Exam 3 concepts

*The question practices will be on a separate set

G1 Phase (cell cycle)

-Cell grows and performs normal functions

-Contains the normal # of DNA

S phase (cell cycle)

-DNA replicated

-Each chromosome is copied

G2 phase (cell cycle)

-Cell prepares for division

-DNA content doubled compared to G1

M phase (cell cycle)

Mitosis and cytokineses occur

Human gamete

23 chromosomes

Somatic cell in human

46 chromosomes

Somatic cell

-Any non reproductive cell

-46 chromosomes

-Diploid (2n)

-Can undergo mitosis

Interphase

-Cell growth

-Replication of chromosomes

Prophase (mitosis)

-Centrosomes move apart

-Spindle fibers begin to form

-Nuclear envelope still intact

-Chromosomes condense

-No nucleolus

Pro-metaphase (mitosis)

-Nuclear envelope fragments

-Centrosomes at opposite poles

-Chromosomes condense more

-Microtubules grow to center

-Microtubules attach to kinetochore

Metaphase (mitosis)

-All kinetochores are attached to microtubules

-Chromosomes at metaphase plate

Anaphase (mitosis)

-Cohesion proteins cleaved

-Sister chromatids separate and move toward opposite poles

-Cell elongates

Telophase

-Nuclear envelope reforms

-Nucleolus reforms

-Chromosomes become less

condensed

-Mitotic spindle dissolves

-MITOSIS complete

Cytokinesis

-Cytoplasm divides

-Two daughter cells form

-In animal cells, cleavage furrow forms, and contractile ring of actin and myosin

Cytokinesis in plants

-Formation of a cell plate

-Vesicles from Golgi move to center and fuse

-Membrane fuses with plasma membrane

Prokaryotes reproduce through ___

Binary fission

Binary fission

-Chromosome replicates at the origin of replication

-Daughter chromosomes actively move apart

Sister chromatids

Two identical copies of a chromosome

Centromere

Region connecting sister chromatids

Kinetochore

Protein structure where the spindle fibers attach

Centromeres

Organize spindle fibers

Cell control cycle → G1 checkpoint

-Is DNA damaged?

Cell control cycle → G2 checkpoint

-Has all DNA replicated?

-Can damaged DNA be repaired?

-Is spindle-making machinery in place?

Cell control cycle → Metaphase checkpoint

-Is spindle built?

-Do chromosomes attach to spindle?

-Are chromosomes aligned down equator?

G0 phase

-Most cells are here

-Non-dividing

Cyclins

Proteins whose concentration fluctuates cyclically in the cell

Protein kinases

Enzymes that activate or inactivate other proteins by phosphorylating them

Cyclin-dependent kinases (Cdks)

Need cyclins attached to be active

MPF (Maturation promoting factor)

-Triggers a cell’s passage past the G2 checkpoint to M phase

-Cyclin-Cdk complex

Example of internal signals that maintain checkpoints

Kinetochores

Example of external signals that maintain checkpoints

Growth factors

Growth factors

Proteins released by certain cells that stimulate other cells to divide

Platelet derived growth factor (PDGF)

Stimulates the division of cells in culture

Anchorage dependence

Cells require a surface for division

Density dependent inhibition

-Cells form a single layer

-Cells divide to fill a gap and then stop

Apoptosis

-Programmed cell death

-Normal and genetically controlled

-Removes damaged or unnecessary cells

-Results when specific proteins that accelerate apoptosis override those that slow apoptosis

Cancer cells

-Ignore density dependent inhibition

-Continue dividing when crowded

-Lose normal cell cycle regulation

-Do not need external growth factors

Benign

Abnormal cells remain at site of organ

Malignant

Abnormal cells invade adjacent tissues

Metastasize

How cancer spreads throughout the body

Purpose of meiosis

-Produces gametes (sperm/egg)

-4 haploid cells that are genetically unique

Meiosis I includes:

-Prophase 1

-Metaphase 1

-Anaphase 1

-Telophase 1

Meiosis II includes:

-Anaphase 2

-End results

What stage of meiosis is similar to mitosis?

Meiosis II

Human haploid cells contain:

-22 autosomes

-1 sex chromosome

Human haploid cells contain:

-22 autosomes

-1 sex chromosome

Sperm chromosome

Can be X or Y

Sperm chromosome

Can be X or Y

Replicated chromosomes have how many sister chromatids?

Two

Crossing over occurs during…

Prophase I of Meiosis I

Crossing over

Nonsister chromatids exchange DNA segments

Chiasmata

A tetrad usually has one or more. These are X shaped regions where crossing over occurs

Prophase 1

-90% of the time required for meiosis

-Chromosomes begin to condense

-Tetrad (4 chromatids)

-Homologous chromosomes aligned

Metaphase I

-Tetrads line up at metaphase plate

-Microtubules are attached to the kinetochore of a chromosome of each tetrad

Anaphase I

-Pairs of homologous chromosomes separate

-One chromosome moves toward each pole

-Sister chromatids remain attached

-Cohesins

Telophase 1

– Each half of the cell has a “haploid set” of

chromosomes

– Each chromosome still consists of two sister

chromatids

Cytokinesis (Meiosis)

-Simultaneous with telophase I. Forms two haploid daughter cells

Interkinesis

NO CHROMOSOMES REPLICATED. Stage in between meiosis I and II

Prophase II

-Spindle apparatus forms

-Chromosomes move towards the metaphase plate

Metaphase II

-Microtubules attach to kinetochores

-Sister chromatids are arranged at the metaphase plate

-Not genetically identical because of crossing over

Anaphase II

-Sister chromatids separate

-Move toward opposite poles

Telophase II

-Chromosomes arrive at opposite poles

-Nuclear envelops reform

-Chromosomes begin decondensing

Nondisjunction

Chromosomes fail to separate. Results in extra or missing chromosomes

Trisomy

One extra chromosome

OY

Fatal

OX

Turner syndrome

XXY/XXXY

Klinefelter syndrome

XYY

Jacobs syndrome

Homologous chromosomes

Chromosomes carrying the same genes

Haploid gametes

Produced by ovaries and testes

Spermatogenesis

Begins at puberty and continues throughout life. Produces 4 functional sperm

Spermarozoa

-Lose cytoplasm, DNA packaged into head

-Develop tails

-Mitochondria in mid piece generates energy to swim

Oogenesis

Begins during development, and arrested in prophase I. Meiosis II complete ONLY after fertilization. Unequal cytoplasm division yields polar bodies that CANNOT be fertilized

If a sperm penetrates an egg…

-Meiosis II completes

-2 nuclei combine to form diploid zygote

Acrosomal reaction

Hydrolytic enzymes in acrosome are released and dissolve zona pellucida. Can result in a fast block to polyspermy in some animal cells

Cortical reaction

-Increase in calcium

-Exocytosis of enzymes in cortical granules

-Slow block to polyspermy

Increase in calcium in eggs cytosol increases…

-Cellular respiration

-Protein synthesis

Diploid nucleus forms ___ the first division of the zygote

After

Cleavage partitions zygote into…

Blastomeres

Blastomere

Each blastomere contains different regions of undivided cytoplasm

Cleavage is rapid cell division without growth. Interphase consists mainly of __ phase

S

Fertilization and cleavage occurs in…

Oviduct

Trophoblast

Develops into fetal portion of placenta

Morphogenesis

Cellular and tissue-based processes by which the animal body takes shape

Gastrulation

Results in formation of gastrula

Gastrula

-Ectoderm

-Endoderm

-Mesoderm

Determination

Process by which a cell becomes committed to a particular fate

Differentiation

The resulting specialization in structure and function

Development must occur in which sequences?

Cleavage → blastula → gastrula

Benefit of sexual reproduction?

Genetic diversity via gene reshuffling and crossing over during meiosis

Mutations

-Original source of genetic diversity

-Creates different alleles

Crossing over produces…

Recombinant chromosomes

Homologous pairs of chromosomes orient ___ at metaphase I of meiosis

Randomly

Gene

Segment of DNA that codes for a trait

Locus

Specific location of a gene on a chromosome

Alleles

-Different forms of a gene, Ex: AA, Aa, BB, Bb

-Variations in a gene’s nucleotide sequence

Particulate hypothesis

Parents pass on discrete heritable units (genes)

Characters

Features

Traits

Variant

Dominant

Expressed when present