1. Genetics
Unit 6

2. What is genetics? Genetics: Is the science of heredity
Genetics began with Mendel
Mendel is considered the “Father of Genetics”
Mendel was a monk who experimented with pea plants to study heredity

3. What is a trait?
Trait: Is a notable feature or characteristic in an organism
Physical traits
Examples - Hair color, eye color, & height
Behavioral traits
Example – Sheepdog has herding instincts
Medical conditions
Examples – Cancer, Sickle cell, cystic fibrosis

4. Why did Mendel study peas?
Peas reproduce and grow quickly
They had easy to observe traits
Can reproduce using 2 different plants or using 1 plant
True-Breeding: Can produce offspring with only 1 parent
Cross Pollination – 2 parents self-fertilizing/true-breeding

5. But what color will the offspring show?
What are alleles?
Allele: Alternative form that a single gene may have for a particular trait. (huh?)
A gene in a particular place on a particular chromosome will express a particular trait….like flower color
Purple is an Allele coming from mom
But what color will the offspring show?
Chromosome from MOM
Chromosome from DAD
White is an Allele coming from dad

6. How do alleles determine what traits will show?
Some alleles are dominant and others are recessive
Do you have to remember which traits are dominant and which are recessive?...
Dominant: A trait that will appear (show)
* Represented with a CAPITAL letter
Example: Tall (T), Black (B), Brown (B)
NO…
Punnett Square questions will give you clues or will tell you in the question! You HAVE TO READ!
Recessive: A trait that is masked (hidden) if a
dominant allele is present, but will show if both
alleles are recessive
* Represented with a lower case letter
Example: short (t), blond (b), blue (b)

7. I do you know a trait will show or not?
Rule #1: If there is a dominant trait present, it will always show that trait.
Tall is dominant over short
Capital “T” bosses the little “t”
T T
T t
Dominant
Dominant
Dominant
Recessive
Shows Tall
Shows Tall

8. I do you know a trait will show or not?
Rule #2: If there is NOT a dominant trait present, then the recessive trait will always show.
Tall is dominant over short
t t
Recessive
Recessive
Shows Short

9. Who is considered the “Father of Genetics”? Darwin Hooke Mendel Paquin
Clicker Question #1
Who is considered the
“Father of Genetics”?
Darwin
Hooke
Mendel
Paquin

10. Clicker Question #2
These plants were used in Mendel’s experiments because they grow & reproduce quickly:
Peas
Corn
Wheat
Roses

11. What is true-breeding? 2 parents reproduce offspring
Clicker Question #3
What is true-breeding?
2 parents reproduce offspring
2 offspring with three parents
Self fertilizing plants
Cross pollinating plants

12. Tall is dominant over short
Clicker Question #4
If a girl has Tt, she will show:
Short
Tall
Both (a) & (b)
None of the above
Tall is dominant over short

13. Before we start Punnett Squares, we have a few more things to learn…

14. What are some terms that will help with understanding Punnett Squares?
Homozygous: Organism with 2 of the same alleles for a particular trait. Also called “pure”.
Examples – TT tt DD dd
Same sized letters!
Same sized letters!
Same sized letters!
Same sized letters!
Same
Homo means: ________
Think: Same SIZED letters

15. What are some terms that will help with understanding Punnett Squares?
Heterozygous: Organism with 2 different alleles for a particular trait. Also called “hybrid”.
Examples – Tt Dd Gg Bb
Different sized letters!
Different sized letters!
Different sized letters!
Different sized letters!
Different
Hetero means: __________
Think: Different SIZED letters

16. What are some terms that will help with understanding Punnett Squares?
Phenotype: The observable characteristic or outward expression of an allele pair
Characteristics you can see with your eyes!
Think: Phenotype -- Physical
Black Hair
Blond Hair
Red Hair
Brown Hair

17. What are some terms that will help with understanding Punnett Squares?
Phenotype
Characteristics you can see with your eyes!
Multi color Butterfly
Blue Butterfly
White Butterfly
Orange Butterfly

18. What are some terms that will help with understanding Punnett Squares?
Genotype: The organism’s allele pairs
Characteristics you can NOT see with your eyes!
Think: Genotype – Genetic Code HH GG bb Gg Hh Bb hh gg BB

19. Another term for heterozygous is:
Clicker Question #5
Another term for heterozygous is:
Allele
Same
Hybrid
Pure

20. tt is an example of: homozygous heterozygous hybrid all of the above
Clicker Question #6
tt is an example of:
homozygous
heterozygous
hybrid
all of the above

21. tt is an example of: phenotype heterozygous hybrid genotype
Clicker Question #7
tt is an example of:
phenotype
heterozygous
hybrid
genotype

22. Tall is dominant over short
Clicker Question #8
If a boy has tt, he will show:
tall
short
both (a) & (b)
none of the above
Tall is dominant over short

23. Tall is an example of: phenotype Heterozygous pure genotype
Clicker Question #9
Tall is an example of:
phenotype
Heterozygous
pure
genotype

24. What is Mendel’s Law of Segregation?
Law of Segregation: States that the two alleles for each trait separate during meiosis.
During meiosis, the alleles separate
During fertilization, the alleles unite into a pair again

25. What’s the difference between monohybrid ?& dihybrid crosses?
Punnett Square: A diagram used to predict the possible outcomes (offspring) of a particular cross or breeding.
Monohybrid Cross: The use of Punnett Square for 1 trait
(will have 4 boxes)

26. Punnett Square Video

27. What’s the difference between monohybrid ?& dihybrid crosses?
Dihybrid Cross: The use of Punnett Square for 2 traits
(will have 16 boxes)

28. What’s the difference between monohybrid ?& dihybrid crosses?
Law of Independent Assortment: Mendelian law stating that two alleles for each trait separate during meiosis
During Dihybrid crosses: The random assortment of alleles results in four possible gametes…each of which is equally likely to occur
I will show you this when I show dihybrid crosses

29. Sometimes two traits can be dominant at the same time

30. What’s the difference between incomplete dominance and co-dominance?
Incomplete Dominance: Complex inheritance pattern in which the heterozygous phenotype is intermediate between those of the two homozygous parent organisms…huh?
Mixes like paint! R R W RW RW W RW RW

31. What’s the difference between incomplete dominance and co-dominance?
Co-Dominance: Complex inheritance pattern that occurs when neither allele is dominant and both alleles are expressed. B B BW BW W BW BW W

32. Each gamete has only one allele for a trait because of:
Clicker Question #10
Each gamete has only one allele for a trait because of:
recessive
Law of segregation
dominance
phenotype

33. Clicker Question #11
When a white flower & a red flower have pink offspring, this is because of:
Co-dominance
Law of segregation
Law of Independent assortment
Incomplete dominance

34. In speckled chickens, both alleles are express because of:
Clicker Question #12
In speckled chickens, both alleles are express because of:
Co-dominance
Law of segregation
Law of Independent assortment
Incomplete dominance

35. The cross with one trait is called:
Clicker Question #13
The cross with one trait is called:
Dihybrid
Trihybrid
Monohybrid
All of the above

36. A dihybrid cross will have how many squares?
Clicker Question #14
A dihybrid cross will have how many squares? 4 16 18 20

37. When a woman is about 25 weeks pregnant… she can go to the doctor to determine the sex of her unborn child. What determines the sex of the child?

38. All eggs that female carries contain a X sex chromosome Sperm can either have a X or Y sex chromosome

39. To be a girl…. She has two x chromosomes.

40. To be a boy….. He has a X and Y sex chromosome.

41. There is 50% chance that you get either be a boy or girl
There is 50% chance that you get either be a boy or girl. Its all depends on which sperm is the first to reach the egg.

42. Sex-linked Inheritance
Definition: A gene carried on either the X or Y chromosome
X-linked – only found on the X
Colorblindness - recessive
Hemophilia - recessive
Y-linked – only found on the Y
Hair on ears
Can a female be born with this trait?

43. Man with hairy ears!

44. Hemophilia Definition: disorder in which the blood does not clot
Not fatal – just lots of treatments to keep blood volume levels appropriate

45. Xh = hemophilia allele XX or XY = normal XhX = carrier – only females XhXh or XhY = hemophilia

46. Why do men get hemophilia more than women?
Because women will have to have both Xh gene in order to get hemophilia.

47. Pedigree Chart
Pedigrees shows how a specific gene trait is passed down from one generation to the next.

48. Pedigree Chart How many female carriers for hemophilia are there?
Can a male be a carrier?
Could a male with hemophilia have a child who is not affected by or a carrier of hemophilia? How?

49. Karyotype Definition: Picture of the chromosomes from a person’s cell.
How many pairs of chromosomes are there?
What is the gender of the person in this karyotype?
How can karyotypes be useful to doctors?

50. Normal Karyotype vs. Down Syndrome Karyotype. Which one is which?

51. Genetic Disorders
Down’s Syndrome – extra chromosome on Pair 21 – happens because of Non-disjunction in Meiosis
Turner Syndrome – Female – has only 1 X Chromosome – tend to be sterile, may not reach full sexual maturity
Cystic Fibrosis – Recessive disorder – lungs and digestive system don’t work properly and thick mucous builds up in respiratory tract
Kleinfelter’s Disease – male who is XXY – may have feminine-type characteristics
Does not mean they are gay!
Hemophilia – blood disorder
Huntington’s Disease – Autosomal Dominant – Neurological Breakdown - fatal
Sickle Cell Anemia – Autosomal Recessive – sickle-shaped blood cells – can’t move through bloodstream as easily – not fatal – typically found in African Americans

52. Genetic Disorders
Tay-Sachs disease is a rare fatal inherited disorder that progressively destroys nerve cells (neurons) in the brain and spinal cord. Tay-Sachs disease becomes apparent in infancy. Infants with this disorder typically appear normal until the age of 3 to 6 months, when their development slows and muscles used for movement weaken.
 Albinism – a genetic disorder characterized by the complete or partial absence of pigment in the skin, hair, and eyes. This is due to a lack of melanin production.
Achondroplasia – an autosomal dominant genetic disorder that causes dwarfism
Galactosemia – an autosomal recessive genetic disorder in which a person cannot digest the sugar galactose properly. Life threatening complications appear after birth such as lethargy, jaundice, liver damage, bleeding, cataracts, mental retardation..