Unit 10 and 11 Combined Vocabulary: https://quizlet.com/_1ypks5
Unit 11 Vocabulary: https://quizlet.com/_ve9xc
Unit 11 Study Guide: https://quizlet.com/_1e9w1s
Unit 11: Applied Genetics CONCISE Notes
a. Determine the alleles for the parents
b. Use the FOIL method to mix up the alleles - multiply the first, outside, inside, last in the group
c. Put them around the Punnett Square
d. Multiply (cross) the alleles beside the square with the alleles above the square
e. Determine the possible genotypes of the offspring in fraction, percent, and ratio
f. Determine the possible phenotypes of the offspring in fraction, percent, and ratio
i. Ex. Right handedness is dominant to left handedness. Freckles is dominant to no freckles. Cross two parents that are heterozygous for both traits: RrFf x RrFf
ii. FOIL: RrFf = RF, Rf, rF, rf (same for both since they are the same)
Then complete the Punnett Square just as you would a 4 square one.
Video: FOIL and Dihybrid Cross
Video: How to Complete a Dihybrid Cross - Go to 4:09
3. Incomplete Dominance – when neither allele is completely dominant, a third phenotype - a trait that exists that between the two traits
a. Ex. Cross Red Snapdragon and White Snapdragon flowers
b. RR = red; R’R’ = white; RR’ = pink
c. Cross a Red snapdragon (RR) with a White snapdragon (R’R’)
d. All of the offspring are Pink (RR’)
Video: How to Complete an Incomplete Dominance Punnett Square - Go to 4:37
4. Codominance – both alleles are dominant, so both show up - are produced
a. Ex. Cross Black feathered chickens and White feathered chickens
b. B = black feathers; W = white feathers
c. Cross a black feathered chicken (BB) with a white feathered chicken (WW)
d. All of the offspring are Black and White feathered (BW)
Video: How to Complete a Codominance Punnett Square
5. Multiple Alleles – when there are more than two alleles in the gene pool for a trait
a. Ex. Blood Type; Three alleles: A, B, O; Four Main Blood Types = A, B, AB, O (positive and negative types are different)
b. If a person receives the wrong blood type in a transfusion they could die because the cells would clump together causing a clot
Video: How to Complete Blood Type Punnett Square Problems
6. Polygenic Traits – traits controlled by two or more genes
a. Eye color, skin color…
Video: Polygenic Traits
7. Linked Genes – when genes are close together on a chromosome and tend to be inherited together (bends the Law of Independent Assortment)
a. Linkage map (chromosome map)
i. Shows the location of genes on a chromosome
ii. Genes that cross over frequently must be farther apart than genes that cross over rarely
b. Ex. Red hair and freckles seem to be linked
Video: Linked Genes
8. Sex-Linked Genes – when linked genes are found on the sex chromosomes (sex-linked traits)
a. Thomas Hunt Morgan experimented with fruit flies and found that one pair of chromosomes controlled the sex of the organism
i. XX – Girl
ii. XY – Boy
iii. Autosomal chromosomes (autosomes) are the other 22 pairs of chromosomes in humans
iv. The 23rd pair of chromosomes are the sex chromosomes and determine if you are male or female
iv. The 23rd pair of chromosomes are the sex chromosomes and determine if you are male or female
Video: Chromosome Theory of Inheritance and The Fruit Fly
b. X chromosome contains more genes than the Y chromosome
i. This means that a male is more likely to inherit a recessive gene if it is located on the X chromosomes and not found on the Y chromosome
c. Main kinds of sex linked genes in humans
i. Hemophilia – a rare bleeding disorder in which the blood doesn't clot normally; people bleed longer than others; usually occurs in males
ii. Color Blindness - people cannot tell the difference between red and green
1. Carried on the X chromosome
2. XB is normal; Xb is colorblind; Y does not have the allele
3. Females have two alleles for the genes, males only have one
True of all recessive X-linked traits:
1. If the mother has the trait, all of her sons will have it.
2. If the father has the trait but the mother does not carry the trait, then all of their daughters will carry the trait.
3. If the mother is a carrier and the father does not have the trait, daughters have a 50% chance of being a carrier and sons have a 50% chance of having the trait.
4. Males cannot carry the trait, they either have the trait or they do not.
True of all recessive X-linked traits:
1. If the mother has the trait, all of her sons will have it.
2. If the father has the trait but the mother does not carry the trait, then all of their daughters will carry the trait.
3. If the mother is a carrier and the father does not have the trait, daughters have a 50% chance of being a carrier and sons have a 50% chance of having the trait.
4. Males cannot carry the trait, they either have the trait or they do not.
Video: How to Complete X-Linked Punnett Squares - Go to 5:46
Video: X-Linked Traits: Hemophilia
9. Pedigrees – shows how traits are inherited in a family; like a family tree of genetic inheritance
a. Males are represented by squares
b. Females are represented by circles
c. Affected persons (show the trait) are shaded
d. Carriers – someone who is heterozygous for a trait; they do not have the trait but can pass is to offspring - are shown by a half shaded circle or square
e. Roman numeral I is the parent generation (P1)
f. The youngest generation is at the bottom
g. Roman numeral II are the children of the P1 parents and their spouses (F1)
h. Roman numeral III are the children of the F1 children and their spouses (F2)
i. A horizontal line between a circle and square represents parents
j. A vertical line between the parents show the offspring of those parents
k. You must determine if the trait is dominant or recessive and figure out the genotype of different individuals by making Punnett Squares and using all of the skills you have learned thus far.
10. Autosomal Dominant and Autosomal recessive Diseases:
a. Some diseases are carried by dominant alleles (B), some are carried by recessive alleles (b).
b. If the disease is carried by a dominant alleles, then the offspring need only inherit one allele to express the disease (BB or Bb).
c. If the disease is carried by a recessive allele, then the offspring needs two recessive alleles to express the disease (bb).
d. If a person has just one defective gene (Bb), then the person is known as a carrier. They will not express the disease but can pass it to their offspring. Only recessive alleles can be carried.
e. With autosomal recessive inheritance, all affected individuals will be homozygous recessive.
e. With autosomal recessive inheritance, all affected individuals will be homozygous recessive.
f. With dominant inheritance, all affected individuals will have at least one dominant allele. They will be either homozygous dominant or heterozygous.
11. Sex-Linked Diseases
a. With sex-linked inheritance, more males (XY) than females (XX) usually have the trait. Sex-linked inheritance is usually recessive.
Videos: Solving Pedigrees 1 - 3
1
2
3
10. Testing For Genetic Diseases
a. Amniocentesis is removing and testing a sample of amniotic fluid (the liquid that surrounds a fetus).
b. Ultrasound (sonogram) is using sound waves to determine the position and anatomy of the offspring.
c. Fetoscopy is the direct observation of the fetus and surrounding tissues.
Video: Ultrasound Amniocentesis
Other Disorders
11. Muscular Dystrophy – sex-linked - cause muscle weakness and loss of muscle tissue, which get worse over time; tends to form in early childhood
12. Icthyosis Simplex (vulgaris) – sex-linked - a common skin disorder passed down through families that leads to dry, scaly skin
13. Sickle Cell Anemia – codominant autosomal recessive- red blood cells have a crescent shape blocking small blood vessels causing pain and anemia (low red blood cell count); common in African Americans
14. Pedigree – a diagram used by geneticists to chart a trait from one generation to the next
15. Chromosome abnormalities – caused by the addition or deletion of a chromosome or part of a chromosome during meiosis or mitosis; a birth defect
16. Down Syndrome – an extra chromosome in the 23rd pair; causes mental retardation, slanted eyes, thick tongue, poor muscle tone, abnormal palm and footprints
17. cri du chat syndrome (cat's cry syndrome) – part of chromosome 5 is missing; heart defects are common
18. Prader-Willi syndrome, part of chromosome 15 is missing, intellectual disability is common
19. Wolf-Hirschhorn syndrome, part of chromosome 4 is missing. Children with this syndrome have profound intellectual disability
20. Cystic Fibrosis (CF) – autosomal recessive – is a disease that forms thick mucus in the lungs and digestive track. It is one of the most common genetic disease in white Americans. It can be treated with physical therapy, special diets, drug therapies, and gene therapy.
21. Tay Sachs – autosomal recessive – Common in Jewish people; this disease is caused by a missing enzyme that breaks down a lipid produced and stored in the tissues of the central nervous system. The child dies by the age of 2 or 3; no cure
22. Phenylketonuria (PKU) – autosomal recessive – caused by a missing enzyme; can cause severe mental retardation but all babies in U.S. are tested soon after birth. Children that have this disease must have a special diet that does not have phenylalanine in it until they reach around 5 or 6. (look at the side of a Coke can)
23. Huntington’s disease – autosomal dominant – the tissue in the middle of the brain begins to die; symptoms begin between ages of 30-50; these people lose control of their muscles.
Crossing over - the exchange of genes between homologous pairs of chromosomes
Cancer - uncontrolled cell division
Karyotype - a chart of matched chromosomes used to determine if there is an unusual number of chromosomes
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