BY322 Exam 1 pt.1

Chapters 1 and 2 study guide material

Genetics

the branch of biology concerned with study of heredity and variation

Theory of Epigenesis

William Harvey, 1600s: Proposed that organisms develop from fertilized eggs \n through developmental events, transforming egg into adult. contrasts the Theory of Preformationism

Theory of Preformationism

fertilized egg contains a complete miniature adult (homunculus)

Cell Theory

(Schleiden and Schwann; 1830): All organisms are composed of cells derived from \n preexisting cells

Spontaneous Generation

Spontaneous Generation: Formation of living organisms from nonliving components. Disproved by Louis Pasteur

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Theory of Natural Selection

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formulated in part by Charles Darwin; which explained the mechanism of \n evolutionary change. Natural selection was independently proposed by Darwin and Alfred Russel \n Wallace. Darwin and Wallace had no understanding of the underlying mechanism of inheritance.

HMS Beagle Voyage

Darwin’s travels provided geological, geographical, and biological observations: \n Existing species arose by descent with modification from ancestral species.

Origin of Species (1859)

Darwin published his ideas on evolutionary theory: Existing species arose from \n other ancestral species by descent with modification

Gregor Mendel (1866)

his work with a model organism (garden peas) provided quantitative data \n that showed traits are passed from parents to offspring in predictable ways. He demonstrated that \n inheritance is “particulate” rather than “blending,” meaning each trait is controlled by a pair of \n “particulates” (what we now call genes) that separate during gamete formation. his work \n formed the foundation of genetics

diploid

2n

haploid

n

Chromosome Theory of Inheritance

Walter Sutton and Theodor Boveri independently formulated **this** theory: \n Inherited traits are controlled by genes residing on chromosomes, faithfully transmitted through \n gametes, and maintain genetic continuity from generation to generation

Alleles

Alternate forms of a gene. Example: Eye color. different forms of the same gene. they occupy the same locus on homologous (paired) chromosomes and control the same characteristics

Mutations

Any heritable trait in DNA sequence; mutations are the source of genetic variation.

Genotype

Set of alleles for given trait

Phenotype

Expression of genotype produces observable features. Different alleles produce different **these**

Chemical Nature of Genes

What chemical component of chromosome carries genetic information? \n DNA or protein? Griffith (1928), Avery, MacLeod, and McCarty (1944), and Hershey and Chase \n (1952): Research showed DNA (nucleic acid), not protein, as carrier of genetic information in \n bacteria. Additional information from research on viruses provided solid proof.

Structure of DNA

described by Watson and Crick (1953): Long ladder-like macromolecule, twisted to \n form a double helix. Helix made of four different subunits (nucleotides); each contains a nitrogenous \n base: Adenine, Guanine, Thymine, and Cytosine. Nucleotides pair across the helix, held together by \n weak chemical bonds (hydrogen bonds)

RNA

Ribonucleic Acid. Chemically similar to DNA; however, it is: (usually) single-stranded; contains a \n different sugar (ribose not deoxyribose); contains nitrogenous base uracil U instead of thymine T

Gene Expression

From DNA to Phenotype. Central Dogma: DNA *makes* RNA *makes* Protein.

What does RNA make?

protein

Transcription

Protein production begins in the nucleus: DNA strand used to construct complementary \n RNA sequence (messenger RNA, mRNA). mRNA moves to cytoplasm and binds to ribosome

Translation

Synthesis of proteins directed by information encoded in mRNA (genetic code): Consists of \n nucleotide triplets called codons. Codon specifies insertion of specific amino acids into protein. \n Protein assembly utilizes adapter molecule transfer RNA (tRNA). Within ribosomes, tRNA recognizes \n information in mRNA codons. tRNA carries proper amino acid for protein assembly during \n **this process**

Proteins (purpose + components)

are the end-product of gene expression. They have enormous structural diversity. Made from a \n combination of 20 different amino acids. Enzymes (biological catalysts) form the largest category. \n Other proteins include: hemoglobin, insulin, collagen, actin, and myosin

What do mutations result in?

**Mutations** altering genes **result in an altered phenotype.** Example: sickle-cell anemia. Caused by a mutant \n form of hemoglobin. Hemoglobin transports oxygen from lungs to cells. Mutation in gene encoding \n β-globin results in amino acid substitution. Sickle-shaped red blood cells are deformed, fragile, and \n break easily. People with two mutant copies of β-globin have sickle-cell anemia. A single-nucleotide \n change in the DNA encoding β-globin (C T C → C A C) leads to an altered mRNA codon (G A G → \n G U G) and the insertion of a different amino acid (Glu → val), producing the altered version of the \n β-globin protein that is responsible for sickle-cell anemia

Recombinant DNA Technology

began with discovery of Restriction Endonucleases (RE): REs cut and \n inactivate invading viral DNA at specific sites. Utilizing vectors (carrier DNA molecules) along with \n REs allowed for recombinant DNA molecules. Recombinant molecules transferred to bacterial \n cells— reproduction of thousands of copies (clones). Recombinant technology accelerated pace of \n research— gave rise to biotechnology industry

Biotechnology

Use of recombinant DNA technology and molecular techniques to make a product. \n Genetic modification of crops → **transgenic organism**. Transferring genes between species (in \n transgenic organisms), scientists developed models of human diseases in model organisms

Genomics

studies structure, function, and evolution of genes and genomes

Proteomics

identifies set of proteins present in cells under a given set of conditions and studies their \n function and interactions

Bioinformatics

created to develop hardware and software for processing nucleotide and protein data.

classical (forward) genetics

relies on naturally occurring mutations or intentionally induced mutations (UV, X-ray, and chemicals)

reverse genetics

DNA sequence for gene of interest is known. role and function studied using gene knockout method.

model organisms

genetics relies on the use of these. easy to grow, short life cycle, produce many offspring, genetic analysis straightforward. good examples: mouse (*Mus musculus*) and the fruit fly (*Drosophilia melanogaster*)

Model Organism Examples

Viruses: T-phages and lambda phages

Microbes: Bacteria *Escherichia coli* and yeast *Saccharomyces cerevisiae*

*Caenorhabditis elegans (*nematodes)

*Arabidopsis thaliana* (thale cress)

*Danio rerio* (zebrafish)

1865

Mendel presents his research on peas

1920s

Chromosome theory of inheritance proposed

1950s

DNA shown to carry genetic information

1990

Human Genome Project Begins

1996

Recombinant DNA Technology- cloning begins

2010

CRISPR/Cas9

What is genetics the study of?

heredity and variation: how traits are passed on from generation to generation and why individuals of a species are similar but not identical

genes

regions in an organism’s DNA that encode information about heritable traits

locus/loci

the location on a chromosome that a gene occupies.

reproduction

the process by which individual cells and organisms produce offspring

What happens when a cell reproduces?

it divides in two. each descendant receives information encoded in DNA and enough cytoplasm to begin operating.

Prokaryotic Cells

in domains bacteria and archaea. no nucleus or membrane-bound organelles. Genetic material: circular DNA molecule compacted into nucleoid area. DNA not as extensively associated with proteins, no extensive coiling. These cells lack a distinct nucleolus but do contain genes for rRNA synthesis. reproduce by fission

fission

the means by which prokaryotic cells reproduce. One cell divides in two (identical to the original)

eukaryotic cells

in domain Eukarya. characterized by nucleus and membrane bound organelles. two different methods of nuclear division, mitosis and meiosis.

domain eukarya

plants, fungi, animals, other lineages (protists)

Mitosis

a form of nuclear division where chromosomes are copied and distributed. Each daughter cell receives a diploid set of chromosomes identical to parental cell. produces new nuclei that are identical to the original nucleus (same chromosome number; two sets: diploid)

Meiosis

a form of nuclear division; Gamete formation—reduction in chromosome number: Gametes receive only half the \\n number of chromosomes (haploid, n). produces new nuclei with half the original number of chromosomes (one set: haploid). this process is in preparation for sexual reproduction

nucleolus

location where rRNA is synthesized and initially assembled.

histones are made of

proteins

chromatin

thin fibers of genetic material

NORs

nucleolus organizer regions. portions of DNA that encode rRNA

cytoplasm

remainder of cell with plasma membrane, excluding nucleus. includes extranuclear cellular organelles.

cytosol

colloidal material that surrounds cellular organelles

cytoskeleton

made of microtubules (derived from protein tubulin) and microfilaments (derived from protein actin) provides lattice of support for structures within cell

Endoplasmic Reticulum (ER)

membranous organelle; compartmentalizes cytoplasm and increase surface area

smooth ER

site of lipid (fatty acid) synthesis

Rough ER

studded with ribosomes; site of protein synthesis (genetic information in mRNA is translated to protein)

mitochondria

found in most eukaryotic cells including animal and plant cells, site of ATP synthesis and the oxidative phases of cellular respiration

chloroplasts

found in plants, algae, and some protozoans; sites of photosynthesis.

what two organelles contain their own DNA?

mitochondria and chloroplasts

Chromosomes

visible as condensed structues during mitosis and meiosis. Each species has a characteristic number of these that vary in length and shape. humans have 46, or 2 sets of 23. advanced microscopy identified **these structures** and established that most eukaryotes have two sets of **them** (homologous pairs ). This is the diploid number (2n). Human diploid number: 46; we have two sets of 23 different **these**. Thus, our haploid number (n) is 23.

chromatin

uncoiled chromosomes. they form a diffuse network within the nucleus.

centromere

a constricted regions on chromosomes. the location dictates the appearance of a chromosome.

haploid

this type of cell has one copy of each chromosome (one set) (n)

diploid

has two copies of each chromosome (two sets) (2n)

homologous pair

the pair of similar chromosomes which code for the same traits, one is maternal and the other paternal

karyotype

a photo showing the complete set of chromosomes from a cell. a preparation of the complete set of metaphase chromosomes in a cell, sorted by length, centromere location and other features

sister chromatids

identical copies of chromatids formed by DNA replication of a chromosome , with both copies joined together at the centromere

cohesin

a protein complex that holds sister chromatids together, formed during S phase of cell cycle

cell cycle

a sequence of three stages (interphase, mitosis, and cytoplasmic division) through which a cell passes between one cell division and the next

interphase

consists of three stages, during which a cell increases in size, doubles the number of cytoplasmic components, and duplicates its DNA

G1

interval of cell growth and activity, most cell activities take place during this stage

G2

interval when the cell prepares for division.

control mechanisms

these can keep a cell in G1 or other points in the cell cycle, loss of control may cause cell death or cancer

G0

a resting or gap phase, in the sense that it is not dividing or preparing to divide, however it may be performing other cellular duties

spindle fibers

composed of microtubules, important role in chromosome movement during cell division

bipolar spindle

dynamic network of microtubules that forms during nuclear division (mitosis and meiosis) and grows into the cytoplasm from opposite poles of the cell and attaches to chromosomes and separates them

centrosome

region near the nucleus that organizes spindle microtubules; includes two centrioles

prophase

chromosomes condense. microtubules form bipolar spindle; nuclear envelope breaks up; spindle fibers bind to kinetochore (protein layers) at the centromere and move chromosomes

metaphase

duplicated chromosomes line up midway between spindle poles (on metaphase plate or equator); cohesin is degraded by the enzyme separase; sister chromatid arms disjoin except at centromere; enzyme shugoshin prevents degradation of cohesin at centromere

prometaphase

period of chromosome movement in early metaphase

anaphase

microtubules separate the sister chromatids and pull them to opposite spindle poles; centromeres split and sister chromatids separate from each other (disjunction). they are no longer chromatids but daughter chromatids. complete disjunction occurs when shugoshin degrades and the cohesin complex is cleaved by separase

telophase

daughter chromosomes reach the opposite spindle poles; a new nuclear envelope forms around each cluster; two new nuclei are formed, each with the same chromosome number as the parent cell

cytokinesis

the process of cytoplasmic divison. variable among eukaryotes. in animal cells, a contractile ring partitions the cytoplasm: a band of actin filaments rings the cell midsection, contracts, and pinches the cytoplasm in two. In plant cells, a cell plate form midway between the spindle poles, partitioning the cytoplasm when it reaches and connects to the parent cell wall

asexual reproduction

one parent transmits genetic information to offspring, producing genetically identical clones

sexual reproduction

offspring inherit information from two parents who differ in their traits. thus, this introduces variation in the combinations of traits among offspring.

why is sex costly?

because each individual only passes 50% of its genes to the next generation vs 100% in asexual reproduction

adaptive traits

tend to spread more quickly through a sexually reproducing population than through an asexually reproducing one; thus sex provides and adaptive advantage for a population. to participate in sexual reproduction, a diploid organism must reduce the number of chromosomes in cells that will be involved in fertilization

meiosis

nuclear division in reproductive cells of sexually-reproducing eukaryotic species. involves two divisions, not one. DNA is replicated once and divided twice forming four haploid nuclei

meiosis in germ cells

havles the diploid number of chromosomes (2n) to the haploid number (n), producing haploid gametes (sex cells). gametes are typically produced in specialized reproductive structures or organs

fertilization

diploid number (2 sets) is restored in this process, when two haploid gametes fuse and form a zygote, the first cell of a new individual

Meiosis I

each duplicated homologous chromosome is separated from its partner. This process is similar to mitosis, except sister chromatids remain together, while homologous chromsomes pair up and then separate

prophase I

diploid cells duplicate its genetic material. nuclear envelope and nucleolus break down and two centromeres of tetrad are attached to spindle fibers

bivalent

a pair of homologous chromosomes (homologs); the number of this equals the haploid number. each of these gives rise to a unit, tetrad

tetrad

two pairs of sister chromatids

synapsis

the grouping of homologous chromosomes