Genetics

Module 1

Genome

The complete set of genetic material in an organism, including all of its genes and DNA sequences.

Genetics

The study of heredity, genes, and genetic variation in living organisms.

Gene

Unit of heredity that may influence the outcome of a trait in an organism. At the molecular level, this is a segment of DNA that contains the information to make a functional product, either an RNA molecule or a polypeptide.

Traits

Characteristics or features of an organism determined by its genes.

Nucleic acids

Biomolecule macromolecules that serve as the building blocks of genetic material, including DNA and RNA.

Protein

Functional unit composed of one or more polypeptides.

Carbohydrates

Organic molecules made of carbon, hydrogen, and oxygen, primarily serving as energy sources and structural components in living organisms.

Lipids

Organic molecule that is insoluble in water. Cell membranes contain large amounts of these.

DNA

Genetic material. Double stranded structure, with each strand composed of repeating units of deoxyribonucleotides

Nucleotides

Repeating structural unit of nucleic acids, composed of a sugar, 1-3 phosphates, and a nitrogen containing base.

Gene expression

The process by which the information within a gene is accessed, first to synthesize RNA and polypeptides, and eventually to affect the properties of cells and the phenotype of multicellular organisms.

Morphological traits

Trait that affects the morphology of an organism. ex. eye color

Physiological traits

Trait that affects a cellular or body function. Ex. rate of glucose metabolism.

Behavioral traits

Trait that affects the way an organism responds to some aspect of its environment. Ex. the ability to learn a maze.

Molecular level

Observation of living things at the level of individual molecules

Cellular level

Observation of living things at the level of individual cells.

Chromosome

Structures within a living cell that contains the genetic material. Genes are located in the chromosomes

Somatic cell

Any cell of the body except for gametes and germ-line cells that give rise to gametes.

Gametes

Reproductive cell (usually haploid) that can unite with another reproductive cell to create a zygote. These are also called germline cells. ex. sperm and egg cells.

Diploid

An organism or cell that contains two sets of chromosomes.

Homologs

Structures that are similar to each other due to descent from a common ancestor. For example, these can be one of the chromosomes in a pair of chromosomes. Genes can also be these when they are descended from a common gene

Alleles

an alternative form of a specific gene

homozygous

describes a diploid individual that has two identical alleles of a particular gene

heterozygous

describes a diploid individual that has different versions (two different alleles) of the same gene.

locus

the site within a genetic map where a specific gene or other DNA segment is found.

cell cycle

in eukaryotic cells, a series of stages through which a cell progresses in order to divide. The phases are G for gap, S for synthesis (of genetic material), and M for mitosis (which includes cytokinesis). There are two G phases, G1 and G2

G1 phase

A phase of the eukaryotic cell cycle in which a cell may prepare to divide, depending on the cell type and conditions.

S phase

A phase of the eukaryotic cell cycle, between the G1 and G2 phases, during which a cell replicates its chromosomes.

chromatids

following chromosomal replication in eukaryotes, the two copies that remain attached to each other in the form of sister chromatids.

centromere

a segment of a eukaryotic chromosomes that provides an attachment site for the kinetochore

sister chromatids

pairs of replicated chromosomes that are attached to each other at the centromere. These are genetically identical. these are also called dyads.

monad

a single chromatid within a dyad.

kinetochore

a protein complex bound to a centromere of a chromosome during meiosis and mitosis.

G2 phase

a phase of the eukaryotic cell cycle between S phase and M phase in which a cell accumulates the materials necessary for nuclear and cell division

M phase

the phase of the eukaryotic cell cycle in which nuclear division, either mitosis or meiosis, occurs. It is divided into prophase, prometaphase, metaphase, anaphase, and telophase.

mitosis

a type of nuclear division into two nuclei, during which each daughter cell receives the same complement of chromosomes.

prophase

the first phase of mitosis. The chromosomes have already replicated and begin to condense. The mitotic spindle apparatus starts to form.

prometaphase

the second phase of mitosis. During this phase, the nuclear membrane vesiculates, and the mitotic spindle is completely formed.

metaphase

the third phase of mitosis. The chromosomes align along the central plane of the spindle apparatus, and the formation of the spindle is complete.

anaphase

the fourth phase of mitosis. As anaphase proceeds, half of the chromosomes move to one pole, and the other half move to the other.

telophase

the fifth stage of mitosis. The chromosomes have reached their respective poles and decondense.

cytokinesis

the division of a single cell into two cells. The two nuclei produced in mitosis are segregated into separate daughter cells during cytokinesis.

meiosis

a form of nuclear division in which the sorting process results in the production of haploid cells from a diploid cell.

haploid

refers to a cell that contains half the genetic material found in somatic cells. For a species that is diploid, these gametes contain a single set of chromosomes.

synapsis

the event in which homologous chromosomes recognize each other and then align themselves along their entire lengths.

sexual reproduction

the process whereby parents make gametes (e.g., sperm and egg) that fuse with each other in the process of fertilization to begin the development of a new organism

genome

all of the chromosomes and DNA sequences that a cell, an organism, or a species can process.

cytogeneticist

a scientist who studies chromosomes under than microscope.

metacentric

describes a chromosome with the centromere near the middle

submetacentric

describes a chromosome in which the centromere is slightly off center.

acrocentric

describes a chromosome with the centromere significantly off center, but not at the end.

telocentric

describes a chromosome with its centromere at one end.

karyotype

a photographic representation of all the chromosomes within a cell. It reveals how many chromosomes are found within an actively dividing somatic cell.

deletion

a type of change affecting a chromosome in which a segment of DNA is removed.

duplication

the repetition of a segment of DNA more than once within a chromosome and/or within a genome.

inversion

a change in the orientation of genetic material along a chromosome such that a segment is flipped or reversed from the normal order.

translocation

rearrangement in which one segment of a chromosome breaks off and becomes attached to a different chromosome or a different part of the same chromosome.

terminal deletion

deletion in which a segment is lost from the end of a linear chromosome.

gene family

two or more genes within a single species that are similar to each other because they were derived from the same ancestral gene.

copy number variation (CNV)

a type of structural variation in which a segment of DNA that is 1000 bp or more in length commonly exhibits copy number differences among members of the same species.

pericentric inversion

an inversion in which the centromere is located within the inverted region of the chromosome

paracentric inversion

an inversion in which the centromere is found outside the inverted region.

telomeres

specialized repeated sequences of DNA found at the ends of eukaryotic chromosomes.

Robertsonian translocation

the structure produced when two telocentric chromosomes fuse their short arms.

euploid

describes an organism in which the chromosome number is an exact multiple of a chromosome set.

triploid

describes an organism or cell with three sets of chromosomes

aneuploid

not euploid. Refers to a variation in chromosome number such that the total number of chromosomes is not an exact multiple of a set.

nondisjunction

event in which chromosome do not segregate properly during mitosis or meiosis.

meiotic nondisjunction

the event in which chromosomes do not segregate properly during meiosis.

mitotic nondisjunction

an event in which chromosomes do not segregate properly during mitosis.

cross

a breeding between two distinct individuals. An analysis of their offspring may be conducted to understand how traits are passed from parent to offspring

hybrids

an offspring obtained from a hybridization experiment.

single-factor cross

a cross in which an experimenter is observing the outcome for only a single character.

monohybrids

an individual produced from a single-factor cross in which the parents had different variants for a single character.

parental generation

in a genetic cross, the first generation in the experiment. In Mendel’s studies, this was true breeding with regard to particular traits.

F1 generation

the offspring produced from a cross of a parental generation.

F2 generation

the offspring produced from a cross or self-fertilization of individuals in the F1 generation.

dominant

describes an allele that determines the phenotype in the heterozygous condition. For example, if a plant is Tt and has a tall phenotype, the T (tall) allele is dominant over the t (short) allele.

recessive

a trait or allele that is masked by the presence of a dominant trait or allele.

Mendels law of segregation

the two copies of a gene segregate (or separate) from each other during the process that gives rise to gametes.

genotype

the genetic composition of an individual, especially in terms of the alleles for particular genes.

phenotype

the observable traits of an organism.

two-factor cross

a cross in which an experimenter follows the inheritance of two different characters.

genetic recombination

the process in which alleles are assorted and passed to offspring in combinations that are different from those found in the parents.

X-linked genes

genes (or alleles of genes) that are physically located on the X chromosome

pedigrees

charts representing family relationships

pedigree analysis

genetic analysis using information contained within family trees. In this approach, the aim is to determine the type of inheritance pattern that a gene follows.

hypothesis testing

one experimental approach for conducting science. It involves the formation of a hypothesis, which is followed by experimentation, so that scientists may reach verifiable conclusions about the world in which they live.