Chapter 10 Cell Reproduction Unit 3

Zygote

The first cell of a new organism formed when a sperm and egg fuse

1 Diploid fertilized egg

Genome

The complete set of DNA (genes) in an organism.

Prokaryote Genome

single circular chromosome

Eukaryote Genome

46 linear (flat) chromosome

Mitotic Cell Division

Enables growth, repair, asexual reproduction, and replacement of cells in multicellular organisms.

Somatic Cell

Body cells are Diploid
= 2 copies of each chromosome
2n = 2x23 = 46 chromosomes

Gamete

Sex cells (egg, sperm)

Diploid

2 copies of each chromosome
2n = 2 x 23 = 46 chromosomes

Haploid

1 copy of each chromosome n = 23

Homologous chromosomes

2 copies of the same chromosome
(one from each parent)

Karyotype

set of stained condensed chromosomes

Autosomes

Non-sex chromosomes

22 pairs

Sex Chromosomes

XX = female

XY = Male

Sex determining

Genes

nucleotide segments of DNA when
expressed (turned on) code for proteins
and determine characteristics (hair color)
& traits (black, brown, blonde)

Loci (Locus)

location of gene on chromosome

Traits

Observable features

Alleles

Version of a gene / Can lead to variations in traits

Histone Proteins

DNA wraps around these for compaction

Nucleosomes

DNA + 8 histones (beads); linker DNA connects nucleosomes

Linker DNA

linker DNA connects nucleosomes

Chromatin Fiber

Loosely packed DNA; chromosomes = condensed chromatin

During Interphase, 30 nm thick

Chromosomes

during Mitosis

(Cell Division) ultra compacted

= condensed, 1400 nm thick,

Visible under light microscope

Duplicated Chromosomes

Chromosome copied during S phase (2 sister chromatids)

held together by cohesion proteins at the Centromere

Sister Chromatids

Identical copies of a duplicated chromosome

Cohesion Proteins

Hold sister chromatids together

Centromere

Region joining sister chromatids; site of kinetochore attachment

Eukaryotic Somatic Cell Cycle

The series of events that produces 2 new daughter cells

Eukaryotic Mitotic Phase

Includes Mitosis (nuclear division) and cytokinesis (cytoplasm division)

G1

Growth/ Prep for DNA replication

S

DNA Replication (Synthesis)

Centrosome replication

G2

Growth

Prep for mitosis

(duplicate organelles cytoskeleton dismantled)

Prophase

Chromatin condenses, spindle forms, centrosomes move apart

Prometaphase

Nuclear envelope breaks down, kinetochores attach to spindle

Metaphase

Chromosomes align at metaphase plate

Anaphase

Sister chromatids pulled to opposite poles

Telophase

Nuclear envelopes reform, chromosomes de-condense

Centrosome

Organizes spindle fibers

Condensin proteins

Help chromosomes condense

Mitotic spindle fibers

Move chromosomes during mitosis

Kinetochore

Protein on centromere; binds spindle fibers

Polar microtubules

Push cell poles apart

Metaphase plate

Equator where chromosomes line up during metaphase

Opposite poles

Where spindle fibers pull chromatids during anaphase

Animal cells

Cleavage furrow forms via actin-myosin ring contraction

Plant Cells

Cell plate forms from vesicles, becomes cell wall

G0 phase

have exited the cell cycle and are not actively

preparing to divide (are quiescent)

Temporary G0 Phase

waiting for nutrients or growth factor stimulation

Permanent G0 Phase

Cardiac & skeletal muscle, and most nerve cells

Cells that never divide again

Cdk/cyclin complex

Gets phosphorylated → then phosphorylates other proteins needed to advance cell cycle

p53

stops cell cycle if DNA is damadged

enzymes will repair or apoptosis (cell suicide) is triggered if DNA is damaged

p21

If p53 levels high, p21 is triggered → binds & inhibits Cdk/cyclin complexes

(Inhibits Cdk/cyclin to allow DNA repair)

Rb

monitors cell size

When small Rb binds E2F & it blocks transcription

As the cell grows, Rb gets phosphorylated & releases E2F, which turns on genes that advance the cell cycle

Cancer

Uncontrolled cell growth due to failed regulation

Proto-oncogenes

code for Positive cell-cycle regulators

If mutated to increase activity becomes Oncogene

Tumor suppressor genes

code for Negative regulator proteins = brakes for cell cycle

If Mutated can’t stop damaged cells from going through the cell cycle

prokaryotic binary fission

No nucleus
Single circular chromosome

Fast, simple

no mitotic spindle

eukaryotic cell division (mitosis)

Has nucleus, Multiple linear chromosomes, Complex involves multiple phases

Spindle required