Exam 1 Flashcards
science
a way of knowing - an approach to understanding the natural world
inquiry
at the heart of science; a search for information and explanations of natural phenomena
data
recorded observations; items of information on which scientific inquiry is based
inductive reasoning
makes broad generalizations from specific observations
ex: the generalization “all organisms are made of cells” was based on two centuries of microscopic observations made by biologists examining cells in diverse biological specimens
deductive reasoning
from general premises, we extrapolate to the specific results we should expect if the premises are true
ex: in the scientific process, deductions usually take the form of predictions of results that will be found if a particular hypothesis is correct
hypothesis
an explanation, based on observations and assumptions that leads to a testable prediction
experiment
a scientific test, often carried out under controlled conditions
independent variable
changed by scientist, manipulated variable
dependent variable
measured by scientist
control variable
unmanipulated group, constants
character
a heritable feature that varies among individuals; ex flower color
trait
each variant for a character; ex purple flowers or white flowers
true-breeding
kind of breeding wherein the parents would produce offspring that would carry the same phenotype, parents are homozygous for every trait
hybridization
the crossing of two true-breeding varieties
parental generation (P generation)
refers to the first set of parents crossed
first filial generation (F1 generation)
offspring of the P generation
second filial generation (F2 generation)
offspring of the F1 generation
alleles
are one or two or more alternative forms of a gene; ex P is the purple allele and p is the white allele
dominant allele
determines organisms appearance, usually represented by a capital letter
recessive allele
type of allele which will not be expressed in an individual unless both of the individual’s copies of that gene have that particular genotype
Law of segregation
states that the two alleles for a heritable character segregate (separate from each other) during gamete formation and end up in different gametes
Punnett square
diagrammatic device for predicting allele composition of all offspring resulting from a cross between individuals of known genetic makeup
homozygote
an organism that has a pair of identical alleles for a gene encoding a character
homozygous
when an organism has identical alleles, they are homozygous for that gene
heterozygote
an organism that has two different alleles for a gene encoding a character
heterozygous
when an organism has two different alleles, they are heterozygous for that character
genotype
genetic makeup; ex Bb
phenotype
organism’s appearance or observable traits; ex flower color
testcross
using a punnett square to test a cross between an organism of unknown genotype with a recessive homozygote
monohybrid
an organism that is heterozygous for the single character being followed
monohybrid cross
a cross between two organisms with different variations at one genetic locus of interest
dihybrid
an organism that is heterozygous for the two characters that are being followed
dihybrid cross
a cross between two individuals who differ in two observed traits that are controlled by two distinct genes
Law of independent assortment
states that two or more genes assort independently - that is, each pair of alleles segregates independently of any pair during gamete formation; applies only to genes (allele pairs) located on different chromosomes or very far away on the same chromosome
pedigree
family tree describing the traits of parents and children across the generations
carriers
organisms who are phenotypically normal, but have the recessive allele for a trait and may transmit it to their offspring
sex-linked gene
a gene located on either sex chromosome
X-linked gene
genes on the X chromosome
zygote
fertilized egg cell, diploid cell
Drosophila
fruit fly
hemizygous
describes an individual who only has one member of a chromosome pair, often used to describe X-linked genes in males who only have one X chromosome
multiplication rule
states that to determine probability, multiply the probability of one event by the probability of the other event
addition rule
states that the probability that any one of two or more mutually exclusive events will occur is calculated by adding their individual probabilities
complete dominance
when a dominant allele takes complete control, meaning that the phenotypes of a heterozygote and a homozygote are indistinguishable
incomplete dominance
when neither allele is completely dominant and heterozygotes have a phenotype that is a mix of the two parental varieties
codominance
when the two alleles are both dominant and heterozygotes exhibit both phenotypes
Tay-Sachs disease
affects children, only homozygotes can have the disease and is codominant
pleiotropy
where one gene affects multiple traits
ex: sickle cell disease, flower color gene also determines seed coat color
epistasis
where one gene influences another gene
ex: coat color in labradors, where the gene for pigment (E) can influence whether or not the gene for coat color (B) is represented or not.
quantitative characters
vary in the population in gradients along a continuum
polygenetic inheritance
where many genes influence a single trait
ex: human height is controlled by around 180 genes
