Chapter 10: Meiosis Flashcards
Locus
a genes specific location on a chromosome
Somatic Cells
normal cells in an organism
Gametes
reproductive cells that pass genes
What are autosomal chromosomes
The first 1 to 22 chromosomes in a human
What are sex chromosomes
The last pair 23 chromosomes in a human the X and Y ones
Haploid and Diploid
Chromosome pairs in a human are diploid because we get one from each parent. Gametes are haploid and only have 1 chromosome instead of a pair
What is the total process of meiosis
Meiosis takes a diploid germ stem cell and produces four haploid gamete
What is the total process of fertilization
The merging of two haploid gametes to form a diploid zygote
What is karotype
the variation between XX (female) and XY (male)
Variations in karotype hormones
Males have higher rations of androgens while females have higher ratios of estrogen
SRY gene
A gene on sex chromosomes that also determines a male, several mutations in this gene can make a female have XY chromosomes (no SRY on y chrome) or a male have XX chromosomes (SRY on X chrome)
Ploidy
the number of sets of chromosomes in a cell
What is homologous recombination?
When meiosis mixes the homologous chromatids in the parent to make something new called recombinant chromosomes
What happens in Meiosis I
homologous recombination changes the duplicated (s phased) sister chromatids and makes them recombinant but duplicated haploids
What happens in Meiosis II
The recombinant haploids fully separate and no longer duplicated
What is crossing over
Another name for homologous recombination, occurs during prophase
When does independent assortment occur?
metaphase and anaphase
What three things contribute to gene variation in a child
homologous recombination, independent assortment and fertilization
What is a chiasmata
An x shaped structure made by two chromosomes undergoing homologous recombination
What are the steps of recombination
Step 1 - DNA in chromosome are broken by protein, only one chromatid of each sister chromatid
Step 2 - Proteins hold the two non sister chromatids and form a synaptonemal complex
Step 3 - Synapsis fuses the pairs, homologous recombination occurs and recombinant chromosomes are created
Step 4 - synaptonemal complex leaves, chiasmata is visible, two pairs of sister chromatids are connected by their crossovers.
How many crossovers are on the average human chromosome?
two to three
What is independent assortment
A variation in meiosis that happens during anaphase caused by a varying of where the homologous chromosome is facing
Why are they 2 PMATs in Meiosis
The first Meiosis PMAT splits of the pair of sister chromatids that are attached to each other, then the second splits the sister chromatids into just chromatids making 4 new cells.
