Mission to Mars. Day 8 Heredity

Transcription

1 Mission to Mars Day 8 Heredity 7.14A define heredity as the passage of genetic instructions from one generation to the next generation 7.14C recognize that inherited traits of individuals are governed in the genetic material found in the genes within chromosomes in the nucleus

2 Genetics: The study of heredity

3 Heredity = the passing of traits from parents to offspring

4 The Incredibles

5 Heredity - Trait = A feature or characteristic of a person. It can describe Physical appearance Behavior tendencies Predisposed to medical conditions A person s traits are influenced by: their genetic inheritance environmental factors What is a trait?

6 Where are these traits located? DNA! The DNA carries the traits that make you who you are!

7 Trait = a feature or characteristic of a person Traits can control or drive Physical appearances Physical appearances are things such as hair color and texture, face shape, height, etc. hair color hair texture eye color face shape smile shape

8 Trait - example Physical appearance (example hair color) Genetics: genes determine natural hair color hair color hair texture eye color face shape smile shape

9 Trait - Physical appearance (hair color) Genetics: genes determine natural hair color Environment: sun or hair dyes can change hair color hair color hair texture eye color face shape smile shape

10 Trait - Traits can also drive or control behavior tendencies Behavior means things such as whether you are left or right handed Your gait (the way you walk) The way you smile, etc.

11 Trait Behavior example Behavior tendencies: to use a certain hand Genetics: genes determine the tendency to use you left hand for tasks

12 Trait - Genetic traits can drive Behavior tendencies Genetics: genes determine the tendency to use a certain hand Environment: can learn to use the opposite hand

13 Trait - Medical Predisposition Your genes can also mean that you are predisposed to certain medical conditions Predisposed means that there is an increased likelihood of developing a particular disease These genetic changes contribute to the development of a disease but do not directly cause it. Some people with a predisposing genetic variation will never get the disease while others will, even within the same family.

14 Trait - Medical predisposition example Predisposed to medical conditions Genetics: genes determine a risk of heart disease

15 Trait - medical example Predisposed to medical conditions Genetics: genes determine a risk of heart disease How might you change that? Environment: eating healthy foods and exercising can reduce risk of heart disease

16 Traits are talked about in two different ways: 1. Genotype = a person s combination of alleles (this is the genetic makeup ) The genotype is the code for the phenotype

17 2. Phenotype - Phenotype = a person s version of a trait physical appearance hair color: black eye color: blue hair texture: straight

18 Gene - Gene = part of a person s DNA that influences a trait Eye color gene Face shape gene Hair color gene

19 Allele - Alleles - different versions of a gene; even within the same family different members can have a different version of the eye color gene (for example) Eye color gene: brown allele Eye color gene: blue allele

20 Brainstorm - List 3 possible alleles (varieties) for the hair color gene. Are there other possibilities for types of hair as well? Hair color gene What about curly, thickness, etc.

21 Let s take a look: How do scientists show genes in action? Did you know you can predict things such as hair color and eye color? Scientists use something called a Punnett square to predict genotypes and phenotypes from parents to offspring

22 Representing Alleles Letters are used to represent the variety of genes, the alleles It is common to pick the dominant trait and make that the letter that is used. For example: brown eyes are dominant, choose B, so the recessive gene would be represented as lower case b

23 Types of Alleles - 1. Dominant Allele (will show) Represented by a capital letter Example: B for brown eyes 2. Recessive allele (not always shown) Represented by a lowercase letter Example: b for blue eyes

24 Number of Alleles - All people have 2 alleles for every gene (one from each parent) Allele of eye color gene from dad Allele of eye color gene from mom

25 Recall that: Genotype = a person s combination of alleles (this is the genetic makeup ) Phenotypes are the physical results from the genes! You can determine both types with letter combinations Allele of eye color gene from dad Allele of eye color gene from mom

26 Genotypes and alleles A person may inherit 2 of the same alleles = this is known as purebred 2 dominant alleles = purebred dominant (also called homozygous) Example: B and B Genotype = Mom Dad Phenotype = B B Child

27 Genotype - how it is represented: A person may inherit 2 of the same alleles = purebred Genes! 2 dominant alleles = purebred dominant Example: B and B Genotype = BB Phenotype = Mom B Child Dad B

28 Genotype and Phenotype A person may inherit 2 of the same alleles = purebred 2 dominant alleles = purebred dominant Example: B and B Genotype = BB Mom Phenotype = brown eyes Dad B Child B

29 Genotype and Phenotype Purebred can be dominant or recessive, it simply means the alleles are the same 2 recessive alleles = Mom Dad b Child b

30 Genotype and Phenotype 2 recessive alleles = purebred recessive Example: b and b Genotype = Phenotype = Mom Dad b Child b

31 Genotype and Phenotype A person may inherit 2 of the same alleles = purebred 2 recessive alleles = purebred recessive Example: b and b Genotype = bb Phenotype = Mom b Child Dad b

32 Genotype and Phenotype A person may inherit 2 of the same alleles = purebred 2 recessive alleles = purebred recessive Example: b and b Genotype = bb Phenotype = blue eyes Mom b Child Dad b

33 A person may inherit 2 different alleles = known as hybrid or heterozygous Dominant allele masks recessive allele Example: B and b Genotype = Phenotype = Mom Dad Mom Dad B b -or- b B Child Child

34 A person may inherit 2 different alleles = hybrid Dominant allele masks recessive allele Example: B and b Genotype = Bb Phenotype = Mom Dad Mom Dad B b -or- b B Child Child

35 A person may inherit 2 different alleles = hybrid Dominant allele masks recessive allele Example: B and b Genotype = Bb Phenotype = brown eyes Mom Dad Mom Dad B b -or- b B Child Child

36 Practice Brown hair (B) is dominant to blond hair (b). Genotype Phenotype purebred dominant purebred recessive hybrid

37 Practice Brown hair (B) is dominant to blond hair (b). purebred dominant purebred recessive hybrid Genotype BB Phenotype Brown hair

38 Practice Brown hair (B) is dominant to blonde hair (b). purebred dominant purebred recessive hybrid Genotype BB bb Phenotype Brown hair Blond hair

39 Practice Brown hair (B) is dominant to blond hair (b). purebred dominant purebred recessive Genotype BB bb Phenotype Brown hair Blond hair hybrid Bb Brown hair Which genotypes are purebred? Which is hybrid?

40 Practice Right-handedness (R) is dominant to left-handedness (r). What genotype(s) could a right-handed person have? RR or Rr What genotype(s) could a left-handed person have? rr

41 Practice In pea plants, green peas (G) are dominant to yellow peas (g). What would be the genotype of a: -purebred green pea? GG -hybrid green pea? Gg -yellow pea? gg

42 Hands on Practice: Make sure you have the Punnett square worksheet Step 1: Identify the parent genotypes and write them down: Homozygous (2 of the same) dominant RED capital R Homozygous recessive WHITE lower case r

43 Hands on Practice Step 2 place the parents genotypes in place to be crossed R = red r = white

44 Hands on Practice Step 3 combine the genotypes for each box R = red r = white

45 Hands on Practice Step 4 write the Write out the genotypes (letters in the box) and then the phenotypes for all offspring

46 Hands on Practice Let s start with the first box: Look at the box as a whole, or 100%. Each square is worth 25% Here are the genotypes and the percentages of each type below - Genotypes: 25% homozygous dominant (RR), 50% heterozygous (Rr), and 25% homozygous recessive (rr)

47 Hands on Practice Now we know the genotypes, what are the phenotypes, or what colors are the flowers? Phenotypes: 75% Red flowers and 25% white flowers

48 Now practice on your own! Punnett square practice

49 Let s do the first one together:

50 Double check you have it! Male Female