Chapter 1: Mendel's Principles of Heredity

Define Gene

the basic unit of biological information; a DNA sequence that encodes an RNA. What we inherit.

Do all RNA’s make proteins?

No

Do we (humans) share the same genes?

Yes, but we have different versions of said genes. (alleles)

Define Allele

alternate form of a gene. example = eye color

Define Heredity

Parental transmission of physiological (ATP), anatomical, and behavioral traits (inherited genes determine individual traits). Alleles → Traits

Define Genetics

Study of biological structures and mechanisms that determine inheritance

Who was Johann Gregor Mendel (1822-1884)

An Augustinian monk (Brno, Moravia (Czech Republic)); expert plant breeder with a background in farming who wanted to teach.

What did Gregor Mendel study

studied the inheritance of alternative traits in pea plants

Who was the first to determine the basic laws of genetics

Gregor Mendel

What were the 4 big findings from Mendel’s Work

1 - Trait variation is widespread in nature (genetic diversity)

2 - Variation is essential for following genes across generations

3 - Variation is inherited in patterns (Mendel’s Principles)

4 - Mendel’s Principles apply to all sexually reproducing organisms

What was the model used in Mendel’s experiment

Pisum sativum, a self-fertilizing, pea producing abundant offspring plant

How did Mendel create 7 pairs of true-breeding (inbred) lines

Snipped off the anthers so plants couldn’t self-fertilize

Mendel’s mating’s were ___ and followed ____

controlled, inheritance of discrete alternative

Mendel used what kind of crosses to show parental contributions

reciprocal crosses

male expressing trait of interest crossed with female not expressing trait of interest and vice versa

if crosses were different then sex matters, if crosses were same then sex doesn’t matter

What 7 traits did Mendel experiment on and analyze

1 - seed color

2 - seed shape

3 - flower color

4 - pod color (unripe)

5 - pod shape (ripe)

6 - stem length

7 - flower position

The stigma is the male/female portion of the flower and the anther is the male/female portion of the flower

female, male

every seed = an ___

individual

In science, a larger n means that test results are more ___

confident

Crosses between ___ traits produces hybrids

antagonistic

this kind of cross results in offspring looking JUST like ONE of the parents

There is __ gene for flower color, but __ alleles for specific color

one, different

ex - purple and white allele

Is yellow or green the dominant seed color

Yellow

Is round or wrinkled the dominant seed shape

Round

Is purple or white the dominant flower color

Purple

Is green or yellow the dominant pod color (unripe)

Green

Is round or pinched the dominant pod shape (ripe)

Round

Is long or short the dominant stem length?

Long

Is along stem or at tip of stem (apical) the dominant flower position

Along the stem

Define Genotype

an individual’s set of alleles

Define Phenotype

physical appearance, manifestation of a trait

Define Homozygote

An individual possessing 2 identical alleles for a given gene

Define Heterozygote

An individual possessing 2 alternate alleles for a given gene

Define monohybrid cross

reciprocal crosses between true breeders with alternate phenotypes

What is the P1 generation

Parental, true breeders

What is the F1 generation

First Filial, heterozygote, express dominant phenotype with no bleeding of recessive

What is the F2 generation

Second Filial, recessive forms reappear at a 3:1 ratio (aka Mendelian Ratio)

“3x more yellow than green seeds”

“75% seeds are yellow (dominant)”

What is the Mendelian Ratio for a monohybrid cross

3 : 1

dominant : recessive

What is Mendel’s first principle?

Mendel’s Law of Segregation

What is Mendel’s Law of Segregation

“The two alleles for each trait segregate during gamete formation (meiosis), and then unite at random (recombination?), one from each parent, at fertilization (zygote formation).”

Who created the Punnett square and in what year?

Reginald Punnett, 1906

What is the purpose of a Punnett square

a visualization of segregation and random union of alleles, shows phenotypic and genotypic ratios. Shows all possible outcomes of a cross, probabilities.

YY and yy will breed ___

true

Yy will breed with what ratios

3:1 phenotypic

1:2:1 genotypic

What are the two basic rules of probability?

Product rule and sum rule

Define the Product Rule

the probability of 2 or more independent events occurring together is the product of their individual probabilities.

P(event 1 and event 2) = P(event 1) x P(event 2)

“and”

Define the Sum Rule

the probability of either of 2 (or more) mutually exclusive events occurring is the sum of their individual probabilities.

P(event 1 or event 2) = P(event 1) + P(event 2)

“or”

What is the multinomial expansion equation

n!

P = ——— p^s q^t r^u

s! t! u!

Define a Dihybrid cross

a cross of two individuals looking at 2 different genes

What does a dihybrid cross produce

Parental and Recombinant types

What is Mendel’s 2nd principle

Law of Independent Assortment

Define Mendel’s Law of Independent Assortment

During gamete formation, different pairs of alleles segregate independently of each other.

(independent events)

What type of individual has the only known genotype

Homozygous Recessive

What is a Testcross

backcrosses between recessive homozygote and individual of unknown genotype. (A__, A__ B__)

What is the purpose of a Testcross

Outcomes allow genotypic determination

Mendel’s laws predict _____, not specific _____

probabilities, outcomes

What were Mendel’s Conclusions and Legacy

• presented and published “Experiments in Plant Hybrids” (1865) Natural Science Society of Brno

• inferred existence of genes and alleles

• explained reappearance of hidden traits

• disproved blended inheritance

• deduced the basic principles of inheritance

• linked inheritance to cell function (gametes)

• results were not appreciated and largely dismissed

In what year was Mendel’s work rediscovered and by whom

1900, Correns, de Vries, and Tschermak

Who created the science of genetics after Mendel

Bateson: termed genetics, zygote, homozygote, heterozygote, allele, P and F generations

Describe Mendelian Inheritance in Humans

• most traits involve interactions of multiple genes

• single gene traits are often disabling / life-threatening, (4300 known, typically recessive)

• Challenges included: long generation time, small # of offspring, random mating, no pure-breeding lines, no true F2 generation (mating between siblings)

• Analyzed human inheritance by using large numbers of families or several generations of large families

What are some common single gene traits in humans

Recessive: Thalassemia, Sicke-cell, Cystic Fibrosis, Tay-Sachs disease, PKU

Dominant: Hypercholesterolemia, Huntington disease

Define Pedigree

orderly diagram of a family’s relevant genetic features; often 2-3 generations

What can a pedigree be used to determine

the probability can be used to determine the mode of inheritance

Explain Huntington Disease

late onset dominant trait; involuntary, uncoordinated movement, personality change, gradual intellectual decline

Define Vertical Inheritance

affected individuals can be seen in every generation, an affected individual has an affected parent. Dominant traits, common alleles.

Explain Cystic Fibrosis

Cl- transport deficiency; 12 million American carriers (10% survive into their 30s). Prevents the trapping of pathogens

Define Horizontal Inheritance

Rare alleles, recessive trait. Offspring from two unaffected parents will be affected.

With recessive traits, unaffected individuals can have affected individuals, what is the term for this

Carriers

What is consanguineous mating and what does it do

mating between close relatives, it concentrates recessive alleles

What are examples of functional alleles in pisum sativum

stay green enzyme (green seed color) and starch branching enzyme 1 (round seed)