BJU 6th Science Chapter 13

trait

Inherited physical characteristic: determined by both your genes and your environment.

gene

A small piece of the DNA strand found in the chromosomes that controls the traits of an organism.

chromosomes

Tight bundles of DNA; usually found in the nucleus of a cell.

DNA

a molecule containing the chemical code that tells the cells what to do; the abbreviation for deoxyribonucleic acid.

heredity

Passing of traits from parents to offspring.

inherited

Traits you receive from your parents.

double helix

The shape of DNA.

genetics

The study of how traits are inherited.

purebred

An organism that is the offspring of parents having the same genetic makeup.

P generation

The parent generation in Mendel's experiments.

hybrid

Produced by crossing parent (purebred) that have two different forms of the same gene.

dominant trait

The characteristic that shows up as the phenotype when an offspring has genes for both traits.

recessive trait

This characteristic is hidden when a dominant gene is present.

expressed gene

The gene that is always shown if present in a person's chromosomes.

phenotype

The physical appearance of an organism.

genotype

The arrangement of genes within an organism.

codominance

The expression of both genes instead of one being recessive while the other is dominant.

incomplete dominance

The blending of genes together, instead of one being dominant while the other is recessive.

Punnett square

A diagram used to show the probability of certain genetic traits for the offspring of any two parents.

pedigree

A chart that traces a particular trait through many generations using lines and symbols.

sex-linked traits

Traits that are usually passed from mothers to children but are usually visible only in sons as they are typically present on the X chromosome (boys only have one X).

sickle cell anemia

A genetic disorder that causes a person's blood cells to become hard and curved, like a farmer's sickle.

cystic fibrosis

A genetic disorder that causes thick mucus to clog the lungs and air passages; can also affect the digestive system.

Down syndrome

A genetic disorder usually caused by an extra chromosome; may cause developmental disabilities, learning disabilities, and hearing, vision, and heart problems.

genetic engineering

Changing a gene or moving some of one organism's genes into another organism. This can be helpful or cause harm so is often risky.

meiosis

A process of cell division in which cells divide a second time, producing reproductive cells with only half as many chromosomes as the parent cell.

mitosis

The step by step process of cell division that ensures that the two new cells formed will be genetically the same as the original cell.

A with T, C with G

Nucleotide base pairing in DNA between A, C, G, and T?

Rosalind Franklin

British scientist was the first person to photograph a DNA molecule.

James Watson and Francis Crick

Rosalind Franklin showed the DNA X-ray picture to these 2 men who discovered the actual shape of the DNA as a twisted spiral.

adenine

Base A in DNA that only fits with T

guanine

Base G in DNA that only fits with C

cytosine

Base C in DNA that only fits with G

thymine

Base T in DNA that only fits with A

sugar phosphate

This type of molecule forms the sides of the DNA ladder (need this and a base).

Gregor Mendel

The father of modern genetics; a monk and scientist who discovered how traits are passed on from generation to generation using pea plants.

23 pairs of chromosomes, 46 total

How many chromosomes come from each human parent? How many total?

Sample size

When doing an experiment and trying to make guesses about traits in a population, this needs to be a large number.

possible uses for DNA testing

help solve crimes, identify soldiers killed in action, identify twins, determine parents of children.