Ch 2: Chromosomes and Cellular Reproduction (BIO 375 - Genetics) Flashcards
karyotype
complete set of an individual’s chromosomes; an image of a set of chromosomes (humans have 46 chromosomes, and 23 homologous pairs)
autosomes
any chromosome that is not a sex chromosome
chromosomes
thread like structures that carry genetic information
prokaryotes
single circular molecule of DNA with no end to chromosome; unicellular organism with simple cell structure; divided into eubacteria or archaea; reproduce through binary fission (chromosome replicates and cell divides)
eukaryotes
have multiple linear chromosomes composed of DNA and histone proteins packed like chromatin, where the chromosomes have identifiable ends; compartmentalized cell structure with components bounded by intracellular membranes; can be unicellular or multicellular
diploid
carry two sets of genetic information
haploid
single set of chromosomes; one copy of each gene
homologous chromosomes
alike in structure and size, each carrying genetic information for the same set of hereditary characteristics (except sex chromosomes); one chromosome of the pair is a maternal chromosome and the other is a paternal chromosome
centromere
region of chromosome where spindle fibers attach during cell division
telomeres
natural ends of a linear chromosome that protect and stabilize the chromosome ends
origins of replication
sites where DNA synthesis begins; sister chromatids
cell cycle
life cycle of a cell between cell divisions where progression through the cycle is regulated at checkpoints (key transition points)
phases of cell cycle
- Interphase (G1/G0, G1/S checkpoint, S, G2, G2/M checkpoint)
- Mitosis (Prophase, Metaphase, Anaphase, Telephase)
- Cytokinesis (cell division)
interphase
period between cell divisions (where cell grows, develops, and functions); nuclear membrane is present and chromosomes are relaxed
G1
Gap 1: cell growth; unduplicated chromosomes/chromatin
G0
Stasis, non-dividing phase
S
Synthesis: DNA duplicates/is synthesized
G2
Gap 2: mitosis preparation; duplicated chromosomes
prophase
chromosomes condense; each chromosome possesses two chromatids; mitotic spindle forms
metaphase
chromosomes line up on metaphase plate
anaphase
sister chromatids separate and move toward opposite poles
telophase
chromosomes arrive at spindle poles; nuclear membrane reforms and chromosomes relax
number of chromosomes per cell
equivalent to number of functional centromeres
number of DNA molecules per cell
equivalent to twice the number of chromosomes IF sister chromatids are present; if NO sister chromatids are present then equivalent to number of chromosomes
mitosis
asexual reproduction; increase in cell numbers; produces identical daughter cells; occurs in most cells; one division of nucleus
meiosis
sexual reproduction; begins in specialized gametic stem cells; produces unique haploid progeny cell; two divisions of nucleus (meiosis I and meiosis II)
meiosis I
reductional division; a diploid cell divides and forms two haploid cells (halving chromosomal number); introduces genetic variation
prophase I
chromatin condenses into chromosomes; nuclear membrane breaks down; homologous chromosomes pair… occurs in 5 substages: Leptotene, Zygotene, Pachytene, Diplotene, and Diakinesis
leptotene
chromosomes condense
zygotene
close pairing and association of homologous chromatin; forms a bivalent or tetrad; where synapsis begins
pachytene
synaptonemal complex develops between homologues; crossing over occurs
crossing over
exchange of genetic information between nonsister chromatids
diplotene
centromeres of homologues move apart and homologues remain attached at chiasmata
diakinesis
centromeres continue to separate, but chromosomes are still attached at chiasmata
metaphase I
homologous pairs of chromosomes line up along metaphase plate; chiasmata are lined up on metaphase plate
anaphase I
homologous chromosomes separate and move toward opposite poles
telophase I
chromosomes arrive at spindle poles and cytoplasm divides; nuclear membrane reforms; chromosomes decondense to chromatin; two haploid cells are produced; priority on cytokinesis so the “reversal of prophase I” is not as regulated and may vary or not always occur in process
meiosis II
equational division (halves amount of genetic material); begins with haploid cells; individual chromosomes line up on equatorial plate -> sister chromatids pull apart and move to opposite poles -> cytokinesis; steps: prophase II, metaphase II, anaphase II, telophase II; gametes remain in G0 upon completion until fertilization or cell death
prophase II
chromosomes recondense
metaphase II
individual chromosomes line up on equatorial plate
anaphase II
sister chromatids separate and move to opposite poles