Biology Exam 3

Cell division

the biological process in which a parent cell splits into two or more daughter cells

Sexual reproduction

where two parent organisms combined their genetic material to produce a genetically unique offspring

Prokaryotes

a single celled organism whose cell lack a distinct, membrane-bound nucleus and other internal membrane-bound organelles. Divides through binary fission.

Binary fission

form of asexual reproduction and cell division where a single organism (typically prokaryote) duplicates its genetic material and splits into two identical daughter cells

Eukaryotic

any organism whose cells contain a distinct membrane-bound nucleus and other internal compartments called organelles. They are larger and more structurally complex than prokaryotic cells. Divide through mitosis and meiosis

Chromatin

a complex of DNA, RNA, and proteins that forms chromosomes inside the nucleus of eukaryotic cells

Chromosomes

thread like structures made of a single molecule of DNA tightly coiled around proteins called histones

Sister chromatids

two identical copies of a single replicated chromosome that are joined together at a region called the centromere

Gap Phases

G₀, G₁, S, and G₂

G₁ Phase

accumulation of DNA replication materials

-favorable conditions

-DNA integrity, cell size, energy reserves

-Irreversible commitment

S Phase

DNA replication; formation of sister chromatids

G₂ Phase

synthesis of proteins for cell division and extra organelles

-succesful chromosome duplication

Mitotic phase (M phase)

Mitosis (nuclear division) and cytokinesis (cellular division)

-correct sister chromatid alignment

Major phases of Mitosis

1. Interphase

2. Mitosis

-Prophase

-Pro-metaphase

-Metaphase

-Anaphase

-Telophase

-Cytokinesis

Interphase

The longest stage of the eukaryotic cell cycle, during which a cell grows, metabolizes, and copies its DNA in preparation for cell division (mitosis or meiosis). Has three stages G₁, S, and G₂

Mitosis

a process of nuclear division in eukaryotic cells where a single parent cell replicates its chromosomes and segregates them into two new nuclei, producing two genetically identical daughter cells

Prophase

>Supercoiling of the chromosomes

>Mitotic spindle starts to form

>Centrosomes start to migrate

>Nuclear envelope fragments

Pro-metaphase

>Kinetochores form

Metaphase

>Centrosomes at poles

>Spindles finish binding

Anaphase

>Separation of the sister chromatids

>Cohesion cleaved centromere separated 1 chromosome becomes 2

>Kinetochore spindles get shorter

>Non-k spindles get longer

Telophase and Cytokinesis

>Nucleu reform

>Spindle breaks down

>Chromosomes start to unwind

>Followed/overlapped by cytokinesis

Regulation of Cell Division

the system of molecular controls, signals, and checkpoints that determine whether a cell grows, replicates its DNA pauses, or divides into two daughter cells

Cancer cells

Tumors and Metastasis

Cancer Tumors

Benign and Malignant

Metastasis

cancer cells break away from the original (primary) tumor, travel through the blood or lymphatic system, and form new secondary tumors in other tissues or organs of the body

Cancer and the Cell Cycle

-Uncontrolled cell division

-Mutations in genes that regulate the cell cycle

-Proto-oncogenes

-Tumor Supressor Genes

Proto-oncogenes

positive cell cycle regulators

Oncogene

mutation leading to excessive cell division

Tumor Supressor Genes

normal genes in your body that encode proteins to regulate cell division, repair damaged DNA, and induce programmed cell death

Sexual Reproduction and the Human Life Cycle

-Meiosis → gametes (n)

-Fertilization → zygote (2n)

-Mitosis → growth

Tradeoffs Regarding Sex

-Advantage: genetic variation

1. Independent assortment of chromosomes

2. Crossing over results in recombinant chromosomes

3. Random fertilization

-Disadvantage:

1. Energetic investment and physical risks

2. Dilution of advantageous versions of genes

Somatic Cells

any cells in a multicellular organism that form the body's tissues and organs

-Diploid or 2n

-46 chromosomes

-23 homologous pairs (1 maternal + 1 paternal)

Gametes

reproductive or sex cells that fuse during sexual reproduction to create a new organism

-haploid or n

-23 chromosomes (1 from each homologous pair)

-22 autosomes + 1 sex chromosome (X or Y)

Homologous Chromosomes

a pair of matching chromosomes in a diploid organism, with one chromosome inherited from the mother and one from the father

Ploidy Levels

the number of complete sets of chromosomes found in the nucleus of a cell

-Haploid (N)

-Diploid (2N)

-Triploid (3N)

Meiosis

cell division in sexually reproducing organisms that reduces the chromosomes number by half, turning one diploid cell into four haploid daughter cells

>Chromosome duplication
>Separation of homologous pairs

>Separation of sister chromatids

Why are the daughter cells of meiosis genetically unique?

Independent orientation, crossing over, and random fertilization

Karyotyping

the laboratory process of collecting, staining, and arranging an indiviual’s complete set of chromosomes to examine their number, size, and shape

Speciation from Errors in Cell Division

-Polyploidy

-Sexual compatibility

-Tetraploid species

Polyploidy

a biological condition in which a cell or organism has three or more complete sets of chromosomes instead of the usual two (diploid)

Tetraploid Species

has four complete sets of chromosomes in its somatic (body) cells

Historical Perspectives on Inheritance

-Domestication

-Hippocrates -pangenes

body to egg and sperm

included acquired traits

-Blending hypothesis

Pea plants as model system

a species used in biological research - most famous by Gregor Mendel - to study how physical traits are inherited across generations

Why was the Common Garden Pea a GREAT model organism for testing inheritance?

-easy to grow

-reproductive cycle is short

-produces large numbers of seeds

-its mating is easy to control

-its traits are easily recognizable

Basics of plant and garden pea reproduction

-Stamens: pollen

-Carpels: eggs

-Pod=fruit

-Peas=seeds

Controlled Breeding

1. Prevention of self-fertilization

2. Promotion of cross-fertilization

3. Collecting seeds

4. Planting seeds

5. Grow plants, observe traits

Character

a heritable feature that varies

Traits

each variant of a character

Alleles

alternative versions of gene that codes for the traits

Genes

-Segments of DNA with protein coding instructions

-Basic unity of heredity

-Alleles are variant genes at the same locus

Genotype

an organism’s complete set of genetic material or the specific combination of alleles

Phenotype

a set of observable characteristics or physical traits of an organism

What traits did Mendel Study?

-An individuals observable features comprise its phenotype

-An individuals sequence of alleles comprise its genotype

Monohybrid Cross

is a genetic experiment that tracks the inheritance of a single trait (controlled by one gene) between two parent organisms

Monohybrid Results

F₁ generation, F₂ generation, and F₁ genotype

F₁ generation

-no variation in phenotype

-No “blending” of traits

F₂ generation

-Resurgence of the lost P generation trait

-Ratios of ~ 3:1 of observed F₁ trait to lost F₁ trait

F₁ genotype

the specific genetic makeup of the first generation of offspring produced by crossing two distinct paternal organisms

Dihybrid Cross Experiment

-P generation in two characters

-P generation cross

-F₁ generation cross

-Observe trait frequency in F₂ generation

What is the result of Dihybrid Cross?

Law of independent assortment

Rules of Probability

-Sum of probabilities of all outcomes = 1

-Probability of independent events

-Rule of multiplication; probability of combination of events

-Rule of addition; probability of alternative events

Pedigrees

a diagram - similar to a family tree - that maps the genetic history and relationships of family members across multiple generations

Incomplete Dominance

a genetic pattern where neither allele is completely dominant over the other, resulting in a blended intermediate phenotype in heterozygous individuals. a heterozygous individual displays an intermediate or blended phenotype.

Additional Variation of Mendel’s Law

-Multiple Alleles: more than two alleles for a gene

-Codominance: both alleles expressed

Pleiotropy inheritance

one gene influences multiple characters (ex. sickle-cell disease, Marfan syndrome, white cat with blue eyes, etc.)

Polygenic inheritance

one character influenced by multiple genes (ex. height, skin color, eye color, etc.)

Monogenic inheritance

the transmission of a genetic trait, characteristic, or disorder controlled by a single gene

Chromosomal Basis of Inheritance

-Separation of homologous chromosomes

-Law of Segregation

-Law of Independent assortment

Linked Genes

-On same chromosome

-Rarely separated in meiosis

-Linked alleles inherited together

Mammalian Sex Determination

-X and Y chromosomes

-SRY gene

-Genetic sex

-Biological sex

-Gender

Sex-linked genes

-X-linked: phenotype of male is inherited from maternal line

-Y-linked only happens rarely

Steps of Meiosis

-Prophase I and II

-Metaphase I and II

-Anaphase I and II

-Telophase and Cytokinesis I and II

Nondisjunction

the failure of homologous chromosomes or sister chromatids to separate properly during cell division

Chromosomal alterations

changes the number or physical structure of chromosomes disrupt normal gene dosage and function, leading to developmental disorders, miscarriages, or diseases like cancer

Independent assortment

a biological principle stating that the alleles of two or more different genes are sorted into gametes (sperm and egg cells) independently of one another

X-Linked Inheritance

Males: XY

Female: XX

because males and females have a different number of X chromosomes, they are affected differently by these genetic variants