in the human body not produced by mitosis. They develop from specialized cells called germ cells in the gonads
What are somatic cells?
Somatic Cells are all the cells of the body minus the gametes and their porecursors
What is asexual reproduction?
Offpring from asexual reproduction have a single parent and are genetical copies which receive copies of all its genes without the fusion of gametes
What is sexual reproduction?
Offspring of sexual reproduction are producted by 2 parents and inherit unique gene combinations
What are sex chromosomes?
X and Y chromosomes
What are autosomes?
Other chromosomes minus X and Y
What are diploid cells?
Diploid cells are any cell with 2 chromosome sets (2n)
What is the diploid number for humans?
2n = 46
What are haploid cells?
Any cell containing a single set of chromosomes (n)
What is the haploid number for humans?
n = 23
This set of 23 chromosomes consists of 22 autosomal chromosomes plus a single sex chromosome
What is fertilization?
The fusion of a haplold sperm from the father with a haploid egg from the mother
What does fertilization do to the number of chromosome sets?
The number of chromosome sets is doubled from 1 to 2
What is the result of fertilization?
Fertilization results in a zygote, a diploid cell which received 2 haploid sets of chromosomes bearing genes representing the maternal and paternal family lines
What is the alternation of generations in a sexual life cycle?
The alternation of generations is a second type of life cycle exhibited by plants and some algae
Incudes both diploid and haploid stages that are multicellular. Cells of the gametophyte give rise to gametes by mitosis; fusion of 2 haploid gametes results in a diploid zygote, which develope into the next sporophyte generation
What is meiosis?
Meiosis is cell division used for gamete formation. It reduced the number of chromosome sets from 2 to 1 in the gametes, counterbalancing the doubling that occurs in fertilization; it produces cells that differ genetically differ from their parents and each other
What does meisos do to the number of chromosome sets?
The number of chromosome sets are reduced from 2 to 1
What is the result of meisos?
Human sperm and eggs are returned to a haploid (n) state
How many daughter cells are produced by mitosis?
2
What events are unique to meiosis?
- Synapsis - during prophase I, replicated homologous chromosomes line up and become physically connected by a zipper-like protein complex called the synaptonemal complex
- The alignment of homologous pairs at the metaphase plate during metaphase I
- In meiosis, homologous pairs line up
- In mitosis, individual chromosomes line up
- The separation of homologous during anaphase I
- In meiosis, duplicated chromosomes of each homologous pair move towards opposite poles, but the sister chromatids remain attached
- In mitosis, the sister chromatids separate
What is mitosis?
Mitosis conserves the number of chromosome sets and produced daughter cells genetically identical identical to their parent cells and each other
How many daughter cells are produced by meiosis?
4, each with only half as many chromosomes as th parent cell (1 set rather than 2)
What mechanisms contribute to genetic variation arising from sexual reproduction?
- Independent assortment of chromosomes - random orientation of homologous pairs at metaphase plate during metaphase I
- 50/50 chance that a daughter cell of meiosis I will get the maternal chromosomes of a certain homolog pair, and a 50/50 chance for the paternal chromosome
- Crossing over - produces recombinant chromosomes with new combinations of maternal and paternal alleles
- Combines inherited DNA from 2 parents into 1 chromosome
- Random fertilization - any sperm can fuse with any egg
