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GeneticsGeneticsSimple InheritanceSimple Inheritance

Learning IntentionsLearning Intentions

Understand that there are three Understand that there are three types of simple inheritancetypes of simple inheritance

Dominant/RecessiveDominant/Recessive Sex linked Sex linked Intermediate/CodominanceIntermediate/Codominance

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I wonder how, I wonder I wonder how, I wonder whywhy

I’m 61% like a fly?I’m 61% like a fly?

Now here’s a shock Now here’s a shock that’s sort of grousethat’s sort of grouse

We’re 99% like a We’re 99% like a mouse!mouse!

It makes you stop, it It makes you stop, it makes you thinkmakes you think

How similar are we to a How similar are we to a chimp?chimp?

Source:Mouse http://animals.timduru.org/dirlist/mouse/mouse.jpgDrosophila: http://www.innate.se/drosophila.jpgChimpanzee: http://www.utalii.com/Hotels/images/Chimpanzee.jpg

WE ARE DIFFERENT IN MANY WAYS, WE ARE DIFFERENT IN MANY WAYS, BUT IN MANY WAYS WE ARE THE SAME!BUT IN MANY WAYS WE ARE THE SAME!

We are 35% like a daffodil!!!We are 35% like a daffodil!!!

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Simple Simple InheritanceInheritance

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Discovering Small Discovering Small DifferencesDifferences

Second toe longer or shorter than your big toe?

Earlobes Attached or unattached?

Cross your arms….are you left over right or right over left?

Pull your hair back. Widows peak or none?

Mid-digit hair on fingers?

GlossaryGlossary PhenotypePhenotype- - The observable traits or characteristics of The observable traits or characteristics of

an organism, for example hair color, weight, or the an organism, for example hair color, weight, or the presence or absence of a disease. Phenotypic traits presence or absence of a disease. Phenotypic traits are not necessarily genetic.are not necessarily genetic.

Genotype-Genotype- The genetic identity of an individual that The genetic identity of an individual that does not show as outward characteristics.does not show as outward characteristics.

Alleles – the forms of the gene e.g. tongue roller or Alleles – the forms of the gene e.g. tongue roller or not tongue rollernot tongue roller

HomozygousHomozygous--Possessing the same form of a Possessing the same form of a particular gene. E.g. TT or ttparticular gene. E.g. TT or tt

HeterozygousHeterozygous--Possessing two different forms of a Possessing two different forms of a particular gene, one inherited from each parent. Eg. particular gene, one inherited from each parent. Eg. TtTt

Dominant/Recessive Dominant/Recessive InheritanceInheritance

Dominant - A gene that almost always results in a specific physical Dominant - A gene that almost always results in a specific physical characteristic, for example, a disease, even though the patient's characteristic, for example, a disease, even though the patient's genome possesses only one copy. With a dominant gene, the genome possesses only one copy. With a dominant gene, the chance of passing on the gene (and therefore the disease) to chance of passing on the gene (and therefore the disease) to children is 50-50 in each pregnancy.children is 50-50 in each pregnancy.

Recessive – used to refer to a gene whose parent phenotype is Recessive – used to refer to a gene whose parent phenotype is expressed only if present in a double “dose”.expressed only if present in a double “dose”.

How to write dominant –How to write dominant –recessive genetic traitsrecessive genetic traits

Widow’s PeakWidow’s PeakWW widow’s peak present widow’s peak present

ww straight hair line straight hair line

Ear LobesEar LobesLL free ear lobe free ear lobe

l l attached ear lobe attached ear lobe

Mid –digital hairMid –digital hairHH hair present hair present

hh hair absent hair absent

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Dwarfism Dwarfism DD dwarf stature dwarf stature

d d normal stature normal stature

Pigment Pigment ProductionProduction

AA normal pigment produced normal pigment produced

aa lack of pigment - albino lack of pigment - albino

Colour Colour BlindnessBlindness

XC Normal Colour Vision

Xc Red green colour blindness

My genetic recipe with My genetic recipe with these traitsthese traits

ww; ll; hh; dd; AA ; ww; ll; hh; dd; AA ; XXCC X XCC

oror

ww; ll; hh; dd; Aa ; ww; ll; hh; dd; Aa ; XXCC X Xcc

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AA means normal pigmentationAA means normal pigmentation Aa means normal pigmentationAa means normal pigmentation Aa means you have albinismAa means you have albinism

XXCC X XCC means no colour blindness in girls means no colour blindness in girls XXCC X Xcc means no colour blindness in girls means no colour blindness in girls XXcc X Xcc means colour blindness in girls means colour blindness in girls

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Genetic wheel ActivityGenetic wheel Activity

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Punnett Squares

T T

T

T

TT TT

TT TT

Genotype: TT

Phenotype: all Tongue Roller

Punnett Squares

t t

t

t

tt tt

tt tt

Genotype: tt

Phenotype: all Non Tongue Roller

Punnett Squares

T t

T

t

TT Tt

Tt tt

Genotype: 1TT : 2Tt : 1tt

Phenotype: 3/4 Tongue Roller :1/4 Non Tongue Roller

Punnett Squares

T t

t

t

Tt tt

Tt tt

Genotype: Tt : tt

Phenotype: 1/2 Tongue Roller 1/2 Non Tongue Roller

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Is any other combination possible??

Sex – linked inheritanceSex – linked inheritance

Review fertilizationReview fertilization Sex organs – testes and ovariesSex organs – testes and ovaries Gametes – sex cells Gametes – sex cells

Ovum (ova)Ovum (ova) SpermSperm

XX – femaleXX – female XY – maleXY – male

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Sex LinkageSex Linkage When characteristics are determined by genes on X When characteristics are determined by genes on X

chromosome. E.g. Haemophaeliachromosome. E.g. Haemophaelia

Xh

Y

XX XXh

XY XhY

Genotype: XX : XhX : XY : XhY

Phenotype:1 Normal Girl :1Carrier girl :I normal boy:I haem boy

What genotype type would parents have to be to give birth to a girl with haemophilia?

XhX (or XhXh) and XhY

X

X

In this case X is normalXh has the disease haemophilia

Pedigree-showing Pedigree-showing inheritance through inheritance through

generationsgenerations A pedigree is used to show the pattern of inheritance of a A pedigree is used to show the pattern of inheritance of a particular characteristic or trait. These pedigrees Can then particular characteristic or trait. These pedigrees Can then be used to work out if the trait is genetically inherited, and be used to work out if the trait is genetically inherited, and whether it is dominant or recessive. whether it is dominant or recessive.

In human pedigrees, a horizontal line joins two individuals In human pedigrees, a horizontal line joins two individuals who are married (or produce children together). A vertical who are married (or produce children together). A vertical line branching out from the marriage line shows their line branching out from the marriage line shows their children.children.

Individuals that show a particular trait that is being Individuals that show a particular trait that is being followed are indicated by shading their symbol.followed are indicated by shading their symbol.

Do handout Royal Family What type of inheritance is this?Do handout Royal Family What type of inheritance is this?

Haemophilia in Royal Family

Pedigree P174 of text Questions 2 and 3worksheet

Textbook Chapter 6.3

HandoutReview question on simple imheritance•P197 q 1-13

•Pedigree Handout

Review questions on pedigree•P204 q 1-7

Intermediate InheritanceIntermediate Inheritance These are examples of partial dominance. There are two These are examples of partial dominance. There are two

different types of intermediate inheritancedifferent types of intermediate inheritance

Incomplete dominance – when the heterozygous genotype Incomplete dominance – when the heterozygous genotype is expressed as a a mixture of either homozygous is expressed as a a mixture of either homozygous genotypes. E.g. when a black mouse (BB) mates with a genotypes. E.g. when a black mouse (BB) mates with a white mouse(WW) and all offspring are grey (BW).white mouse(WW) and all offspring are grey (BW). See Punnett Square activity on next slideSee Punnett Square activity on next slide

Co-dominance – where both alleles are present in a Co-dominance – where both alleles are present in a heterozygote are expressed heterozygote are expressed

E.g. Human Blood Groups such as ABO blood group E.g. Human Blood Groups such as ABO blood group

Punnett Squares

B B

W

W

BW BW

BW BW

Genotype: BW

Phenotype: All Grey

Intermediate/CoDominance

WS

Blood Groups

Example of Dominant/Recessive and Codominance

•A and B are codominant

•O is recessive to A and B

•Rhesus Factor i.e. whether you are positive or negative is dominant/recessive

Antibodies and AntigensAntibodies and Antigens

AntibodiesAntibodies are Y-shaped proteins that are Y-shaped proteins that are found in blood or other bodily fluids of are found in blood or other bodily fluids of vertebrates, and are used by the immune vertebrates, and are used by the immune system to identify and neutralize foreign system to identify and neutralize foreign objects, such as bacteria and viruses.objects, such as bacteria and viruses.

An An antigenantigen or or immunogenimmunogen is a molecule is a molecule that stimulates an immune response.that stimulates an immune response.

Rhesus factorRhesus factor

You can also inherit Rh antigen;You can also inherit Rh antigen;

If you are Rh+ you have the antigenIf you are Rh+ you have the antigen If you are Rh- you do notIf you are Rh- you do not

What type of inheritance is this?What type of inheritance is this? W/S Baby may be ABW/S Baby may be AB