1. Unit 5

2. Haploid vs Diploid
Mitosis creates Diploid cells, which are cells that contain two complete sets of chromosomes.
We abbreviate this 2n.

3. Haploid vs Diploid
In a Haploid cell, only ONE complete set of chromosomes is present.
We abbreviate it n.

4. Meiosis
Meiosis is sexual reproduction. Only occurs in the sex organs – ovaries and testes.
Results in the production of gametes, which are sex cells.
Meiosis begins with a diploid cell, and the end result is 4 haploid cells.
Meiosis is similar to Mitosis because there is still Interphase and PMAT, but in Meiosis, PMAT occurs twice.

5. Stages of Meiosis Interphase MEIOSIS I Prophase I
The DNA replicates
MEIOSIS I
Prophase I
Spindle fibers form and the chromosomes pair up.
These paired chromosomes are called Homologous Chromosomes.
While the Homologous Chromosomes are paired up, crossing over occurs.

6. Crossing Over
During crossing over, genetic information (DNA) is exchanged.
The result is chromatids that are no longer identical.

7. Meiosis I Metaphase I The homologous chromosomes line up in the cell.
Anaphase I
The chromosomes pull apart.

8. Meiosis I Telophase I The cells begin to divide into 2 cells.
Cytokinesis
2 individual, haploid cells are created.

9. Meiosis II Prophase II Chromosomes form, spindle fibers form
Metaphase II
Chromosomes line up

10. Meiosis II Anaphpase II Sister chromatids pull apart Telophase II
The 2 cells are now dividing into 4

11. Meiosis II Cytokinesis
4 haploid cells are formed. All are genetically different.

12. Stages of Meiosis Gamete formation in males
Gamete formation in females

13. Meiosis Video

14. Genetic Variation
How do we each become our own individual with our own unique set of genes? How does genetic variation occur?
Genetic variation occurs during
crossing over (Prophase I)

15. Genetic Variation cont.
Occurs during random assortment of chromosomes during the different stages of meiosis.
This is the Law of Independent Assortment.

16. Genetic Variation
Law of Segregation – during meiosis, the chromosome splits and the chromatids segregate.
Each gamete gets half of the genetic information.

17. Genetic Variation cont.
Occurs during fertilization – ½ of DNA comes from each parent
Gene mutation
Non-disjunction – chromosomes did not properly split

18. Karyotype
A karyotype is a picture or profile of a person’s chromosomes.
Chromosomes are paired up and numbered 1-22, and the 23rd chromosome is labeled XY and determines gender.
We use karyotypes to show chromosomal abnormalities.

20. What can you notice about this Karyotype – what is it missing?
On the X and Y chromosomes, there is only 1 X chromosome. It is missing a second sex chromosome.
This is called Turner’s Syndrome.

21. More practice with karyotypes
Open your textbook to…Pg. 318
Chromosomes for Male ?
Female?
Pg. 329
Male of Female?
Normal or not?
Pg. 335
Male or Female?

22. This is a Karyotype for Trisomy 21.
Notice there are 3 chromosomes on the 21st chromosome.
This was caused by a non-disjunction.
Trisomy 21 is also known as Down Syndrome.

23. Gregor Mendel Father of genetics Austrian Monk
He did experiments on Pea plants to show how traits were passed down
He studied the shape, seed color, outer coat, pea pod, and stem to see which traits occurred more or less often.
He was the first to observe:
The Law of Independent Assortment
The Law of Segregation

25. Genotype Phenotype The genes of the organism
What the organism looks like

26. Allele – one or more versions of a gene.
Located at a specific position on a specific chromosome
Dominant Allele
What will be expressed.
It “masks” other alleles.
Written in upper case.
Recessive Allele
It will only be expressed if the dominant allele is not present.
Written in lowercase.

27. Heterozygous
Hybrid
Having 2 different alleles for a gene
Homozygous
Same; purebred
Have 2 of the same alleles for a gene

28. Punnett Squares
The diagram used to predict the genotype and phenotype.
As a class do the Simpson’s genetics lab. Academic complete #1-4. Honors #4.

29. Punnett Squares B BB Bb b Bb bb
Ex. You have 2 mice that are heterozygous for their brown coats. Brown is the dominant color and white is the recessive. Create a Punnett Square that shows the cross between these two mice.
B b
B BB Bb
b Bb bb
What are the ratios of genotypes you will get?
1:2:1
What percent of each phenotype will you see?
75% brown
25% white
Simpson’s Genetics worksheet.
Academic do #1-4. Honors do #4 - ___

30. Incomplete Dominance Punnett Square

31. Incomplete Dominance
When one allele is not completely dominant over the other.
The heterozygous genotype will result in a blend.
Ex. Snapdragons

32. Co-dominance Co-dominance results in the expression of both traits.
Baby lab hair type through skin tone

33. Polygenic Traits Traits which are coded for by more than one allele.
Usually results in blending of traits.
Ex. Hair color, eye color, skin color

34. Blood Types Blood types are an example of codominance.
A and B are both dominant.
O is recessive.

36. Sex-Linked Traits Trait is more likely to be inherited by males.
Recessive
Genes for these traits are found on the X and not the Y chromosome.
This is why the X is bigger than the Y.

37. Sex-Linked Traits

38. Examples of Sex-linked Traits
Red/Green Colorblindness
Hemophilia – the inability of the blood to properly clot
Show Ameoba sisters video on sex-linked traits:

39. Pedigrees
Charts are made to show how traits are passed down through the generations.
Things to note:
Generations are denoted by
Roman numerals.
Number individuals from
left to right.

40. Pedigrees Symbols: Female Male Married Divorced Deceased Affected Male
Siblings

41. Hemophilia in the Royal Family

42. Bellwork
From Genetics practice problems, finish the page on Blood Type Punnett Squares
Finish reading and answering questions on blood types

43. What else can Punnett Squares be used for?
Punnett Squares can also be used to show how genetic disorders get passed down from parent to offspring.
PKU is a recessive gene.
Ex. Phenylketonuria (PKU)
A genetic disorder that causes the build up of the amino acid phenylalanine in the body.
Symptoms: delayed development
Intellectual disability P p
Behavioral, emotional and social problems
Psychiatric disorders P PP Pp
Neurological problems that may include seizures
Hyperactivity
Poor bone strength p Pp pp
Skin rashes (eczema)

44. Genetic Disorders Cystic Fibrosis
Most commonly caused by a deletion of 3 base pairs on the 7th chromosome.
Approx babies are born each year in US with Cystic Fibrosis.
It is estimated that 10 million Americans
are carriers of the gene.
Recessive
Symptoms:
Respiratory problems
Mucous in the lining of the lungs

45. Genetic Disorders Huntington’s Disease Dominant Trait
Caused by a mutation on the 4th chromosome
Approx. 1 in 30,000 people in US have Huntington’s
Symptoms:
Affects thinking, motion,
and movement
Symptoms do not usually
appear until age 30-50

46. Genetic Disorder Chart
Recessive, Dominant, or Chromosome Affected
Symptoms/Traits