GeneticsGenetics-the scientific study of inheritance-the scientific study of inheritance

inheritanceinheritance- the process in which genetic - the process in which genetic material is passed from parents to their material is passed from parents to their offspringoffspring

Gregor MendelGregor Mendel

Austrian monk-Austrian monk-studied pea plantsstudied pea plants

Mathematical basis Mathematical basis for experimentsfor experiments

Kept careful records Kept careful records of numbersof numbers

Studied simple traits Studied simple traits (seed color, shape, (seed color, shape, flower color, height, flower color, height, etc.)etc.)

Monohybrid CrossMonohybrid Cross A cross between two parents that A cross between two parents that

are identical in all but one are identical in all but one characteristic.characteristic.

Example: cross a short pea Example: cross a short pea plant and a tall pea plantplant and a tall pea plant

P is parent generation, P is parent generation, F1 is first filial generation,F1 is first filial generation, F2 is second filial generationF2 is second filial generation

Result of cross: F1-all tall, F2-3 Result of cross: F1-all tall, F2-3 tall:1 shorttall:1 short

Modern GeneticsModern Genetics AlleleAllele: Alternate forms of the same gene. Each : Alternate forms of the same gene. Each

trait has two alleles:trait has two alleles: DominantDominant: masks the effects of the recessive (ex. T): masks the effects of the recessive (ex. T) RecessiveRecessive: is masked by the dominant (ex. t): is masked by the dominant (ex. t)

Modern Genetics cont’dModern Genetics cont’d Gene LocusGene Locus: the place on a : the place on a

homologous pair of chromosomes homologous pair of chromosomes where the alleles occur, one on each where the alleles occur, one on each chromosome.chromosome.

Homozygous (true-breeding)Homozygous (true-breeding): Both : Both copies of the allele are identical (TT copies of the allele are identical (TT or tt)or tt)

HeterozygousHeterozygous: Each copy of the : Each copy of the allele is unique (Tt)allele is unique (Tt)

Genotype vs. PhenotypeGenotype vs. Phenotype GenotypeGenotype: the alleles an individual receives at fertilization. : the alleles an individual receives at fertilization.

TT is homozygous dominant, tt is homozygous recessive, TT is homozygous dominant, tt is homozygous recessive, and Tt is heterozygous.and Tt is heterozygous.

PhenotypePhenotype: refers to the physical characteristics of an : refers to the physical characteristics of an individual. individual. Homozygous dominant and heterozygous Homozygous dominant and heterozygous individuals both show the dominant phenotype (tall), while individuals both show the dominant phenotype (tall), while homozygous recessive shows the recessive phenotype homozygous recessive shows the recessive phenotype (short).(short).

autosomal

chromosomes

sexchromosomes

Classes of chromosomesClasses of chromosomes

In humans & other mammals, there are 2 sex In humans & other mammals, there are 2 sex chromosomes: X & Ychromosomes: X & Y

22 X chromosomesX chromosomes• develop as a female: develop as a female: XXXX

an X & Y chromosomean X & Y chromosome• develop as a male: develop as a male: XYXY

Genetics of SexGenetics of Sex

X Y

X

X

XX

XY

XY

50% female : 50% maleXX

Sex-Linked TraitsSex-Linked Traits Sex-linked traits are produced by genes only on the X Sex-linked traits are produced by genes only on the X

chromosome. chromosome. They can be Dominant or Recessive.They can be Dominant or Recessive.

A = dominant a = recessiveA = dominant a = recessive

What would be the genotypes of a male and female that have a What would be the genotypes of a male and female that have a Sex-Sex-linked Dominant traitlinked Dominant trait and do not express the trait? and do not express the trait?

Expresses Trait: Expresses Trait: Male - XMale - XAA Y Y Female - XFemale - XAA X XAA or X or XAA X Xaa

No Expression: No Expression: Male - XMale - Xaa Y Y Female - XFemale - Xaa X Xaa

What would be the genotypes of a male and female that have a What would be the genotypes of a male and female that have a Sex-Sex-linked Recessive traitlinked Recessive trait and do not express the trait? and do not express the trait?

Expresses Trait: Expresses Trait: Male - XMale - Xaa Y Y Female - XFemale - Xaa X Xaa

No Expression: No Expression: Male - XMale - XAA Y Y Female - XFemale - XAA X XAA or X or XAA X Xaa (Carrier)(Carrier)

Most Sex-linked traits are Recessive!Most Sex-linked traits are Recessive!

Dihybrid CrossDihybrid Cross A cross between two A cross between two

individuals that differ from individuals that differ from each other in regards to each other in regards to two traits. two traits.

Ex: pod color and pea Ex: pod color and pea color: GGYY and ggyy. color: GGYY and ggyy.

• F1 generation will be GgYy.F1 generation will be GgYy.

Polygenic InheritancePolygenic Inheritance phenotype determined by combination phenotype determined by combination

effects of 2 or more genes at a different effects of 2 or more genes at a different loci on different chromosomes. loci on different chromosomes.

Phenotypes usually found onPhenotypes usually found on a bell-shaped curvea bell-shaped curve human traitshuman traits

• skin colorskin color• heightheight• weightweight• intelligenceintelligence• behaviorsbehaviors

Multiple alleles- Multiple alleles- more than 2 forms of a gene controlling more than 2 forms of a gene controlling the expression of a traitthe expression of a trait

Ex: Blood type: Ex: Blood type: • In humans, 3 alleles: A,B,OIn humans, 3 alleles: A,B,O

Co-dominanceCo-dominance- A pattern of inheritance in which the - A pattern of inheritance in which the phenotypic effect of two alleles in a heterozygous phenotypic effect of two alleles in a heterozygous genotype express each phenotype of each allele fully genotype express each phenotype of each allele fully and equally; a phenotype which would not be expressed and equally; a phenotype which would not be expressed in any other genotypic combination.in any other genotypic combination.

Ex: Checkered chickens have both white and black feathers.Ex: Checkered chickens have both white and black feathers.

Environmental EffectsEnvironmental Effects

Phenotype is controlled by Phenotype is controlled by both environment & genesboth environment & genes

Color of Hydrangea flowers is influenced by soil pH

Human skin color is influenced by both genetics & environmental conditions

Coat color in arctic fox influenced by heat sensitive alleles

What are Chromosomal Mutations?What are Chromosomal Mutations?Damage to chromosomes due to physical or chemical disturbances or errors during Damage to chromosomes due to physical or chemical disturbances or errors during meiosis.meiosis.

Mutations might also be inherited from the sex cells of your parents. If you inherit a mutation from your parent, all of your DNA will be made with the mutation already in it.

The only way to inherit mutations from your parent is through sex cells – not through other types of cells.

Ex: Skin cancer is not passed on to your kid.

Mutations may cause certain types of diseases or make you susceptible to certain types of diseases.

Two Types of Chromosome Mutations:Two Types of Chromosome Mutations:

1.1. Chromosome StructureChromosome Structure

2.2. Chromosome NumberChromosome Number

Problems with Chromosome Structure:Problems with Chromosome Structure:

2 main types of chromosome structure mutations:

1. Point mutation - A point mutation is a simple change in one base of the gene sequence. This is equivalent to changing one letter in a sentence.

22. Frameshift mutation- . Frameshift mutation- a change in the bases that causes a change in the bases that causes the sequence to be read in different sets of codons. the sequence to be read in different sets of codons. Equivalent to changing the spacing of the sentence.Equivalent to changing the spacing of the sentence.

Gene MutationsGene Mutations Nonsense substitution- Nonsense substitution- a change in 1 base that changes an amino a change in 1 base that changes an amino

acid to a stop codon acid to a stop codon

Silent substitution- Silent substitution- a change in 1 base that does not cause a a change in 1 base that does not cause a change in the amino acid produced change in the amino acid produced OR a change in the DNA that causes a change in the protein, but not the function of the protein.

Missense substitution- Missense substitution- a change in 1 base that changes the amino a change in 1 base that changes the amino acid producedacid produced

Deletion-Deletion- a deletion of a base a deletion of a base

InsertionInsertion- an addition of a base- an addition of a base

Chromosomal MutationsChromosomal Mutations translocationtranslocation- a portion of a chromosome breaks off - a portion of a chromosome breaks off

and attaches to a non-homologous chromosomeand attaches to a non-homologous chromosome

inversioninversion- a portion of a chromosome breaks off and - a portion of a chromosome breaks off and reattaches “upside down”reattaches “upside down”

deletiondeletion- a portion of a chromosome breaks off- a portion of a chromosome breaks off

duplicationduplication- a portion of a chromosome is duplicated- a portion of a chromosome is duplicated

Problems with Chromosome NumberProblems with Chromosome Number

nondisjunction nondisjunction – members of homologous – members of homologous chromosomes do not move apart in Meiosis I or chromosomes do not move apart in Meiosis I or sister chromatids do not separate during Meiosis II sister chromatids do not separate during Meiosis II leaves one cell with too few chromosomes and one leaves one cell with too few chromosomes and one cell with too many.cell with too many.

monosomymonosomy – only one of a particular type of chromosome (2n -1) – only one of a particular type of chromosome (2n -1)

trisomytrisomy – having three of a particular type of chromosome (2n + 1) – having three of a particular type of chromosome (2n + 1)

polyploidypolyploidy – having more than two sets of chromosomes; triploids (3n = 3 – having more than two sets of chromosomes; triploids (3n = 3 of each type of chromosome), tetraploids (4n = 4 of each type of of each type of chromosome), tetraploids (4n = 4 of each type of chromosome). chromosome).

BiotechnologyBiotechnology

-any procedure or methodology that uses biological -any procedure or methodology that uses biological systems or living organisms to develop or modify either systems or living organisms to develop or modify either products or processes for specific use. products or processes for specific use.

Genetic engineering- Genetic engineering- a technology that includes the a technology that includes the process of manipulating or altering the genetic material process of manipulating or altering the genetic material of a cell resulting in desirable functions or outcomes that of a cell resulting in desirable functions or outcomes that would not occur naturally.would not occur naturally.

genetically modified organism- genetically modified organism- an organism whose genetic an organism whose genetic material has been altered through some genetic engineering material has been altered through some genetic engineering technology or technique.technology or technique.

gene therapy- gene therapy- the intentional insertion, alteration, or deletion of genes within an the intentional insertion, alteration, or deletion of genes within an individual’s cells and tissues for the purpose of treating a disease.individual’s cells and tissues for the purpose of treating a disease.

gene splicing- gene splicing- a type of gene recombination in which the DNA is intentionally a type of gene recombination in which the DNA is intentionally broken and recombined using laboratory techniquesbroken and recombined using laboratory techniques

CloningCloning- a process in which a cell, cell product, or organism is copied from an - a process in which a cell, cell product, or organism is copied from an original sourceoriginal source

DNA cloning- DNA cloning- making exact copy of a DNA fragmentmaking exact copy of a DNA fragment Reproductive cloning- Reproductive cloning- transfer of genetic material from the nucleus of a transfer of genetic material from the nucleus of a

donor adult cell to an egg that has had its nucleus removed ; the embryo is donor adult cell to an egg that has had its nucleus removed ; the embryo is an exact genetic copy of the donor organism.an exact genetic copy of the donor organism.

Therapeutic cloning- Therapeutic cloning- using STEM cells for use in researchusing STEM cells for use in research• STEM cells- undifferentiated cells; have not decided “what they want to be” when they STEM cells- undifferentiated cells; have not decided “what they want to be” when they

“grow up”“grow up”