1. Chapter 4 - Modern GENETICS
Cells and Heredity Textbook

2. What organisms did Mendel study?
Gregor Mendel did a lot to initiate and progress the Genetics--study of heredity.
What organisms did Mendel study?
He studied pea plants.
Why were traits in pea plants (like tallness)easy to study?
These traits were clearly defined—like tall and short, green or yellow, wrinkled or smooth. There is often a definite dominant and definite recessive trait.
A Single gene with 2 alleles controls a trait.

3. REVIEW of TRAITS: One of the most important principles that governs life is inheritance of genes. There are over 200 traits that are transmitted from generation to generation in humans. The physical traits are those that are expressed and what makes every individual an 'individual'. These genes reside on specific segments of the DNA. Each gene is grouped to form a chromosome and each chromosome is found in the nucleus of the cell. There are two copies of each gene present in an individual's body with the exception of sex cells. It is generally believed that the dominant alleles are the most common traits observed in a population. However, this is not a complete fact. Many times the alleles may be dominant, but the allele for expression of a trait may be recessive. Thus, many times the dominant trait is not expressed in an individual. Let me explain this inheritance pattern in the following examples.

4. Now , we are going to look at:
“Mendelian” traits in humans.
Many of these traits have been claimed to be controlled by ONE gene with just 2 alleles. As we continue to learn more, some scientists disagree.

19. As you can see….
Traits like hitchhikers thumb, mid-digit hair, cleft-chin, curly hair, handedness, etc are examples of…
“Mendelian Inheritance”
What is mendelian inheritance???
Traits are controlled by a single gene with 2 alleles, and one alleles is generally dominant over the other.

20. HOWEVER……
There are a variety of inheritance patterns for the many traits that humans have.
Right now , brainstorm traits that are more complicated than “Mendelian traits”
Ex: height, skin color, eye color, hair color, metabolism, body build, etc.

21. Some Inheritance Patterns
1. Single gene with 2 alleles
2. Single Gene with multiple alleles
3. Traits controlled by many genes
4. Sex – linked genes

22. Single Genes with Multiple Alleles
These genes have 3 or more forms (alleles).
Humans can only carry 2 of them
Ex: Blood
Alleles:
IA, IB, I
IA and IB are codominant
Blood Types
A, B, AB, O

23. Traits controlled by many genes
At least 4 different genes control height
3 or more genes control skin color

24. Sex Chromosomes carry genes that determine whether a person is male or female, and some other traits.
XX = female
All female sex cells have an X chromosome
XY = male
Half of the male sex cells have an X chromosome and half have a Y chromosome

25. Sex Linked Genes
These genes are carried from parent to offspring on the sex chromosomes.
Sex-linked traits
Ex: red/green colorblindness
Occur more often in males.

26. If there is a sex-linked trait controlled by a recessive allele,
If a guy gets it, he will have the trait because he only has one X chromosome.
If a girl gets it, there’s a good chance her other X chromosome will be normal and she will not express the trait.

27. Ex: Colorblindness
It’s a trait controlled by a recessive allele on the X chromosomes
Carrier = a person who has one recessive allele for a trait and one dominant allele. They do not have the trait.

28. Effect of Environment
Many of a person’s characteristics are determined by an interaction between genes and the environment
Ex: bad dietaffects height
Ex: hair dye

29. DO NOW
Pg 117 Discover Activity

30. Human Genetic Disorders
Genetic Disorder = abnormal condition that a person inherits through genes or chromosomes
Caused by
mutations in DNA
Change in overall structure of chromosomes
Change in number of chromosomes

31. Genetic Disorders Cystic Fibrosis Sickle-cell disease Hemophilia
Down syndrome

32. Cystic Fibrosis
Body produces too thick of mucus in lungs and intestines
Mucus fill the lungs so the person has trouble breathing
The disease is carried on a recessive allele
The recessive allele has a mutation with 3 bases missing from the DNA

33. Sickle-Cell Disease
Red blood cells has a special protein that carries oxygen—called hemoglobin
People with this disease have abnormal hemoglobin, so their red blood cells have abnormal shapes that clog blood vessels and can’t carry oxygen well.
The sickle-cell allele is codominant. A person with one normal and one sickle-cell allele will produce half normal and half sickled blood cells.

34. Hemophilia A person’s blood clots slowly or not at all.
They are at danger for internal bleeding from small bumps and bruises.
It occurs on the recessive allele of the X chromosome
It’s a sex-linked disorder

36. A person with this has an extra copy of chromosome 21 in their cells.
Down Syndrome
A person with this has an extra copy of chromosome 21 in their cells.
Why does this happen? Chromosomes fail to separate properly in meiosis.

38. Pedigrees
A chart or “family tree” use to track witch members of a family have a particular trait

39. Which trait do you think is dominant? Which is recessive?

40. Managing Genetic Disorders
Doctors use tools such as karyotypes to help diagnose genetic disorders.
People with genetic disorders are helped through medical care, education, job training, and other methods

41. What’s a Karyotype??
It’s a picture of all the chromosomes in a cell. Chromosomes are arranged in pairs.
They can reveal whether a person has the correct number of chromosomes.

42. Sec 3 - ADVANCES IN GENETICS
Genetic Techniques to produce organisms with desirable traits:
1. Selective Breeding
2. Cloning
3. Genetic Engineering

43. HISTORY: 1. Selective Breeding
In Mexico thousands of years ago, Mexican farmers saved seeds from the healthiest corn plants each year. Then, in the spring, they planted those seeds. After a while, plants produced better corn and crops were improved.

44. SELECTIVE BREEDING Inbreeding
Crossing 2 individuals that have similar characteristics. Inbred organisms have alleles very similar to those of their parents.
Ex: Take male and female turkeys that are both plump and both grow quickly. Their offspring will too.
THE BAD: these organisms are genetically very similar and often inherit alleles that lead to genetic disorders

45. SELECTIVE BREEDING Hybridization
Cross 2 genetically different organisms so that the offspring will have the best traits from both.
Ex: cross a McIntosh apple with a Red Delicious to get Empire.

46. 2. Cloning PLANTS: ANIMALS:
Clone = organism that has exactly the same genes as the organism from which it was produced
PLANTS:
African violet, just cut a stem from one plant and put it in soil.
ANIMALS:
Sheep and pigs have been cloned

47. 3. Genetic Engineering
Genes from one organism are transferred into the DNA of another organism.
make medicines
improve crops

48. Genetic Engineeringin Bacteria
Pg 126

49. Genetic Engineering…
Scientists take human genes and insert them into cells of cows so that they start to produce a human protein in their milk. This protein is needed by people with hemophilia.

50. Genetic Engineering……
Scientists insert genes into the cells of plants like tomatoes and rice so that they will survive despite cold temperatures or poor soil.

51. Gene Therapy- A Thing of the Future
Inserting copies of a gene DIRECTLY into a person’s cells.

52. Concerns about Genetic Engineering
What are long-term effects?
Are they safe?
Are genetically engineered crops okay to eat?
Will these crops harm the environment?
Will these foods cause health problems?
Scientists are needed to study these concerns!

53. Learning about Human Genetics
THE HUMAN GENOME PROJECT
Genome = ALL the DNA in one cell of an organism
Scientists are trying to identify the DNA sequence of every single gene
Chromosome 1 was completed in yay.
DNA FINGERPRINTING