Bio Unit 4 Topic 1

DNA

The molecule that stores genetic information in living organisms.

Double Helix

The twisted ladder shape of DNA.

Nucleotide

The basic building block of DNA, consisting of a sugar, phosphate group and nitrogenous base.

Nitrogenous Base

The information-carrying part of DNA (A, T, C or G).

Complementary Base Pairing

The rule that A pairs with T and C pairs with G.

Hydrogen Bonds

Weak bonds that hold complementary DNA bases together.

Gene

A section of DNA that contains instructions for making a protein or trait.

Chromosome

A long strand of DNA packaged with proteins.

Prokaryote

A simple cell without a nucleus, such as bacteria.

Eukaryote

A cell with a nucleus and membrane-bound organelles.

Circular Chromosome

A ring-shaped chromosome found in prokaryotes, mitochondria and chloroplasts.

Plasmid

A small circular piece of DNA found in bacteria that can be transferred between cells.

Intron

A non-coding section of a gene removed during RNA processing.

Exon

A coding section of a gene that remains in mature mRNA.

Promoter Region

A DNA sequence where transcription begins.

Homologous Chromosomes

A matching pair of chromosomes containing the same genes.

Sister Chromatids

Identical copies of a chromosome joined together.

Centromere

The region that holds sister chromatids together.

Telomere

Protective DNA sequences found at the ends of chromosomes.

Gene Locus

The specific position of a gene on a chromosome.

Allele

An alternative form of a gene.

Histone

A protein that DNA wraps around to help package chromosomes.

DNA Replication

The process of copying DNA before cell division.

Helicase

The enzyme that unzips DNA during replication.

DNA Polymerase

The enzyme that adds new nucleotides to a growing DNA strand.

Okazaki Fragments

Short DNA segments produced on the lagging strand during replication.

Mutation

A change in the DNA sequence.

Point Mutation

A mutation involving a change to a single nucleotide.

Frameshift Mutation

A mutation caused by insertion or deletion that changes the reading frame.

Insertion

The addition of one or more nucleotides into DNA.

Deletion

The removal of one or more nucleotides from DNA.

Meiosis

Cell division that produces gametes with half the normal chromosome number.

Crossing Over

The exchange of DNA between homologous chromosomes during meiosis.

Independent Assortment

The random distribution of chromosome pairs into gametes.

Random Fertilisation

The chance combination of sperm and egg during reproduction.

Gamete

A reproductive cell such as a sperm or egg.

Spermatogenesis

The process of producing sperm cells.

Oogenesis

The process of producing egg cells.

Duplication

A chromosome mutation where a section is copied more than once.

Inversion

A chromosome mutation where a segment is reversed.

Translocation

A chromosome mutation where a segment moves to another chromosome.

Aneuploidy

An abnormal number of chromosomes in a cell.

Karyotype

A display of all chromosomes arranged in pairs.

Genetic Disorder

A condition caused by changes in genes or chromosomes.

Protein Synthesis

The process of making proteins from genetic information.

Transcription

The process of copying DNA information into mRNA.

Messenger RNA (mRNA)

RNA that carries genetic instructions from DNA to the ribosome.

RNA Processing

The modification of RNA before it leaves the nucleus.

5' Cap

A protective structure added to the beginning of mRNA.

RNA Splicing

The removal of introns and joining of exons in mRNA.

Poly-A Tail

A string of adenine nucleotides added to the end of mRNA.

Translation

The process of converting mRNA information into a protein.

Ribosome

The structure where proteins are assembled.

Transfer RNA (tRNA)

RNA that carries amino acids to the ribosome.

Codon

A three-base sequence on mRNA that codes for an amino acid.

Anticodon

A three-base sequence on tRNA that pairs with a codon.

Amino Acid

The building block of proteins.

Polypeptide

A chain of amino acids that forms a protein.

Gene Expression

The process by which information in a gene is used to make a product.

Chromatin

DNA and proteins packaged together in the nucleus.

Heterochromatin

Tightly packed chromatin with low levels of gene activity.

Euchromatin

Loosely packed chromatin with active genes.

Transcription Factor

A protein that controls whether a gene is transcribed.

Cell Differentiation

The process by which cells become specialised for different functions.

Environmental Signal

A stimulus that can influence gene expression.

HOX Genes

A family of genes that control body structure and development.

Morphology

The form and structure of an organism.

Inheritance

The passing of genetic information from parents to offspring.

Dominant Allele

An allele that is expressed when present.

Recessive Allele

An allele that is only expressed when two copies are present.

Autosomal Inheritance

Inheritance involving genes on non-sex chromosomes.

Sex-Linked Inheritance

Inheritance involving genes on the X or Y chromosome.

Polygenic Inheritance

Inheritance of traits controlled by multiple genes.

Multiple Alleles

More than two allele forms of a gene existing in a population.

Genotype

The genetic makeup of an organism.

Phenotype

The observable characteristics of an organism.

Punnett Square

A diagram used to predict offspring genotypes and phenotypes.

Pedigree

A family tree used to study inheritance patterns.

Recombinant DNA

DNA created by combining DNA from different sources.

Restriction Enzyme

An enzyme that cuts DNA at specific sequences.

DNA Ligase

An enzyme that joins DNA fragments together.

Polymerase Chain Reaction (PCR)

A technique used to make millions of copies of a DNA segment.

Gel Electrophoresis

A method used to separate DNA fragments by size.

DNA Profiling

Identifying individuals using unique patterns in their DNA.

DNA Fragment

A piece of DNA produced by cutting or amplification.

Banding Pattern

The pattern of DNA bands produced during gel electrophoresis.

Recombinant Organism

An organism that contains DNA from another species.