AP Bio - Genetics

Apoptosis

Programmed cell death to remove cells that have become harmful to the organism or are no longer needed.

Allele

One of two or more alternative states of a gene.

Bacteriophage

A virus that infects bacterial cells

Chromatid

One of the two daughter strands of a duplicated chromosome; held together by a centromere

Cytokinesis

Division of the cytoplasm of a cell after nuclear division; last part of the cell cycle.

Crossing over

During meiosis I, an exchange of pieces of genetic material between homologous chromosomes; causes genetic recombination

Codominance

When two or more alleles are equally represented in a heterozygote; example AB blood type.

Codon

Three consecutive nucleotides that code for a specific amino acid

Conjugation

Transfer of DNA from one unicellular organism to another

CRISPR

A segment of bacterial DNA containing repeating nucleotide sequences that can be used in genetic engineering to alter an organism's DNA

Diploid

Having two sets of chromosomes (2n); characteristic of non-gamete cells

DNA Polymerase

Enzymes that synthesize DNA; only synthesize in the 5' to 3' direction

DNA methylation

Addition of a methyl group (CH3) to the DNA strand resulting in a change in gene expression

Epigenetics

The study of changes in an organism caused by gene expression rather than changes to the genetic code

Epistasis

Interaction in which one gene modifies the phenotype of another.

Frameshift Mutation

A mutation in which a nucleotide is added or deleted from DNA, creating a downstreaming effect on other codons.

Gamete

A haploid reproductive cell (sperm/egg)

Genotype

The genetic constitution that causes a trait or set of traits

Gel Electrophoresis

A laboratory method that separates DNA, RNA, or proteins based on molecular size; used to show genetic relationships between organisms

Haploid

Having only one set of chromosomes (n); such as in sex cells

Heterozygous

Having two different alleles of the same gene (ex. Tt)

Homozygous

Having two identical alleles for a given gene (ex. TT or tt)

Homologous Chromosomes

Two of the same chromosome found in a diploid cell, one being derived from each parent

Interphase

The period between two mitotic divisions during which the cell grows and DNA replicates

Intermediate Inheritance

When two alleles are expressed to create a phenotype that blends both traits.

Missense Mutation

A mutation in which one base is substituted, causing a change in one amino acid

Mitosis

Division of somatic cells to create two identical daughter nuclei

Meiosis

Division of gametes to create four unique, haploid cells

Nondisjunction

When sister chromatids fail to separate during meiosis, resulting in cells that have one too many or one too few chromosomes; can cause Down Syndrome

Nucleotide

The building block of nucleic acids (DNA and RNA); composed of a phosphate, a 5-carbon sugar, and a nitrogen base (A,T,C,G, or U).

Okazaki Fragment

A short segment of DNA produced by the discontinuous replication of DNA in the 5' to 3' direction

Operon

A cluster of genes transcribed together to create a single mRNA molecule

Operator

A site on DNA that a repressor can bind to to prevent transcription of mRNA

Phenotype

The physical appearance or functional expression of a trait

Pleiotropy

When one allele has more than one effect on the production of a phenotype

Promoter

A DNA sequence that RNA polymerase attaches to in order to begin transcription of a gene

Point Mutation

A change in one nucleotide in a DNA molecule; can be missense (changes amino acid); nonsense (codes for Stop codon), or silent (no change in amino acid)

Plasmid

A small circular fragment of bacterial DNA that can self-replicate independent of chromosomal DNA

Prion

Infectious proteins that cause cell death; cause of Mad Cow disease

PCR

A process which uses DNA polymerase to create millions of copies of a desired DNA sequence.

RFLP's

Fragments of DNA with varying lengths that have been cut by restriction enzymes and can be separated by size during gel electrophoresis

Restriction Enzymes

An enzyme that cuts DNA at a specific sequence of nucleotides

Recombinant DNA

Fragments of DNA from two different species, spliced together through genetic engineering.

Regulator Gene

A gene that controls the expression of other genes

Repressor

A protein that regulates DNA transcription by preventing RNA polymerase from attaching to the operator

RNA Primer

A short sequence of RNA nucleotides used as the starting point for replication by DNA polymerase

RNA Polymerase

An enzyme that synthesizes mRNA molecules based on a DNA template

Retrovirus

A virus containing RNA instead of DNA, and an enzyme (reverse transcriptase), that uses the infected cell's machinery to build DNA

Somatic Cell

Body cells; any cell of a multicellular organism except for gametes

Semiconservative Replication

Each parent strand of DNA is paired with a strand of new DNA during replication.

Transduction

The transfer of genetic material from one organism to another by way of a virus/vector

Translation

The assembly of a protein from amino acids coded for by mRNA codons

Transformation

The uptake of DNA from the environment; occurs in some bacterial species

Transcription

Synthesis of an mRNA molecule based on a DNA template

Telomere

A specialized region of DNA that caps each end of a chromosome

Nonsense Mutation

Point mutation where one base changes and instead of coding for an amino acid, it codes for STOP

Phenotypic Plasticity

the ability of an organism to change its phenotype in response to changes in the environment.

Monohybrid inheritance

The study of how the alleles of just one gene are passed from parents to offspring. Specifically in a cross between two heterozygotes

Dihybrid Inheritance

The inheritance of two characteristics which are controlled by different genes. Specifically in a cross between parents that are heterozygous for both traits.

Sex-linked Inheritance

pattern of inheritance in which certain characteristics carried on the X chromosome inherited from the mother are transmitted differently to her male and female offspring

Gene Linkage

Traits that tend to be inherited together as a consequence of their genes being on the same chromosome

Helicase

An enzyme that untwists the double helix of DNA to prepare for replication

Topoisomerase

Enzyme that functions in DNA replication, helping to relieve strain in the double helix ahead of the replication fork.

Ligase

An enzyme that connects two fragments of DNA to make a single fragment

mRNA

messenger RNA; type of RNA that carries instructions from DNA in the nucleus to the ribosome

rRNA

ribosomal RNA; type of RNA that makes up part of the ribosome

tRNA

transfer RNA; type of RNA that carries amino acids to the ribosome

Poly-A tail

Modified end of the 3' end of an mRNA made up of a chain of adenine molecules

GTP cap

a molecule that is attached to the 5' head of the mRNA after transcription

Intron

sequence of DNA that is not involved in coding for a protein

Exon

expressed sequence of DNA; codes for a protein

Alternative Splicing

Removal of introns in a pre-mRNA that occurs in different ways, leading to different mRNAs that code for different proteins. Increases the diversity of proteins.

Operon

group of genes operating together

Promoter

specific region of a gene where RNA polymerase can bind and begin transcription