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DNA & Genetics Notes

Notes for the Genetics Unit Phenotype, Genotype Dominant, Recessive Sex-linked Punnett Pedigree

Devin Weiss

on 31 July 2013

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Transcript of DNA & Genetics Notes

Key: B = brown eyes
b = blue eyes

Cross of Bb x Bb (brown x brown)
DNA & Genetics
Dominant--when one gene prevents the expression of its allele
ex. brown eyes
Recessive--the gene not expressed if there is a dominant gene
ex. blue or green eyes
Phenotype--the trait that you observe
Genotype--the actual genetic makeup
Punnett Square--determine the probable offspring from a set of parents
So, we're going to use symbols to represent this: B for Brown eyes and b for blue. (The dominant trait is uppercase).
If you have brown eyes your genotype could be ___ or ___
If you have blue eyes what is your genotype?
Homozygous--trait whose alleles are identical yy or RR.
Heterozygous--trait whose alleles are different Bb
The A allele codes for antigen “A”
The B allele codes for antigen “B”
The O allele codes for no antigen and is recessive to A and B

If A and B occur together, both “A” and “B” antigens will be expressed equally on your red blood cells. This pattern of inheritance is called CO-DOMINANCE.

Blood type is determined by the genes you inherited from your parents. However, unlike some traits we have been studying, there are three alleles for the gene for blood type: A, B, and O.

The blood type gene codes for a marker protein on the surface of your red blood cells. If you get a transfusion of the wrong kind you body will attack it.
All X chromosomes have locations for the genes for hemophilia, as well as color-blindness and other sex-linked traits. Therefore, we still use the system of letters, such as E and e, to represent forms of these genes as superscripts on the X chromosome. For example, the normal gene for blood clotting is X, and the defective recessive gene is X.

Because the gene is located on the X chromosome, females have two genes and males have one. Heterozygous females have one recessive copy of the gene, but do not have the disease. They are called carriers because they are able to pass the gene on to their offspring.
SEX LINKED TRAITS: Color blindness

Why are there more colorblind men than colorblind women? Certain traits are controlled by gene located on the sex chromosomes, usually the X chromosome. These traits are called SEX-LINKED TRAITS.

Color blindness is a recessive disorder caused by a mutation on the X chromosome. The dominant allele codes for normal color eyesight. The recessive allele codes for colorblindness
TAGACG This is a portion of _____.
Karyotypes: the chromosomes are arranged in pairs and by size (you can see their centromeres and bands). They are used to determine if the person is normal (23 pairs) or has extra chromosomes.
Turner Syndrome: they have one X chromosome, so they only have 45 total. They are infertile, have normal intelligence, short, and have webbed necks
Down Syndrome: 3 copies of chromosome 21 and that makes 47 total chromosomes. They have distinct facial features, some degree of mental disability, and short stature.
Klinefelter's Syndrome: A person has XXY (1 in 500 have XXY but 1 in 1000 have KS). They are physically male, infertile with small testes, and may have enlarged breasts.
In addition to dominant and recessive traits there are also traits that are controlled by genes that are not entirely dominant because the gene does not work very well. The alleles for these traits are both expressed somewhat, often resulting in a blend of the dominant and recessive phenotypes. This is called INCOMPLETE DOMINANCE.

Snapdragons can have a R allele for red or r for white. RR has red phenotype and rr is white, but Rr is PINK!
1. You have decided to breed a RED and WHITE flower. (a) Draw a Punnett square of the cross and (b) what are the genotypes and phenotypes of the offspring.

2. Then, you cross 2 pink flowers. (a) Draw a Punnett square for this cross. (b) What is the phenotype ratio?
11.What is the technology called that modifies DNA to take new genes from other organisms? [ex. In Jurassic Park they added frog DNA to the missing holes in their Dino DNA]

12.Down syndrome is caused by having an extra 21st chromosome. In a karyotype, how many chromosomes would each cell have?

13.What is cloning? What is a common example of a clone?
21.Beginning with DNA, describe the process that forms a protein [you MUST include the forms of RNA and organelles]
1.If I'm looking at a segment of nucleotides I can figure out if its DNA or RNA because they are different in what 2 ways?
DNA has a T!!!
2.What is meiosis?
Makes sex cells with half the number of chromosomes. Like a cell that started with 46 and ends with 23
Brown Eyes!
Blue Eyes!
Punnett Squares do what?
provide probable offspring from parents
6. A girl is colorblind. What gene did her father give her. So what's her dad's phenotype?
Dad gave: X
Dad is X Y so he's colorblind
8.Your DNA has 37% G. How much T does it have?
C=37%, so
A=13% and T=13%
9.To create you, your mom's egg with 23 chromosomes had to be fertilized by your dad's sperm that had 23 chromosomes resulting in a _________ with _______ chromosomes. Are you Haploid or Diploid? [circle one]
Recombinant DNA! mixing genes into other organisms
Making identical copies
14.Arrange these terms to show the steps of the expression of a trait: trait, gene, protein. Explain why you arranged them this way.
15.A Baby has blood type 0, but who is the father?
a)Circle all the possible genotypes that could be the father:
AB AA Ao BB Bo oo
b)What are all the possible phenotypes that the father could have:
_______ ________ ________
Both parents need a recessive 0!
16.I collect caterpillars from a grey moth and a black moth. Grey is dominant (G) to black (g). The moths that grew out of the caterpillars were 22 grey and 24 black.
a)What is the most likely genotype for the parent moths?

b)Draw a Punnett Square to confirm your answer.
Gg x gg with give 50% of each
18.In your cell the DNA unzipped and made RNA. What is this process called?
It's tranSCRIPTION: which is like writing down what someone says
20.What does crossing over do in Meiosis?
Makes gametes with varied traits.
22.A normal protein is coded from CGUCTT and non-functioning protein is coded from CGUCAT. Describe how a change in the DNA could result in a change in the protein.
Transcription happens first in the nucleus and it makes mRNA from DNA
Translation happens second at the ribosome where the mRNA codes for a protein
It's a Substitution Mutation

The CTT will code for a different amino acid, which will make a different protein. This protein doesn't work :(
Your Traits!
Drill: On a separate sheet of paper. Analyze yourself for the traits below. Answer Y/N for each trait.
1. Tongue Rolling 8. Brown eyes
2. Widow's Peak 9. Chin cleft
3. Hitchhiker's thumb 10. Shorter big toe
4. Free earlobe 11. Dimples
5.Curly Hair
6. Hair on middle joints of fingers
7. Bent little fingers
-Threadlike and are made of genes
Humans have 46
Segment of DNA that codes for a particle protein, which codes for a trait
-Chemical that chromosomes & genes are made of and forms a double helix
controls protein production in the cell
Building block of DNA in repeating strands of nucleotides
Deoxyribose sugar:
sides of the DNA ladder
Phosphate Group:
Sides of the ladder
Nitrogen Bases-
rungs of the DNA ladder
Base Pairs
Base Pairs
RNA: Used in protein production and made of nucleotides
BUT: RNA has ribose sugar instead of deoxyribose and Uracil instead of T
Exit Ticket: Write your answers on the top right side of your paper!
1. Look at the DNA sequence: GAA TTC GCA
What do the G and A represent in the DNA sequence?
A. sugars
B. amino acids
C. phosphates
D. nitrogen bases
2. Which of these are the repeating units that form a DNA molecule?
A. fatty acids
B. nucleotides
C. amino acids
D. chromosomes
3. Which of these is a nucleotide?
A. 1
B. 2
C. 3
D. 4

4. Which of these is a sugar?
A. 1
B. 2
C. 3
D. 4
DNA & Karyotypes
Drill: 1. What is abnormal about this karyotype?
2. What sex is this person?
How does DNA replicate?
Use the textbook to answer the question: p.210-211 about DNA replication.
Steps of DNA Replication made easy!
DNA molecule separates into 2 strands

It make 2 new complementary strands following the rules of base pairing

Each original strand is a template for the new strand

At the end you have 2 complete double helices with 1 original strand and 1 new strand

1. Rate your skills from 1 to 10. (10 being awesome)
DNA Structure
Genetics Terms
Making Punnett Squares
Analyzing Punnett Squares
Sex-Linked Traits
2. Circle the ONE topic that Mr. Weiss should review most
Old Vocab: Heterozygous, Homozygous, Dominant, Recessive, Codominant, Sex-linked, Carrier
New Vocab: Pedigree
What do you think of when you hear the word Pedigree?
Alternative Inheritance
Use the numbers on the pedigree when answering the questions.

Show how traits are passed on through a family tree. Females are circles and males are squares. Colored in circles or squares indicate expressed traits.
Color Blind Testing:
1.What combination of alleles results in an organism showing the RECESSIVE trait?

2.Colorblindness is sex-linked. A couple has 15 kids. All have normal eyes. What is the MOST LIKELY genotype of the parents?

3.Colorblindness effects 7% of the CEHS male population and .5% of the females. Describe how colorblindness is passed on. Circle two
Dominant trait / Recessive trait on the X chromosome / Y chromosome

4. Using this pedigree, how is this trait passed on? Circle one
Dominant Recessive Sex-Linked Recessive

5. Gregor Mendel figured out most of what we talked about genetics. He figured out how traits are passed to offspring. How does this apply to our unit?

6.A. How does a trait not evident in the parents, show up in the offspring?
B. What are the parents genotypes? Circle one:
Homozygous Recessive, Homozygous Dominant, or Heterozygous

7.A. Draw a Punnett square of a cross of RR x Rr.
B. What is the PHENOTYPIC RATIO of the expected offspring of the cross? __ :__

C. What are the expected genotypes of RR x Rr (use homo/heterzygous and dominant recessive

8.A. Draw a Punnett square of a cross of Rr x Rr.
B. What is the PHENOTYPIC RATIO of the expected offspring of the cross?

9. If I cross a TT and tt, how will the offsprings phenotype compare to the parents? How will the genotype compare?
10. There are 6 dominant and 4 recessive kids for brown eyes. What are the phenotypes of the parents

11. A egg has 20 chromosomes. How many chromosomes does it have when its fertilized?

12. Draw a punnett square for a normal female and colorblind male (its sex-linked)

B. Using your punnett square, circle the genotype of a normal girl.

13. What's the genotype of a sex-linked carrier?

Final Jeopardy.
14. A boy is more likely to be colorblind IF his mom is a carrier OR his dad is colorblind. Prove your answer with 2 punnett squares
Creative Review
--Assign Groups and Topics
--Give students 5 minutes to find the information they need to answer their questions.
1. Now that you've had some time to find your background information, we are going to add the creative element. Your job is to share the information with your classmates in an interesting, creative way.
2. You must find a creative way to convey your topic. You could:
a) Write a story, poem, song
b) Use the Flipcam and make a video
• Perform a rap or song
• Perform your story
• Host a talk show
c) Create a game for the class to participate in
d) Create a comic strip to explain your concept
3. You must have a visual to explain your presentation
4. You will be graded on content, creativity, quality and presentation.
5. You are going to get 25 minutes to prepare.
6. When your group leader has decided what your going to do, please send your supply person to get the guided outlines to help your move forward (like poem outlines)
Gallery Walk: Presentation
You have 3 minutes at every station to see their project and write down 3 facts that the project taught you and you didn't know.
Your Genes
More Questions
1. Which people are the oldest? ______
2. Which people are infected? _______
3. Which people are male? ________
4. How are 5 and 6 related? ________
5. How are 3 and 6 related? _______
6. How are 1 and 7 related? ______
Below is a pedigree for an inherited lung disease. Provide the genotypes of each of the individuals marked with lower case letters
Whiteboard Review
~Jacobs syndrome or XYY syndrome
: Straight thumb (dominant trait) vs. Curved thumb (recessive trait)
: Straight pinky (recessive trait) vs. Bent pinky (dominant trait)
Mid-digit hair
: Mid-digit hair (dominant trait) vs. No mid-digit hair (recessive trait)
Dimples (dominant trait) vs. No dimples (recessive trait)
Widow's Peak
(dominant trait) vs. No Widow's Peak (recessive trait)
Free ear lobes (dominant trait) vs. Attached ear lobes (recessive trait)
Longer 2nd toe (dominant trait) vs. 2nd toe shorter than big toe (recessive trait)
: Rolling up edges (dominant trait) vs not rolling (recessive)
Genotype Ratio: 1BB:2Bb:1bb
Phenotype Ratio: 3Brown:1blue
Exit Ticket
You have 20% T, How much C do you have?
5.B is dominant for brown eyes and b is recessive for blue. I cross parents that are Bb x Bb.
b)The parents are heterozygous / homozygous and dominant / recessive
c)Draw the Punnett square of the cross
d)What is the phenotype of the bottom right square? ______________
e)What is the genotypic ratio of this cross? _______________
a)How would you describe the parents phenotype? ____________
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