Biology 140 (Cell Signaling, Mitosis and Meiosis, and Genetics)

What is binary fission?

The cell division process used by many bacteria (has a single chromosome)

What structure contains bacterial DNA?

The nucleoid (tight compressed of DNA floating in cytoplasm)

What proteins help condense bacterial DNA?

Structural Maintenance of Chromosome (SMC) proteins

Chromosomes is

replicated and collected at opposite ends

Origin of replication (OriC)

DNA is replicated

Terminator Site (Ter)

Replication for both strands, making of two double-stranded DNA

What happens after terminator site?

Cell elongates as DNA replicates and OriC move out

Septation

The formation of septum or separation between two segments (bacterial cells)

Septum is formed by

FtsZ Protein (Cytoskeleton protein that forms septum ring at division site)

What happens at the end of bacterial cell division?

Septum will pinch inward and divide cell into two

Mitosis

First word to describe eukaryotic chromosomal division

How many chromosomes do humans have?

46 chromosomes arranged in 23 pairs

What are the parts of eukaryotic chromosome?

Two identical chromatids (exact copy of each other and each contain one DNA molecule), p-arm, centromere, q arm, and DNA molecule

p-arm

Short arm

q-arm

Long arm

DNA molecule

Long string that is formed into a compact structure by proteins called histones

What is chromatin?

DNA and proteins packaged together in chromosomes (40% DNA, 60% protein)

What is heterochromatin?

Chromatin that is not expressed, repressed, and closed chromatin

What is euchromatin?

Chromatin that is expressed, active, and open chromatin

What is a nucleosome?

DNA wrapped around histone proteins (Positively charged)

8 histone proteins

200 nucleotides

Solenoid

Histone proteins interact

What is a karyotype?

Array of chromosomes by an individual

What is the human haploid number?

23 chromosomes

How many copies of chromosomes does humans have?

Two copies (Diploid number)

What is the human diploid number?

46 chromosomes

What is the replicated karyotype for humans?

92 chromatids

Homologous

Matched pairs of chromosomes in diploid organisms—one inherited from the mother and one from the father (Homologues)

What are sister chromatids?

Two identical copies of a replicated chromosome

Where are sister chromatids held together?

Centromere (Center of chromosomes) by cohesins

Cohesins

Protein that helps hold sister chromatids together

What is termed with Interphase

G and S phase

What is termed with M phase

Mitosis and Cytokinesis

Mitosis (Cell cycle)

Cell begins to divide

Cytokinesis

When two new cells are completely divided (Process that happens last)

What are the three phases of interphase?

G1, S, and G2

What happens during G1 phase?

Start of growth

What happens during S phase?

DNA replicates

What happens during G2 phase?

Growth phase leading into mitosis

G1 and G2 in Interphase (Purpose)

Cells grow and DNA encoded information to build proteins

S Phase in Interphase

Chromosomes are replicated and help together as sister chromatids

Kinetochore

Structure outside of the centromere responsible for binding microtubules which pull chromatids apart during M phase

What are the five stages of mitosis?

Prophase, Prometaphase, Metaphase, Anaphase, and Telophase

During which stage do chromosomes become visible?

Prophase

Prophase

Chromosomes from S phase in Interphase condensed, visible, and spindle apparatus

Spindle Apparatus

Centrioles and Microtubules

Centrioles

Cylindrical protein structures (spindles form)

Microtubules

Long proteins that attach to chromosomes kinetochores

What does spindle apparatus form?

Asters (Microtubules attached to an array to plasma membrane)

Last step of Prophase

Nuclear envelope breaks and DNA separation occurs

Prometaphase

Kinetochores of each sister chromatid attach to spindles and then opposite sides of the cell

Metaphase

Chromosomes align in the cell center (metaphase plate) Plane perpendicular to the spindle fibers, form a circle

Anaphase

Sister chromatids pull to oppostie ends of the cells with two seprate movements

Anaphase A

Shortening of microtubules pull kinetochores to poles

Anaphase B

Pushing apart of the poles

Telophase

Dissemble spindle fibers and reassembly of nucleus, new nucleus envelope forms set of chromosomes, chromosomes expand their original state with nucleus and expression of genes begins again

What is the final process of Mitosis?

Cytokinesis (The physical division of one cell into two daughter cells)

What is Mitosis-Promoting Factor?

A cyclin-Cdk (Cyclin-dependent kinase) complex that drives cells into mitosis, an unknown factor, was revealed as an enzyme that added phosphate groups to other proteins

Cyclins

The presence of proteins

What is Cdk?

Cyclin-dependent kinase, an enzyme that works with cyclins to regulate division

What are three cell cycle control processes?

G1/S, G2/M, and Spindle checkpoints

G1/S

Commitment to DNA replication after a cell divide

G2/M

MPF’s active and cell division

Spindle Checkpoint

Measure to ensure that all chromosomes are attached to spindles

What did the 1880’s Beneden discover?

Different cell types from Ascaris had different numbers of chromosomes; sex cells (gametes) had half as many chromosomes as somatic cells, and gametes form zygote

Gametes

Sex cells (egg and sperm)

Somatic cells

Diploid, two sets of chromosomes- one inherited from mother and one from father

Zygote

Two gametes fuse (two copies)

What is fertilization?

Fusion of gametes to form a zygote

What is meiosis?

The process of gamete formation that reduces chromosome number by half

Reproduction with meiosis and fertilization is called

Sexual reproduction

what are early zygotes undergoing to produce all cells?

Mitosis

What are germ-line cells?

Diploid cells that undergo meiosis to form gametes

How many rounds of division occur in meiosis?

Two rounds: Meiosis I and Meiosis II

What does each round of meiosis contain?

Prophase, Metaphase, Anaphase, Telophase

What is synapsis?

Pairing of homologous chromosomes during Prophase I

What is the synaptonemal complex?

A structure that holds homologous chromosomes together during meiosis I

What is crossing over?

Exchange of genetic material between homologous chromosomes

What are chiasmata?

Sites where crossing over occurs

What does crossing over result in?

Slightly different structures, increasing genetic diversity

How does meiosis I compare to mitosis?

Due to DNA replication taken place, meiosis I similar to mitosis with each daughter cell will have two copies of each chromosome

Meiosis II is

Identical to mitosis without DNA replication

Stages of Meiosis

Two separate rounds of meiosis with steps similar to mitosis

Prophase I

Homologous pair during Prophase I when synaptonemal complexes form, crossing over occurs between homologous DNA regions at chiasmata

Metaphase I

Four chromosomes, two pairs of sister chromatids are locked together to form a single structure from cross over events, bivalents attach to spindle fibers and move to the center of the cell (homologues),

Bivalent

A paired structure of homologous chromosomes during Metaphase I

Anaphase I

Paternal and maternal chromosomes is randomized into cells, preparing for meiosis II

What is independent assortment?

Random distribution of homologous chromosomes into daughter cells

Telophase I

Similar process like mitosis but sister chromatids are no longer identical (cross over from prophase I)

Meiosis II

Exactly like mitosis without DNA replicated, has 46 chromosomes (human germ-line)

Telophase II (End of Meiosis II)

New nuclear envelope forms 1 copy of 23 chromosomes (Similar process with Meiosis I)

What is hybridization?

The crossing of different strains of organisms

Who performed the first documented hybridization experiments?

Josef Kölreuter

What did Kölreuter observe in hybrid offspring?

Offspring had characteristics intermediate between the parents; different strands were crossed, and offspring had characteristics in between the founders, found when F1 generation was crossed, had characteristics like the grandparents and parents

What is a true-breeding?

A strain that passes traits from generation to generation without change

What does segregation mean in genetics?

True plants are crossed and different forms of a trait separate among offspring, while others will display the alternative form

Who is known as the Father of Genetics?

Gregor Mendel

What organism did Mendel use in his experiments?

Pea plants (Pisum sativum)

Why were pea plants useful for Mendel's studies?

They are self-fertilizing and have easily observed traits (Readily available)

How many traits did Mendel study?

Seven traits (One of two forms and could be easily followed from one generation to the next)