Ch. 10 Flashcards
What are homologous chromosomes?
- a pair of chromosomes of the same length and centromere position
- passes genes for the same characters at corresponding loci
What are loci?
specific places along the length of a chromosome where a given gene is located
What are autosomes?
chromosomes not directly involved in determining sex
not sex chromosomes
What are sex chromosomes?
chromosomes responsible for determining the sex of an individual
How many autosomes and sex chromosomes do humans posses?
- 44 autosomes (22 pairs)
- 2 sex chromosomes (1 pair)
What are diploid cells?
cells containing 2 sets of chromosomes
denoted as 2n
What are haploid cells?
cells containing one set of chromosomes
denoted as n
What is the purpose of meiosis?
to produce gametes w/ half the genetic complement of the parent cells
gametes = sperm and eggs
What happens in prophase I?
- chromosomes become visible
- nuclear envelope breaks down
- crossing over occurs
What happens in metaphase I?
paired homologous chromosomes line up across the center of the cell
What happens in anaphase I?
homologous chromosomes separate and are paired to opposite ends of the cell
What happens in telophase I?
- 2 daughter cells are formed
- each contains only 1 chromosome of the homologous pair
What happens in prophase II?
- chromosomes condense
- spindles form in each new cell
- spindle fibers attach to chromosomes
What happens in metaphase II?
centromeres of chromosomes line up randomly at the equator of the each cell
What happens in anaphase II?
sister chromatids separate and move to opposite poles
What happens in telophase II?
- nuclear envelope reforms
- cytoplasm divides
- 4 daughter cells form
What is independent assortment?
the independent segregation of genes during the formation of gametes
What is crossing over?
- the exchange of genetic material between homologous chromosomes
- results in a mixture of parental characteristics in offspring
What is random fertilization?
the combination of each unique sperm w/ each unique egg increases genetic variability
What is recombination?
contributes to genetic variation by shuffling parental DNA and creating new combinations of variants
When does independent assortment occur?
metaphase I
When does crossing-over occur?
prophase I
