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Biology 4 Genetics

Page history last edited by Isaac4 15 years, 11 months ago

Biology 4 Genetics and Pedgrees

 

 

VOCABULARY:

 

Allele~ One version of a particular gene. Each human cell has two copies of each gene. It can be dominant or recessive.

 

Blood Typing~ The process of determining a person's blood type. There are four types, A, B, AB, and O. Each letter represents a protein on the surface of the blood cells in exception to O. O blood has no proteins on it. Rh factor is also considered. Depending on whether it is present, the blood is considered positive if it does have it or negative if it doesn't.The Rh factor becomes most important during birth where differing factors between mother and baby could cause death. This happens when the mother would be Rh+ and the father Rh- so if the baby had Rh-, when leaving the womb, it would come into contact with the Rh+ blood and die. A and B blood types are dominant. If crossed they display incomplete dominance resulting in AB blood.

               - http://youtube.com/watch?v=yqGaX6W6CY8 - video on blood typing

Dominant~ A trait that is always shown and appears over any recessive traits it is typically shown as a captial letter.

 

Genotype~Someone's actual genes that govern a trait. Shown with an allele like "B" or "b" to show dominant and recessive respectivly.

 

Gregor Mendel~ an Austrian Augustinian priest and scientist often called the "father of modern genetics" for his study of the inheritance of traits in pea plants

 

Homozygous~ Where the same two alleles are present in a person. Like BB, bb, AA, aa, RR, rr.

 

Heterozygous~ Where two different alleles are in a person, like a dominant and recessive trait toghether. Bb, Aa, Rr.

 

Phenotype~ Someone's genes expressed as a trait. Like Long hair, Blue eyes, or Bent pinky.

 

Recessive~ A trait that is not shown when a dominant trait is present, but does show up when there are only recessive traits it is typically shown as a lower case letter.

 

Trait~ an attribute that is passed down from parents to offspring. like bent pinky, eye color, hair color and ability to curl tongue.

 

Heredity~ Genetic material that can potentially be passed from parent to child.

 

P1 Generation~ The generation in which 2 genotypes mate together in a genetic cross.

 

F1 Generation~ The first generation of offsprings created from the P1 generation.

 

Law of Independent Assortment~ Allele pairs separate independently of each other during the formation of gametes. So traits are passed independently.

 

Law of Segregation~ Allele separate and recombine randomly during the formation of gametes, and fertilization. Another part to this is there are alternate forms for genes.

 

Complete Dominance~ When a dominant trait is always expressed over the other trait.

 

Co dominance~ Where both traits are expressed at the same time. Like in blood type, a person can be AB blood type which means they got the A alelle and the B alelle combined.

 

Incomplete dominance~ When the traits blend together in the phenotype forming a mixed allele with neither recessive nor dominant being fully expressed. In some plants this can be shown with red and white flowers. If the two are incomplete dominant, they will form a pink flower.

 

RH Factor~ Named after the Rhesus Monkey, The RH factor is a protein found in a persons blood. You can either be RH+, meaning you possess that protein, or RH-, meaning your blood lacks the protein. It is most common to possess the protein.  Rh+ blood can take blood donations from Rh- blood, but Rh- can not take blood from an Rh+ donor or else it will cause coagulation.

 

Roan~ mix of colors, such as pink and white hairs on a horse. This shows co-dominance when both phenotypes exist.

 

This is an example of a blue roan horse.  It is a mix of the colors white and black.  This shows co-dominance because both black and white are shown in the coat color.

 

MONOHYBRID CROSS

 

A monohybrid cross is a breeding experiment between P generation (parental generation) organisms that differ in one trait.

 

 

DIHYBRID CROSSES:

 

 

A dihybrid cross is a cross between two individuals that differ in two traits. For example: RRyy/rrYY or RRYY/rryy. A dihybrid cross is often used to test for dominant and recessive genes in two separate characteristics.

 

 

Black (B) is dominant to white (b).

Tall (T) is dominant to short (t).

 

Say that this is your cross:

(heterozygous black, heterozygous tall) x (homozygous black, heterozygous tall)

 

BbTt x BBTt

  BT Bt bT bt
BT BBTT BBTt BbTT BbTt
Bt BBTt BBtt BbTt Bbtt
BT BBTT BBTt BbTT BbTt
Bt BBTt BBtt BbTt Bbtt

 

In box #1 for example, the phenotype would be black, tall.

In box #6 the phenotype would be black, short.

 

GENOTYPIC RATIO:

1. What are all possible genotypes?

BBTT, BBTt, BBtt, BbTT, BbTt, Bbtt, bbTT, bbTt, bbtt

2. Find how many there are of each genotype.

BBTT:BBTt:BBtt:BbTT:BbTt:Bbtt:bbTT:bbTt:bbtt

2:4:2:2:4:2:0:0:0

3. This simplifies to...

1:2:1:1:2:1:0:0:0

 

PHENOTYPIC RATIO:

 

To find the phenotypic ratio, first find the phenotypes and order your ratio;

 

Black and Tall : Black and Short : White and Tall : White and Short

 

Now find how many of each phenotype there are;

 

12 : 4 : 0 : 0;

 

this can be simplified to..

 

3 : 1 : 0 : 0

 

In this case, there are no white coat-colored animals, because the second parent was homozygous for black coat color.

 

 

 

BLOOD TYPES:

 

Are blood types co-dominant or in-complete dominant?

Blood types are co-dominant.

 

Phenotype:

1. Type A - Can only accept blood from Type A or Type O

2. Type B - Can only accept blood from Type B or Type O

3. Type AB - Can accept blood from all blood types, "universal recipient"

4. Type O - Can only accept blood from O, "universal donor"

 

*When the blood type is negative, it can only accept blood that is negative.

*When the blood type is positive, it can accept blood that is positive. For example:

        ~O+ blood is a universal donor for any type of positive blood. 

 

 

 

Genotypes:

For Type A: homozygous IAIA

For Type A: heterozygous IA i

 

For Type B: homozygous IBIB

For Type B: heterozygous IBi 

 

For Type AB: heterozygous IAIB

For Type O: homozygous i i

 

 

Coagulation is what occurs when two blood types clot in the blood. It is caused when two blood types that are not meant to be mixed together are. Results can be anywhere from mild symptoms to death.

 

How does the RH factor come into blood type?? What is the purpose of it? The Rh factor becomes very important during blood tranfusions. The Rh + or Rh- represent of a certain antigen. Rh+ symbolizes the prescence of the antigen on blood cells. Rh- means the antigen is absent. This factor is called the Rh factor because it was first observed in Rhesus monkeys. Normally, the presence or absence of the factor doesn't affect a human's health. This becomes increasingly important during pregnancy if the wife is Rh- and the Husband Rh+. It could lead to the death of the baby with Rh+ blood then gets Rh- blood from the mom inside the womb. It would cause coagulation resulting in death for the baby. Also, if the fetus's blood enters the mothers bloodstream, the reaction could create antibodies that attack the fetus's blood, seeing the baby's blood as some sort of infection or harmful substance to the body.

 

Here is a link to a website that has a blood typing game...Blood Typing Game

 

 

PEDIGREES:

 

A pedigree is a diagram of family relationships that uses symbols to represent people and lines to represent genetic relationships. These diagrams make it easier to visualize relationships within families, particularly large extended families. Pedigrees are often used to determine the mode of inheritance (dominant, recessive, etc.) of genetic diseases. A sample pedigree is below.

 

 

 

 

***BE SURE TO LABEL GENERATIONS AND INDIVIDUAL PEOPLE BY NUMBER***

 

 

 

 

 

Mode of inheritiance for genetic traits or diseases can be autosomal dominant (Huntington's disease), autosomal recessive (Tay-Sachs) or x-linked recessive/dominant (muscular dystrophy).

 

 

AUTOSOMAL vs. SEX LINKED TRAITS:

 

Autosomal Traits

  • Not dependant on sex
  • Dominant shows up in every generation
  • Recessive skips generations

Sex- Linked or "x-linked" Traits

  • Based on sex
  • Usually shows up in males
  • Always carried on the X chromosome (that's why girls don't usually have it... if the males are dominant or recessive for it depending on the disease, it will appear since they only have one X chromosome)

 

On women that carry the trait, if autosomal recessive it would be notated by XB Xb

Sex-linked, or x-linked traits appear more in men because they only have one X chromosome, whereas women have two.  You can't have a disease related gene on the Y chromosome.

 

 

Genetic Diseases:

Huntington's Disease

  • symptoms:  gradual deterioration of brain tissue in middle age; shortened life expectancy
  • autosomal dominant

 

 

 

Cystic Fibrosis

  • symptoms: mucus clogs lungs, liver, and pancreas; victims usually don't survive adulthood
  • autosomal recessive

 

Sickle Cell Anemia

  • symptoms:  impaired blood circulation, organ damage
  • autosomal recessive

 

Tay-Sachs Disease

  • symptoms: fatty acids accumulate in the nerve cells, red spot on the retina
  • autosomal recessive

 

 

 

Hemophilia

  • symptoms: blood coagulation throughout the body
  • sex-linked recessive
     
     
     
     

 Achondroplasia

  • symptoms: severely shortened bones
  • autosomal dominant
Gattaca Review: Why did it move you?

 

 

 

The ending of it was so sad. But I guess I can understand why he killed himself. How would you feel if your parents created you to be a perfect child then when you try to do something you come in second best? I think that would be really hard to  live with. Any other opinions??

 

I thought the movie was fabulously done and it makes me sad that it is not as well known as it should be. I really applaud the directors and writers for their work. The movie was informational, yes, but to me, that wasn't the real point of the story. I think the genetic aspect of it was just there to help communicate the pressures of society today. By the end of the movie, I felt like I knew the characters and that's why Jerome's suicide was so touching. Of course, I can also relate it to a personal experience which was why it hit me so hard. But to know that he spent all of those hours making samples for the rest of Vincent's life was heartbreaking. It was so bittersweet to me. I'm really glad I got to see this movie because without biology class, I don't think I ever would have.

 

I totally agree. Perfection is NOT the answer. The world in the time of Gattaca and its pressures to be perfect are somewhat extreme, but think about today's world. We have people dying from eating disorders left and right becasue they think they aren't good enough or not worthy, just like Vincent. Not only was this a good scientific movie, it was an entertaining comment on society.

 

I am not sure if I can totally agree with not wanting my kid to have the best traits possible. It is wrong to discriminate people over anything, especially genes. However, parents always want the best for their kids and this is just taking that mindest a little farther is that such a horrible idea?

 

I think the movie was very well put together for being as old as it was and the point of segregation even in the future made me think.  The future holds so much potential but without a little lenience nobody will get anywhere.

 

 

 

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