Zoo-Lec (Sem-1) Chapter 3: Cell Division and Inheritance

most basic level of reproduction

involves a single cell reproducing itself

cell division

asexual reproduction of unicellular organisms

molecular level of reproduction

the cell's unique capability of manipulating large amounts of DNA, DNA's ability to replicate, and DNA's ability to carry information that will determine the cell's characteristics in the next generation

proteins

manifestation of information carried in DNA; contribute to observable traits; enzymes that regulate the rates of chemical reactions in organisms

organismal level of reproduction

involves passing of DNA from individuals of one generation to the next generation

Gregor Mendel (1822-1884)

father of genetics

genetics

the study of how biological information is transmitted from one generation to the next

gennan

Greek word for "to produce"

genetic mechanisms

explain how traits are passed between generations; explain how species change over time

chromosomes

long strands of DNA associated with proteins in eukaryotic cells

chromatin

the highly dispersed state of chromosomes during most of the life of the cell; consists of DNA and histone proteins

chromosome condensation

process by which a duplicated chromosome becomes packed into a more compact structure prior to cell division

genes

the units of inheritance that transmit information from parents to offspring

genos

Greek word for "race"

histone proteins

a simple protein bound to DNA, involved in the coiling of chromosomes

nucleosome

repeating subunit of chromatin fibers, consisting of DNA coiled around histones

solenoid

a winding chain of nucleosomes

linker protein

when DNA-wrapped histones condense into nucleosomes, this protein holds the DNA in place but is also particularly exposed to enzymatic action

chromatin loop

looped string of solenoids

scaffold proteins

organize groups of intracellular signaling molecules into signaling complexes

rosette

the cross-section shape of a chromosome (chromatin loops around a scaffold protein)

inactive

regions around centromeres are always ________

inactive chromosomal regions

base sequences in the DNA in these regions are not transcribed (processed) to produce protein

heterochromatic regions

inactive portions of chromosomes that produce dark banding patterns with certain staining procedures

euchromatic regions

active portions of chromosomes

Nettie M. Stevens

demonstrated that chromosomes can be represented differently in male and females

XX

female sex chromosomes

XY

male sex chromosomes

somatic cells

any cell of a living organism other than the reproductive cells

sex chromosomes

chromosomes that determine the sex of an individual

autosomes

any chromosome that is not a sex chromosome; alike in both sexes

autos; soma

Greek for "self"; "body"

homogametic sex

the sex with identical types of sex chromosomes; the human female

heterogametic sex

the sex with two different sex chromosomes; a human male

ZW system

female is heterogametic sex (ZW), male is homogametic (ZZ or ZZZ); found in fishes, amphibians, reptiles, and birds

heterochromatin

one of two X chromosomes of female embryonic cells is randomly converted to _______________ by the addition of methyl groups

X inactivation

one of two X chromosomes is randomly inactivated and remains coiled as a Barr body

nondisjunction

error in meiosis in which homologous chromosomes fail to separate

2-450

variation of number of chromosomes

10-50

usual variation of number of chromosomes

N

identifies the number of different kinds of chromosomes

diploid

(genetics) an organism or cell having two sets of chromosomes or twice the haploid number (2N chromosomes)

di; eoides

Greek for "two"; "doubled"

haploid/monoploid

(genetics) an organism or cell having only one complete set of chromosomes (N chromosome)

hapl; mono

Greek for "single"; "one"

haplodiploidy

sex inheritance in which males are haploid and females are diploid

polyploidy

condition in which an organism has extra sets of chromosomes

cell cycle

series of events that cells go through as they grow and divide

mitosis

distribution of chromosomes between daughter cells

mitos

Greek for "thread"

cytokinesis

partitioning of the cytoplasm between two daughter cells

kytos; kinensis

Greek for "hollow vessel"; "motion"

interphase

the period between the end of cytokinesis and beginning of mitotic division; a time of cell growth and DNA synthesis

inter

Latin for "between"

Gap phase 1/G1

usually the longest interval of interphase and is a period of cell growth and the metabolic activities characteristic of the particular cell type

Synthesis/ S phase

the phase of the cell cycle during which DNA is synthesized and chromosomes are replicated.

replication

in which the double-stranded DNA duplicates or makes a copy of itself

sister chromatids

identical copies of a chromosome; full sets of these are created during the synthesis phase of the interphase

chromatids

a copy of a chromosome produced by replication

centromere

a point of constriction at which a chromatid attaches to its other copy or sister; a specific DNA sequence of about 220 nucleotides and has a specific location on any given chromosome

nucleotide

monomer of nucleic acids made up of a 5-carbon sugar, a phosphate group, and a nitrogenous base

kinetochore

a disk of protein bound to each centromere; an attachment site for the microtubules during mitosis

Gap phase 2/G2

chromosome condensation; replication of centrioles; protein synthesis (microtubules)

Gap phase 0/G0

resting phase; cell is neither dividing nor preparing for division

prophase

first phase of mitosis; chromosomes become visible; the nucleoli and nuclear envelope begin to break up, and the two centriole pairs move from the microtubule organizing center to opposite poles of the cell

centrioles

a minute cylindrical organelle near the nucleus in animal cells, occurring in pairs and involved in the development of spindle fibers in cell division

asters

array of microtubules

mitotic spindle

asters; spindle; centrioles; and microtubules

prometaphase

second phase of mitosis; break-up of nuclear envelope; bipolar attachment of spindle fibers to chromatids

metaphase

third phase of mitosis; chromosomes (consisting of two replicated chromatids) begin to align in the center of the cell, along the spindle equator; (towards the end) the centromeres divide and detach the two sister chromatids from each other, although the chromatids remain aligned next to each other. After the centromeres divide, the sister chromatids are considered full-fledged chromosomes (called daughter chromosomes)

anaphase

fourth phase of mitosis; the shortening of the microtubules in the mitotic spindle, and perhaps the activity of motor proteins of the kinetochore, pulls each daughter chromosome apart from its copy and moves it toward its respective pole

telophase

fifth phase of mitosis; daughter chromosomes are now at their respective opposite poles; mitotic spindle disassembles; reformation of nuclear envelope around each set of daughter chromosomes

cleavage furrow

the first sign of cytokinesis during cell division in an animal cell; a shallow groove in the cell surface near the old metaphase plate

cyclin

one of a family of proteins that regulates the cell cycle in eukaryotic cells; act as guards at different checkpoints

kinase enzymes

move a phosphate group from one molecule to a different molecule

p53

This tumor suppressor gene causes cell cycle arrest in G1, providing time for DNA repair. If repair is successful, cells re-enter the cycle. If unsuccessful, apoptosis

apoptosis

programmed cell death