Chapter 2: Mendelian Inheritance

theory of pangenesis

“seeds” are produced by all parts of the body and then collected and transmitted to the offspring at the time of conception

Hippocrates, seeds, all, offspring, first

theory of pangenesis:

* explanation for hereditary traits by Greek physician, _____
* “_____” are produced by _____ parts of the body and then collected and transmitted to the _____ at the time of conception
* _____ attempt to explain the transmission of hereditary traits from generation to generation

theory of preformationism

a “homunculus” unfolds and grows to adult proportions with proper nourishment

homunculus

diminutive fully formed human body, historically believed to inhabit a germ cell (an egg or a sperm) and to have the capacity to increase in size, giving rise to an adult human

homunculus, spermists, ovists

theory of preformationism:

* a “_____” unfolds and grows to adult proportions with proper nourishment
* _____ and _____

blending hypothesis of inheritance

traits can blend together generation after generation

intermediate, blend

theory of blending:

* first systematic studies of genetic crosses were carried out by German botanist Joseph Kolreuter from 1761 to 1766
* in cross between different strains of tobacco plants, he found that the offspring were usually _____ in appearance between two parents
* this observation led Kolreuter to conclude that both parents make equal genetic contribution to their offspring
* blending hypothesis of inheritance: the factors that dictate hereditary traits could _____ together from generation to generation

Gregor Mendel

“father of genetics”

Pisum sativum, varieties, crosses, hybridization

Mendel’s pea plants:

* garden pea: _____ _____


1. the species was available in several _____, which varies in height and in the appearance of their flowers, seeds, and pods
2. Structure of the plant allowed for easy and well controlled _____
* “Experiments on Plant Hybrid” 1866
* _____: mating/crossing between individuals that have different characteristics

cross/hybridization

* a breeding between two distant individuals. An analysis of their offspring may be conducted to understand how traits are passed from parent to offspring.
* the breeding of two organisms of the same species with different characteristics

gamete

a reproductive cell (usually haploid) that can unite with another reproductive cell to create a zygote

sperm cell

* a male gamete
* are small and usually travel relatively far distances to reach the female gamete

pollen grain

the male gametophyte of flowering plants

anther

the structure in flowering plants in which pollen grains form

sperm cells, pollen grains, anthers

_____ _____ are produced within _____ _____ that form in the _____

egg cell

* a female gamete
* is usually very large and nonmotile

ovule

the structure in flowering plants where the female gametophyte is produced

ovary

in plants, the structure in which the ovules develop

egg cells, ovules, ovaries

_____ _____ are produced within _____ that form in the _____

stigma

the structure in flowering plants on which the pollen grain lands, stimulating the growth of the pollen tube so that sperm cells can reach the egg cells

self-fertilization

fertilization that involves the union of male and female gametes derived from the same parent

cross-fertilization

a cross in which the male and female gametes come from separate individuals

anthers, pollen, pollen, stigma, anthers

How Mendel cross-fertilized pea plants:

* Mendel was able to pry open immature flowers and remove the _____ before they produced pollen
* therefore, these flowers could not self-fertilize
* he then obtained _____ from another plant by gently touching its mature anthers with a paintbrush
* Mendel applied this _____ to the _____ of the flower that already had its _____ removed

character

in genetics, a general characteristic such as eye color

trait/variant

characteristics of an organism; also specific properties of a character, such as tall and dwarf pea plants

true-breeding line

strain of a particular species that continues to produce the same trait after several generations of self-fertilization (in plants) or inbreeding

single-factor cross

a cross in which an experimenter is following the outcome of only a single character

monohybrid

a individual produced from a single-factor cross in which the parents had different variants for a single character

2 variants, 1 trait

monohybrid cross

* crossing _____ _____ of _____ _____

parental generation

in a genetic cross, the first generation in the experiment. In Mendel’s studies, the parental generation was true-breeding with regard to particular traits

first, true-breeding, homozygous

parental generation:

* _____ generation in the experiment
* in Mendel’s studies, the parental generation was _____ with regard to particular traits (_____)

F1 generation

the offspring produced from a cross of a parental generation

F2 generation

the offspring produced from a cross or self-fertilization of the F1 generation

dominant

describes an allele that determines the phenotype in the heterozygous condition

recessive

a trait or gene that is masked by the presence of a dominant trait or gene

particulate theory of inheritance

a theory proposed by Mendel. It states that traits are inherited as discrete units that remain unchanged as they are passed from parent to offspring.

two, two, identical, different, dominant, recessive, randomly

particulate theory of inheritance:

* _____ discrete hereditary factors - one from each parent
* the _____ factors can be _____ or _____
* one factor is _____ (seen) and the other is _____ (not seen)
* paired factors segregate _____
* Mendel’s Law of Segregation

gene

a unit of heredity that may influence the outcome of a trait in an organism. At the molecular level, a gene is a segment of DNA that contains the information to make a functional product, either RNA or a polypeptide.

allele

an alternative form of a specific gene

Mendel’s law of segregation

the two copies of a gene segregate (or separate) from each other during transmission from parent to offspring

homozygous

describes a diploid individual that has two identical alleles of a particular gene

heterozygous

describes a diploid individual that has different versions (i.e., two different alleles) of the same gene

genotype

the genetic composition of an individual, especially in terms of the alleles for particular genes

phenotype

the observable traits of an organism

Punnett square

a diagrammatic method in which the gametes that two parents can produce are aligned next to a square grid as a way to predict the types of offspring the parents will produce and in what proportions

two-factor cross

a cross in which an experimenter follows the outcome of two different characters

2 variants, 2 traits

dihybrid cross:

* crossing plants with _____ _____ of _____ _____

traits linked, traits independent

two possible results from a two-factor cross

traits linked

the two genes always stay associated with each other

traits independent

the two different genes randomly segregate into haploid cells

RrYy, RY, ry

trait linked:

* P generation seeds: RRYY x rryy
* F1 generation seeds: _____
* Haploid gametes: 1/2 _____, 1/2 _____

RrYr, RY, Ry, rY, ry

traits independent:

* P generation seeds: RRYY x rryy
* F1 generation seeds: _____
* Haploid gametes: 1/4 _____, 1/4 _____, 1/4 _____, 1/4 _____

2, 2, 3/4, 1/4, parental phenotypes

traits linked:

* Punnett square will be _____ x _____
* offspring:
* _____ round yellow
* _____ wrinkled green
* _____ _____: all phenotypes are similar to the parents

4, 4, 9/16, 3/16, 3/16, 1/16, non parental phenotypes

traits independent:

* Punnett square will be _____ x _____
* offspring:
* _____ round yellow
* _____ round green
* _____ wrinkled yellow
* _____ wrinkled green
* _____ _____: see phenotypes different from the parents

Mendel’s law of independent assortment

two different genes will randomly assort their alleles during gamete formation

segregation

monohybrid cross → principle of _____

independent assortment

dihybrid cross → principle of _____

pedigrees

charts representing family relationships

female

\

male

deceased individual

unaffected individual

affected individual

heterozygote

25%, 100%, skipping generation

autosomal recessive patten:

* 2 normal heterozygous individuals → _____ recessive offspring
* 2 affected individuals (homozygous recessive) -> _____ recessive offspring
* _____ _____

one

dominant pattern:

* affected individuals will inherit gene from _____ affected parent

males

sex linked:

* affects on sex more often than the other
* more common in _____

probability

the chance that an outcome will occur in the future

chance, size, large, small

probability:

* the _____ that an outcome will occur in the future
* the accuracy of the prediction depends to a great extent on the _____ of the sample
* random sampling error:
* _____ for small sample sizes
* _____ for large sample sizes

sum rule

the probability that one of two or more mutually exclusive events will occur is equal to the sum of the individual probabilities of the events

product rule

the probability that two or more independent events will occur is equal to the product of their individual probabilities

binomial expansion

represents all of the possibilities for a given set of unordered events

chi square test

a commonly used statistical method for determining the goodness of fit