Unit 4 Biology

DNA

Deoxyribonucleic acid that is responsible for storing genetic information in cells. Located in the nucleus and bound in histones. Double helix-shape. Made up of a sugar, nitrogenous base (guanine, cytosine, adenine and thymine) and a phosphate group.

Nucleus

The membrane-bound organelle in eukaryotic cells that houses the cell's genetic material and controls cellular activities.

Histone

Proteins that provide structure for DNA to wrap around, creating chromosomes.

Chromatin

The complex formed when DNA wraps around histones, making up chromosomes

Chromosome

Condensed chromatin that contains genes (DNA). Humans have 23 homologous pairs of chromosomes (46 chromosomes in total, 92 chromatids). 22 of these pairs are autosomes, and 1 pair are sex chromosomes.

Autosomes

Chromosomes that code for body cells.

Sex chromosomes

Chromosomes that code for sex characteristics. Can be X or Y. Women have XX chromosomes and men have XY chromosomes. We get one chromosome from each parent.

Gene

Regions of DNA that contain the instructions for making proteins.

Karyotype

Map of chromosomes.

Telomeres

Non-coding DNA that act as repeating ends that work as a protection layer.

Chargaff’s Rule

The proportion of adenine to thymine and the proportion of cytosine to guanine are always equal. A%=T% and G%=C%.

Homologous chromosomes

Chromosomes that have the same structure and carry genes for the same traits, one inherited from each parent.

Genome

The genetic material of an organism.

Coding Regions

Regions of DNA that code for proteins.

Non-Coding Regions

Regions of DNA that are not directly involved in protein synthesis

Structural DNA

Regions of DNA that uphold the structure of the gene (eg. telomeres and centromeres) that are NOT transcribed at all.

Functional RNA

Regions of RNA that are not translated (eg. tRNA or rRNA).

Introns

Regions of DNA that are edited in splicing.

Methylation

Form of gene regulation that prevents transcription by making the chromatin coil too tightly.

Acetylation

A form of gene regulation that prevents transcription by loosening the chromatin.

Activators

A form of gene regulation that involves proteins that promote transcription.

Repressors

A form of gene regulation that involves proteins that bind to DNA and prevent transcription.

Environmental exposure as gene regulation

A form of gene regulation that edit genes (eg. diet, alcohol, disease, toxic chemicals, drugs, exercise)

DNA replication

Replication that occurs in mitosis and meiosis, occurring prior to cell division and resulting in single-stranded chromosomes becoming double-stranded.

Stages of DNA replication

1. Unwinding of the DNA strand (helicase unwinds the two strands of DNA by breaking the hydrogen bonds between the bases)

2. Formation of new complementary strands (DNA polymerase makes a new strand by binding free nucleotides to the single strands in a 5’ to 3’ direction). This occurs continuously for the leading strand, and discontinuously for the lagging strands, producing okazaki fragments.

Okazaki fragments

Fragments of DNA that get sealed by DNA ligase.

RNA

Ribonucleic acid (single-stranded) that make messages to give to the ribosomes to create proteins.

Asexual Reproduction

A form of reproduction that results in genetically identical clones of the parent organism. Results in organisms that are more vulnerable to environmental changes.

Sexual Reproduction

A form of reproduction that results in offspring through the coming-together of gametes (sperm and eggs) that are produced through meiosis.

Mitosis

A type of cell division where one parent cell is divided into two identical diploid daughter cells, used for growth and repair of body cells.

Diploid

2n. Cells that contain two sets of chromosomes (one from each parent).

Haploid

N. Cells that contain only one set of chromosomes.