meiosis Flashcards
“genetics is study of heredity and variation”
heredity vs variation
heredity= passing genes thru generations
variation=diff in appearances from parents to siblings
what are the units of heredity
genes –made up of segments of dna, diff versions of a specific gene are called alleles
locus
each gene has a specific location (locus) on a certain chrom
homologous chroms
-aka homologs
-its the pair of chroms (one paternal and ne maternal)
-can be replicated (two bow looking things) or unreplicated (two strings)
-they are chroms that are the same size and have genes arrangeed in the same order
which protein has the most impact in packaging dna into chroms
condensins not histones
karyotype
-ordered display of chroms in an individual cell
-numbered from longest (1) to shortest (22)
-23rd chrom pair is the sex chroms (xy or xx)
-can help determine dna abnormalities or chromosomal disorders
t or f:
a human diploid cell undergoing meiosis will have 23 bivalents duringprophase II and metaphase II
f (only bivalents in meiosis I)
chiasmata and bivalents are seen in prophase O
t
t or f: meiosis I refers to equational division
f
t or f: down syndrome and turner sundrome are 2 examples of autosomal disorders
f (turner syndrome is sex-linked its X- female. down syndrom is autosomal disorder)
homologous replicated chroms are seperated at which stage of meiosis
anapase I
what is the original source of genetic variation
mutations create diff versions of genes. then the reshuffling of diff genes during sexual reproduciton givesgenetic variation
3 m3chanisms that contribue to gnetic variation (past mutations)
- independent assortment of chroms
- crossing over
- random fertilization
homologs orient randomly at metaphase of meiosis (what is this)
independent assortment of chroms (one of 3 ways of genetic variation thru sexual reproduction)
what is the number of combinations possible when independent assortment of chroms
2^n (for humans n=23)
eg) a diploid cell w 6 chroms (2n=6)
2^n=8 possible combinations
