Biology Final

Natural selection

Mechanism of evolution developed by Darwin, based on four ideas exfess reproduction, variations, inheritance, adnthe advantages of specific traits in the enviornment.

Evolution

Any change in the heritable traits within a population across generations.

Derived trait

New feature that had not appeared in common ancestors

Ancestral trait

more-primitive characteristic that appeared in common ancestors

Homologous structure

Similar structure inherited from a common ancestor.

Vestigial structure

A "leftover" structure. It is non-functional and indicates shared ancestry.

Analogous structure

same function but different structure that is not inherited from a common ancestor

Embryo

Organism's early prebirth stage of development.

Biogeography

Stiff of the distribution of plants and animals on earth.

Fitness

The ability of an individual to survive and reproduce in its specific enviornment.

Camoflauge

Morphological adaptations that allow organisms to blend into their surroundings.

Mimicry

morphological adaptation in which one species evolves to resemble another species for protection.

Genetic drift

A change in the gene pool of a population due to chance; changes the frequency of alleles.

Founder effect

Can occur when a small population settles in an area separated from the rest of the population and interbreeds.

Bottleneck

Process in which a large population declines in number and rebounds with a different allele frequency.

Stabilizing selection

most common form of natural selection in which organisms with extreme expressions of a trait are removed

Gradualism

Theory that evolution occurs in gradual steps over time.

Fossil

Preserved remains or evidence of an ancient organism.

Artificial selection

Selection by humans for breeding of useful traits from the natural variation among different organisms

Adaptation

Any characteristic that helps an organism survive and reproduce in its enviornment.

Survival of the fittest

Individuals with adaptations well suited to their enviornment survive and reproduce.

Comparative anatomy

Study the body structures of different species in order to understand the adaptive changes.

Cell cycle

Cells reproduce by this cycle of growing and dividing.

Interphase

the stage during which the cell grows, carries out cellular functions, and replicates, or makes copies of its DNA in preparation for the next stage of the cycle. Cell spends most of its time here.

Mitosis

the stage of the cell cycle during which the cell's nucleus and nuclear material divide

Cytokinesis

the method by which a cell's cytoplasm divides, creating a new cell

Chromosomes

The structures that contain the genetic material that is passed from generation to generation of cells.

Chromatin

relaxed form of DNA in the nucleus of a cell

Prophase

The first stage in mitosis-the longest phase- in this stage the cells chromatin condenses into chromosomes and the nuclear envelope disappear.

Sister chromatids

are structures that contain identical copies of DNA.

Centromere

the structure at the center of the chromosome where the sister chromatids are attached

Spindle apparatus

structure made of spindle fibers, centrioles, and aster fibers that is involved in moving and organizing chromosomes before the cell divides

Metaphase

Sister chromatids are pulled along the spindle apparatus toward the center of the cell, they line up in the middle of the cell.

Anaphase

The microtubules of the spindle apparatus begin to shorten, the sister chromatids separate, the chromosome move toward the poles of the cell.

Telephase

Chromosomes arrive at the poles and the two nuclear membranes begin to form as the nucleoli begins to reappear, the spindle fibers begin to dissolve.

Cyclin

One of the specific proteins that regulates/stimulates the cell cycle.

Cancer

uncontrolled growth and division of cells

Apoptosis

programmed cell death

Stem cells

Unspecialized cells that can develop into specialized cells when under the right conditions.

Selective permeability

Process in which a membrane allows some substances to pass through while keeping other out.

life cycle

The sequence of growth and development stages that an organism goes through during its life.

Nucleotide

Sub unit that makes up DNA and RNA molecules

Centrioles

Cell organelle that aids in cell division in animal cells only

Centrosome

A structure in animal cells containing centrioles from which the spindle fibers develop.

S phase

The synthesis phase of the cell cycle; the portion of interphase during which DNA is replicated.

G1

In interphase-cell grows rapidly, builds new organelles; also performs regular cell functions.

G2

The final period of interphase during which the cell prepares for mitosis.

Microtubules

Thick hollow tubes that make up the cilia, flagella, and spindle fibers.

Meiosis

A process in cell division during which the number of chromosomes decreases to half the original number by two divisions of the nucleus, which results in the production of sex cells.

Genotype

An organism's genetic makeup, or allele combinations. Usually expressed as letters (ex. TT, Tt, tt)

Recessive

an allele that is only expressed when there is no dominant allele of the gene present

Dominant

An allele or a gene that is expressed in an organism's phenotype, masking the effect of the recessive allele or gene when present.

Crossing over

Process in which homologous chromosomes exchange portions of their chromatids during meiosis. Provides genetic variation

Sex-linked trait

a trait that is determined by a gene found on one of the sex chromosomes, such as the X chromosome or the Y chromosome in humans

Phenotype

An organism's physical appearance, or visible traits.

Monohybrid cross

A cross between individuals that involves one pair of contrasting traits

Genetics

branch of biology that studies heredity

Gene

A segment of DNA on a chromosome that codes for a specific trait

Gamete

A haploid cell such as an egg or sperm. Gametes unite during sexual reproduction to produce a diploid zygote.

Haploid

An organism or cell having only one complete set of chromosomes.

Law of independent assortment

The alleles of different genes separate independently of one another during gamete formation; Genes for different characters (and on different chromosomes) are inherited independently of one another.

Homologous chromosomes

Chromosomes that are similar in size, shape, and genetic content

Allele

An alternative form of a gene.

Homozygous

An organism that has two identical alleles for a trait

Law of Segregation

Mendel's law that states that the pairs of homologous chromosomes separate in meiosis so that only one chromosome from each pair is present in each gamete; Alleles segregate independently when forming gametes.

Heterozygous

An organism that has two different alleles for a trait

Autosomal trait

Trait located on any chromosome other than sex chromosomes, determined by genes found on one of the first 22 pairs of chromosomes.

Diploid

an organism or cell having two sets of chromosomes or twice the haploid number (2n)

Gene linkage

tendency for genes located close together on the same chromosome to be inherited together

Fertilization

Male sex cell (sperm) unites with female sex cell into one cell (46 chromosomes \-- 23 from each).

Genetic recombination

The general term for the production of offspring with new combinations of traits inherited from the two parents.

Ribonucleic acid (RNA)

single-stranded nucleic acid that contains the sugar ribose

Messenger RNA (mRNA)

RNA molecule transcribed from a DNA template

Transfer RNA

type of RNA that carries each amino acid to a ribosome during protein synthesis

Ribosomal RNA

type of RNA that combines with proteins to form ribosomes

RNA polymerase

enzyme that links together the growing chain of RNA nucleotides during transcription using a DNA strand as a template

Promoter

A specific nucleotide sequence in DNA that binds RNA polymerase and indicates where to start transcribing RNA.

Transcription

Process in which mRNA is made from DNA

Polypeptide

long chain of amino acids that makes proteins

Codon

A specific sequence of three bases on a strand of RNA; code for a specific amino acid.

Translation

Process by which mRNA is decoded and a protein is produced

Anticodon

group of three bases on a tRNA molecule that are complementary to an mRNA codon

Gene expression

Process by which a gene produces its protein through transcription and translation and the product carries out its function (trait).

Ribosome

A cell organelle that is the site of protein synthesis.

Amino acid

Building blocks of protein

Single-stranded

Structure/shape of RNA

Ribose

A five-carbon sugar present in RNA

Insertion

A mutation in which one nucleotide pair is added to a gene.

Mutation

change in DNA sequence

Gene expression

process by which a gene produces its product and the product carries out its function

Polyploidy

condition in which an organism has extra sets of chromosomes

Point mutation

A change in a gene at a single nucleotide pair.

Deletion

A mutation in which one nucleotide pair is lost from a gene.

Promoter

A specific nucleotide sequence in DNA that binds RNA polymerase and indicates where to start transcribing RNA.

Substitution

A mutation in which a nucleotide or a codon in DNA is replaced with a different nucleotide

Polypeptide

A long chain of amino acids that makes proteins

Mutagen

A chemical or physical agent that interacts with DNA and causes a mutation.

Ribosome

A cell organelle that is the site of protein synthesis

Frameshift mutation

Mutation that shifts the "reading" frame of the genetic message by inserting or deleting a nucleotide.

Where does transcription take place?

inside the nucleus