CHAPTER 14 Human Heredity"MUTATIONS IN GENES" . . Mutation- change in DNA sequence that affects genetic information.. . GENE MUTATIONS- a chemical change resulting from a change in a single gene.EX: Point Mutations
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1. BIOLOGY CHAPTER 12-4 Mutations
2. CHAPTER 14 Human Heredity"MUTATIONS IN GENES"
3. Mutation- change in DNA sequence that affects genetic information.
4. GENE MUTATIONS- a chemical change resulting from a change in a single gene.EX: Point Mutations & frameshift mutations
5. The majority of gene mutations involve just one nucleotide.
6. POINT MUTATION- mutation that affects a single nucleotide, usually by substituting one nucleotide for another.
7. These substitutions usually change one of the amino acids in a protein.
8. When a point mutation inserts or deletes a nucleotide- a bigger change results.
9. Genetic codes are read in groups of three bases known as CODONS. If a nucleotide is inserted or deleted the groupings are shifted for every nucleotide that follows. These types of changes are called:
10. FRAMESHIFT MUTATIONS…because there is a shift in the reading frame of the genetic message.
11. Frameshift mutations affect every amino acid that follows the point of the insertion or deletion.
12. These mutations can alter a protein so that it is unable to function normally.
13. Figure 12-19: Substitution, Insertion, Deletion
14. CHROMOSOMAL MUTATIONS- mutations that involve changes in a whole chromosome….changes in the number of chromosomes or in the structure of chromosomes….
15. Chromosomal mutations can even change the locations of genes on chromosomes & even the # of copies of some genes.
16. .Deletion- the loss of all or part of a chromosome.
17. .Dulpication- (opposite of deletion) a segment of a chromosome is repeated.
18. .Inversion- when part of a chromosome becomes oriented in the reverse of its usual direction.
19. Translocation- when part of one chromosome breaks off & attaches to another NON-homologous chromosome.
20. *In most cases non-homologous chromosomes exchange segments so that 2 translocations occur at the same time.
21. page 308 Section Assessment #1-5 Write the Questions!
22. 14-1 Human Heredity page 341Human traits are inherited by the action if dominant and recessive genes, but some traits are determined by more complicated gene interactions.
23. Diploid cell- has 2 sets of homologous chromosomes...human diploid cells contain 46 chromosomes arranged in 23 pairs;
24. The 46 chromosomes contain 6 billion nucleotide pairs of DNA.
25. Nucleotide- a unit of nucleic acid that is made up of a 5 carbon sugar, a phosphate group, and a nitrogenous base;
26. Nucleic acids (RNA, DNA) store and transmit the genetic information that is responsible for life itself.
27. EX: In this textbook there are approximately 1500 letters on each page...In complete human DNA sequence were written in the same size type of this textbook, it would take a book of more than 4 million pages long to express how long the sequence is;
28. According to Mendel, organisms inherit a single copy of each gene from each parent.
29. In Humans, gametes (reproductive cells) contain a single copy of each gene.
30. Gametes (sperm and eggs) are formed in reproductive organs by the process of meiosis;
31. Each egg and sperm cell contain 23 chromosomes, or the HAPLOID number of chromosomes.
32. During fertilization, an egg and sperm unite and a ZYGOTE (fertilized egg) is formed.
33. The zygote contains 46 chromosomes (23 pairs) or the DIPLOID number of chromosomes;...the number characteristic of the organism;
34. **Of the 46 chromosomes found in a human diploid cell...two are the sex chromosomes X and Y or X and X.
35. Females are 46 XX and males are 46 XY…see Punnett Square on page 342
36. The remaining 44 chromosomes are AUTOSOMES.
37. Autosome- (autosomal chromosomes)…a chromosome that is NOT a sex chromosome. Autosomes are found in the body cells…
38. Dominant and recessive traits can be inherited on any of the 44 autosomes.
39. Human genes carried on the sex chromosomes are sex-linked.
40. HUMAN TRAITS
41. The phenotype of an organism is only partially determined by its genotype.
42. Some traits are influenced by environmental factors such as nutrition and exercise.
43. Improvements in infant and childhood nutrition in the U.S. and Europe have greatly increase the average height of these populations.
44. Environmental influence is an important consideration...HOWEVER, the environmental influences on gene expression are not inherited...only the genes are;
45. Genes that are denied proper environment in which to reach full expression in one generation can, in proper environment, achieve full potential in a later generation.
46. KARYOTYPE-set of photographs of chromosomes that are grouped in order, in pairs.
47. See page 341…figure 14-1
48. THE INERITANCE OF HUMAN TRAITS
49. Pedigree- a chart that shows the relationship within a family…
50. Pedigree charts are most often used by geneticists when tracking the inheritance of genetic disorders,such as hemophila or colorblindness.
51. They are used to help parents understand the probability of having a child with a genetic disorder.
52. Carriers are heterozygous for a trait and do not exhibit the trait.
53. Pedigree charts are based on observable traits- phenotypes.
54. * Females who have one allele for the trait are only carriers, while males who have one allele for the trait express the trait.
55. POLYGENIC- traits that are controlled by many genes.
56. HUMAN GENOME- our complete set of genetic information.Page 344
57. HUMAN BLOOD GROUPS
58. Genes can have 2 contrasting forms (alleles..such as short or tall)...some genes have more than 2 forms.
59. MULTIPLE ALLELES- three or more alleles of the same gene that code for a single trait;
60. In a diploid organism, only 2 of the alleles can exist.
61. ABO and Rh blood groups are examples of human traits determined by multiple alleles.
62. ABO BLOOD GROUPS....
63. In 1900, Karl Landsteiner, and Austrian physician discovered that human blood could be classified into 4 general groups.
64. Today we know these types as Landsteiner blood groups.
65. These four blood types are determined by the presence or absence of certain chemical substances in the blood.
66. When certain blood types are mixed they AGGLUTINATE or clump together.
67. Red blood cells can carry 2 different antigens, which he called A and B.
68. ANTIGEN- molecules that can be recognized by the immune system.
69. The presence or absence of the A and B antigens produces the four possible blood types:
70. A = RBC's carry only the A antigen
71. B= RBC's carry only the B antigen
72. AB= RBC's carry the A and B antigen
73. O = RBC's do not carry either antigen
74. Blood type information is very important in Blood Transfusions...the wrong blood type can cause a violent and even fatal reaction.
75. The immune system does not recognize the antigen and sees the blood as a foreign intruder.
76. People who have AB blood can receive blood from any of the four groups...UNIVERSAL RECIEPTIANT ;
77. People who have type O blood can donate blood to someone who has any of the 4 blood types but can only receive type O blood..Type O = UNIVERSAL DONOR.
78. The ABO blood groups are determined by a single gene with 3 alleles;
79. See figure 14-4 pg 344
80. IA and IB are codominant and i is recessive;
81. A person with IAIB produces both antigens making their blood type AB.
82. A person with IAIA or IAi produce only the A antigen making them blood type A.
83. IBIB or IBi produce only the B antigen making them blood type B.
84. Those who are homologous for the i allele (ii) produce no antigen and are said to have blood type O.
85. Rh BLOOD GROUPS
86. In addition to AB antigens there is another antigen on RBC's...called the Rh antigen..so named after the rhesus monkey in which the antigen was first discovered.
87. Lansteiner and Alexander Wiener discovered the Rh factor.
88. People who have the Rh antigen on their blood cells are said to be Rh positive..those who do not are said to be Rh negative.
89. Simple dominance is displayed in the gene expression of the Rh factor..
90. Rh+ and Rh + = dominant positive
91. Rh + and Rh negative = dominant positive
92. Rh- and Rh- = Rh negative
93. RECESSIVE ALLELES
94. Phenylketonuria (PKU)- people who lack the enzyme that is needed to break down phenylalanine….an amino acid found in milk and many other foods.
95. Build up of phenylalanine in the tissues during the child's first years of life and could cause mental retardation…caused by a recessive allele carried on chromosome 12.
96. Tay-Sachs disease- caused by autosomal recessive alleles…found mostly Jewish families of central & eastern European ancestary. This disease results in nervous system break down and death in the first few years of life.
97. There is no treatment for this disease- however-there is a test for this allele.
98. DOMINANT ALLELES
99. Remember that the effects of a dominant allele are expressed even when the recessive allele is present….therefore-if you have the dominant allele for a genetic disorder- it will be expressed.
100. EX: Dwarfism (Achondroplasia…pronounced ay-kahn-droh-PLAY-zhuh) & Huntington’s Disease
101. HUNTINGTON DISEASE
102. This disease involves a slow and progressive destruction of brain cells....a loss of muscle control and mental function; A person usually dies 10-20 years after the first onset of the symptoms....usually between the ages of 30-50;
103. This disease is caused by a dominant allele and the symptoms do not show up until middle age.
104. (Extra Information)
105. In 1993 the gene for HD was located on chromosome 4 and isolated. The DNA sequence for the gene was determined...this allows researchers to see how the disease works and how to fix it.
106. Tests are available to see if you have this disease...Would you want to know whether or not you carry this allele?
107. (Extra Information)The frequency of this disease is higher in South Africa than in any other part of the world...All affected persons in South Africa were directly or indirectly descended from a Dutchman who settled there in 1658;
108. FOUNDER EFFECT- the phenomenon of one or a few individuals with a genetic abnormality causing the establishment of a new population...most likely to occur in regions that are remote and have a relatively small total population;
109. CODOMINANT ALLELES