Genetics and Human Genome Project Quiz

Genetics Overview

• Genetics is the study of heredity and variation.
• A gene is classically defined as a "unit" of heredity, but a modern definition is a segment of DNA that produces a functional product (e.g., a polypeptide).
• Traits are observable characteristics of an organism.
• Traits are a result of the interaction between genes and the environment (e.g., diet and height/weight).
• In some cases, the environment dictates whether a disease manifests (e.g., Phenylketonuria, or PKU).
• During reproduction, genes are passed from parent to offspring.
• Humans have 46 chromosomes (23 homologous pairs).
• The X and Y chromosomes are not homologous in males.
• Gametes (sperm and egg cells) are haploid, having one set of 23 chromosomes.
• There are four levels of biological organization relevant to genetics, including molecular, cellular, organism, and population levels.

DNA Structure and Function

• DNA is deoxyribonucleic acid, the genetic material in all living organisms (some viruses use RNA).
• DNA encodes information for cellular proteins.
• Each nucleotide in a DNA molecule contains a nitrogenous base (adenine, thymine, cytosine, and guanine).
• Genetic information is stored in the linear sequence of bases.
• DNA is a double helix and has a ladder-like structure.
• A double helix consists of a sequence of nucleotides, each composed of a deoxyribose sugar, a phosphate group, and a nitrogenous base.
• The bases pair up specifically: adenine with thymine and guanine with cytosine.

Protein Structure and Function

• Proteins are composed of one or more polypeptides.
• A polypeptide is a linear sequence of amino acids.
• Characteristics of a cell depend on proteins.
• All the proteins a cell makes at any given time are called the proteome.
• Proteins have various functions, including structural roles in cell shape and movement, aiding ion transport across cell membranes, and acting as enzymes.
• Enzymes are proteins that catalyze (speed up) chemical reactions in the body.
• Catabolic enzymes break down large molecules into smaller ones, releasing energy.
• Anabolic enzymes synthesize large molecules from smaller ones, building cellular components.

Gene Expression

• Gene expression has two key steps: transcription and translation.
• Transcription (DNA → RNA): The genetic information in DNA is copied into a nucleotide sequence of messenger RNA (mRNA).
• Translation (RNA→ protein): The mRNA sequence provides the information, using the genetic code, to make the amino acid sequence of a protein.
• The functioning of proteins within living cells influences an organism's traits.

Fields of Genetics

• Transmission genetics studies how traits are passed from parents to offspring.
• Molecular genetics examines the molecular aspects of DNA, including how they underlie gene expression, gene organization, and function.
• Population genetics analyses genetic variation in a population and its roles in evolution, as well as mathematical theories explaining the prevalence of alleles.

Genetic Variation

• Genetic variation refers to differences in inherited traits among individuals in a population.
• Genetic variation can occur due to changes to the DNA at the molecular level. Variations include gene mutations, changes in chromosome structure (loss, duplication, re-attachment), and changes in chromosome number.
• Contrasting forms within a single species are called morphs.
• Example of gene mutations: base pair substitutions leading to different forms/alleles (e.g., different flower colours)
• Example of variation in chromosome number: individuals with Down Syndrome have 47 chromosomes rather than 46.

The Scientific Method

• The scientific method is a standard process used to validate or invalidate hypotheses.
• A typical approach involves making observations, formulating hypotheses, designing experiments, analyzing results, and drawing conclusions.