BIOL 111 Chapter 11: Meiosis and Reproduction

what are autosomes?

everything but sex chromosomes (pairs 1 - 22)

homologous pairs

one from each parent

what are sex chromosomes?

distinct from each other in characteristics in gene composition

represented as X and Y

XX = female

XY = male

what are karyotypes?

the complete set of chromosomes

a visual layout of chromosomes

what is diploid?

two sets of chromosomes, 2n

humans have 23 pairs, 46 chromosomes in total

what is haploid?

a single set of chromosomes, n

found in gametes

n = 23 in humans

what is the result of meiosis?

chromosome go from diploid to haploid

4 unduplicated, haploid cells (sperm or egg)

what happens during meiosis I

chromosomes reduce from diploid to haploid

what happens during meiosis II?

chromosomes divide from duplicated to unduplicated

what happens during interphase?

G1, S, G2

chromosomes replicate during S phase

2 identical sister chromatids are attached to centromere

still diploid

what happens during prophase I during meiosis I?

homologous chromosomes pair up and connect to each other

crossing over can occur

what is the difference between mitosis/meiosis II and meiosis I during prophase?

crossing over only happens during meiosis I

what happens during metaphase I of meiosis I?

tetrads are arranged at the cell equator with kinetochores facing opposite poles

chromatids undergo independent assortment: maternal and paternal chromosomes orient at random

what is the difference between mitosis and meiosis I during metaphase?

during meiosis I, homologous pairs (not sister chromatids) separate and become haploid

during mitosis, sister chromatids align and separate, they become unduplicated

what happens during anaphase I of meiosis I?

microtubules pull tetrads apart

homologous pairs move towards opposite poles

chiasmata are broken but sister chromatids remain attached at the centromere

difference between mitosis and meiosis I during anaphase?

during meiosis I, homologous chromosomes separate, not sister chromatids

what happens during telophase I and cytokinesis in meiosis I?

separated chromosomes arrive at opposite poles

nuclear envelopes form

cytokinesis causes cells to go from 2n to n

sister chromatids may not be identical due to crossing over

how do humans go from 2n to n to 2n?

meiosis goes from diploid to haploid, making a sperm and an egg

fertilization fuses the sperm and egg, gametes come together to make a diploid cell

what is spermatogonia?

diploid cells embedded into walls of seminiferous tubules within the testes

spermatogonia becomes primary spermatocyte (2n)

what happens during spermatogenesis?

primary spermatocyte undergoes meiosis I to form 2 secondary spermatocytes (n)

secondary spermatocytes undergo meiosis II to form 4 spermatids (n)

spermatids differentiate to spermatozoa (sperm, (n))

what happens during oogonium?

2n cell in the outer cortex of ovary becomes primary oocyte

what happens during oogenesis?

primary oocyte undergoes meiosis I to produce a large secondary oocyte and a polar body (n)

secondary oocyte undergoes meiosis II to form large ootid and polar body

results in 1 large ootid and 2-3 polar bodies

ootid differentiates into large ovum and polar bodies disintegrate