Science 1.9

Science 1.9Demonstrate understanding of genetic variation.

SLOs.The roles of, and the relationship between, chromosomes, genes, alleles and DNA.How DNA carries instructions and how they are passed on through generations.The importance of variations within populations for survival and how this variation occurs.The purpose of mitosis and meiosis, where they occur and the effect on chromosome number (note: the names of stages are not required).The difference between phenotypes and genotypes.Simple monohybrid inheritance patterns showing complete dominance, sex determination, possible genotypes, and phenotype ratios.

Chromosome.

The chromosome, is the DNA strand, which has coiled up.DNA (Deoxyribonucleic acid)

The DNA strand, consists of ribose sugars, phosphate atoms and base pairs (nucleotides).

Gene

The gene, is a section of the DNA strand, which codes for a trait.Allele

A T T C C G G A T T A A G G C C A A A A T T C C C G A T T A A G G C C A A A The mutant allele has one base that is different, this causes the allele to code for a different trait.Putting it all together.A chromosome is a tangle of DNA, when the DNA is unwound, bands can be seen, these are genes.Each gene codes for a protein, which codes for a trait.The variations of a gene, are called the alleles.

DNA proteins.DNA is a code, when it is read by molecules within the cell, it is translated into a protein.DNA is made up of base pairs of nucleotides.A- AdenineT- ThymineC- CytosineG- GuanineA bonds with T, while C bonds with G.A = T

C G

DNA replication.Before a cell can divide, the DNA must make an exact copy of itself.This is so each cell can have a full set of DNA.This occurs in mitosis and the first stage of meiosis.How does it happen?Helicase enzymeParent strandNew strandAfter the DNA strand is cut in half, new nucleotides come in from the cytoplasm and match up, making 2 strands. Semi-conservative replicationoldnewTriplets.Each base pair is read as a set of 3.Each set of 3 codes for an amino acid.When many amino acids join together, they make a protein.When the DNA is coding for a protein it is changed to RNA and T becomes U.

http://www1.teachertube.com//googleSearch.php?cx=012339422634307447803%3Ah-vlw-wg9yy&cof=FORID%3A11&ie=UTF-8&q=DNA+translation&sa=SearchVideo linkExample.CAA-TTG-GCA-ACTBecomes the RNAGUU-AAC-CGU-UGABecomes the proteingly-asn-arg-stopCTA-GAA-ACA-ACTBecomes the RNAGAU-CUU-UGU-UGABecomes the proteinasp-leu-cys-stopSo what does this mean for us?We each have a unique DNA code, which we have inherited form our parents, we must then make different variations of these proteins...what does this mean for us?

We all look different!Complete the transcription worksheet.Human chromosomes.

Karyotype.

Human chromosomes.Each of your body cells has 23 pairs of chromosomes, you inherited from your parents.22 normal chromosomes, which code for your height, hair colour, skin tone etc.1 set of sex chromosomes, which code for your gender.XX female, XY male.

Male or female?In every pregnancy there is 50% chance the zygote will be male or female . Half of the mans sperm carry an X chromosome and the other half a Y chromosome.Complete Pgs 74&5.

XXXXX XX YXY XY Male; spermFemale; egg

Why do we look different to each other?Variation is the difference between you and the person sitting next to you.We are all humans, so the variation tends to be traits such as height, eye colour skin tone.There are 2 types of variation; continuous and discontinuous.

Continuous variation.The trait fits on a range.E.g. height, hand span.With a large sample, most traits will form a bell curve.

Complete the exercise on Pg 70.

Discontinuous variation.Also know as either/or variation.You either have the trait, or you dont.E.g. Widows peak

Complete the exercise on Pg 69.

So what causes variation?Why do we all look different?Discuss in pairs why we each look different, yet have the same number of eyes, ears and noses.Why is variation important to species?Cell division 1; mitosis.Cell division for growth and repair, is called mitosis (my-toes grow).Identical copies of the daughter cell are created through a series of steps, each cell has 2 copies of each chromosome.You can remember IPMATC to help you learn the stages.Pg 72.Mitosis.DNA unwinds.DNA copies.Copies move to equator.Copies divide.Cell pulls apart.Cell divides.Two new cells.

Cell division 2; meiosis.Cell division for sexual reproduction, is called meiosis.One germ cell becomes 4 daughter cells, each with half the chromosome number of a full body cell.E.g. egg and sperm have only 1 copy of each chromosome.Pg 73 & meiosis square dance.MeiosisDNA unwinds.DNA crosses over & copies.Copies move to equator.Copies divide.Cell pulls apart.Cell divides.Two new cells.DNA moves randomly to each side of the cell.Cells divide again.Four new cells.

Early Prophase.

Late prophase.

Metaphase.

Anaphase.

Telophase.

Cytokinesis.

Why only 1 set?

Egg + Sperm = zygote.One set from the egg + one set from the sperm = full set for the zygote.Egg cell 23 chromosomes

Zygote 46 chromosomes (2n)Full set2 important processes.Crossing over; pieces of DNA are swapped between chromatids.

2 important processes.Random assortment; which chromatid goes to which cell is random.

Summary notes.Meiosis halves the number of chromosomes, so when the egg and sperm join at fertilization, the zygote has a full set. Each gamete has a unique combination of DNA.The zygote then grows by mitosis, into an embryo.If the sperm or egg has a mutation or wrong number of chromosomes, the whole embryo is affected.So why use meiosis and sexual reproduction?Why go to all the hassle of meiosis?Why go and find a mate to reproduce with?

More on that later. Gene-ious words!GenotypeThe genes the organism have inherited from its parents.Organisms have two copies of each gene.E.g. Hair colour BB, Bb, bb.PhenotypeThe appearance of the genes inherited.The phenotype is how the organism looks or how it functions.E.g. Hair colour Brown, blonde, ginga.Ingene-ious words.AlleleThe variations of a gene.If it wasnt for alleles we would all have the same eye colour.B- brown eyesb- blue eyesBoth genes code for eye colour but there are 2 alleles.Mutations.The only source of new alleles.Mutations can occur in may ways, they alter the DNA so a new allele is created.W- long wingsw- short wingsw*- curled wingsSo thats why Ive got Mums eye colour, but Dads hair!As you have one chromosome from each parent, your homologous pairs have 2 copies of each gene.The genes may be the same allele, or two different alleles.Pg 75.

Some alleles are DOMINANT!And some are recessive.You can have 3 possible allele combinations; AA, Aa, aa.AA= homozygous dominant (dominant seen).Aa= heterozygous (dominant seen).aa = homozygous recessive (recessive seen).Keyword alert!Homozygous; 2 of the same alleles.Heterozygous; 2 different alleles.Dominant; 1 copy needed to show.Recessive; 2 copies needed to show.Genotype; gene code (bb).Phenotype; what shows (blue eyes).

Simple examples.B = brown eyes.b = blue eyes.BB = brown eyes.Bb = brown eyes.bb = blue eyes.

Working out inheritance.We use Punnet squares to figure out inheritance.First look at the parents genotypes.Female- AaMale- aa Female A aa aMaleWorking out inheritance 2.Fill in the offspring's genotypes.

Work out the genotype ratio or percentage.50% Aa50% aa 1 : 1 A aAaaaAaaaa a

Working out inheritance 3.Work out the phenotype ratio or percentage.50% auburn50% brown1 : 1 A aAaaaAaaaa a

Tounge rollers.3 rollers, 1 non roller.What are the parents genotype?Red flowers (R).1000 red flowers + 0 white flowers.1000 white flowers + 0 red flowers.750 red flowers, 250 white flowers.Examples.Work through the examples of monohybrid crosses Pg 44 & 45.Extra for experts; move onto the dihybrid crosses sheet also.

Pedigree charts.

Pedigree charts.Pedigree charts show inheritance of traits, particularly in human diseases.E.g. haemophilia in the British royal family,Key; NormalCarrierSufferer

SoIs haemophilia dominant or recessive?How did you know?Complete the worksheet.

1. Using the pedigree, state why the gene for mid-digital hair is a dominant characteristic.Mid-digital hair is a dominant characteristic as more family members show the trait (9) than do not (4). This indicates that the gene is expressed more often and also the offspring C1,2,3 all show the trait. 2. Which individual(s) from A1 and A2 is/are heterozygous?Both parents are heterozygous (Hh) as they have produced 2 off spring with mid-digital hair (B1,6) and two without mid-digital hair (B2, 4).3.What is the probability that individual B1 is heterozygous; show your reasoning.There is a 50% chance that B1 is heterozygous. As shown in the Punnet square below; when two heterozygous individuals conceive a child, they have a 50% chance of being heterozygous, a 25% chance of being homozygous dominant and a 25% chance of being homozygous recessive

Hh HHHHh hHhhh

4.Individuals C1, C2 & C3 are all heterozygous. Using H to represent mid-digital hair and h to represent no hair, give the genotype of their mother; show your reasoning.Their mother was HH, homozygous dominant. As shown in the Punnet square below; when a homozygous recessive individual and a homozygous dominant individual conceive a child, there is a 100% chance they will be heterozygous for that trait, (unless a mutation occurs).

hhHHhHhHHhHh

The Royal Family of Spain.Gaze upon the family tree,If the level of inbreeding is clear to thee,Then, I feel, it is time to flee.

AncestryCharles was born in Madrid, the only surviving son of his predecessor, King Philip IV of Spain and his second Queen (and niece), Mariana of Austria, another Habsburg. His birth was greeted with joy by the Spanish, who feared the disputed succession which could have ensued if Philip IV had left no male heir.17th century European noble culture commonly matched cousin to first cousin and uncle to niece, to preserve a prosperous family's properties. Charles's own immediate pedigree was exceptionally populated with nieces giving birth to children of their uncles: Charles's mother was a niece of Charles's father, being a daughter of Maria Anna of Spain (160646) and Emperor Ferdinand III. Thus, Empress Maria Anna was simultaneously his aunt and grandmother and Margarita of Austria was both his grandmother and great-grandmother. This inbreeding had given many in the family hereditary weaknesses. That Habsburg generation was more prone to still-births than were peasants in Spanish villages.

There was also insanity in Charles's family; his great-great-great(-great-great, depending along which lineage one counts) grandmother, Joanna of Castile ("Joanna the Mad"), mother of the Spanish King Charles I (who was also Holy Roman Emperor Charles V) became insane early in life. Joanna was two of Charles' 16 great-great-great-grandmothers, six of his 32 great-great-great-great-grandmothers, and six of his 64 great-great-great-great-great-grandmothers.

Dating to approximately the year 1550, outbreeding in Charles II's lineage had ceased. From then on, all his ancestors were in one way or another descendants of Joanna the Mad and Philip I of Castile, and among these just the royal houses of Spain, Austria and Bavaria. Charles II's genome was actually more homozygous than that of an average child whose parents are siblings. He was born physically and mentally disabled, and disfigured. Possibly through affliction with mandibular prognathism, he was unable to chew. His tongue was so large that his speech could barely be understood, and he frequently drooled. It has been suggested that he suffered from the endocrine disease acromegaly, or his inbred lineage may have led to a combination of rare genetic disorders such as combined pituitary hormone deficiency and distal renal tubular acidosis.

Consequently, Charles II is known in Spanish history as El Hechizado ("The Hexed") from the popular belief to which Charles himself subscribed that his physical and mental disabilities were caused by "sorcery." The king went so far as to be exorcised.Not having learned to speak until the age of four nor to walk until eight, Charles was treated as virtually an infant until he was ten years old. Fearing the frail child would be overtaxed, his caretakers did not force Charles to attend school. The indolence of the young Charles was indulged to such an extent that at times he was not expected to be clean. When his half-brother Don John of Austria, a natural son of Philip IV, obtained power by exiling the queen mother from court, he covered his nose and insisted that the king at least brush his hair.

How do genotypes become phenotypes?PROTEINS!!!Your DNA codes for proteins to be made in your body, it is these proteins that create the look of your phenotype.

DNA sequence; AAAATGCTTCTCCAAProtein coded for; KeratinVariation.How does variation occur in a species?Gene mutations.Chromosome mutations.Independent assortment.Recombination.Mate selection & sexual reproduction.Environmental factors.

Clay modelMutations.Gene mutation.The DNA strand is changed, so the protein made to express the gene is different.Some mutations are harmful, others are helpful.

Chromosome mutation.The chromosome is changed in a large way, this often changes the proteins the chromosome codes for.This type of mutation is almost always harmful.ATCTAGATCAAGA T G G C C T T A A T T C C G A T G G C C T T A A T T C C G A T C T A G A T C A A GMutations.Whole chromosome insertion1 or more whole extra chromosome is present in every cell.E.g. Downs syndrome.An extra chromosome 21.

Whole chromosome deletion.1 or more whole chromosome is absent from every cell.E.g. Turners syndrome.Missing one X chromosome.

Mutations.Mutations can occur in both gametes (sperm and egg) and also in body cells (cancer).In order to be passed on to offspring, the mutation must occur in a gamete (meiosis).A body cell mutation can not be passed on.Mutations are the only source of new genetic material.Mutations can be; beneficial, silent or harmful.Mutations.Helpful; gives organism an advantage.Silent; no effect on organism.Harmful; kills, disables or makes the organism sterile.Variation- 2 important processes.Random assortmentThe chromosomes are randomly sorted into the gametes in meiosis.This makes each gamete unique in their gene combination.Crossing overPieces of chromosome are swapped during crossing over, creating new combinations of alleles on each chromosome.

Non genetic variationMate selectionMany animals choose their mate for the desirable characteristics.Different combinations of alleles will be present on the offspring depending on the mate selected.Sexual reproduction creates new combinations of alleles.

Environmental factors.Environmental factors may influence the expression of the genotype.E.g. Temperature, pH, wind exposure, availability of food, level of parental care.Mate selection

Environmental factors.Tomato with sunlightTomato without adequate light

To re-cap...As you can see many traits are inherited from parents to offspring. These are called inheritable traits.Some variations are not inherited, they are controlled by the environment. These are called non-inheritable traits.Why is variation so important?Imagine swine flu rampaged through Lawrence; who would survive? Who would die? How would you know?

DEADDEADWhy are there some many people with red hair in Waitahuna? What if the climate heated up and the red heads couldnt survive? How would this impact on the (Homer) population?Disease & environmental changes effect populations.

DEADDEADSO DEAD

Darwin thinks you look like a monkey...

94

Survival of the fittest.Evolution is the modern theory of how organisms change and adapt over time.Charles Darwin (1809-1882) wrote the book on evolution The theory of Evolution by natural selection.His theory has now been proven using evidence from the fossil record.

Everyone out of the gene pool!The gene pool is all of the genes and alleles in one population.How an individual is effected by pest infestations, disease, drought etc, is often determined by their genes.

Gene pool exercise.Initial gene pool.Natural selection (favours dominant individuals.)Founder effect. Immigration and emigration.Initial gene pool.The gene pool of the un-disturbed population.It represents all of the alleles in the population.Natural selection (favours dominant individuals.)Stabilising selectionNatural selection.Natural selection (favours dominant individuals.)Directional selection; selects against one extremeNatural selection (favours dominant individuals.)Disruptive selection; selects against the middleFounder effect. A small number of individuals are isolated from the main population.Only the alleles that are contained within the founding population are present in the new population.The new population may be completely different to the original population.Immigration and emigration.Individuals moving in to a population may bring in new alleles (immigration).Individual moving out of a population may eliminate alleles (emigration).Displays.http://www.youtube.com/watch?v=HyvxlUpEjgI&feature=related

Why do the male birds put on a display?What is the advantage it gains them?Plumage.

So why is variation so important?It ensures the survival of a species!Applications of genetics.Animal breeding.Genetic engineering.Cloning.

Animal breeding.For thousands of years people have chosen animals for their specific traits and bred them with one another. In this way they controlled (to some extent) what the offspring would look like, act like and what type of product they would gain from them.Animals which are homozygous for the desired trait are called pure breeding.Example. Purebred dogs; the generations of animals are recorded and any animals which do not display the traits are not allowed to breed.

Advantages and disadvantages to selective breeding.Breeders can mostly control the traits of the offspring.Breeders can remove offspring which do not show the correct traits.Groups of animals can have very limited gene pools.Animals may display more recessive traits.Animals can have less diversity leaving them more vulnerable to disease.Genetic engineering.Genetic engineering, also called genetic modification, is the direct human manipulation of an organism's genome using modern DNA technology. It involves the introduction of foreign DNA or synthetic genes into the organism of interest. The introduction of new DNA does not require the use of classical genetic methods, however traditional breeding methods are typically used for the propagation of recombinant organisms.Reading.We shall read the information sheet on GE and try and re-frame it into English!

Cloning.Cloning is the process of creating new organisms from one body cell of another individual. The most famous example is Dolly the sheep.

118Nuclear Transfer(as used with Dolly)Dolly was created by transplanting a nucleus from a cell of one sheep into the enucleated egg of another. The nucleus-egg combination was stimulated with electricity to fuse the two and to stimulate cell division. The new cell divided and was placed in the uterus of a ewe to develop. Dolly was born months later.

120Therapeutic cloning(Stem Cell Technology)Therapeutic cloning is the process by which a person's DNA is used to grow an embryonic clone. However, instead of inserting this embryo into a surrogate mother, its cells are used to grow stem cells. These stem cells can be used as a human repair kit. They can grow replacement organs, such as hearts, livers and skin. These organs would not suffer from rejection. They can also be used to grow neurons to cure those who suffer from Alzheimer's or other diseases.

Summary.Time to summarize the notes from this topic and begin to study for your exam.Check the SLOs and make sure you understand everything we have covered.Check your key words list and vocab understanding.Genes determine many of the features of organisms, such as the eye colour of humans.A gene is a part of a DNA molecule. Brown eyes are due to a dominant allele and blue are due to a recessive allele.

Discuss how information in DNA gives organisms (like the humans above) their individual features, such as eye colour. In your answer, you should:Explain the difference between a gene and an alleleDraw a labelled diagram in the box on page 3 to show the relationship between a gene and an allele and the structure of a DNA moleculeExplain how the base sequence on DNA determines a particular feature (e.g. eye colour) and different forms (variations) of that feature (e.g. brown or blue eyes).Chart142021

Hand span (cm)Number of peopleHandspan of Year 11

Sheet1Handspan19-20420-21221-22022-23223-241

Sheet2

Sheet3