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Science Knowledge: Science 2: Life Processes and living things

K2.4 Variation, Inheritance & Evolution

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• Download K2.4_2.0a Authored by Liz Lakin and Keith Ross, University of Gloucestershire. accessed from http://www.ase.org.uk/scitutors/

• date created March 2006

http://www.ase.org.uk/scitutors/




Variation, Inheritance & Evolution Learning Objectives

• To explore the science behind the headlines

• To establish a timeline of events leading to our current scientific understanding

• To identify the ‘big ideas’ in this field of biology and recognise how they are interlinked

• To discuss modern applications & their associated issues


http://www.ncseweb.org/evc/EvsC-cover_400.jpg


http://users.hol.gr/~dilos/prehis/Darwcar.jpg


http://www.healthcastle.com/images/vegetables.jpg &

: www.picture-newsletter.com/ vegetables/index.htm

Variation

http://www.healthcastle.com/images/vegetables.jpg

http://www.picture-newsletter.com/vegetables/index.htm

http://www.picture-newsletter.com/vegetables/index.htm


www.nmm.ac.uk/.../ outputRegister/lowhtml

Charles Darwin recognised the significance of variation in a range of organisms

http://www.nmm.ac.uk/server/show/conMediaFile.3815/outputRegister/lowhtml







The Story of the Peppered Moth


Human Evolution


Selection?

• What we are is determined by our genes and our environment


Father of Modern Genetics

• Gregor Mendel• Austrian Monk

(1850s)• Identified the patterns

of inheritance• Laws of Inheritance


Multiple choice questions

The questions in the slides that follow are taken from a set of over 100 available from

www.escalate.ac.uk/1141 Percentages quoted in the slides are for a group of 100

trainee primary teachers on entry to ITE, having obtained a ‘C’ or better at GCSE, usually two or three years previously.

This gives secondary trainees an insight into the misconceptions that survive a GCSE course, and all trainees some comfort that they are not alone with their own misconceptions about how genetics and evolution works.

http://www.escalate.ac.uk/1141

Recessive GenesIf you and your partner both carry the disease for cystic fibrosis (but are not

sufferers), what would be the probability that your children will then inherit

the actual disease?

a. 25% (1 in 4) 5%

b. 33.3% (1 in 3) 19%

c. 50% (1 in 2) 35%

d. 100% (1 in 1 - certainty) 39%(% are for a survey of post GCSE students – see notes)


Mendelian Cross

Both parents carry the recessive gene for cystic fibrosis (c) they also carry the ordinary gene (C). The cross can be summarised as follows:

Father

Mother

C

C CC CcCF carrier

c CcCF carrier

ccCF

sufferer

CC

c


Eye Colour

In eye colour the allele for brown eyes is dominant (B) and the allele for blue eyes is recessive (b). Try some different crosses with homozygous parents (BB or bb) and heterozygous parents (Bb):

Father

Mother

B b

b Bb bb

b Bb bb


So what are Genetics?

• Look at the person next to you and identify as many external similarities between the two of you, as you can.

• Now identify as many differences as possible.

Our common inheritance as humans

The tiny amount of variation in our genesWe share half our genes with bananas and 99% with the chimpanzee


One fertilised cell to an organism!


Development of an egg

What will happen to the weight of a fertilised bird's egg from time of laying to just before the chick hatches?

• It gets lighter 6%• It gets heavier 54%• It stays much the same 35%(% are for a survey of post GCSE students – see notes)


Genes

• What are your genes?

• Do bacteria have genes?

• Is the genetic information in the sex cells the same as in other cells?


Let’s look at cells …

• Several types • 75 billion in a human

being• Capable of carrying

out many different functions e.g. …– Protection– Movement– Excretion


Importance of Proteins

Click on the one statement you most agree with about why proteins are so important to living things.

a. They are a nutritious food 8% b. They are the enzymes in our bodies which enable our cells

to work. 37% c. When combined with oxygen, lots of energy is given off

6% d. Protein provides the structural material in all living things

45% (% are for a survey of post GCSE students – see notes)


Material of Inheritance …

• What are the requirements of hereditary material?

– Store information

– Permanence

– Ability to change (mutate)


Unique function of DNA

• Stores information for protein synthesis

• Makes copies of itself ~ self replication

• Able to change/vary/mutate


DNA• Deoxyribonucleic Acid• Molecular language ~ 4 different

letters• Codon – three letter word – most

code for an amino acid• GENE ~ sentence of many words

(amino acids) which enables it to build PROTEINS

• Proteins are enzymes that enable reactions to take place in cells


… base, nucleotide, gene, chromosome

The following terms all relate to the DNA molecule. List them in relation to their size, starting with the smallest

a gene b nucleotide c chromosome d bases (4% of the BEd Students got it right)

http://en.wikipedia.org/wiki/Nucleotide

http://en.wikipedia.org/wiki/Nucleotide

DNAClick on the four sentences about human DNA that are true.

a. It carries the code to make proteins. 50%

b. It can pass from one generation to the next. 83%

c. It can make copies of itself. 68%

d. It is a single stranded molecule. 26%

e. It is made of protein. 51%

f. It is identical in almost every cell of our body. 66% (% are for a survey of post GCSE students – see notes)


Protein Synthesis

• A simulation …


Link to HOME Quiz


Variation from mutation

Which two of the following processes leads to 'variation' in the offspring:

a. Cell cloning. 4%

b. Gamete formation. 34%

c. Mitosis (normal cell division). 51%

d. Meiosis (sex cell formation) 55% (% are for a survey of post GCSE students – see notes)


Tracing your ancestry

A mutation of which of the following could be inherited from both your parents?

a. Messenger RNA 20

b. Nuclear DNA 29

c. Ribosomal RNA 13

d. Mitochondrial DNA 35 (% are for a survey of post GCSE students – see notes)


Artificial Selection


Manipulation of genes …

• Genotype

• Phenotype & selective breeding

• Manipulation of genes

• Biotechnology


How genes work …

• Inheritance

• Mutations

• Stem cells


Genetic Engineering


What do we need to do to genetically engineer something?

• Location of genes

• Isolation of genes

• Removal of genes

• Transfer of genes

• Cultivation of genes


Where do we go from here …?

• Dolly ~ cloned from a mature cell by nuclear transfer

• Polly ~ cloned from an embryo cell, but contains a human gene which produces the human protein in the sheep’s milk

• Why are they scientifically significant?


What are the issues … ?

• Monsanto monopoly

• 1998 Government moratorium on the growth of GM crops

• Media hype and scare mongering

• Human cloning & designer babies


So what do you think?


So what do you really think?

• Should scientist be allowed to alter animal genes:– For medical

reasons?– For healthier or

more efficient food production?

– For commercial reasons?

• Should scientists be allowed to alter Human genes:– For medical

reasons?– For commercial

reasons?


Recap …

• What do genes do?

• Where do we find genes?

• What makes DNA so good as hereditary material?

• What information does DNA store?

• How does it store it?

• What happens next …


Protein (enzyme) Synthesis• Key points:

– Copy DNA– Messenger RNA copy to site of synthesis– Collect (Transfer RNA) selection of amino

acids and arrange amino acids in correct sequence

– Builds a polypeptide chain (= protein)– Several produced at one time– Allows chemical reactions to take place in cell.


Gene Expression

• Switching genes on and off …

• Stem cells and mature differentiated cells

• Growth = cell division and cell differentiation


Gene Therapy

• Treatment of diseases by the introduction of powders containing working copies of the defective gene ~ saturation approach

• Cystic Fibrosis• Problems:

– Disease is rare in the population– Expensive to treat– Research pressure into common ailments


Genetic Engineering

• Transfer of genes from one species to another.

• How is it done?

• Gene Splicing

• Limitations ~ can only add genes


• http://www.food.gov.uk/gmdebate/aboutgm/?view=GM%20Microsite

Countries which are already growing some GM crops


Concept map

• Compare building a house and cell?

• DNA, genes and enzymes

• Mitosis (cell division) and meiosis (sex)

• Phenotype and genotype – recessive genes

• Growth = cell division & differentiation

• Mutation - natural and artificial

• GM debate and other issues


Learning log

• Look at the questions – where were your conceptual misunderstandings?

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