Unit 4 Genetics Ch. 11 Introduction to Genetics. The Work of Gregor Mendel Genetics - the scientific study of heredity Mendel is considered the “Father”

Unit 4 GeneticsUnit 4 Genetics

Ch. 11 Introduction to Genetics

Ch. 11 Introduction to Genetics

The Work of Gregor Mendel

The Work of Gregor Mendel

Genetics - the scientific study of heredity

Mendel is considered the “Father” of genetics

Genetics - the scientific study of heredity

Mendel is considered the “Father” of genetics

Gregor Mendel’s PeasGregor Mendel’s Peas

Mendel was an Austrian monk, that worked on pea plants

His experiments with pea plants laid the foundation of the science of genetics

Mendel was an Austrian monk, that worked on pea plants

His experiments with pea plants laid the foundation of the science of genetics


Fertilization - when male & female sex cells join together

Pea flowers are normally self-pollinating, meaning the sperm cells in the pollen fertilize the egg cells in the same flower

Fertilization - when male & female sex cells join together

Pea flowers are normally self-pollinating, meaning the sperm cells in the pollen fertilize the egg cells in the same flower


Seeds produced by self-pollination inherit all of their characteristics from the single plant that bore them

True-breeding - if plants were allowed to self-pollinate, they would produce offspring identical to themselves

Seeds produced by self-pollination inherit all of their characteristics from the single plant that bore them

True-breeding - if plants were allowed to self-pollinate, they would produce offspring identical to themselves


Mendel wanted to produce seeds by joining male & female sex cells from 2 different plants

He cut off the pollen (male) parts of a plant, & dusted pollen from another plant onto the flower (female)

Mendel wanted to produce seeds by joining male & female sex cells from 2 different plants

He cut off the pollen (male) parts of a plant, & dusted pollen from another plant onto the flower (female)


Cross-pollination - produces seeds that had 2 different parent plants

Cross-pollination - produces seeds that had 2 different parent plants

Genes & DominanceGenes & Dominance

P - parent generationF1 - First generation (first generation of offspring)

F2 - Second generation (offspring from the F1 generation)

P - parent generationF1 - First generation (first generation of offspring)

F2 - Second generation (offspring from the F1 generation)


Trait - a specific characteristicEx.) seed color, plant height

Hybrids - offspring of crosses between parents with different traitsEx.) cross between plant with yellow seed color & plant with green seed color

Trait - a specific characteristicEx.) seed color, plant height

Hybrids - offspring of crosses between parents with different traitsEx.) cross between plant with yellow seed color & plant with green seed color


Mendel concluded that biological inheritance is determined by factors that are passed from 1 generation to the next

Genes - chemical factors that determine traits

Mendel concluded that biological inheritance is determined by factors that are passed from 1 generation to the next

Genes - chemical factors that determine traits


Alleles - different forms of a geneEx.) gene for plant height occurs in 1 form that produces tall plants & in another form that produces short plants

Mendel’s 2nd conclusion is the principle of dominance

Alleles - different forms of a geneEx.) gene for plant height occurs in 1 form that produces tall plants & in another form that produces short plants

Mendel’s 2nd conclusion is the principle of dominance


The principle of dominance states that some alleles are dominant & others are recessive

Dominant allele for a trait will always be exhibited (expressed or shown)

Recessive allele will only be expressed when a dominant allele is not present

The principle of dominance states that some alleles are dominant & others are recessive

Dominant allele for a trait will always be exhibited (expressed or shown)

Recessive allele will only be expressed when a dominant allele is not present

Mendel’s Seven F1 Crosses on Pea PlantsMendel’s Seven F1

Crosses on Pea Plants

SegregationSegregation

Gametes - sex cells (sperm or egg)

Segregation - during gamete formation, alleles segregate (separate) from each other so each gamete only carries a single copy of each gene

Gametes - sex cells (sperm or egg)

Segregation - during gamete formation, alleles segregate (separate) from each other so each gamete only carries a single copy of each gene

SegregationSegregation

Therefore, each F1 plant produces 2 types of gametes, those with the allele for tallness & those with the allele for shortness

Therefore, each F1 plant produces 2 types of gametes, those with the allele for tallness & those with the allele for shortness

Punnett SquaresPunnett Squares

Punnett square - a diagram that might result from a genetic cross

Punnett squares can be used to predict & compare the genetic variations that will result from a cross

Punnett square - a diagram that might result from a genetic cross

Punnett squares can be used to predict & compare the genetic variations that will result from a cross


Homozygous - organisms that have 2 identical alleles for a particular traitEx.) TT or tt

Heterozygous - organism that has 2 different alleles

for the same traitEx.) Tt

Homozygous - organisms that have 2 identical alleles for a particular traitEx.) TT or tt

Heterozygous - organism that has 2 different alleles

for the same traitEx.) Tt


Phenotype - physical characteristicsEx.) Tall plants

Genotype - genetic makeupEx.) TT

Phenotype - physical characteristicsEx.) Tall plants

Genotype - genetic makeupEx.) TT

Independent AssortmentIndependent Assortment

Independent assortment - genes for different traits can segregate (separate) independently during gamete formation

Independent assortment increases genetic variation (genetic diversity, helps create genetically different organisms)

Independent assortment - genes for different traits can segregate (separate) independently during gamete formation

Independent assortment increases genetic variation (genetic diversity, helps create genetically different organisms)

A Summary of Mendel’s Principles


1. The inheritance of biological characteristics is determined by individual units - genesGenes are passed from parents to their offspring

1. The inheritance of biological characteristics is determined by individual units - genesGenes are passed from parents to their offspring



2. In cases where 2 or more forms (alleles) of the gene for a single trait exist, some forms of the gene may be dominant & others may be recessive

2. In cases where 2 or more forms (alleles) of the gene for a single trait exist, some forms of the gene may be dominant & others may be recessive



3. In most sexually producing organisms, each adult has 2 copies of each gene (1 from each parent)These genes are segregated (separated) from each other when gametes are formed

3. In most sexually producing organisms, each adult has 2 copies of each gene (1 from each parent)These genes are segregated (separated) from each other when gametes are formed



4. The alleles for different genes usually segregate (separate) independently of 1 another

4. The alleles for different genes usually segregate (separate) independently of 1 another

Beyond Dominant & Recessive AllelesBeyond Dominant & Recessive Alleles

Some alleles are neither dominant nor recessive, & many traits are controlled by multiple alleles or multiple genes

Some alleles are neither dominant nor recessive, & many traits are controlled by multiple alleles or multiple genes


Incomplete dominance - when 1 allele is not completely dominant over anotherThe heterozygous phenotype

is somewhere in between the 2 homozygous phenotypes

Incomplete dominance - when 1 allele is not completely dominant over anotherThe heterozygous phenotype

is somewhere in between the 2 homozygous phenotypes


Codominance - where both alleles contribute to the phenotypeFlowers would not be pink, (a blend of red & white), but both red & white speckled

Codominance - where both alleles contribute to the phenotypeFlowers would not be pink, (a blend of red & white), but both red & white speckled


Multiple alleles - when genes have more than 2 allelesIt does not mean that an individual can have more than 2 alleles

It only means that more than 2 possible alleles exist in a population

Multiple alleles - when genes have more than 2 allelesIt does not mean that an individual can have more than 2 alleles

It only means that more than 2 possible alleles exist in a population

Multiple AllelesMultiple Alleles


Polygenic traits - traits controlled by 2 or more genesEx.) at least 3 genes are responsible for making the reddish-brown pigment in the eyes of fruit flies

Polygenic traits - traits controlled by 2 or more genesEx.) at least 3 genes are responsible for making the reddish-brown pigment in the eyes of fruit flies

Genetics & the Environment


The characteristics of any organism are not determined solely by the genes it inherits

Characteristics are determined by interaction between genes & the environment

The characteristics of any organism are not determined solely by the genes it inherits

Characteristics are determined by interaction between genes & the environment



Ex.) genes may affect a sunflower plant’s height & the color of its flowers

However, these conditions are also influenced by climate, soil conditions, & the availability of water

Ex.) Rabbit fur color in winter & summer

Ex.) genes may affect a sunflower plant’s height & the color of its flowers

However, these conditions are also influenced by climate, soil conditions, & the availability of water

Ex.) Rabbit fur color in winter & summer

Chromosome NumberChromosome Number

All cells of an organism (except for sex cells, gametes) have the same # of chromosomes

Each body cell has 2 sets of chromosomes

Homologous chromosomes - the same chromosomes, 1 set from each parent

All cells of an organism (except for sex cells, gametes) have the same # of chromosomes

Each body cell has 2 sets of chromosomes

Homologous chromosomes - the same chromosomes, 1 set from each parent

Homologous ChromosomesHomologous Chromosomes

Chromosome NumberChromosome Number

Diploid - (2n) - a cell that has both sets of homologous chromosomes

Haploid - (n) - a cell that has half the normal set of chromosomes, or 1 set (only sex cells are haploid)

Diploid - (2n) - a cell that has both sets of homologous chromosomes

Haploid - (n) - a cell that has half the normal set of chromosomes, or 1 set (only sex cells are haploid)

Phases of MeiosisPhases of Meiosis

Meiosis - process of reduction division, where the # of chromosomes per cell is cut in 1/2, through the separation of homologous chromosomes in a diploid cell

Meiosis - process of reduction division, where the # of chromosomes per cell is cut in 1/2, through the separation of homologous chromosomes in a diploid cell


During meiosis 1, crossing-over may occur

Crossing-over - when chromosomes exchange portions of their chromatids

During meiosis 1, crossing-over may occur

Crossing-over - when chromosomes exchange portions of their chromatids


Crossing-over results in the exchange of alleles between homologous chromosomes & produces new combinations of alleles

Crossing-over increases genetic variation (genetic diversity, helps create genetically different organisms)

Crossing-over results in the exchange of alleles between homologous chromosomes & produces new combinations of alleles

Crossing-over increases genetic variation (genetic diversity, helps create genetically different organisms)


Meiosis II, begins with 2 genetically different haploid (n) cells, & results in 4 (n) genetically different haploid cells

Therefore, Meiosis II is a mitotic division

Meiosis II, begins with 2 genetically different haploid (n) cells, & results in 4 (n) genetically different haploid cells

Therefore, Meiosis II is a mitotic division

Meiosis IMeiosis I

Meiosis IIMeiosis II

Gamete FormationGamete Formation

In males, the haploid gametes are sperm

In females, the haploid gametes are eggs

In males, the haploid gametes are sperm

In females, the haploid gametes are eggs

Comparing Mitosis & Meiosis

Comparing Mitosis & Meiosis

Mitosis results in the production of 2 genetically identical diploid (2n) cellsMitosis produces all cells of the body, except sex cells

Meiosis produces 4 (n) genetically different haploid cellsMeiosis produces ONLY sex cells (gametes)

Mitosis results in the production of 2 genetically identical diploid (2n) cellsMitosis produces all cells of the body, except sex cells

Meiosis produces 4 (n) genetically different haploid cellsMeiosis produces ONLY sex cells (gametes)

Gene LinkageGene Linkage

Each chromosome is a group of linked genes

It is the chromosomes, however, that line up independently, not individual genes (Principle of Independent Assortment)

Each chromosome is a group of linked genes

It is the chromosomes, however, that line up independently, not individual genes (Principle of Independent Assortment)

Documents

Unit 4 Genetics Ch. 11 Introduction to Genetics. The Work of Gregor Mendel Genetics - the scientific study of heredity Mendel is considered the “Father”