LECTURE 3: GENE SEGREGATION AND INTERACTION

gene

It is the inherited factor on the chromosome responsible for a trait

locus

It is the location of a gene on a chromosome

Genotype

It is the genetic constitution of an individual

Allele

Ex. Gene for a flower color

• Allele for purple color

• Allele for white color

It is the alternative forms of a gene

Allele

One type could be coding for purple while another codes for white, these are called alternative forms of a gene.

Gene pair

It is a pair of alleles (for diploid) of the same gene each allele is carried by homologous chromosomes

Phenotype

Discernible or observable trait or characteristic of an organism

Phenotype

Physical, physiological, biochemical, and behavioral traits of an individual

Phenotype

Determined by its genotypes and its interaction with the environment

Phenotype

_________ = genotype + environment

Dominant

• Ex. Gene for seed color, in a heterozygous genotype Yy

  • Yellow (Y) is dominant

  •  Green (y) is recessive

A type of allele exerting full effect despite the presence of another allele of the same gene

Recessive

• Ex. Gene for seed color, in a heterozygous genotype Yy

  • Yellow (Y) is dominant

  •  Green (y) is recessive

A type of allele not expressed in the presence of another allele (dominant) of the same gene

Homozygous

Two copies of the same allele of a gene (e.g., YY, yy)

Heterozygous

Two different alleles of the same gene (e.g., Yy)

• One allele comes from the mother while the other comes fro the father

An allele coding for a characteristic may belong to the same loci on homologous chromosomes but they do not necessarily code for the same type of the characteristic

locus

Alleles of the same gene occupy the same ___________ on the chromosome

Hybridization

It is the cross between two individuals with contrasting traits

The generation is produced after mating between parents that are pure-breeding/homozygous for different alleles

What is the F1 or first filial generation?

The generation produced by self fertilization or sib-mating of F1 individuals

What is the F2 or second filial generation?

Backcrossing

Cross of a heterozygote with one of its parents

selfing or self-fertilization

It is the union of male and female sex cells produced by the same organism

Heredity

It is the sum of all biological processes by which particular characteristics are transmitted from parents to their offspring.

true-breeding

plants that are “___________,” are self-pollinating, and will produce offspring identical to themselves.

• He emasculated the female parent to prevent selfing

• Then acted as the polinator by brushing the polen from the white flower and placing it on the purple flower

  

• from this it can be interpreted that:

  • 

  

Explain Mendels experiment and the interpreted results

What is the genotypic and phenotypic ratio of a monohybrid cross and why? Explain each generation.

• Complete dominance

  • One

  • Same

• Complete dominance

  • How many dominant allele/s is enough to express the dominant trait?

  • Homozygous dominant and heterozygous have the _____ phenotype

When an organism makes gametes, each gamete receives just one gene copy, which is selected randomly.

What is the Law of Segregation?

one dominant is to one heterozygous

Given this cross, predict the progeny of this cross

one heterozygous is to one recessive

Given this cross, predict the progeny of this cross

Mendel's law of independent assortment states that genes do not influence each other with regard to the sorting of alleles into gametes; every possible combination of alleles for every gene is equally likely to occur.

What is the Law of independent assortment?

Dihybrid Cross

This combination of gametes consider two traits at the same time

Based on the dihybrid cross:

State what the genotypic and phenotypic ratios are, specifically each genotype and the corresponding phenotype.

Note: do not yet simplify or combined the ratios.

Given this dihybrid cross determine the final ratio using the branching method.

1. Chromosomes exist in pairs

   Mendelian factors exist in pairs

• Maternal and paternal origin

2. Homologous chromosomes separate at anaphase I.

   Mendelian factors separate at anaphase l.

3. Fertilization restores the diploid chromosome number.

   Alleles of a gene also pair up.

What are the 3 Correlations between Chromosomes and Mendelian Factors

1. Chromosomes exist in _________

   Mendelian factors exist in ________

• Maternal and paternal origin

2. Homologous chromosomes ___________ at __________.

   Mendelian factors ___________ at _____________.

3. Fertilization restores the ________ _________ _______.

   ________ of a gene also pair up.

Mendel’s principles

• Discoveries before the chromosomal theory of inheritance (before 1903)

  • 1865 ________________

Friedrich Miescher

• Discoveries before the chromosomal theory of inheritance (before 1903)

  • 1871 _________________

    • Isolated nuclein from nuclei of pus cells
      

O. Hertwig

• Discoveries before the chromosomal theory of inheritance (before 1903)

  • 1875 _____________

    • Discovered the nucleus required in cell division and fertilization

• E. Strassburger and Walter Fleming

• Discoveries before the chromosomal theory of inheritance (before 1903)

  • 1882-1885 ________ and ___________

    • Discovered that the chromosomes are in the nucleus

• Hugo de Vries, Carl Correns, Erich von Tschermak

• Discoveries before the chromosomal theory of inheritance (before 1903)

  • 1900 _____________, _______________, and _______________

    • confirmed Mendel's principles in plants

• William Bateson, E. Rebecca Saunders, Lucien Cuenot

• Discoveries before the chromosomal theory of inheritance (before 1903)

  • 1902 _________. ___________, _________

    • confirmed Mendel's principles in animals

• Walter Sutton and Theodor Boveri

• Discoveries before the chromosomal theory of inheritance (before 1903)

  • 1903 ____________and _______________

    • Chromosome Theory Inheritance

• Walter Sutton and Theodor Boveri

• Discoveries before the chromosomal theory of inheritance (before 1903)

  • 1903 ____________and _______________

    • Resemblance between Mendelian factors and chromosomes

Parental (P) Generation

The generation which is pure-breeding/homozygous for a trait

monohybrid cross

It is a cross between homozygous individuals that are different from each other at one gene locus.

Dihybrid cross

It is a cross between homozygous individuals that differ in two traits/characteristics

Independent Events

Events that can occur at the same time

e.g. Getting a progeny with green and wrinkled seeds from rrYy × RrYy

Use of product rule

hint: use of “and” in the question

Mutually Exclusive Events

Events that cannot happen at the same time

e.g. Getting a green seed-producing progeny with round and wrinkled seeds from RrYy × RrYy

Use of sum rule

Hint: use of “or” in the question

Conditional Probability

Probability of an event occurring in the light of another event

What is the formula for a conditional probability and the meaning of each variable?

Binomial Probability

Used when the number of offspring is indicated in the problem

What is the formula for a binomial probability and the meaning of each variable?

Allelic interactions

They result when alleles of a single gene pair interact with each other (A ↔ a).

• Complete dominance

• Incomplete dominance

• Codominance

• Overdominance

• Lethal genes

  • Dominant Lethal

  • Recessive Lethal

What are all the types of Allelic Interactions?

Complete Dominance

It is the allelic interaction described as:

type of gene interaction where the recessive allele is completely masked by the dominant allele

• Complete dominance

• Incomplete dominance

• Codominance

• Overdominance

• Lethal genes

  • Dominant Lethal

  • Recessive Lethal

Complete Dominance

It is the allelic interaction described as:

This interaction results in indistinguishable phenotypes between homozygous dominant and heterozygous genotypes.

• Complete dominance

• Incomplete dominance

• Codominance

• Overdominance

• Lethal genes

  • Dominant Lethal

  • Recessive Lethal

Complete Dominance

It is the allelic interaction described as:

This this type of allelic interaction AA and Aa plants look the same they both have purple flowers!

• Complete dominance

• Incomplete dominance

• Codominance

• Overdominance

• Lethal genes

  • Dominant Lethal

  • Recessive Lethal

Overdominance

It is the allelic interaction described as:

pattern observed when the heterozygotes exhibit superior phenotypes over homozygotes

• Complete dominance

• Incomplete dominance

• Codominance

• Overdominance

• Lethal genes

  • Dominant Lethal

  • Recessive Lethal

Overdominance

It is the allelic interaction described as:

• E.g. Corn cob size (L –long; l –short)

  • Parents: LL (long cob) × ll (short cob)

  • F1: 1 Ll (very long cob)

  • F2, GR: 1 LL: 2 Ll: 1 ll

  • F2, PR: 1 long: 2 very long: 1 short

• Complete dominance

• Incomplete dominance

• Codominance

• Overdominance

• Lethal genes

  • Dominant Lethal

  • Recessive Lethal

Heterosis/hybrid vigor

It is the term used to describe the superiority of the F1 over its parents in terms of yield or other characteristics.

Overdominance

It is the allelic interaction described as:

• Complete dominance

• Incomplete dominance

• Codominance

• Overdominance

• Lethal genes

  • Dominant Lethal

  • Recessive Lethal

Overdominance

It is the allelic interaction described as:

• Complete dominance

• Incomplete dominance

• Codominance

• Overdominance

• Lethal genes

  • Dominant Lethal

  • Recessive Lethal

Incomplete Dominance

It is the allelic interaction described as:

It is a pattern observed when neither allele is completely dominant, resulting in a blended phenotype in heterozygotes

• Complete dominance

• Incomplete dominance

• Codominance

• Overdominance

• Lethal genes

  • Dominant Lethal

  • Recessive Lethal

Incomplete Dominance

It is the allelic interaction described as:

For example,

Gene Notation:

R - red

r - white

• Complete dominance

• Incomplete dominance

• Codominance

• Overdominance

• Lethal genes

  • Dominant Lethal

  • Recessive Lethal

Incomplete Dominance

It is the allelic interaction described as:

• Complete dominance

• Incomplete dominance

• Codominance

• Overdominance

• Lethal genes

  • Dominant Lethal

  • Recessive Lethal

Codominance

It is the allelic interaction described as:

pattern observed when the alleles are expressed separately in the heterozygote

• Complete dominance

• Incomplete dominance

• Codominance

• Overdominance

• Lethal genes

  • Dominant Lethal

  • Recessive Lethal

Codominance

It is the allelic interaction described as:

• Complete dominance

• Incomplete dominance

• Codominance

• Overdominance

• Lethal genes

  • Dominant Lethal

  • Recessive Lethal

Codominance

It is the allelic interaction described as:

• Complete dominance

• Incomplete dominance

• Codominance

• Overdominance

• Lethal genes

  • Dominant Lethal

  • Recessive Lethal

Lethal Genes

It is the allelic interaction described as:

genes that can cause mortality in the receiving offspring

• Complete dominance

• Incomplete dominance

• Codominance

• Overdominance

• Lethal genes

  • Dominant Lethal

  • Recessive Lethal

Dominant Lethal Genes

It is the allelic interaction described as:

lethal in the presence of the dominant allele; AA and Aa individuals are affected and succumb to death

• Complete dominance

• Incomplete dominance

• Codominance

• Overdominance

• Lethal genes

  • Dominant Lethal

  • Recessive Lethal

Dominant Lethal Genes

It is the allelic interaction described as:

• Complete dominance

• Incomplete dominance

• Codominance

• Overdominance

• Lethal genes

  • Dominant Lethal

  • Recessive Lethal

Recessive Lethal Genes

It is the allelic interaction described as:

lethal in the presence of the recessive allele; aa individuals are affected

• Complete dominance

• Incomplete dominance

• Codominance

• Overdominance

• Lethal genes

  • Dominant Lethal

  • Recessive Lethal

Recessive Lethal Genes

It is the allelic interaction described as:

• Complete dominance

• Incomplete dominance

• Codominance

• Overdominance

• Lethal genes

  • Dominant Lethal

  • Recessive Lethal

Recessive Lethal Genes

It is the allelic interaction described as:

• Complete dominance

• Incomplete dominance

• Codominance

• Overdominance

• Lethal genes

  • Dominant Lethal

  • Recessive Lethal

Sickle cell anemia

Overdominance

Recessive Lethal Genes

Why is sickle cell anemia both an Overdominance and Recessive Lethal Genes allelic interaction?

Non-Allelic Interactions

involve interactions of two or more genes; alleles of a gene can affect the expression of alleles in a second gene

Non-Allelic Interactions

results to modified F2 phenotypic ratios of dihybrid crosses

Epistasis

It is the phenomena wherein an allele of a gene masks the effect of the allele of the other gene.

first gene is able to mask the phenotypic effect of the alleles of a second gene

Hypostatic gene

In epistasis it is the gene with its effect being masked

Epistatic gene

In epistasis it is the gene masking the effect of the hypostatic gene

• Dominant Epistasis Type I (12 : 3 : 1)

• Dominant Epistasis Type 2 (13 : 3)

• Recessive Epistasis (9 : 3 : 4)

• Duplicate Genes (Duplicate Dominant Epistasis) (15:1)

• Complementary Genes (Duplicate Recessive Epistasis) (9 : 7)

• Novel Phenotypes (9:3:3:1)

What are all the Non-Allelic Interactions?

• Dominant Epistasis Type I (12 : 3 : 1)

• Dominant Epistasis Type 2 (13 : 3)

• Recessive Epistasis (9 : 3 : 4)

• Duplicate Genes (Duplicate Dominant Epistasis) (15:1)

• Complementary Genes (Duplicate Recessive Epistasis) (9 : 7)

• Novel Phenotypes (9 : 3 : 3 : 1)

What are the respective ratios of all the Non-Allelic Interactions?

Dominant Epistasis Type 1

It is the Non-Allelic Interaction described as:

Dominant Epistasis Type I

Dominant Epistasis Type 2

Recessive Epistasis

Duplicate Genes (Duplicate Dominant Epistasis)

Complementary Genes (Duplicate Recessive Epistasis)

Novel Phenotypes

Dominant Epistasis Type 1

It is the Non-Allelic Interaction described as:

Dominant Epistasis Type I

Dominant Epistasis Type 2

Recessive Epistasis

Duplicate Genes (Duplicate Dominant Epistasis)

Complementary Genes (Duplicate Recessive Epistasis)

Novel Phenotypes

Dominant Epistasis Type 1

It is the Non-Allelic Interaction described as:

Dominant Epistasis Type I

Dominant Epistasis Type 2

Recessive Epistasis

Duplicate Genes (Duplicate Dominant Epistasis)

Complementary Genes (Duplicate Recessive Epistasis)

Novel Phenotypes

Dominant Epistasis Type 2

It is the Non-Allelic Interaction described as:

• Dominant allele at epistatic gene (B) mask the expression of the hypostatic gene (A/a)

• Only two phenotypes are possible.

Dominant Epistasis Type I

Dominant Epistasis Type 2

Recessive Epistasis

Duplicate Genes (Duplicate Dominant Epistasis)

Complementary Genes (Duplicate Recessive Epistasis)

Novel Phenotypes

Dominant Epistasis Type 2

It is the Non-Allelic Interaction described as:

Dominant Epistasis Type I

Dominant Epistasis Type 2

Recessive Epistasis

Duplicate Genes (Duplicate Dominant Epistasis)

Complementary Genes (Duplicate Recessive Epistasis)

Novel Phenotypes

Recessive Epistasis

It is the Non-Allelic Interaction described as:

Dominant Epistasis Type I

Dominant Epistasis Type 2

Recessive Epistasis

Duplicate Genes (Duplicate Dominant Epistasis)

Complementary Genes (Duplicate Recessive Epistasis)

Novel Phenotypes

Recessive Epistasis

It is the Non-Allelic Interaction described as:

Dominant Epistasis Type I

Dominant Epistasis Type 2

Recessive Epistasis

Duplicate Genes (Duplicate Dominant Epistasis)

Complementary Genes (Duplicate Recessive Epistasis)

Novel Phenotypes

Duplicate Genes

It is the Non-Allelic Interaction described as:

Dominant Epistasis Type I

Dominant Epistasis Type 2

Recessive Epistasis

Duplicate Genes (Duplicate Dominant Epistasis)

Complementary Genes (Duplicate Recessive Epistasis)

Novel Phenotypes

Duplicate Genes

It is the Non-Allelic Interaction described as:

Dominant Epistasis Type I

Dominant Epistasis Type 2

Recessive Epistasis

Duplicate Genes (Duplicate Dominant Epistasis)

Complementary Genes (Duplicate Recessive Epistasis)

Novel Phenotypes

Complementary Genes

It is the Non-Allelic Interaction described as:

Duplicate recessive epistasis

Dominant Epistasis Type I

Dominant Epistasis Type 2

Recessive Epistasis

Duplicate Genes

Complementary Genes

Novel Phenotypes

Complementary Genes

It is the Non-Allelic Interaction described as:

A homozygous recessive genotype (aa or bb) at either gene will result in a masking of the other gene.

Dominant Epistasis Type I

Dominant Epistasis Type 2

Recessive Epistasis

Duplicate Genes (Duplicate Dominant Epistasis)

Complementary Genes (Duplicate Recessive Epistasis)

Novel Phenotypes

Complementary Genes

It is the Non-Allelic Interaction described as:

Dominant Epistasis Type I

Dominant Epistasis Type 2

Recessive Epistasis

Duplicate Genes (Duplicate Dominant Epistasis)

Complementary Genes (Duplicate Recessive Epistasis)

Novel Phenotypes

Novel Phenotypes

It is the Non-Allelic Interaction described as:

New phenotypes are produced in interactions of dominants and homozygous recessives.

A ↔ B; aa ↔ bb

Dominant Epistasis Type I

Dominant Epistasis Type 2

Recessive Epistasis

Duplicate Genes (Duplicate Dominant Epistasis)

Complementary Genes (Duplicate Recessive Epistasis)

Novel Phenotypes

Novel Phenotypes

It is the Non-Allelic Interaction described as:

Dominant Epistasis Type I

Dominant Epistasis Type 2

Recessive Epistasis

Duplicate Genes (Duplicate Dominant Epistasis)

Complementary Genes (Duplicate Recessive Epistasis)

Novel Phenotypes

Pseudoalleles

two genes located closely to each other on the same chromosome that behave like alleles

Phenotype is not only dependent on the genotype but also on the position of the genes on the chromosome

What is the Lewis Effect?