1. Anatomy & Physiology I
Unit Five

2. The Characteristics and Functions of Meiosis
Production of gametes
Assures correct chromosome numbers in offspring
Creates new combinations of genes
Begins with a diploid sex cell & ends with non-identical haploid gametes

3. Meiosis
Meiosis is the cell division process by which gametes are produced
It occurs only in sex cells that are found in the gonads

4. Meiosis
The process goes through two meiotic divisions – meiosis I and meiosis II

5. Meiosis
Homologous chromosomes

6. Meiosis

7. Meiosis

8. Meiosis

9. Meiosis vs. Mitosis

10. Genetics Genetics – the study of heredity
Heredity – the passing of traits from one generation to the next
Trait – a physical or physiological characteristic coded for by a gene
Gene – a portion of a chromosome that codes for a particular protein
Allele – a form of a gene

11. Genetics
Dominant allele – an allele that masks the effects of the other
Recessive allele – an allele that can be masked by a dominant allele
Locus – the position of a gene on a chromosome

12. Genetics
Homologous chromosomes – a pair of chromosomes, one each from the female & male parent, that have identical structure and gene loci

13. Homologous chromosomes
Genetics
Mom (female)
Dad (male)
Recessive allele
Dominant allele
Homologous chromosomes

14. Genetics Genotype – the set of genes an organism has
Homozygous – alleles are the same type
Heterozygous – alleles are different

15. Genetics Phenotype – the expression of the genotype
Purebred – having a homozygous genotype
Hybrid – having a heterozygous genotype

16. Genetics
Codominance – the two alleles at a locus are equally expressed
Karyotype – a chart of the chromosomes of an organism, arranged in order by size and structure

17. Genetics

18. D D d d D d

19. D D Dd d
Punnett Square

20. D D d d D d D d D D d d

21. D d DD Dd dd D d Complete Dominance Monohybrid Cross
Genotypic Ratio – 1:2:1
Phenotypic Ratio – 3:1

22. Complete Dominance

23. D d Dd dd d Complete Dominance Monohybrid Cross Genotypic Ratio – 2:2
Phenotypic Ratio – 2:2

24. A O AB BO AO OO B O Codominance Genotypic Ratio – 1:1:1:1
Phenotypic Ratio – 1:1:1:1

25. Autosomal vs. Sex Linked
Autosomes – all chromosomes except for the ones that determine sex
Sex chromosomes – chromosomes that determine sex
Sex linked traits – traits controlled by genes on the sex chromosomes

27. XB Xb
XBXb
XbXb
XBY
XbY Xb Y
Sex Linked Cross

29. Human Sex Chromosomes ♀ ♂ X X X Y

30. Human Sex Chromosomes ♀ ♂

31. Mutations A mutation is any change in the DNA of an organism
Mutations occur due to:
- pathogen infection
- exposure to radiation
- introduction of chemicals
- nondisjunction

32. Mutations Mutations involve: - base pair substitutions
- base pair insertions or
deletions
- DNA segments

33. Mutations

34. Genes, Genetic Code & Genetic Disease
Remember, genes are portions of DNA that code for a particular protein
In order for the protein to be functional, the DNA nitrogen base sequence must be correct

35. Genes, Genetic Code & Genetic Disease
Any variance of that sequence can cause the wrong amino acid to be inserted into the polypeptide which could result in:
- a non-functioning protein
- a protein that changes the
outcome of a process

36. Nondisjunction
Nondisjunction is the failure of chromosomes to separate during anaphase I of meiosis
The normal separation, disjunction, produces daughter cells with 23 chromosomes each

37. Nondisjunction
Nondisjunction results in one daughter cell with 24 chromosomes and the other with 22 chromosomes

38. Nondisjunction
Monosomy is the result of the fertilization of a normal gamete and one that has only 22 chromosomes
Trisomy is the product of the fertilization of a normal gamete and one that has 24 chromosomes

39. Disjunction
Nondisjunction

40. Genetic Disorders
Several genetic disorders are sex linked and found predominantly in men, but can also be present in women
The shorter Y chromosome means there is only one allele that determines these traits

41. Genetic Disorders
Male pattern baldness and color blindness are two examples that are inconvenient, but non-life threatening
Hemophilia, a condition in which the blood does not clot correctly, can be deadly

42. Genetic Disorders Remember:
Any variance of the DNA base sequence can cause the wrong amino acid to be inserted into the polypeptide which could result in:
- a non-functioning protein
- a protein that changes the
outcome of a process

43. Genetic Disorders
These mutations can lead to a number of human health disorders
Some of these abnormalities are inconvenient, while others can be lethal

44. Genetic Disorders
Albinism is a condition in which the body does not produce the pigment melanin
The phenotypic results are white hair, pale skin and pink colored eyes

45. Genetic Disorders
Albinism is the result of a homozygous recessive genotype that produces a nonfunctional tyrosinase enzyme
Melanin is synthesized from tyrosine by way of the enzyme tyrosinase

46. Genetic Disorders
Sickle cell disease is a condition in which red blood cells are deformed due to the substitution of one amino acid in a hemoglobin chain

47. Genetic Disorders
The deformation of the RBCs inhibits the binding of oxygen, causing anemia
The deformation also causes the sickled RBCs to be sticky and agglutinate

48. Genetic Disorders
Without treatment a child will usually die before age two
Even with treatment most affected people die before the age of fifty

49. Genetic Disorders
The substitution of one amino acid is caused by a recessive allele
Sickle cell is the result of a homozygous recessive genotype that produces the malformed hemoglobin

50. Genetic Disorders
Approximately 8.5% of people of central and southern African descent are carriers of the allele

51. Genetic Disorders
Phenylketonuria (PKU disease) is a disorder in which the amino acid phenylalanine is not metabolized due to the lack of an enzyme

52. Genetic Disorders
PKU disease is the result of a homozygous recessive genotype that does not produce the enzyme that converts phenylalanine into tyrosine

53. Genetic Disorders
Phenylalanine accumulates in the blood and acts as a neurotoxin, causing brain damage and retardation
Required tests on newborns now identify those affected, which will be put on a low phenylalanine diet

54. Genetic Disorders Remember:
Nondisjunction in gametes causes a change in chromosome numbers that affects the development of an embryo
Approximately 90% of nondisjunction events are maternal in origin

55. Genetic Disorders
The presence of an extra chromosome (trisomy) or lack of one (monosomy) accounts for approximately 50% of all spontaneous abortions

56. Genetic Disorders Only three autosomal trisomies are survivable:
* trisomy 13 – Patau syndrome
* trisomy 18 – Edward syndrome
* trisomy 21 – Down syndrome

57. Genetic Disorders
Most fetuses with Patau or Edward syndrome will die before birth
The few that are born are severely deformed and usually die within their first year

58. Genetic Disorders
Karyotype of Down syndrome (trisomy 21)

59. Genetic Disorders
Down syndrome is the most survivable of the trisomies, but approximately 75% die before birth and 20% of those born will die before the age of ten

60. Genetic Disorders Down syndrome effects: * short stature
* a flat face with almond shaped
eyes
* enlarged protruding tongue
* broad hands with short fingers
* varying degrees of mental
retardation

61. Genetic Disorders
Of those that survive past the age of ten, life expectancy has been extended to sixty years
However, after the age of forty many develop early onset Alzheimer disease

62. Genetic Disorders Nondisjunction also occurs with the sex chromosomes:
* trisomy 23 – Klinefelter
syndrome (XXY)
* trisomy 23 – Triplo-X syndrome
(XXX)
* monosomy 23 – Turner
syndrome (XO)

63. Genetic Disorders
Triplo-X syndrome (XXX) results in a female phenotype that is usually infertile and may exhibit some intellectual impairment

64. Genetic Disorders
Klinefelter syndrome (XXY) results in a sterile male phenotype that is of normal intelligence and upon the onset of puberty exhibits unusually long arms, sparse body hair, undeveloped testes and enlarged breasts

65. Genetic Disorders
Turner syndrome (XO) results in a sterile female phenotype that fails to develop secondary sex characteristics at puberty and is usually short in stature
Approximately 97% of all (XO) fetuses die before birth