2.5 The next Generation

Inheritance

• Passing down of a characteristic from one generation to the next.

Genotype - Genetic info. From your DNA from the gametes (sperm and egg) from your parents.

Phenotype –Characteristics and features we have determined by our genetics and environment

+ Environment

Eg. Weight, food, activity, exposure to chemicals, stress, sun etc.

Chance

• Fertilization the sperm and egg gametes come together to make a zygote.• Egg gamete (23 single maternal chromosomes)

• Sperm gamete (23 single paternal chromosomes)

• This zygote contains 23 pairs of homologous chromosomes (paired up – 1 maternal chromosome from the mum and 1 paternal chromosome from the dad)

• What characteristics you end up with is chance.

• There are two different expressions for each characteristic in a gene.

• These are called alleles. • 1 allele is dominant and the other is recessive• Eg. Eye colour – see over

» Phenotype» Genotype

Read

• Read pg. 73 • Define alleles, dominant, recessive,

homozygous, heterozygous, carrier

Heterozygous dominant Homozygous

recessive

Homozygous dominant

Activity

• Traits Activity Sheet Note: Dominant allele = Capital letter eg. B (Brown eyes)Recessive allele = lowercase letter eg. b (blue eyes)

Complete a postie on LIFE on:how someone could have one blue and one brown eye?

Why do we have so many variety of eye colours when there are only two alleles?

What is hazel and green classed as? Blue or brown? Dominant or recessive?

Activity• Map and graph your traits and your

classmates• Investigation 2.4 pg. 74

Exercises

• Textbook pg. 77 Q 1

Pipe Cleaner Babies

• See activity sheet for this practical activity.