Human and applied genetics

Section 1 Vocabulary:

• 1. Carrier: an individual that is heterozygous for a recessive disorder

• 2. Pedigree: a diagram that traces the inheritance of a particular trait through several generations using symbols to illustrate the inheritance of the trait

Pedigree Charts Video

• http://www.youtube.com/watch?v=PuWhstNgRpk&feature=youtube_gdata_player

PEDIGREE CHARTS • Pedigree charts show a record of the family

of an individual.

• It can be used to study the transmission of a hereditary condition.

• It is particularly useful when there are large families and a good family record over several generations.

• You cannot make humans of different types breed together so pedigree charts provide one of the few ethical ways of studying human genetics.

• Today genetic engineering has new tools to offer doctors studying genetic diseases but a genetic counselor will still use pedigree charts to help determine the distribution of a disease in an affected family.

Symbols used in pedigree charts

•

• In a marriage with five children, two daughters and three sons. The second son is affected by the condition

Organizing the pedigree chart

• Below is a pedigree chart of a family showing four generations. A total of 20 individuals.

• Generations are identified by Roman numerals. Individuals in each generation are identified by Arabic numerals numbered from the left. Therefore the affected individuals are II3, IV2 and IV3.

•

What does this show?

Examples of traits

hemophilia

• Inborn Errors of Metabolism - non-functional enzymes              PHENYLKETONURIA - [PKU]     pp                   1/10,000 births            disfunctional phenylalanine hydroxylase               PHE --x-->   PHE-pyruvate    --> -->   degraded & excreted                   accumulates - blood/brain barrier = mental retardation

•         ALKAPTONURIA         aa       A. Garrod in 1908      1/200,000            homogentisic acid oxidase --x--> ALKAPTON*  [urine oxidizes black]                    1st suggestion that effect of genes was to make proteins                    and disease is due to a defective enzyme/protein.

•         TAY SACHS                tt                                   1/300,000 births             defective lysosomal (gangliosidase) enzyme = lysosomes swell burst -> death            Ashkenazic Jewish ancestry show   1/ 3,600 births   &  1 / 30  is  Tt

•         SICKLE CELL  s            ss                             1/6,000 births                        defective beta polypeptide of Hb                        improper folding of Hb --> clogs capillaries                                 

•  

• Section 1

• 1. What is the genotype of a person who is a carrier for a disease?

• heterozygous

Cystic Fibrosis• Cystic fibrosis happens most often in white

people of northern European ancestry, occurring in about 1 out of 3,000 live births.

• In cystic fibrosis, the lungs fill with thick mucus; a perfect breeding ground for bacteria and viruses. Most people with cystic fibrosis have almost constant infections in their lungs and sinuses.

• In cystic fibrosis, a defective gene alters a protein that regulates the normal movement of salt (sodium chloride) in and out of cells. This results in thick, sticky secretions in the respiratory and digestive tracts, as well as in the reproductive system. It also causes increased salt in sweat.

• 2. What ions are to blame for the problem of mucus clogging the ducts in people with cystic fibrosis? chloride

Albinism

• Albinism is an inherited condition that is present at birth. It is characterized by a lack of melanin, the pigment that normally gives color to the skin, hair, and eyes. Many types of albinism exist, all of which involve lack of pigment in varying degrees. The condition, which is found in all races, may be accompanied by eye problems and may ultimately lead to skin cancer .

• 3. What is missing in people with albinism?

• Melanin

Tay Sachs

• Tay-Sachs carriers are found most frequently among families of eastern European Jewish descent (Ashkenazi Jews). In the United States today, approximately one in every 27 Jews is a Tay-Sachs carrier.

What happens if you have Tay-Sachs?

• Children with Tay-Sachs disease lack a vital enzyme, hexosaminidase A (Hex-A). Hex-A is needed for the body to break down a fatty waste substance found in brain cells. Without Hex-A, this substance accumulates abnormally and causes progressive damage until the nervous system can no longer sustain life.

• In its most common variant, known as infantile Tay–Sachs disease, it causes a relentless deterioration of mental and physical abilities that commences around six months of age and usually results in death by the age of four

• 4. What is the effect of Tay-Sachs disease?

• Build up of fats in the brain causing mental disfunctions

• 5. Why are there no cures for these diseases?

• They are all recessive genetic disorders and occur due to defects in every cells DNA.

• 6. If all of the above genetic diseases are recessive, then what genotype is necessary to have the disorder?

• 7. Are there any disorders that are dominant?_________ If so, Name 2

• 8. In a pedigree chart, what symbol represents a male? ___________ a female? __________

• 9. What is the purpose of a pedigree chart? • 10. Draw a pedigree of a boy with galactosemia if

his father has it, his paternal grandparents are phenotypically normal and his mother and maternal grandparents are all phenotypically normal.

• 6. If all of the above genetic diseases are recessive, then what genotype is necessary to have the disorder? Homozygous recessive

• 7. Are there any disorders that are dominant?_yes________ If so, Name 2 Huntingtons disease and Achondroplasia__

• 8. In a pedigree chart, what symbol represents a male? _a square _____ a female? A circle __________

• 9. What is the purpose of a pedigree chart? To trace the inheritance of a trait over the generations and to be able to predict the possibilities of the offspring inheriting the trait

• 10. Draw a pedigree of a boy with galactosemia if his father has it, his paternal grandparents are phenotypically normal and his mother and maternal grandparents are all phenotypically normal.

Section 2 Vocabulary:

• 1. Incomplete dominance

• 2. Codominance

• 3. Multiple alleles

• 4. Epistasis

• 5. Sex chromosome

• 6. Autosome

• 7. Sex-linked trait

• 8. Polygenic trait

SC.912.L.16.2 Ch 8

• Discuss observed inheritance patterns caused by various modes of inheritance, including dominant, recessive, codominant, sex-linked, polygenic, and multiple alleles.

Dominant and recessive traits

Advanced Genetics

• http://www.youtube.com/watch?v=YoEgUqHOcbc&feature=youtube_gdata_player

1. Incomplete dominance , ( 302 )

• Define: (1 pt ) _when the heterozygous genotype results in an intermediate between the two parent’s homozygous phenotypes

Incomplete dominance

Incomplete dominance

• A mixture of the two phenotypes

• Produces a new

• Phenotype.

• Red X White = Pink

Co dominance• 2. Codominance 302

• Define: (1 pt ) when both alleles are equally expressed in the heterozygous condition

Both are expressed

• Like a dog or cat with

several colors fur

Blood groups

A and B are co dominant!

This is also an example of multiple alleles

A, B and O

3. Multiple alleles, ( 304 )

• Define: (1 pt ) when a trait is determined by more than 2 alleles

Multiple alleles

• More then two alleles for a trait.

• Blood types A B O

.

4. Epistasis , ( 305 )

• Define: (1 pt ) when one allele hides or alters the effects of another allele.

• example: coat color in dogs 2 sets of alleles E determines if the fur is going to be dark. Ee no dark pigment, B determines how dar. EEbb Edbb will be chocolate brown eebb or eeBb will be yellow because e masks the effect of the dominant B allele!_

5. Sex chromosome , ( 305 )

• Define: (1 pt ) the one pair of chromosomes that determines the sex of the organism. In humans the X and the Y.

6. Autosome, ( 305 )

• Define: (1 pt ) All of the chromosomes that are not sex chromosomes. These contain the genes for everything necessary for life. 22 pair in humans

7. Sex-linked trait: , ( 307 )

• Define: (1 pt ) traits controlled by genes on the X chromosome.

• Introduction--Sex Linked Inheritance (Video Clip)

Sex linked traits• The genes for these traits are on the X

chromosome, because boys only receive one X chromosome they are more likely to inherit disorders passed to them from their mother who would be a carrier.

• Color Blindness (Video Clip)

• Coat color in cats is an X-linked gene, with alleles for black and orange-brown, so XBXB and XBY cats will have a black coat, while XOXO and XOY will have an orange-brown coat. Another possible combination for female cats would be XBXO. Both of the color alleles would be expressed, so the cat would end up being partially brown and partially black.

Q: Can a male cat ever be calico?

– A: Yes, if he’s XXY, which would be abnormal. It turns out that abnormal numbers of X chromosomes aren’t as serious as other chromosome number abnormalities, because all but one X turn off, so an XXX individual would have two Barr bodies, an XXY individual would have one, etc.

• Hemophylia (Video Clip)

• Inherited human traits and patterned sex linked inheritance (Video Clip)

• Organizing information about Sex Linked Inheritance in Pedigree charts (Video Clip)

8. Polygenic trait, ( 309 )

• Define: (1 pt ) traits controlled by many genes skin tone, height and eye color are examples.

Height is polygenic

• 1. Define dominant:

• 2. Define recessive:

• 3. What is it called when a red flower and a white flower are crossed and the result is a pink flower results?

• 4. When the F1 generation of this cross (above) is crossed, what do you get for a phenotypic ratio? _______________

• 5. What does it mean to be codominant? What is an example of co dominance?

• 6. Why is sickle cell an advantage with regard to malaria?

• 7. Human blood groups have several alleles to determine the blood type. What is this called?

• 8. What are the alleles for blood type?

• 9. What happens to the number of possible phenotypes when you have multiple alleles?

• 10. What is epistasis?

• 1. Define dominant: The trait that masks the trait it is crossed with in the parental cross and shows up 100% in the F1 generation.

• 2. Define recessive: the trait that is not seen when crossed with another in the P cross and does not show up again until the F2 generation.

• 3. What is it called when a red flower and a white flower are crossed and the result is a pink flower results? Incomplete dominance red X white = Pink

• 4. When the F1 generation of this cross (above) is crossed, what do you get for a phenotypic ratio? 1:2:1 red : pink : white

• 5. What does it mean to be codominant? Both traits equally show in the phenotype.

• What is an example of co dominance? Blood types A and B are co dominant and sickly cell trait is co dominant.

• 6. Why is sickle cell an advantage with regard to malaria? The sickle cell trait rbc’s are resistant to the malaria disease_ thus keeping this trait around as an advantage.

• 7. Human blood groups have several alleles to determine the blood type. What is this called? _multiple alleles

• 8. What are the alleles for blood type? _A_ ___B_ and O or i

• 9. What happens to the number of possible phenotypes when you have multiple alleles? It increases the number of possible phenotypes and genotypes

• 10. What is epistasis? When one alleles causes another to be masked or to not show

• 11. What is an example of it?

• 12. What are the sex chromosomes? How many are there in humans?

• Females have __ males have

• 13. What are the autosomes? How many in humans?

• 14. What are traits on the X chromosome called?

• 15. Do males or females more often have recessive sex-linked disorders? why ?

• 16. Do males or females more often carry the disorders? why ?

• 17. What are some examples of sex-linked traits?

• 18. What does polygenic mean?

• 19. What is an example of a polygenic trait?

• 20. Can you usually tell if a trail is polygenic?

• 21. Can the environment have an effect on the expression of a gene?

• 11. What is an example of it? _coat color in dogs from yellow to black.

• 12. What are the sex chromosomes? Chromosomes responsible for determining if an organism is a male or a female X or Y How many are there in humans? _2 1 pair Females have _XX_ males have XY

• 13. What are the autosomes? All chromosomes that are not sex chromosomes _How many in humans? 22 pair or 44

• 14. What are traits on the X chromosome called? Sex linked

• 15. Do males or females more often have recessive sex-linked disorders? males_ why ? females have a second X with the other gene to “correct the recessive one males do not!

• 16. Do males or females more often carry the disorders? Females why ? they have 2 X chromosome , one cn be the recessive while the other can be the “normal” one. They can be heterozygous.

• 17. What are some examples of sex-linked traits? Red-green colorblindness is an example. Hemophilia is another

• 18. What does polygenic mean? Traits that have many genes that cause them.

• 19. What is an example of a polygenic trait? Skin color, height, eye color, and fingerprint.

• 20. Can you usually tell if a trail is polygenic? When there is a range of phenotypes that forms a bell curve

• 21. Can the environment have an effect on the expression of a gene? Yes, such as the temperature, things people eat, exercise, sunlight, genes that are cooler are darker as in the Siamese cat and pigment production.

Section 3 vocabulary:

• 1. Karyotype 2. nondisjunction

karyotype

Karyotype activity

• http://learn.genetics.utah.edu/content/begin/traits/karyotype/

Using karyotypes to predict disorders

• http://learn.genetics.utah.edu/content/begin/traits/predictdisorder/

• Section 3 vocabulary: 1. Karyotype 2. Nondisjunction

• 1. Where in a Karyotype would you look to see if a person would have Down’s syndrome? __________________________

• 2. What is the usual cause of Down’s syndrome? _________________________________________________________

• Section 3 vocabulary: 1. Karyotype 2. Nondisjunction

• 1. Where in a Karyotype would you look to see if a person would have Down’s syndrome? At the 21st chromosomes, look for an extra chromosome there.

• 2. What is the usual cause of Down’s syndrome? Non disjunction due to older maternal eggs.

Summary of genetics video

• http://www.bing.com/videos/search?q=genetic+videos&view=detail&mid=E7AEA272F3FDDB885163E7AEA272F3FDDB885163&first=0&FORM=LKVR19

Summary of genetics video

• http://www.bing.com/videos/search?q=genetic+videos&view=detail&mid=E7AEA272F3FDDB885163E7AEA272F3FDDB885163&first=0&FORM=LKVR19

• . Do the genetic problems on the web site: http://biology.clc.uc.edu/Courses/Bio105/geneprob.htm for practice with a variety of types of problems. Write out your answers to the first 4 problems as you do them on a sheet of paper.

Trisomy 21

Chromosomal Aberrations  -  Mistakes of Meiosis

   • Aneuploidy - Variation in chromosome #   • monosomy - 1 less than normal

                                                                       • disomy - normal (diploid)

                                                                       • trisomy - 1 more than normal 

       via   non-disjunction    • (trisomy 21 - Down Syndrome )

Alterations of Chromosome Structure

         

• breakage of chromosomes can lead to 4 types of structural changes                                                          1) deletions - chromosome fragment without centromere is lost     cri du chat: deletion on chromosome 5

• mental retardation, small head & face, cry of a cat, fatal               2) duplications - a segment is repeated               3) inversions - a segment reverses is linear sequence               4) translocations - both segments moves form one chromosome to another

amniocentesis

MUTATIONS

•Any change

in

DNA

Point mutations

• A single base pair is changed.

• THE DOG BIT THE CAT

• THE DOG BIT THE CAR

• Only one letter is different yet….

Frame shift Mutation

• A single base is added or deleted

• This causes the entire line to be read differently!!!

• CCG AAU GGU

• ADD ONE C AND

• CCCGAAUGGU READS

• CCC GAA UGG U

CHROMOSOMAL MUTATIONS

• Parts of chromosomes break off

• Join to the wrong chromosome

• Chromosomes do not separate correctly during meiosis: non disjunction

Trisomy monosomy

• Three where there should be two

• Or

• One where there should be two.

Class Traits Data Table

•

Dominant

Trait

Number of Students

Recessive Trait Number ofStudents

Free earlobes Attached earlobes

Hair on finger No hair on finger

Widow's peak No widow's

Curly hair Straight hair

Cleft chin Smooth chin

Smile dimples No smile dimples

Take a Class Survey

• The traits illustrated above are determined by the presence of dominant and recessive alleles. Survey the members of your class to complete the Class Traits Data Table.

Results of 1000 students surveyed• Free earlobes 65.07• Attached earlobes 34.93• Hair on fingers 62.29• No hair on fingers 37.71• Widow's peak 50.52• No widow's peak 49.48• Curly hair 50.24• Straight hair 49.76• Cleft chin 47.65• Smooth chin 52.35• Smile dimples 62.60• No smile dimples 37.40

• answer the following questions.

• 1.Which traits controlled by dominant alleles were shown by a majority of students in your class? Which were shown by a majority of all students?

• 2. Which traits controlled by recessive alleles were shown by a majority of students in your class? Which were shown by a majority of all students?

• 3. Compare your answers to questions 1 and 2. Are traits controlled by dominant alleles more common than traits controlled by recessive alleles?

• 4. Compare the data for your class with the data for all students. How do the percentages compare?

• 5. Suggest a hypothesis that might explain any large (plus or minus 10%) differences found between the data for the class and for all students.

BIOETHICS

• 1. What are some of the consequences of using selection to create breeds of dogs?

• 2. What are some of the benefits of selecting traits in plants or crops?

• 3. What effect might selective breeding of crops and animals have on the human population?

Look at this pedigree

1. Is the trait dominant or recessive?

2. How do you know?

Trait shows in phenotype

Types of DNA videos

• http://learn.genetics.utah.edu/content/extras/molgen/index.html

Review Questions

• 1. Where are genes located?• On a chromosome• 2. How many alleles does one person have for

each trait?• Two• 3. What is another name for a graphic

representation of a family tree?• Pedigree chart• 4. An example of continuous variation is• Skin color• 5. A trait that results from blending two traits is

called • Incomplete dominance

• 6. When two traits both show up in the phenotype it is called• Co dominance• 7. If a trait is sex linked it usually shows up in the • Male• 8. Any change in the DNA is called a • Mutation• 9. A mutation that changes one nitrogen base into another is

called • Substitution/ point mutation• 10. A mutation that is caused by an additional base being

added to the code is called• An addition• 11. If the base is removed from the code, it is called a • Deletion• 12. The addition of an extra base causes the entire chain of

codons to be miss-read, this is called a • Frame-shift mutation

• 13. When an entire chromosome is added it is called • Trisomy• 14. When an entire chromosome is missing it is called• Monosomy• 15. Where is the DNA of a cell located?• In chromosomes in the nucleus• 16. What molecule makes a copy of the DNA and

moves it out into the cytoplasm/• Messenger RNA /mRNA• 17. What is the process of copying the DNA into RNA

called?• Transcription• 18. What molecule has an amino acid on one end and

an anticodon on the other?• Transfer RNA/ tRNA

• 19. What does the code in the DNA tell the cell how to put together?

• Amino acids to form proteins• 20. What are the nitrogen bases found in DNA?• Adenine, guanine, thymine, cytosine• 21. What base replaces thymine in RNA?• URACIL• 22. Is DNA usually a single or double strand?• Double• 23. Is RNA usually single or double stranded?• Single• 24. What happens in DNA replication?• DNA unzips and new nucleotides match up to

form 2 strands of DNA from the original one• 25. How many nitrogen bases are found in a codon?• Three