Chapter 1_Overview Of Genetics Flashcards
Define “genome”
The DNA found within all our chromosomes
DNA, the molecule of life, contains trillions of cells. Each cell contains:
- 46 chromosomes, found in 23 pairs
- 2 meters of DNA
- Approximately 3 billion DNA base pairs per set of chromosomes, containing the bases A, T, G, and C
- Approx 20,000 to 25,000 genes coding for proteins that perform most life functions
What are some examples of controversial genetic technologies?
- DNA fingerprinting, a molecular method to identify an individual based on a DNA sample
- Mammalian cloning, which could allow for homogeneous herds
- Modifying traits in animals and plants
Define “Genetics”
- The branch of biology that deals with heredity and variation
- It stands as the unifying discipline in biology by allowing us to understand how life can exist at all levels of complexity
Define “genes”
- At the molecular level, a gene is a segment of DNA that produces a functional product
What is the functional product of most genes?
Polypeptide, a linear sequence of amino acids that folds into units that constitute proteins
What is another name for genes?
They are commonly described as traits, which are characteristics of an organism (eye color, hair texture, and height)
The chemical properties of organic molecules are essential for cell vitality in two key ways:
- The breaking of chemical bonds during the degradation of small molecules provides energy to drive cellular processes
- A second imporant function is their role as the bulding blocks for the synthesis of larger molecules
Four important categories of larger cellular molecules. Three of them form what?
- Nucleic acids (i.e., DNA and RNA)
- Proteins
- Carbohydrates
- Lipids
- The first three form macromolecules that are composed of many repeating units of smaller building blocks
What is the largest macromolecule in living cells?
DNA. A single DNA molecule can be composed of a linear sequence of hundreds of millions of nucleotides!
The formation of cellular structures relies on…
…the interactions of molecules and macromolecules
The characteristics of a cell depend on…
…the types of proteins that it makes
What is a proteome?
- All of the proteins that a cell makes at a given time
- Proteins are the workhorses of all living cells
What are some of the functions of proteins?
- Some proteins help determine the shape and structure of a given cell
- Others are inserted into cell membranes and aid in the transport of ions and small molecules across the membrane
- They also function as biological motors
- Within multicellular organisms, certain proteins also function in cell to cell recognition and signaling
Define “Enzymes”
Accelerate chemical reactions. They are a particularly important category of proteins.
Catabolic vs. Anabolic Enzymes
- Catabolic enzymes breakdown molecules or macromolecules into smaller units
- Anabolic enzymes (and accessory proteins) function in the synthesis of molecules and macromolecules throughout the cell
Define “DNA”
- (Deoxyribonucleic Acid) is what the genetic material of living organisms is made of. It stores the info needed for the synthesis of all cellular proteins.
- Basically, the main function of the genetic blueprint is to code for the production of cellular proteins in the correct cell, at the proper time, in suitable amounts
DNA is composed of…
…a linear sequence of nucleotides. Each nucleotides contains one of four nitrogen containing bases: adenine (A), thymine (T), cytosine (C), or guanine (G)
Explain how the genetic code works.
- In the code, a 3 base sequence specifies one particular amino acid among the 20 possible chocies
- One or more polypeptides form a functional protein
Define “Gene Expression”
The process of using a gene sequence to affect the characteristics of cells and organisms
Transcription
The DNA sequence within a gene is copied into a nucleotide sequence of ribonucleic acid (RNA)
Messenger RNA (mRNA)
- Contain the information for the synthesis of a particular polypeptide.
- Most genes encode RNAs that contain the information for the synthesis of a particular polypeptide
For polypeptide synthesis to occur…
…the sequence of nucleotides transcribed in an mRNA must be translated (using the genetic code) into the amino acid sequence of a polypeptide.
Does a protein structure affect its function?
The distinctive structure of each protein determines its function within a living cell or organism
Morphological traits
Affect the appearance of an organism (color, height)
Physiological traits
Affect the ability of an organism to function (the rate at which a bacterium metabolizes a sugar). Like morphological traits, physiological traits are controlled, in part, by the expression of genes.
Behavioral traits
Affect the ways that an organism responds to its environment (mating calls). In animals, the nervous system plays a key role in governing such traits.
What are the four levels of biological organization?
- Molecules
- Cells
- Organisms
- Populations
Molecular level
- Genes are expressed at the molecular level.
- Gene transcription and translation lead to the production of a particular protein, which is a molecular process.
Cellular level
- Proteins often function at the cellular level.
- The function of a protein within a cell affects the structure and workings of that cell.
Organism level
- An organism’s traits are determined by the characteristics of its cells.
- The trait of red flower color is an observation at the organism level.
- The trait is rooted in the molecular characteristics of the organism’s cells.
Species
A group of organisms that maintains a distinctive set of attributes in nature.
Population level
- The occurrence of a trait within a species is an observation at the population level.
Genetic variation
The differences in inherited traits among individuals within a population.
Morphs
Contrasting forms within a single species.
Give three ways genetic variation can occur.
- Gene mutations, small or large differences can occur within gene sequences. They result in genetic variation in which a gene is found in two or more alleles. In many cases, gene mutations alter the expression or function of the protein that the gene specifies.
- Major alterations can also occur in the structure of a chromosome. A large segment of a chromosome can be lost, rearranged, or reattached to another chromosome.
- Variation may also occur in the total number of chromosomes. In some cases, an organism may inherit one too many or one too few chromosomes. In other cases, it may inherit an extra set of chromosomes.
What does an environment affect?
It can affect morphological and physiological features.
Norm of reaction
The effects of environmental variation on an individual’s traits.
phenylketonuria (PKU)
- phenylalanine hydroxylase is an enzyme coded by a specific gene. Most people have two functional copies of this gene.
- A rare variation results in a nonfunctional version of this protein.
- These people can’t break down the amino acid phenylaline.
Somatic cells
Cells not directly involved in sexual reproduction. They contain 46 chromosomes.
Gametes
Sperm and egg cells, contain half the number of somatic cell’s chromosomes and are haploid.
Model organisms
Organisms studied by man different researchers so they can compare their results and determine scientific principles that apply more broadly to other species.
The study of genetics has been traditionally divided into three areas
Transmission, molecular, and population genetics
Transmission genetics
- The relationship between the transmission of genes from parent to offspring and the outcome of the offspring’s traits.
Where did transmission genetics begin?
With Gregor Mendel. IN particular, he orginiated the idea that factors, which we now call genes, are passed as discrete units from parents to offspring via sperm and egg cells.
What is the goal of molecular genetics?
To understand how the genetic material works at the molecular level.
Genetic approach
Study mutant genes that have abnormal function.
Loss of function mutation
Gene mutations that eliminate the function of a gene. The resulting gene is called a loss of function allele.
Population genetics
Concerned with genetic variation and its role in evolution
Hypothesis testing
(Scientific method) Scientists follow a series of steps to reach verifiable conclusions about the world.
Discovery based science
The collection and analysis of data without the need for a preconceived hypothesis.