Sickle Cell Anaemia – page 126 Now lets see how sickle.

Sickle Cell Anaemia – page 126• http://www.youtube.com/watch?v=9UpwV1tdxcs

• http://www.youtube.com/watch?v=bCOJkpL7MVw&feature=related

• Now lets see how sickle cell can be inherited

Symbols for alleles =HA = healthyHS = sickle cellComplete question 4, booklet page 7

Symbols for alleles = HA = healthyHS = sickle cell

• A heterozygous sickle cell trait mother has a child with a husband who has the sickle cell disease. What is the chance of the child inheriting the disease?

• 50% sickle cell disease and 50% sickle cell trait.

ABO Blood Groups – Multiple Alleles (showing codominance) for one gene.

• http://www.medindia.net/animation/blood-groups.asp

• http://waynesword.palomar.edu/aniblood.htm

• Allele IA is codominant with IB, but Io is recessive to both.

• Write out all the possible genotypes and their phenotypes

Genotype Phenotype – Blood Group

IA IA A

Roan (pinkish) cattle are produced by codominant alleles – explain.

Complete question 1 and 2 page 127

Answer to question 1

1. What are genotypes of parents?• Cows = red, so must be CR CR

• Calves = 50% red (CR CR) or roan (CRCW)

• So, dad was CRCW

CW CW CB CB

Answer Question 2

Grey Swedish Blue Ducks!

Answer to question 2

• What are genotypes of offspring?• Grey = CWCB, White = CWCW, Black = CBCB

• How could he always get Swedish blue ducks?• Swedish blue = grey, so breed CWCW with CBCB

to always get CWCB (grey) offspring.

• Now for Dihybrid crosses, page 8, 9 and 10

Dihybrid Cross – investigating 2characteristics(phenotypes) at a time.2 genotypes aretherefore writtenside by side.e.g. SSbb x ssBB

See page 8, 9 and 10.

Dihybrid Cross Animation – see booklet page 8

• http://trc.ucdavis.edu/biosci10v/bis10v/media/ch08/dihybrid_v2.html

• http://science.nhmccd.edu/Biol/dihybrid/dihybrid.html

• Websites for practise• http://www.ksu.edu/biology/pob/genetics/intro.htm

• Mono and dihybrid problems for brain warm ups• http://www.biology.arizona.edu/mendelian_genetics/

problem_sets/monohybrid_Cross/monohybrid_cross.html

AIMS• Collect in homework questions (I can start

marking them!)• Promonitor Test• Give out Question Sheets to those not at

yesterday’s lesson.• Test Crosses Starter• Sex linkage • Chi squared• Homework for tomorrow – Question 7 on

sheets from yesterday

Starter - The Test Cross• If breeders have e.g. a bitch showing the

dominant characteristic (black coat colour) then how can they find out by breeding her, if she is homozygous or heterozygous for black?

• Always breed with a double recessive dog, (brown). What will the two possible alternative outcomes for the puppies be?

• She is homozygous – no chance of brown; always all black

• She is heterozygous – a chance that brown puppies might be born – even one will show bitch is heterozygous.

• See ratio summary page in booklet.

KARYOTYPES

What makes one male and one female?

Male or female?

Linkage of genes can be on any chromosomesincluding the X and Y sex chromosomes.

Linkage

• LINKAGE - 2 or more genes are located (linked) on the same chromosome.

Tall plant

Smooth seed

Linkage reduces the possible combinations of genes during meiosis and therefore reduces thephenotypes resulting from a cross.

So, no ____________ ______________ at ___________ __

Why is this boy still bleeding after a fall?

Haemophilia – page 124

http://www.youtube.com/watch?v=a8s8Al3rX_4&feature=related

• http://www.youtube.com/watch?v=F0ZoEGnTAM0&feature=related

• So clotting can not take place.

• How is it inherited?• See Royal Family Tree page 13

Albert

Sex-linkage in theRoyal Family.See page 12

Alice LeopoldLeopold

Beatrice

Queen Victoria

• Queen Victoria's male descendants were cursed with poor health. The 19th century British monarch's son Leopold, Duke of Albany, died from blood loss after he slipped and fell. Her grandson Friedrich bled out at age 2; her grandsons Leopold and Maurice, at ages 32 and 23, respectively. The affliction, commonly known as the "Royal disease," spread as Victoria's heirs married into royal families across Europe, decimating the thrones of Britain, Germany, Russia, and Spain. Based on the symptoms, modern researchers concluded that the royals suffered from hemophilia--a genetic disease that prevents blood from clotting--but there was never any concrete evidence. Now, new DNA analysis on the bones of the last Russian royal family, the Romanovs, indicates the Royal disease was indeed hemophilia, a rare subtype known as hemophilia B.

Hemophilia prevents proteins known as fibrins from forming a scab over a cut or forming clots to stop internal bleeding. Even minor injuries can lead to bleeding, which lasts for days or weeks and can be fatal. The disease is recessive and is carried on the X chromosome, meaning that men are more likely to develop it, whereas women usually act as carriers and don't show symptoms.

Such was the case with Prince Alexei Romanov, son of Tsar Nicholas II, great-grandson of Queen Victoria, and heir to the Russian throne. From an early age, Alexei was prone to prolonged bleeding, and his family feared that he wouldn't make it through his first month of life, says Evgeny Rogaev, a geneticist at the University of Massachusetts Medical School in Worcester. The disease didn't kill Alexei, however: He was murdered at age 13 in 1918 along with the rest of the Russian royal family following the Russian Revolution. Earlier this year, Rogaev and his colleagues reported that, based on DNA analysis, the bodies of two children found near the murder site were indeed those of Alexei and his sister Maria. They further confirmed that the other bodies near the site belonged to the rest of the Romanov family. But Rogaev wanted to solve the final Romanov riddle: Did they really suffer from hemophilia?

He and colleagues analyzed DNA from the royal bone fragments again, this time looking for genetic markers of hemophilia. The most common type of the disease, hemophilia A, accounts for about 80% of hemophilia cases and is caused by a mutation to a gene called F8, which encodes a protein involved in blood clotting. They didn't find the mutation. So Rogaev moved on to looking for a rarer form of the disease, hemophilia B, which involves another gene, F9. This time, the team found a mutation in F9, which would have inhibited clotting, in bones from Alexei, his sister Anastasia, and their mother Alexandra. So they had the rare form of Haemophilia B

Inheritance of Sex-linked Haemophilia – page 11

There is generally no roomfor any other genes besides sex genes on the Ychromosome.

Answer question 1, page 125, and use page 12See above punnett square!

Red – green colour blindness.

• What numbers can you see?

• How is it inherited?

• Answer question 2, page 125

Mother! He passes his Xc to his daughter and his Y to a son.

In Fruit flies the gene for eye colour is on the X chromosome.

• Answer question 3 on page 125

See board for answer

Use pages 21 to 24 to find out about and use the Chi squared Test.

• Key definition (Note down)• The Chi 2 statistical test finds out if the

difference between observed and expected data is small enough to be due to chance.

• If the observed is significantly different from the expected, then the genetic theory behind the expected data must be wrong and a new theory must be found.

• (See next slide)

Chi squared can be used:

• When data is in categories.• Where we have a strong theory to

predict the expected data.• The sample size is large.

• Remember – only real (raw) data can be used.

Starter – question 2, A4 Genetics Problems sheet and 4 c) ii (A3 sheet)

Xb Y

AIMS • Check Homework page 15 (cats) and quest 7• Autosomal Linkage, page 16/17.• Epistasis• Genetic Challenge• Polygenic inheritance• Effect of Environment• Homework – Complete questions already set

and then Stretch and challenge page 133 + questions 5 and 6 and complete pages 25 - 27 of booklet.

Sex – linkage in Cats.

• How are both black and ginger expressed in female cat coats?

Duchenne Muscular Dystrophy

Answer question 4/5, page 125