Punnett squares and uses. Genes (Alleles). Why are some genes dominant and

others recessive? How do we write symbols for these genes?

What is homozygous and heterozygous?

Predict phenotypes from genotypes. Test crosses. Blood Types.

Diagram used to determine genetic crosses

A a A a

Diagram used to determine genetic crosses

A a A a

AA

Diagram used to determine genetic crosses

A a A a

AA Aa

Diagram used to determine genetic crosses

A a A a

AA

Aa aa

Aa

Use different Letters or Symbols

G @ B @

Use different Letters or Symbols

G @ B @

BG

Use different Letters or Symbols

G @ B @

BG B@

Use different Letters or Symbols

G @ B @

BG

G@ @@

B@

Worksheet Q 1-6 Planners - Tuesday 13/3/12

Genes are how living organisms inherit features from their ancestors

What did you inherited from your parents' genes

Genetics tries to identify which features are inherited, and explain how these features are passed from generation to generation.

Different forms of a gene Your ear lobes are inherited From your DNA Genes (Alleles) are inherited as

units, with two parents dividing out copies of their genes to their offspring.

The ear lobe is controlled by 2 alleles.

Mum and Dad

YOU

A DOMINANT allele covers up the recessive form.

A recessive allele gets covered up in the presence of a dominant allele

A DOMINANT allele is represented in CAPITALS

i.e. L – for an attached lobe as this is dominant

a recessive allele is represented in lower case

i.e. l – for an unattached lobe as this is a recessive allele

The dominate allele will be seen.

Phenotype – is the physical characteristic of the gene ie attached lobe

Genotype is the combination of alleles (genes) that make up the gene – represented in letters. LL, Ll (lL), ll

L – for an attached lobe l – for an unattached lobe 2 alleles.

LL ll Ll

L – for an attached lobe l – for an unattached lobe

LL ll Ll

L – for an attached lobe l – for an unattached lobe

Phenotypes

LL ll Ll

L – for an attached lobe l – for an unattached lobe

Phenotypes

Genotypes LL ll Ll

Homozygous – the same allele – LL or ll

Heterozygous – different allele - Ll

Mum has a heterozygous ear lobe, Ll and Dad has a recessive ear lobe, ll (thus Homozygous). What ear lobe will their children have?

Mum = Ll Dad = ll I I L Ll Ll I ll llPunnett Square

Mum has a homozygous ear lobe that is attached and Dad has a recessive allele ear lobe. What ear lobe will their children have?

Mum = LL Dad = ll I I L Ll Ll L Ll LlAll the childen will have Ll Genotypes

their ear lobe genes are hetrozygous.

LL Ll ll

Two black fish look the same but have different genotypes. The fish with genotype BB is said to be homozygous, or pure breeder because both the alleles for the skin colour gene are the same. The other fish is said to be heterozygous or Hybrid, because its two alleles for skin colour gene are different.

What offspring can occur when the fish cross breed, that is BB & Bb.

What offspring can occur when 2 heterozygous breed?

Incomplete dominance is a condition when neither allele inherited is dominant or recessive over the other

This will result in a blend/fusion of characteristics

An example of this is in snapdragons, a flower where its colour can be red, pink, or white. A white (WW) snapdragon crossed with a red

(RR) snapdragon produces all pink offspring The heterozygous (RW) condition results in

pink flowers.

RED = RR White = WW RW RW RW RW All the off spring will be RW –

Pink

R RWW

When both alleles contribute to the phenotype of an organism

Ex.) Speckled Chickens

Black = BB White = WW

BW BW BW BW All the off spring will be BW –

Black with White

B BWW

BW offspring = BW White = WW

BW WW BW WW The off spring ratio would be 1:1 BW:WW

B WWW

When more than two possible alleles exist in a population

Ex.) blood type IA

IB

i

Dominant

Recessive

Video on blood types

Human Blood TypesPhenotype Genotype

A

B

AB

O

IAIA or IAi

IBIB or IBi

IAIB

ii

Traits controlled by two or more genes

Ex.) eye color, skin color

The characteristics of any organism, is not only determined by the genes it inherits

Characteristics are determined by interactions between genes and the environment

Ex.) genes may affect a plants height but the same characteristic is influenced by climate, soil conditions and availability of water

Human hair is inherited by incomplete dominance. Human hair may be curly (CC) or straight (cc). The heterozygous genotype (Cc) produces wavy hair. Show a cross between two parents with wavy hair

A man is suing his wife on grounds of infidelity. The man claims that the child is blood type O and therefore must be fathered by someone else. Can he use this evidence in court if he and his wife both have heterozygous B genotypes?

Show the cross of the two parents