Chapter 2 - Chromosomes and Cellular Reproduction

eukaryote

- both unicellular and multicellular with compartmentalized cell structure - its genetic material is surrounded in a nuclear envelope to form a nucleus - DNA is closely associated with histones to form tightly packed chromosomes

synapsis

- close pairing of homologous molecules - allows matching-up of homologous pairs prior to their segregation, and possible chromosomal crossover between them

interphase

- extended period in cell cycle between divisions where cell grows, develops, and prepares for cell division - three phases: G1, S, and G2

telomere

- natural ends, or tips of a linear chromosome - meant to stabilize the chromosome ends - can play role in aging and cancer

virus

- neither prokaryotic nor eukaryotic because they do not possess a cellular structure - can only reproduce within host cells - composed of an outer protein coat surrounding nucleic acid (either DNA or RNA)

tetrads

- once the homolog pairs synapse they are called ______ (each has four chromatids) or bivalents

M phase

- period of active cell division - includes mitosis (nuclear division) and cytokenesis (cytoplasmic division)

cohesin

- protein molecule that holds the two sister chromatids of a chromosome together - allows sister chromatids to separate when broken down in anaphase of mitosis or anaphase II of meiosis

meiosis

- sexual process in which chromosomes of a eukaryotic cell divide to give rise to haploid reproductive cells - consists of two cell divisions

cell cycle

- stages through which a cell passes from one cell division to the next - genetic instructions for all characteristics are passed from parent to daughter cells

sister chromatids

- two copies of a chromosome that are held together at the centromere - each chromatid consists of a single DNA molecule

prokaryote

- unicellular, with no nucleus or compartmentalized cell structure - DNA does not exist in the highly ordered and packed arrangement but rather in a "nucloid" region - made up of eubacteria and archaea

checkpoint

a key transition point at which progression to the next stage of the cell cycle is regulated

haploid

cells that carry ONE set of genetic information

diploid

cells that carry TWO sets of genetic information

chromatin

complex of DNA and histone proteins to create the stuff that makes up a chromosome

crossing over

exchange of genetic material between homologous but nonsister chromatids in prophase I of meiosis

second polar body

female production of gametes - contains a set of chromosomes but little of the cytoplasm - one of the products of meiosis II in oogenesis

first polar body

female production of gametes - contains half of the chromosomes but little of the cytoplasm - may or may not divide further - one of the products of meiosis I in oogenesis

oogonium

female production of gametes - diploid cells in the ovaries that are capable of undergoing meiosis to produce a sperm

primary oocyte

female production of gametes - diploid oogonium that has entered prophase I of meiosis

secondary oocyte

female production of gametes - haploid cells that are product of meiosis I in female animals - recieves most of the cytoplasm

ovum

female production of gametes - large and mature female gamete that recieves most of the cytoplasm as a final product of oogenesis

oogenesis

female production of gametes - production of gametes in ovaries of a female animal

fertilization

fusion of gametes to form a zygote

histones

in eukaryotes, DNA is closely associated with this special class of proteins to form tightly packed chromosomes

locus

location of an allele on a chromosome

spermatogonium

male production of gametes - diploid cells in the testis that are capable of undergoing meiosis to produce a sperm

primary spermatocyte

male production of gametes - diploid spermatogonium that has entered prophase I of meiosis

secondary spermatocyte

male production of gametes - haploid cells that are product of meiosis I in male animals

spermatid

male production of gametes - immediate product of meiosis II in spermatogenesis - matures to sperm

spermatogenesis

male production of gametes - production of gametes in the testes of a male animal

microsporocyte

meiosis in plants - diploid reproductive cell in the stamen of a plant - undergoes meiosis to produce four haploid microspores

microspore

meiosis in plants - haploid product of meiosis in plants

megasporocyte

meiosis in plants - in the ovary of a plant, a diploid reproductive cell that undergoes meiosis to produce haploid macrospores

megaspore

meiosis in plants - one of the four products of meiosis in plants

interkinesis

period between meiosis I and meiosis II

karyotype

picture of aligned chromosomes

cytokinesis

process by which the cytoplasm divides after/during telophase

mitosis

process of a singular nuclear division

recombination

process that produces new combinations of alleles

archea

prokaryote known as "ancient bacteria"

eubacteria

prokaryote known as "true bacteria"

bivalent

refers to a synapsed pair of homologous chromosomes

origin of replication

sites where DNA synthesis begins

telophase II

stage of meiosis - chromosomes arrive at spindle poles

telophase I

stage of meiosis - chromosomes arrive at the spindle poles

prophase I

stage of meiosis - chromosomes condense and pair - crossing over takes place - nuclear membrane breaks down - spindle forms

metaphase I

stage of meiosis - homologous pairs of chromosomes align in the center of the cell

prophase II

stage of meiosis - after interkinesis - chromosomes condense - the nuclear membrane breaks down - the spindle forms

anaphase I

stage of meiosis - homologous chromosomes separate and move toward the spindle poles

metaphase II

stage of meiosis - individual chromosomes align on the midline of the cell

metaphase

stage of mitosis - chromosomes align in the center of the cell

telophase

stage of mitosis - chromosomes arrive at spindle poles - nuclear membrane re-forms - chromosomes relax and lengthen

prophase

stage of mitosis - chromosomes contract and become visible - cytoskeleton breaks down - mitotic spindle begins to form

anaphase

stage of mitosis - chromosomes separate and move toward the spindle poles

prometaphase

stage of mitosis - nuclear membrane breaks down - spindle microtubules attach to chromosomes at kinetochore

diplotene

stage of prophase I - centromeres of paired chromosomes move apart - two homologs remain attached at each chiasmata

diakinesis

stage of prophase I - chromosome condensation continues - chiasmata move toward the ends of the chromosomes as the strands slip apart - homologs remain paired only at tips

pachytene

stage of prophase I - chromosomes become shorter and thicker - three-part synaptonemal complex develops between homologous chromosomes - crossing over takes place

zygotene

stage of prophase I - chromosomes continue to condense - homologous chromosomes pair up and begin synapsis - each synapsed chromosome consists of 4 chromatids called a bivalent or tetrad

leptotene

stage of prophase I - chromosomes contract and become visible

anaphase II

stages of meiosis - chromatids separate and move toward the spindle poles

homologous pair

two chromosomes that are usually alike in structure and size, each carrying genetic information for the same set of heredity characteristics