Biology 0150 - Chapter 3: Genetics

Cell division main events

cell division signals, DNA replication, DNA segregation, cytokinesis

DNA replication

genetic material (DNA) must be duplicated so the two cells have the same genetic information

DNA segregation

the replicated DNA must be distributed correctly to the two daughter cells so that each receives a copy of each chromosome

Cytokinesis

the cytoplasm must divide to form the two new cells, the cell membrane pinches in and protein fibers form a ring

Binary fision

reproduction of a prokaryote by division of a cell into two identical progeny cells

Cell division signals in prokaryotes

Usually external factors such as nutrient concentration and environmental conditions

Ori

where replication starts in prokaryotes

Ter

where replication ends in prokaryotes

DNA replication in prokaryotes

occurs as DNA moves through a protein replication complex

DNA separation in prokaryotes

ori regions move to opposite ends of the cell, segregating daughter chromosomes

Z-ring

protein fibers that form between two new progeny cells

Mitosis

process that separates the newly replicated chromosomes into two nuclei

Cell cycle

phases a cell passes through to produce daughter cells by cell division

Interphase

the nucleus is visible and cell functions occur (includes G1, S, G2)

M phase

includes mitosis and cytokinesis

G1 phase

each chromosome is a single, unreplicated, DNA molecule. The cell grows

S phase

Where DNA replication occurs, producing sister chromatids

Sister chromatids

the copies of DNA that are formed as a product of replication. Stay together until mitosis

G2 phase

the cell prepares for mitosis. Grows to double the size of the original cell and synthesizes the structures that move chromatids during division

Enzyme

speed up biochemical transformations by bringing the reactants together

Substrates

reactants in biochemical transformation that involves an enzyme

Active site

where substrate molecules bind to the enzyme

Cyclin-dependent kinases

the molecule involved in regulating the progress through the cell cycle

Cell cycle checkpoints

points of transition between different phases of the cell cycle, which are regulated by cyclins and CDK’s

G1 checkpoint

Is there DNA damage? Is the environment favorable?

S checkpoint

Is all DNA replicated? Is all DNA damage repaired?

G2 checkpoint

Is all DNA damage repaired?

Mitosis checkpoint

are all chromosomes attached to the mitotic spindle?

Restriction point (R)

a particular CDK control point that controls the G1-S transition

Retinoblastoma protein (RB)

substrate of G1-S cyclin-CCDK complex

Nucleosomes

DNA wrapped around histone proteins

Chromatin fiber

condensed nucleosomes

Metaphase chromosome

wound together chromatin fiber

Centrosomes

contains the centrioles and the spindle fibers needed for cell division to continue developing

Centromeres

region where the sister chromatids remain together until mitosis

Prophase

the sister chromatids condense and the mitotic spindle assembles

Mitotic spindle

microtubules extending from the centrosomes

Prometaphase

the nuclear envelope breaks down and the chromosomes can attach to spindle microtubules through kinetichores

Kinetichores

protein complexes that attach the duplicated chromatids to the spindle fibers

Metaphase

chromosomes are aligned at the metaphase plate

Anaphase

the sister chromatids separate to form two daughter chromosomes and each is pulled toward a spindle pole

Daughter chromosomes

M phase cyclin CDK

control the separation of sister chromatids

Cohesin

holds together the sister chromatids after DNA replication

Telophase

the two sets of daughter chromosomes arrive at the poles of the spindle and decondense and a new nuclear envelope is formed

Contractile ring

made of actin and myosin

Somatic cell

cells of the body of eukaryotes

Diploid

have two versions of each chromosome (one from each parent)

Homologous chromosomes

have the same genes in the same locations and each inherited from a different parent

Allele

different versions of the same gene

Gametes

sperm and egg cells

Haploid

only one copy of each chromosome

Zygote

the diploid cell formed during fertilization

Meiosis

Synapsis

process in which homologous chromosomes pair by adhering along their lengths

Bivalent

Chiasmata

regions of attachment that form between nonsister chromatids

Recombinant chromatids

have exchanged parts with a nonsister chromatid, contributing to genetically diverse products

Metaphase 1

homologous chromosomes pair together and align at the metaphase plate

Anaphase 1

homologous chromosomes separate

Independent assortment

each haploid cell receives an entire set of genes from the diploid cell in a random fashion which contributes to genetic diversity

Meiosis II

sister chromatids separate

Genetics

the study of heredity

Heredity

genetic information is passed on from one generation to another

Blending inheritance

theory that inheritance involves the blending or mixing of the characteristics of the parents

Particulate inheritance

True breeding plants

plants that always produce offspring of the same phenotype when self fertilized

Character

observable physical feature

Trait

specific form of a character

Genotype

the set of alleles in a cell

Phenotype

observable properties of an individual resulting from the genotype and environmental factors

Homozygous

a homologous pair of chromosomes that has two alleles that are the same

Heterozygous

a homologous pair of chromosomes that has two different alleles of a gene

Cell division signals

initiate cell division