Genetics Quiz Friday

Your Genetics Quiz will test your ability to solve for the following. Be prepared to draw a punnet square for

Complete dominance
Co-dominance
Sex linked alleles

I will expect you to draw a pedigree, practice from this website, which is an educational resource for health professionals who provide sensitive genetic counselling.
You will answer a question on medical ethics for which I will accept any ethical answer where I can follow your reasoning.

Practice problems

 worksheet for Monohybrid crosses : http://www.biologycorner.com/worksheets/genetics_practice.html

And here is its answer key: http://www.biologycorner.com/worksheets/genetics_practice_key.html

 sex linkage questions here: http://www.k-state.edu/biology/pob/genetics/intro.htm

More Genetics problems, this time focussing on Bioethics - taking a family history and the role of a health professional in disclosure

We will do some more practice of Genetics and go over some questions. Today we will also learn about pedigrees.  In fact, I'll dictate a pedigree for our test.

Angelina Jolie wrote about  a very public double mastectomy , raising awareness of the risks associated with the BRCA 1 and BRCA 2 gene.

 I will give you a patient scenario and you will draw a family history.  an example is below:  BRCA 1 and BRCA 2 are autosomal alleles which are strongly linked to cancer, particularly Breast cancer.  (see this fact sheet).  Genetic counsellors interview patients to assess their risk by drawing a pedigree.  You can practice drawing a pedigree here.  As you watch this video, and read the links, make conclusions about the type of allele which may lead to the breast cancer phenotype.

This illustration is from a worksheet created by the National Genetics and Genomics Education Centre

Genetic Counsellors use detective work to sensitively discern a patient's risk for a genetic disease.  There are bioethical guidelines which govern disclosure.  And there's no easy answers for communication.  Have a look at this scenario to see some of the ethical concerns, and imagine that you are a health professional in this situation:

http://www.geneticseducation.nhs.uk/downloads/1846_Ethics_discussion_sheet_-_carrier_testing_for_AR_disorders.pdf

Test on Protein Synthesis and Genetics

1.  Steps for Transcription of DNA to RNA, including the processing of the mRNA
2.  Steps for Translation of the mRNA, including INITIATION, ELONGATION AND TERMINATION. Look at the raycroft notes And cartoon notes.
3.  Know the answers of the DNA worksheet given out.  Emphasis on transcription and translation. Key here 
4.  optional questions :Know how to solve Genetics Questions  including drawing a pedigree
5.  optional questions :Read about the kinds of mutation and be prepared to write about two of them.
6.  optional question:What are the three forms of protein:  primary structure, secondary structure, tertiary structure.

Test date is Feb 11, 2016

Practice problems in Genetics and the topic of Sex Linkage

Here's a worksheet for Monohybrid crosses : http://www.biologycorner.com/worksheets/genetics_practice.html
And here is its answer key: http://www.biologycorner.com/worksheets/genetics_practice_key.html
try some sex linkage questions here: http://www.k-state.edu/biology/pob/genetics/intro.htm

SEX LINKED GENES

The sex chromosomes are XX and XY in humans. Some alleles are located on the X chromosome. But very few on the Y chromosome.  Remember that females have the genotype XX and males have XY.

The Y chromosome carries very little information, only enough to influence the embryo on the path towards male primary and secondary characteristics.

Meanwhile, many RECESSIVE ALLELES are located on the X chromosome, including
1. hemophilia, the inability to clot blood
2. colourblindness inability to tell the difference between red and green colour
3.  baldness

These characteristics are far more common in men than women because men have only one X. And if that X contains the recessive allele, they will show the phenotype.  Meanwhile, women may have the recessive and their "normal" dominant X will protect them.  For example

An example of using a punnet square to calculate probability is here:

Some things to note about sex linkage:  Signs of sex linked alleles are:
1. more males get the phenotype, but women can be carriers
2.  men can inherit from mother but not father (because men get their X from mom)
3.  Women have an extra X and this protects them.  Women must be homozygous to show the sex linked phenotype.
Further reading on sex linkage here http://learn.genetics.utah.edu/content/pigeons/sexlinkage/

FYI if you are a guy and you want to know if you're colourblind:  Test yourself here: Apparently most men find out they are colourblind from their science teacher...
http://colorvisiontesting.com/home.html

codominant alleles: Blood type

What if the heterozygous trait exhibited codominance?  in this case, two homologous alleles can code for co-dominant traits.  That is neither is dominant over the other.  Blood type is an example of this:
A is codominant to B
A is dominant over O
B is dominant over O

Possible genotypes:

heterozygous AB blood gives both type A and B on the erythrocytes
homozygous AA gives blood type A  protein on the erythrocytes
homozygous BB is blood type B protein on the erythrocytes
Heterozygous AO is gives blood type A
Heterozygous BO is blood type B

homozygous recessive OO gives blood type O or neither A or B on erythrocytes.

You have heard that blood type is important for blood transfusions. That is because the immune system will always attack an unknown protein.  Thus

type A person can receive  type A blood, and will reject type B blood
type B person can receive type B blood and will reject type A
type AB person can receive type A blood and Type B blood
Type O person can receive nobody's blood except from another type O

Everyone can receive type O, No-one can receive type AB

Blood type is heritable and that means you can sometimes deduce genotype by looking at phenotype. Here is a sample question:

Dominant, Recessive alleles and using Punnet Squares.

Alleles come in pairs and a GENOTYPE IS a pair of alleles which code for a PHENOTYPE.  Phenotype refers to the observed characteristic.
For example:

B= brown eyed allele   and    b = blue eyed allele
Genotype   Bb will give the PHENOTYPE of brown eyes because B is dominant over b.

GENOTYPE BB is homozygous dominant = brown eyes
GENOTYPE Bb is heterozygous = brown eyes
bb is homozygous recessive = blue eyes.

This is a case of COMPLETE DOMINANCE and it results in grandparents passing traits to grandchildren:

If a BB person mates with a bb person, we can calculate probability of their offspring traits using a punnet square:

When Baby grows up, she mates with this guy who happens to have the same GENOTYPE!

Note that a recessive allele can be hidden inside a HETEROZYGOUS genotype.

Introduction to Genetics

Gregor Mendel, monk, was the father of Genetics.

Last day we had an introduction to Genetics and we defined these terms:
Gene
Allele
Chromatin, Chromatid, Chromosome
Homologous pair of Chromosomes
diploid number vs haploid number or 2n vs n
Human diploid number = 46 chromosomes or 23 pairs, here they are below for a male human

Courtesy National Human Genome Institute http://www.genome.gov/glossary/resources/karyotype.pdf

Each of the HOMOLOGOUS CHROMOSOMES above  can contain many pairs of alleles.  To understand this, we considered an analogy of shoes...