Chapter 13 Flashcards
Genetics
Study of heredity and variation
Heredity
Transmission of traits from one generation to next
What are genes composed of?
DNA
Somatic cells have how many pairs of chromosomes?
23
What do somatic cells consist of?
22 autosomes, 1 sex chromosome
A diploid cell has how many sets of chromosomes?
2
Why do homologs separate in meiosis I?
So 2 of the same chromosome don’t go to same cell
What does fertilization form?
Zygote
Why does meiosis create haploid cells?
So a zygote can have 1 pair from mom and another from dad
What separates in meiosis I? Meiosis II?
I - homologous chromosomes
II - sister chromatids
In which process do diploid cells become haploid?
Meiosis I
Why does chromatin coil up?
So not to tangle and break and so each cell receives the correct amount of genetic information
What occurs in synapsis? What follows this process?
- Homologous chromosomes align gene to gene
- Crossing over, where nonsister chromatids exchange alleles of similar gene
What is chiasmata?
Region where crossing over has occurred and that keeps the tetrad together
How many times are cohesins cleaved?
Twice, one to separate homologs, another to separate sister chromatids
What is the original source of genetic diversity?
Mutations
What three mechanisms contribute to genetic variation?
- Independent assortment
- Crossing over
- Random fertilization
What is independent assortment?
That there is a 50% chance that haploid cells after meiosis I receives either a maternal or paternal chromosomes due to the tetrads’ random assortment at the metaphase plate
What does crossing over create?
Recombinant chromosomes, which combine genes inherited from each parent
What is random fertilization?
Fact that any sperm can fuse with any ovum
