Meiosis (tutorial #10) Flashcards
Asexual Reproduction
Reproduction in which organisms produce genetically identical offspring (clones)
Sexual Reproduction
When the genetic material from two parents combines to form offspring that are genetically distinct from their parents.
Gene
A heritable unit that codes for the production of a protein.
Allele
The different alternative forms of a gene
How many chromosomes are in the human genome?
46
Homologous chromosomes
paired chromosomes that carry the same genes, one from each parent.
Gametes
Reproductive cells termed sperm and eggs; each gamete cell only has 23 chromosomes, which makes it haploid (n)
What ploidy level are somatic cells?
Diploid (2n) because they have one complete set of chromosomes from each parent (23 from mom, 23 from dad, 46 total).
What does 2n mean?
2n means there are two complete sets of chromosomes. 2n is associated with the term diploid.
What does n mean?
n means that there is one complete set of chromosomes. n is associated with the term haploid.
fertilization
when male gametes (sperm) and female gametes (egg) unite together. This begins the formation of a zygote during a process called sexual reproduction.
Zygote
A diploid cell resulting from the fusion of two haploid gametes.
Homologous pair
A pair of chromosomes with the same genes in the same locations, but different versions of those genes.
What is the primary function of meiosis?
The proper distribution of homologous chromosomes to gametes
What are the three phases of meiosis?
- pairing up the homologous chromosomes
- synapsis of the chromosomes together (crossing over)
- separating the chromosomes into daughter cells
If a diploid cell goes through meiosis, how many daughter cells will be produced? what is the ploidy level of each of those daughter cells?
Four haploid daughter cells are produced.
What is the difference between sister chromatids and non-sister chromatids?
Sister chromatids are two identical copies of a chromosome that are joined together by a centromere. Non-sister chromatids are two chromatids from two different homologous chromosomes.
What are the two factors that give rise to genetic diversity in meiosis?
independent assortment and crossing over (or recombination).
Independent assortment
Occurs during metaphase I when the homologous chromosomes line up on the metaphase plate. The orientation of the pairs is random, which allows for different combinations of chromosome pairs in daughter cells.
How do you find the number of different combinations of pairs of chromosomes in a daughter cell?
2^n, where n is equal to the number of chromosome pairs
crossing over/recombination
when pieces of one chromosome may be exchanged with the identical portion of the other chromosome in a homologous pair. This means that the resulting chromosomes are a unique mixture of maternal and paternal chromosomes.
Approximately how many times does crossing over occur in humans?
2-3 times per chromosome pair; ONLY HAPPENS IN NON-SISTER CHROMATIDS IN MEIOSIS I).
