Chapter 23 Textbook Notes

Genetics

Genetics

The study of ways in which biological information is passed from one generation to the next.

Gregor Mendel

An Austrian monk who pioneered the field of genetics and conducted experiments with pea plants to understand the inheritance of physical characteristics.

Hybrid

The offspring of two different strains, such as tall and short pea plants.

Gene

The "unit of inheritance" that determines the characteristics of an organism. Mendel used this term to explain his findings, although he had no knowledge of its physical existence.

Dominant gene

A gene that is expressed and determines the physical characteristics of an offspring when present with a recessive gene.

Recessive gene

A gene that is present in the offspring but does not determine the physical characteristics when paired with a dominant gene.

Classical genetics rules:

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Physical characteristics or traits are passed from parents to offspring by genes.

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Each offspring has two genes for each trait, one from each parent.

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Some genes are dominant and some are recessive. Dominant traits are expressed in preference to recessive traits.

Molecular genetics

The study of the mechanism that passes genetic information from parents to offspring at the molecular level.

Chromosomes

Distinctive structures that carry genetic information and divide during cell division.

DNA

Deoxyribonucleic acid, the primary component of chromosomes and the molecule that carries and interprets the genetic code.

Nucleotides

The building blocks of nucleic acids, including DNA and RNA. They follow the principles of modularity and geometry.

Proteins

Chains of amino acids that can form large structures from a single kind of building block.

Carbohydrates

Clusters of sugar molecules that can form large structures from a single kind of building block.

Nucleic acids

Assembled from subunits called nucleotides, which are made from three different kinds of smaller molecules.

Nucleotide

The assemblage of three molecules - a sugar, a phosphate, and a base - that make up nucleic acids.

Deoxyribose

The sugar molecule in DNA, which is similar to ribose but is missing one oxygen atom.

Ribose

The sugar molecule in RNA, containing five carbon atoms.

Phosphate ion

Includes one phosphorus atom surrounded by four atoms of oxygen, a key component of nucleotides.

Bases

Four different kinds of molecules in DNA - adenine (A), guanine (G), cytosine (C), and thymine (T).

DNA

Made by linking nucleotides together in a specific way, forming a ladder-like double strand with base pairs.

RNA

Built in a similar manner to DNA, but with ribose as the sugar and uracil (U) replacing thymine (T) as a base.

DNA replication

The process of copying DNA, where special enzymes break the hydrogen bonds between bases and reconstruct the missing strand.

Genetic code

The information carried by DNA and translated into proteins by RNA.

Transcription

The process of using RNA to copy the information from DNA and carry it out into the cell.

Messenger RNA (mRNA)

The type of RNA that carries the coded message from DNA to the site of protein synthesis.

Transfer RNA (tRNA)

The type of RNA that reads the coded message on mRNA and brings the corresponding amino acids to the site of protein synthesis.

Codon

A set of three bases on the mRNA that determines which tRNA molecules will attach and determines a single amino acid.

Genetic code

The connection between codons on mRNA and the amino acids they select, shared by all living things.

Protein synthesis

The process of assembling a protein using ribosomes, mRNA, tRNA, and amino acids.

Ribosomes

Large organelles made of proteins and ribosomal RNA (rRNA) that align mRNA and tRNA during protein assembly.

Gene

A stretch of DNA that codes for a specific protein enzyme and determines traits in an organism.

Central dogma of molecular biology

The rule that one gene codes for one protein.

Exons

The coding sections of DNA within a gene that code for the protein.

Introns

The noncoding sections of DNA within a gene that are interspersed between exons.

DNA repair

Mechanisms that fix damage to the DNA molecule, which occurs at a high rate due to various agents.

Gene expression

The process by which certain genes are activated in specific cells to carry out their functions.

Viruses

Non-living entities consisting of genetic material (RNA or DNA) wrapped in a protein coating that rely on cellular machinery to reproduce.

HIV

A complex virus that contains RNA and enzymes to insert its DNA into a host cell, leading to the destruction of immune system cells.

Antibiotics

Drugs that can destroy invading bacteria without harming the human cells.

Viral diseases

Diseases caused by viruses that cannot be treated as effectively with commonly available drugs as bacterial infections.

Vaccination

A countermeasure for viral diseases that stimulates the human immune system to produce antibodies that neutralize the virus.

Mutation

The rapid rate of change in viruses, such as HIV and influenza, due to the lack of proofreading mechanisms during DNA copying.

Human Genome Project

A scientific project aimed at determining the complete description of all the base pairs in human DNA.

Chromosomes

Bundles of DNA that contain genes and are the packaging into which the DNA is put.

DNA sequencing

The process of determining the exact order of bases along a DNA molecule.

Genetic map

Shows the location and sequence of genes along a chromosome, used to identify genes for specific traits.

Epigenetics

New modes of influence on genetic inheritance that do not involve changes in the sequence of base pairs.

Methylation

A process in which a methyl molecule attaches itself to a spot on the DNA chain, preventing the normal process of gene expression from starting.

Gene

Units of inheritance that are passed from parent to offspring and contribute to the inheritance of physical characteristics or traits.

Dominant gene

A gene that, when present together with a recessive gene, will be expressed and determine the trait.

Recessive gene

A gene that will only appear if no dominant gene is present.

Nature versus nurture

The debate about the relative influence of genetic inheritance (nature) and environmental factors (nurture) on the development of characteristics in organisms.

Replication

The process of copying DNA before cell division, which involves splitting apart the two sides of the DNA double helix and forming two complete DNA strands.

Transcription

The process in which the DNA message is read by RNA, specifically messenger RNA (mRNA), which copies the sequence for one gene and carries it out of the nucleus.

Genetic code

The correspondence between base-pair sequences in DNA or RNA and the amino acids that they code for, shared by every living organism.

Mutation

Errors in the coded sequence of DNA that can occur and cause changes in the genetic information.

Genome

The complete description of an organism's genetic code, including the positions of every gene on every chromosome and the exact order of base pairs on every gene.

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