BIOL 111 - Exam 3

Binary fission

Binary fission

Cell division in prokaryotes

Binary fission step 1

DNA replication

Binary fission step 2

Chromosome segregation - chromosomes separate and move to opposite poles of the cell

Binary fission step 3

Separation - a new plasma membrane starts growing into the center of the cell, the cytoplasm splits apart and two daughter cells form that are genetically identical to each other and the parent cell

FtsZ Proteins

A protein that enables complete separation of the cell by assembling a cytoskeletal scaffold of the Z ring that constricts to divide the cell into two

FtsZ

Filamenting temperature sensitive mutant z

Organelle that divides via binary fission

Mitochondria

Mitochondrial fusion

Helps mitigate stress by combining partially damaged mitochondria

Mitochondrial fission

Needed to help create new mitochondria for quality control (removes the damaged mitochondria and can facilitate apoptosis during high levels of cellular stress)

G1-Phase duration

11 hours

S-Phase duration

8 hours

G2-Phase duration

4 hours

M-Phase duration

1 hour

How does cancer begin?

Gene mutation results in a faulty protein that regulates cell reproduction; tumors result when reproduction of mutated cells surpass growth of normal cells

Gametes

Eggs and sperm; have half the number of chromosomes (haploid)

Somatic cells

Body cells; have 2 matched sets of chromosomes (diploid)

Homologous chromosomes

Chromosomes that pair in reproduction of diploid cells

Heterologous pairs

Genomes with pairs that do not match such as X and Y chromosomes in humans

Karyotype

Arranging the chromosomes by size

Eukaryotic DNA must be condensed into compact ______ to fit into the nucleus

Chromosomes

8 Histone proteins

Short stretches of DNA wrap around a core of this, like a string of beads

Nucleosome

The histone-DNA complex (the bead)

Linker DNA

DNA that connects to the nucleosome

Chromatin fiber

The resulting coiled structure from DNA wrapping around the histone-DNA complex and linker DNA

Interphase

1 - the time for normal cell growth and preparation for cell division

G0

Interphase - when the cell fully quiescent (not preparing to divide)

G1-Phase

Interphase - (first gap) cell grows and organelles are copied

S-Phase

Interphase - the cell synthesizes a complete copy of DNA in its nucleus

G2 Phase

Interphase - (second gap) the cell grows more, makes proteins, organelles and structures/proteins necessary for cell divison

Mitotic phase

2 - phase in which the replicated DNA and cytoplasm are split and the cell divides

G1 Checkpoint

Checks for cell size, nutrients, growth factor, and DNA damage

G2 Checkpoint

Checks for DNA damage and DNA replication completeness

Spindle checkpoint

Checks for chromosome attachment to spindle at metaphase plate

MPF

Maturation promoting factor - induces M-phase; made of Cyclin and CDK

Positive regulators

Move the cell cycle forward; cyclins and cyclin dependent kinases

Negative regulators

Stops the cell cycle (cued by DNA damage and overcrowding)

Retinoblastoma protein (Rb)

Negative regulator - monitors cell size and blocks DNA replication

p53

Negative regulator - halts cell cycle and recruits DNA repair proteins

p21

Negative regulator - inhibits CDK/cyclin complexes

How many mutations does it take on average for a cell to turn into a cancer cell?

6 mutations

T53

The most commonly mutated gene in cancer; codes for p53

HER2

A protein that helps breast cancer cells grow quickly

BRCA1/BRCA2

Genes that code for proteins that are key DNA repair proteins

BRCA 1 deficiency

Leads to abnormalities in most cell regulation checkpoints

Proto-oncogenes

Genes that control positive cell cycle regulators; pre-mutated does not cause disease until mutated (ex: HER2)

Oncogenes

Genes that cause a cell to become cancerous (ex: too many copies of HER2)

Tumor suppressor genes

Segments of DNA that codes for proteins that prevent the cell from undergoing uncontrolled division (ex: Rb, p53, and p21; not disease causing until mutated)

Cervical cancer

Associated with oncogenic human papillomavirus (HPV); the HPV E6 protein binds to p53 and promotes its degradation)

Benign tumors

Abnormal noncancerous collection of cells that grow slowly with even borders; can turn malignant

Malignant tumors

Abnormal cancerous collection of cells that grow quickly and spread via metastasis

Early Prophase

• 1

• Chromosomes start condensing

• Mitotic spindle starts forming

Late Prophase

• 1

• Mitotic spindle starts organizing chromosomes

• Nuclear envelope breaks down

Kinetochore

A complex of proteins at centromere that spindle fibers attach to

Centromere

Constricted region of duplicated chromosome

Spindle fibers

Made of microtubules; protein structures that pull apart the genetic material in a cell during division

Centrosome

Contains the centrioles (in animal cells); location from which spindle fibers develop in cell division

Chromatids

Half of a duplicated chromosome

Metaphase

• 2

• Chromosomes are lined up at the plate

• Kinetochores should be attached to microtubules on opposite spindle poles (M-checkpoint)

Anaphase

• 3

• Sister chromatids seperate

• Non-kinetochore microtubules elongate and push ends farther apart via motor proteins

Telophase

• 4

• Mitotic spindle degraded

• New nuclei form

• Chromsomes recondense

Cytokinesis

• 5

• Cells start separating overlapping with telophase

• Cytoplasm divides

• Animal cells - cleavage furrow

• Plant cells - cell plate

Plant cell division

• Golgi vesicles with cell wall components are produced in interphase

• Vesicles fuse and form cell plate which merges with the cell wall

Purpose of meiosis

• Reduce the number of chromosomes in gametes

• Provide genetic diversity

• Restricted to germ cells

Meiosis I

Homologous chromosomes separate

Meiosis II

Sister chromatids separate resulting in 4 haploid cells

Interphase

1- G1, S1, G2

Prophase I

2 - Crossing over

Metaphase I

3 - Tetrads line up (two homologous chromosomes that each already replicated into a pair of sister chromatids)

Anaphase I

4 - Homologous chromosomes separate

Telophase and Cytokinesis

5 - Homologs arrive at the opposite poles of the cell and a new nuclear membrane forms around each set of chromosomes; the cytoplasm is then divided into two daughter cells

Prophase II

6 - Spindle fibers reform and attach to centromeres

Metaphase II

7 - The sister chromatids align at the plate

Anaphase II

8 - Chromosomes divide at the centromeres and each chromosome (previous chromatid) moves toward opposite poles of the cell

Telophase II and Cytokinesis

9 - Results in four distinct haploid cells with a single copy of each chromosome

How many autosome homologous pairs in humans?

22 autosomes

How many sex chromosomes in humans?

1 pair

Chiasma

Recombinant chromatids

Synapsis

Fusion of chromosome pairs

Genes further apart are more/less likely to cross over?

More

Genes closer together are more/less likely to cross over?

Less

Nondisjunction

Separation errors; results in genetic abnormalities

When does nondisjunction occur?

Anaphase of mitosis, meiosis I, or meiosis II

Aneuoploidy

Daughter cells with too many or too few chromosomes; lethal

Mendel’s law of independent assortment

The alleles of two or more different genes get sorted into gametes independently of one another which results in genetic variability in meiosis

Down syndrome

Trisomy 21

Klinefelter syndrome

• 47, XXY; males

• Low testosterone

• Reduced muscle mass, facial hair and body weight

• Produce little to no sperm

Turner syndrome

• Missing X; females

• Short stature

• Delayed puberty; infertility

• Heart defects and learning disabilities

Jacob’s syndrome

• XYY; males

• Low muscle tone

• Very curved pinky finger

• Tall and developmental delays

Gregor Mendel

Father of genetics; believed that traits were inherited as discrete units, demonstrating that traits are transmitted from parents of offspring independently of other traits and in dominant and recessive patterns

Blending Theory of Inheritance

The theory that progeny inherits characteristics as the average of the parents’ values of that characteristic; offspring create an intermediate

Dichotomous traits

Discrete traits that have only two contrasting phenotypic probabilities

Monoecious

Having male and female sex organs in the same plant

Genotype

Genetic makeup; the alleles are carried by an individual for each gene and traits are found at the same locus on corresponding chromosomes

Phenotype

Physical appearance

True breeding

A kind of breeding in which parents produce offspring that would carry the same phenotype; the parents are homozygous for every trait

Allele

A trait

Locus

Location on the chromosome that contains a certain allele

Gene

Codes for a certain characters (ex: flower color) and has its own genotype with two alleles one on each of homologous chromosomes

Testcross

An experimental cross of an individual organism of dominant phenotype but unknown genotype and an organism with a homozygous recessive genotype and phenotype